University of Virginia

Post-Doc

Brief Post-Doc role, writing grants, creating research projects at UVA in between Ph.D. and move to Los Alamos. Worked with J R Scully and M Neurock on corrosion of nanomaterials and impurity interactions on surfaces.

University of Virginia

Graduate Student

Development and application of quantum chemical techniques for understanding the interplay between metallic band structure, electrochemical charging, metal solvation and surface adsorption, especially regarding corrosion chemistry of metals and fuel cell electrocatalysis.

The Ohio State University

Research Associate Professor

Theory, Modeling and Simulation of Molecular Transformations at the Material/Environment Interface and the Study of Related Materials Degradation Phenomena

Los Alamos National Laboratory

Post-Doc

Metal-hydride technologies and processes
Development of simulation techniques for materials with complex crystallography
Corrosion in the oil and gas industry

Los Alamos National Laboratory

Materials Scientist

Principal Investigator for various projects in functional materials design; comprised of computation, modeling and experiment in the areas of nuclear waste disposition, catalysis and energy generation, corrosion in the oil and gas industry, actinide science, oxidation processes in metallic systems and advanced simulation of light water reactors.

Los Alamos Postdoc Association

President

LAPA seeks to promote a spirit community among Los Alamos post-docs, to advocate for the needs and concerns of Los Alamos post-docs, and to provide services that enhance the career development of Los Alamos post-docs.

DNV GL

Senior Researcher

Advanced modeling of materials and science-based approaches to risk assessment

LifeCare Alliance

Meals pickup and delivery routes in the Columbus Ohio area

NACE International

The Local Southwest Ohio section provides opportunities for NACE members in the Southern Ohio, Indiana, West Virginia and Kentucky areas to connect via networking, informational and educational opportunities and to stay up to date on corrosion issues in our area.

Towards Materials Sustainability through Materials Stewardship

Sustainability

Materials sustainability requires a concerted change in philosophy across the entire materials lifecycle, orienting around the theme of materials stewardship. In this paper, we address the opportunities for improved materials conservation through dematerialization, durability, design for second life, and diversion of waste streams through industrial symbiosis.

Towards Materials Sustainability through Materials Stewardship

Sustainability

Materials sustainability requires a concerted change in philosophy across the entire materials lifecycle, orienting around the theme of materials stewardship. In this paper, we address the opportunities for improved materials conservation through dematerialization, durability, design for second life, and diversion of waste streams through industrial symbiosis.

Molecular Modeling of Corrosion Processes: Scientific Development and Engineering Applications

ECS / Wiley

This book demonstrates how molecular modeling has the potential to yield unique and unprecedented insights into the multitude of interconnected and complex processes that comprise corrosion of metals. In any given environment, numerous competing mechanisms can lead to corrosion. These include competitive surface adsorption, electron transfer via cathodic and anodic processes, dissolution of metals and dealloying, the formation of pre-passive oxide films, localized corrosion and passivity breakdown, the adsorption of inhibitors, and hydrogen embrittlement. This book therefore explains via molecular modeling how these pathways can be individually assessed and compared to one another. The book describes both the strengths and limitations of the current molecular and atomistic modelling toolkit so that the professional interested in using these techniques can determine whether or not a given tool is appropriate for simulating the corrosion phenomenon at hand. The book also can serve as a reference for researchers seeking to build new research programs that will extend the current molecular modelling toolkit into exciting new directions.

Towards Materials Sustainability through Materials Stewardship

Sustainability

Materials sustainability requires a concerted change in philosophy across the entire materials lifecycle, orienting around the theme of materials stewardship. In this paper, we address the opportunities for improved materials conservation through dematerialization, durability, design for second life, and diversion of waste streams through industrial symbiosis.

Molecular Modeling of Corrosion Processes: Scientific Development and Engineering Applications

ECS / Wiley

This book demonstrates how molecular modeling has the potential to yield unique and unprecedented insights into the multitude of interconnected and complex processes that comprise corrosion of metals. In any given environment, numerous competing mechanisms can lead to corrosion. These include competitive surface adsorption, electron transfer via cathodic and anodic processes, dissolution of metals and dealloying, the formation of pre-passive oxide films, localized corrosion and passivity breakdown, the adsorption of inhibitors, and hydrogen embrittlement. This book therefore explains via molecular modeling how these pathways can be individually assessed and compared to one another. The book describes both the strengths and limitations of the current molecular and atomistic modelling toolkit so that the professional interested in using these techniques can determine whether or not a given tool is appropriate for simulating the corrosion phenomenon at hand. The book also can serve as a reference for researchers seeking to build new research programs that will extend the current molecular modelling toolkit into exciting new directions.

Corrosion Management for a Sustainable Concrete Infrastructure

Materials Performance (NACE)

Analysis of materials flows through society reveals that infrastructure construction is one of the most significant contributors to global materials consumption, as well as other sustainability impacts such as energy and water consumption and carbon dioxide (CO2) generation. Furthermore, due to degradation these lifecycle costs may recur within one to two generations. Effective corrosion control through understanding the degradation of reinforced concrete, optimizing concrete composition, and implementing corrosion protection can extend the lifetime of existing structures and decrease net CO2 emissions.

Towards Materials Sustainability through Materials Stewardship

Sustainability

Materials sustainability requires a concerted change in philosophy across the entire materials lifecycle, orienting around the theme of materials stewardship. In this paper, we address the opportunities for improved materials conservation through dematerialization, durability, design for second life, and diversion of waste streams through industrial symbiosis.

Molecular Modeling of Corrosion Processes: Scientific Development and Engineering Applications

ECS / Wiley

This book demonstrates how molecular modeling has the potential to yield unique and unprecedented insights into the multitude of interconnected and complex processes that comprise corrosion of metals. In any given environment, numerous competing mechanisms can lead to corrosion. These include competitive surface adsorption, electron transfer via cathodic and anodic processes, dissolution of metals and dealloying, the formation of pre-passive oxide films, localized corrosion and passivity breakdown, the adsorption of inhibitors, and hydrogen embrittlement. This book therefore explains via molecular modeling how these pathways can be individually assessed and compared to one another. The book describes both the strengths and limitations of the current molecular and atomistic modelling toolkit so that the professional interested in using these techniques can determine whether or not a given tool is appropriate for simulating the corrosion phenomenon at hand. The book also can serve as a reference for researchers seeking to build new research programs that will extend the current molecular modelling toolkit into exciting new directions.

Corrosion Management for a Sustainable Concrete Infrastructure

Materials Performance (NACE)

Analysis of materials flows through society reveals that infrastructure construction is one of the most significant contributors to global materials consumption, as well as other sustainability impacts such as energy and water consumption and carbon dioxide (CO2) generation. Furthermore, due to degradation these lifecycle costs may recur within one to two generations. Effective corrosion control through understanding the degradation of reinforced concrete, optimizing concrete composition, and implementing corrosion protection can extend the lifetime of existing structures and decrease net CO2 emissions.

Computational Investigation of Technetium(IV) Incorporation into Inverse Spinels: Magnetite (Fe3O4) and Trevorite (NiFe2O4)

Environmental Science and Technology

Iron oxides and oxyhydroxides play an important role in minimizing the mobility of redox-sensitive elements in engineered and natural environments. For the radionuclide technetium-99 (Tc), these phases hold promise as primary hosts for increasing Tc loading into glass waste form matrices, or as secondary sinks during the long-term storage of nuclear materials. Recent experiments show that the inverse spinel, magnetite [Fe(II)Fe(III)2O4], can incorporate Tc(IV) into its octahedral sub-lattice. In that same class of materials, trevorite [Ni(II)Fe(III)2O4] is also being investigated for its ability to host Tc(IV). However, questions remain regarding the most energetically favorable charge-compensation mechanism for Tc(IV) incorporation in each structure, which will affect Tc behavior under changing waste processing or storage conditions. Here, quantum-mechanical methods were used to evaluate incorporation energies and optimized lattice bonding environments for three different, charge-balanced Tc(IV) incorporation mechanisms in magnetite and trevorite (~5 wt% Tc). For both phases, the removal of two octahedral Fe(II) or Ni(II) ions upon the addition of Tc(IV) in an octahedral site is the most stable mechanism, relative to the creation of octahedral Fe(III) defects or increasing octahedral Fe(II) content. Following hydration-energy corrections, Tc(IV) incorporation into magnetite is energetically favorable while an energy barrier exists for trevorite.

Towards Materials Sustainability through Materials Stewardship

Sustainability

Materials sustainability requires a concerted change in philosophy across the entire materials lifecycle, orienting around the theme of materials stewardship. In this paper, we address the opportunities for improved materials conservation through dematerialization, durability, design for second life, and diversion of waste streams through industrial symbiosis.

Molecular Modeling of Corrosion Processes: Scientific Development and Engineering Applications

ECS / Wiley

This book demonstrates how molecular modeling has the potential to yield unique and unprecedented insights into the multitude of interconnected and complex processes that comprise corrosion of metals. In any given environment, numerous competing mechanisms can lead to corrosion. These include competitive surface adsorption, electron transfer via cathodic and anodic processes, dissolution of metals and dealloying, the formation of pre-passive oxide films, localized corrosion and passivity breakdown, the adsorption of inhibitors, and hydrogen embrittlement. This book therefore explains via molecular modeling how these pathways can be individually assessed and compared to one another. The book describes both the strengths and limitations of the current molecular and atomistic modelling toolkit so that the professional interested in using these techniques can determine whether or not a given tool is appropriate for simulating the corrosion phenomenon at hand. The book also can serve as a reference for researchers seeking to build new research programs that will extend the current molecular modelling toolkit into exciting new directions.

Corrosion Management for a Sustainable Concrete Infrastructure

Materials Performance (NACE)

Analysis of materials flows through society reveals that infrastructure construction is one of the most significant contributors to global materials consumption, as well as other sustainability impacts such as energy and water consumption and carbon dioxide (CO2) generation. Furthermore, due to degradation these lifecycle costs may recur within one to two generations. Effective corrosion control through understanding the degradation of reinforced concrete, optimizing concrete composition, and implementing corrosion protection can extend the lifetime of existing structures and decrease net CO2 emissions.

Computational Investigation of Technetium(IV) Incorporation into Inverse Spinels: Magnetite (Fe3O4) and Trevorite (NiFe2O4)

Environmental Science and Technology

Iron oxides and oxyhydroxides play an important role in minimizing the mobility of redox-sensitive elements in engineered and natural environments. For the radionuclide technetium-99 (Tc), these phases hold promise as primary hosts for increasing Tc loading into glass waste form matrices, or as secondary sinks during the long-term storage of nuclear materials. Recent experiments show that the inverse spinel, magnetite [Fe(II)Fe(III)2O4], can incorporate Tc(IV) into its octahedral sub-lattice. In that same class of materials, trevorite [Ni(II)Fe(III)2O4] is also being investigated for its ability to host Tc(IV). However, questions remain regarding the most energetically favorable charge-compensation mechanism for Tc(IV) incorporation in each structure, which will affect Tc behavior under changing waste processing or storage conditions. Here, quantum-mechanical methods were used to evaluate incorporation energies and optimized lattice bonding environments for three different, charge-balanced Tc(IV) incorporation mechanisms in magnetite and trevorite (~5 wt% Tc). For both phases, the removal of two octahedral Fe(II) or Ni(II) ions upon the addition of Tc(IV) in an octahedral site is the most stable mechanism, relative to the creation of octahedral Fe(III) defects or increasing octahedral Fe(II) content. Following hydration-energy corrections, Tc(IV) incorporation into magnetite is energetically favorable while an energy barrier exists for trevorite.

Design and Prediction of Corrosion Inhibitors from Quantum Chemistry II. A General Framework for Prediction of Effective Oil/Water Partition Coefficients and Speciation from Quantum Chemistry

Journal of the Electrochemical Society

Quantum chemistry is a powerful tool for computing the properties of molecules and their interactions with one another in a variety of environments. In this second paper of a two-part series, the technique is applied in this work to calculate fundamental properties of inhibitor molecules important to the overall corrosion inhibitor performance. The study focuses on the issue of oil/water partitioning as quantified by the partition coefficient (log P) and the important issue of inhibitor speciation according to the acid dissociation constant (pKa). pKa and log P values are then calculated from first-principles for a series of imidazole derivatives and integrated into a model for inhibitor availability as a function of the water cut. Applications to lifetime prediction and inhibitor design are then discussed.

Towards Materials Sustainability through Materials Stewardship

Sustainability

Materials sustainability requires a concerted change in philosophy across the entire materials lifecycle, orienting around the theme of materials stewardship. In this paper, we address the opportunities for improved materials conservation through dematerialization, durability, design for second life, and diversion of waste streams through industrial symbiosis.

Molecular Modeling of Corrosion Processes: Scientific Development and Engineering Applications

ECS / Wiley

This book demonstrates how molecular modeling has the potential to yield unique and unprecedented insights into the multitude of interconnected and complex processes that comprise corrosion of metals. In any given environment, numerous competing mechanisms can lead to corrosion. These include competitive surface adsorption, electron transfer via cathodic and anodic processes, dissolution of metals and dealloying, the formation of pre-passive oxide films, localized corrosion and passivity breakdown, the adsorption of inhibitors, and hydrogen embrittlement. This book therefore explains via molecular modeling how these pathways can be individually assessed and compared to one another. The book describes both the strengths and limitations of the current molecular and atomistic modelling toolkit so that the professional interested in using these techniques can determine whether or not a given tool is appropriate for simulating the corrosion phenomenon at hand. The book also can serve as a reference for researchers seeking to build new research programs that will extend the current molecular modelling toolkit into exciting new directions.

Corrosion Management for a Sustainable Concrete Infrastructure

Materials Performance (NACE)

Analysis of materials flows through society reveals that infrastructure construction is one of the most significant contributors to global materials consumption, as well as other sustainability impacts such as energy and water consumption and carbon dioxide (CO2) generation. Furthermore, due to degradation these lifecycle costs may recur within one to two generations. Effective corrosion control through understanding the degradation of reinforced concrete, optimizing concrete composition, and implementing corrosion protection can extend the lifetime of existing structures and decrease net CO2 emissions.

Computational Investigation of Technetium(IV) Incorporation into Inverse Spinels: Magnetite (Fe3O4) and Trevorite (NiFe2O4)

Environmental Science and Technology

Iron oxides and oxyhydroxides play an important role in minimizing the mobility of redox-sensitive elements in engineered and natural environments. For the radionuclide technetium-99 (Tc), these phases hold promise as primary hosts for increasing Tc loading into glass waste form matrices, or as secondary sinks during the long-term storage of nuclear materials. Recent experiments show that the inverse spinel, magnetite [Fe(II)Fe(III)2O4], can incorporate Tc(IV) into its octahedral sub-lattice. In that same class of materials, trevorite [Ni(II)Fe(III)2O4] is also being investigated for its ability to host Tc(IV). However, questions remain regarding the most energetically favorable charge-compensation mechanism for Tc(IV) incorporation in each structure, which will affect Tc behavior under changing waste processing or storage conditions. Here, quantum-mechanical methods were used to evaluate incorporation energies and optimized lattice bonding environments for three different, charge-balanced Tc(IV) incorporation mechanisms in magnetite and trevorite (~5 wt% Tc). For both phases, the removal of two octahedral Fe(II) or Ni(II) ions upon the addition of Tc(IV) in an octahedral site is the most stable mechanism, relative to the creation of octahedral Fe(III) defects or increasing octahedral Fe(II) content. Following hydration-energy corrections, Tc(IV) incorporation into magnetite is energetically favorable while an energy barrier exists for trevorite.

Design and Prediction of Corrosion Inhibitors from Quantum Chemistry II. A General Framework for Prediction of Effective Oil/Water Partition Coefficients and Speciation from Quantum Chemistry

Journal of the Electrochemical Society

Quantum chemistry is a powerful tool for computing the properties of molecules and their interactions with one another in a variety of environments. In this second paper of a two-part series, the technique is applied in this work to calculate fundamental properties of inhibitor molecules important to the overall corrosion inhibitor performance. The study focuses on the issue of oil/water partitioning as quantified by the partition coefficient (log P) and the important issue of inhibitor speciation according to the acid dissociation constant (pKa). pKa and log P values are then calculated from first-principles for a series of imidazole derivatives and integrated into a model for inhibitor availability as a function of the water cut. Applications to lifetime prediction and inhibitor design are then discussed.

A First-Principles Surface Reaction Kinetic Model for Hydrogen Evolution under Cathodic and Anodic Conditions on Magnesium

Journal of the Electrochemical Society

A surface kinetic model is developed using a proposed mechanism for the anodic and cathodic branches of the hydrogen evolution observed over magnesium (i.e. the negative difference effect). The key element to the model is that hydrogen evolution requires the removal of adsorbed OH from the surface. This step is achieved in the cathodic branch by reductive desorption of OH to form OH− from the surface, and in the anodic branch by the dissolution of both adsorbed OH along with the Mg atom to which it is attached (thus combined desorption of OH− alongside dissolution of Mg2+). Steady state theory is applied to derive expressions for the hydrogen evolution rate as a function of potential. First-principles parameters obtained from the literature are used to compute the rate constants for the individual mechanistic steps, where available, and reasonable values based on cohesive energies are used to estimate the remaining parameters where first-principles information is not available. These rate constants are then applied to the surface kinetic model to show that the model provides reasonable agreement with the observed phenomenology for hydrogen evolution over magnesium, both in terms of the shape and order of magnitude of hydrogen evolved, and the transition potential (i.e. the open circuit potential) between the anodic and cathodic hydrogen evolution branches.

Towards Materials Sustainability through Materials Stewardship

Sustainability

Materials sustainability requires a concerted change in philosophy across the entire materials lifecycle, orienting around the theme of materials stewardship. In this paper, we address the opportunities for improved materials conservation through dematerialization, durability, design for second life, and diversion of waste streams through industrial symbiosis.

Molecular Modeling of Corrosion Processes: Scientific Development and Engineering Applications

ECS / Wiley

This book demonstrates how molecular modeling has the potential to yield unique and unprecedented insights into the multitude of interconnected and complex processes that comprise corrosion of metals. In any given environment, numerous competing mechanisms can lead to corrosion. These include competitive surface adsorption, electron transfer via cathodic and anodic processes, dissolution of metals and dealloying, the formation of pre-passive oxide films, localized corrosion and passivity breakdown, the adsorption of inhibitors, and hydrogen embrittlement. This book therefore explains via molecular modeling how these pathways can be individually assessed and compared to one another. The book describes both the strengths and limitations of the current molecular and atomistic modelling toolkit so that the professional interested in using these techniques can determine whether or not a given tool is appropriate for simulating the corrosion phenomenon at hand. The book also can serve as a reference for researchers seeking to build new research programs that will extend the current molecular modelling toolkit into exciting new directions.

Corrosion Management for a Sustainable Concrete Infrastructure

Materials Performance (NACE)

Analysis of materials flows through society reveals that infrastructure construction is one of the most significant contributors to global materials consumption, as well as other sustainability impacts such as energy and water consumption and carbon dioxide (CO2) generation. Furthermore, due to degradation these lifecycle costs may recur within one to two generations. Effective corrosion control through understanding the degradation of reinforced concrete, optimizing concrete composition, and implementing corrosion protection can extend the lifetime of existing structures and decrease net CO2 emissions.

Computational Investigation of Technetium(IV) Incorporation into Inverse Spinels: Magnetite (Fe3O4) and Trevorite (NiFe2O4)

Environmental Science and Technology

Iron oxides and oxyhydroxides play an important role in minimizing the mobility of redox-sensitive elements in engineered and natural environments. For the radionuclide technetium-99 (Tc), these phases hold promise as primary hosts for increasing Tc loading into glass waste form matrices, or as secondary sinks during the long-term storage of nuclear materials. Recent experiments show that the inverse spinel, magnetite [Fe(II)Fe(III)2O4], can incorporate Tc(IV) into its octahedral sub-lattice. In that same class of materials, trevorite [Ni(II)Fe(III)2O4] is also being investigated for its ability to host Tc(IV). However, questions remain regarding the most energetically favorable charge-compensation mechanism for Tc(IV) incorporation in each structure, which will affect Tc behavior under changing waste processing or storage conditions. Here, quantum-mechanical methods were used to evaluate incorporation energies and optimized lattice bonding environments for three different, charge-balanced Tc(IV) incorporation mechanisms in magnetite and trevorite (~5 wt% Tc). For both phases, the removal of two octahedral Fe(II) or Ni(II) ions upon the addition of Tc(IV) in an octahedral site is the most stable mechanism, relative to the creation of octahedral Fe(III) defects or increasing octahedral Fe(II) content. Following hydration-energy corrections, Tc(IV) incorporation into magnetite is energetically favorable while an energy barrier exists for trevorite.

Design and Prediction of Corrosion Inhibitors from Quantum Chemistry II. A General Framework for Prediction of Effective Oil/Water Partition Coefficients and Speciation from Quantum Chemistry

Journal of the Electrochemical Society

Quantum chemistry is a powerful tool for computing the properties of molecules and their interactions with one another in a variety of environments. In this second paper of a two-part series, the technique is applied in this work to calculate fundamental properties of inhibitor molecules important to the overall corrosion inhibitor performance. The study focuses on the issue of oil/water partitioning as quantified by the partition coefficient (log P) and the important issue of inhibitor speciation according to the acid dissociation constant (pKa). pKa and log P values are then calculated from first-principles for a series of imidazole derivatives and integrated into a model for inhibitor availability as a function of the water cut. Applications to lifetime prediction and inhibitor design are then discussed.

A First-Principles Surface Reaction Kinetic Model for Hydrogen Evolution under Cathodic and Anodic Conditions on Magnesium

Journal of the Electrochemical Society

A surface kinetic model is developed using a proposed mechanism for the anodic and cathodic branches of the hydrogen evolution observed over magnesium (i.e. the negative difference effect). The key element to the model is that hydrogen evolution requires the removal of adsorbed OH from the surface. This step is achieved in the cathodic branch by reductive desorption of OH to form OH− from the surface, and in the anodic branch by the dissolution of both adsorbed OH along with the Mg atom to which it is attached (thus combined desorption of OH− alongside dissolution of Mg2+). Steady state theory is applied to derive expressions for the hydrogen evolution rate as a function of potential. First-principles parameters obtained from the literature are used to compute the rate constants for the individual mechanistic steps, where available, and reasonable values based on cohesive energies are used to estimate the remaining parameters where first-principles information is not available. These rate constants are then applied to the surface kinetic model to show that the model provides reasonable agreement with the observed phenomenology for hydrogen evolution over magnesium, both in terms of the shape and order of magnitude of hydrogen evolved, and the transition potential (i.e. the open circuit potential) between the anodic and cathodic hydrogen evolution branches.

Technetium Incorporation into Goethite (α-FeOOH): An Atomic-Scale Investigation

Environmental Science & Technology

During the processing of low-activity radioactive waste to generate solid waste forms (e.g., glass), technetium-99 (Tc) is of concern because of its volatility. A variety of materials are under consideration to capture Tc from waste streams, including the iron oxyhydroxide, goethite (α-FeOOH), which was experimentally shown to sequester Tc(IV). This material could ultimately be incorporated into glass or alternative low-temperature waste form matrices. However, questions remain regarding the incorporation mechanism for Tc(IV) in goethite, which has implications for predicting the long-term stability of Tc in waste forms under changing conditions. Here, quantum-mechanical calculations were used to evaluate the energy of five different charge-compensated Tc(IV) incorporation scenarios in goethite. The two most stable incorporation mechanisms involve direct substitution of Tc(IV) onto Fe(III) lattice sites and charge balancing either by removing one nearby H+ (i.e., within 5 Å) or by creating an Fe(III) vacancy when substituting 3 Tc(IV) for 4 Fe(III), with the former being preferred over the latter relative to gas-phase ions. When corrections for hydrated references phases are applied, the Fe(III)-vacancy mechanism becomes more energetically competitive. Calculated incorporation energies and optimized bond lengths are presented. Proton movement is observed to satisfy undercoordinated bonds surrounding Fe(III)-vacancies in the goethite structure.

Towards Materials Sustainability through Materials Stewardship

Sustainability

Materials sustainability requires a concerted change in philosophy across the entire materials lifecycle, orienting around the theme of materials stewardship. In this paper, we address the opportunities for improved materials conservation through dematerialization, durability, design for second life, and diversion of waste streams through industrial symbiosis.

Molecular Modeling of Corrosion Processes: Scientific Development and Engineering Applications

ECS / Wiley

This book demonstrates how molecular modeling has the potential to yield unique and unprecedented insights into the multitude of interconnected and complex processes that comprise corrosion of metals. In any given environment, numerous competing mechanisms can lead to corrosion. These include competitive surface adsorption, electron transfer via cathodic and anodic processes, dissolution of metals and dealloying, the formation of pre-passive oxide films, localized corrosion and passivity breakdown, the adsorption of inhibitors, and hydrogen embrittlement. This book therefore explains via molecular modeling how these pathways can be individually assessed and compared to one another. The book describes both the strengths and limitations of the current molecular and atomistic modelling toolkit so that the professional interested in using these techniques can determine whether or not a given tool is appropriate for simulating the corrosion phenomenon at hand. The book also can serve as a reference for researchers seeking to build new research programs that will extend the current molecular modelling toolkit into exciting new directions.

Corrosion Management for a Sustainable Concrete Infrastructure

Materials Performance (NACE)

Analysis of materials flows through society reveals that infrastructure construction is one of the most significant contributors to global materials consumption, as well as other sustainability impacts such as energy and water consumption and carbon dioxide (CO2) generation. Furthermore, due to degradation these lifecycle costs may recur within one to two generations. Effective corrosion control through understanding the degradation of reinforced concrete, optimizing concrete composition, and implementing corrosion protection can extend the lifetime of existing structures and decrease net CO2 emissions.

Computational Investigation of Technetium(IV) Incorporation into Inverse Spinels: Magnetite (Fe3O4) and Trevorite (NiFe2O4)

Environmental Science and Technology

Iron oxides and oxyhydroxides play an important role in minimizing the mobility of redox-sensitive elements in engineered and natural environments. For the radionuclide technetium-99 (Tc), these phases hold promise as primary hosts for increasing Tc loading into glass waste form matrices, or as secondary sinks during the long-term storage of nuclear materials. Recent experiments show that the inverse spinel, magnetite [Fe(II)Fe(III)2O4], can incorporate Tc(IV) into its octahedral sub-lattice. In that same class of materials, trevorite [Ni(II)Fe(III)2O4] is also being investigated for its ability to host Tc(IV). However, questions remain regarding the most energetically favorable charge-compensation mechanism for Tc(IV) incorporation in each structure, which will affect Tc behavior under changing waste processing or storage conditions. Here, quantum-mechanical methods were used to evaluate incorporation energies and optimized lattice bonding environments for three different, charge-balanced Tc(IV) incorporation mechanisms in magnetite and trevorite (~5 wt% Tc). For both phases, the removal of two octahedral Fe(II) or Ni(II) ions upon the addition of Tc(IV) in an octahedral site is the most stable mechanism, relative to the creation of octahedral Fe(III) defects or increasing octahedral Fe(II) content. Following hydration-energy corrections, Tc(IV) incorporation into magnetite is energetically favorable while an energy barrier exists for trevorite.

Design and Prediction of Corrosion Inhibitors from Quantum Chemistry II. A General Framework for Prediction of Effective Oil/Water Partition Coefficients and Speciation from Quantum Chemistry

Journal of the Electrochemical Society

Quantum chemistry is a powerful tool for computing the properties of molecules and their interactions with one another in a variety of environments. In this second paper of a two-part series, the technique is applied in this work to calculate fundamental properties of inhibitor molecules important to the overall corrosion inhibitor performance. The study focuses on the issue of oil/water partitioning as quantified by the partition coefficient (log P) and the important issue of inhibitor speciation according to the acid dissociation constant (pKa). pKa and log P values are then calculated from first-principles for a series of imidazole derivatives and integrated into a model for inhibitor availability as a function of the water cut. Applications to lifetime prediction and inhibitor design are then discussed.

A First-Principles Surface Reaction Kinetic Model for Hydrogen Evolution under Cathodic and Anodic Conditions on Magnesium

Journal of the Electrochemical Society

A surface kinetic model is developed using a proposed mechanism for the anodic and cathodic branches of the hydrogen evolution observed over magnesium (i.e. the negative difference effect). The key element to the model is that hydrogen evolution requires the removal of adsorbed OH from the surface. This step is achieved in the cathodic branch by reductive desorption of OH to form OH− from the surface, and in the anodic branch by the dissolution of both adsorbed OH along with the Mg atom to which it is attached (thus combined desorption of OH− alongside dissolution of Mg2+). Steady state theory is applied to derive expressions for the hydrogen evolution rate as a function of potential. First-principles parameters obtained from the literature are used to compute the rate constants for the individual mechanistic steps, where available, and reasonable values based on cohesive energies are used to estimate the remaining parameters where first-principles information is not available. These rate constants are then applied to the surface kinetic model to show that the model provides reasonable agreement with the observed phenomenology for hydrogen evolution over magnesium, both in terms of the shape and order of magnitude of hydrogen evolved, and the transition potential (i.e. the open circuit potential) between the anodic and cathodic hydrogen evolution branches.

Technetium Incorporation into Goethite (α-FeOOH): An Atomic-Scale Investigation

Environmental Science & Technology

During the processing of low-activity radioactive waste to generate solid waste forms (e.g., glass), technetium-99 (Tc) is of concern because of its volatility. A variety of materials are under consideration to capture Tc from waste streams, including the iron oxyhydroxide, goethite (α-FeOOH), which was experimentally shown to sequester Tc(IV). This material could ultimately be incorporated into glass or alternative low-temperature waste form matrices. However, questions remain regarding the incorporation mechanism for Tc(IV) in goethite, which has implications for predicting the long-term stability of Tc in waste forms under changing conditions. Here, quantum-mechanical calculations were used to evaluate the energy of five different charge-compensated Tc(IV) incorporation scenarios in goethite. The two most stable incorporation mechanisms involve direct substitution of Tc(IV) onto Fe(III) lattice sites and charge balancing either by removing one nearby H+ (i.e., within 5 Å) or by creating an Fe(III) vacancy when substituting 3 Tc(IV) for 4 Fe(III), with the former being preferred over the latter relative to gas-phase ions. When corrections for hydrated references phases are applied, the Fe(III)-vacancy mechanism becomes more energetically competitive. Calculated incorporation energies and optimized bond lengths are presented. Proton movement is observed to satisfy undercoordinated bonds surrounding Fe(III)-vacancies in the goethite structure.

A Multiphysics Perspective on Mechanistic Models for Chemical Corrosion Inhibitor Performance

Journal of the Electrochemical Society

The emergence of multiphysics modeling tools that span molecular interactions, solid-state physics, and materials microstructure through to thermodynamics, fluid mechanics and electrochemical kinetics provides new opportunities for the construction of predictive modeling tools for corrosion science and engineering. One particular field in which models have been actively developed from the atomistic to macroscopic levels includes the problem of the prediction of performance and the molecular design of chemical corrosion inhibitors. Herein we provide a concise review of these historical and contemporary approaches. Afterwards, a general outline for a multiphysics model is presented for the prediction of corrosion inhibitor efficiency (i.e. % reduction in corrosion rate) as a function of environment, material, inhibitor concentration, and the molecular identity of the inhibitor. Applications to experimental design and analysis, lifetime prediction and inhibitor design are then discussed.

Towards Materials Sustainability through Materials Stewardship

Sustainability

Materials sustainability requires a concerted change in philosophy across the entire materials lifecycle, orienting around the theme of materials stewardship. In this paper, we address the opportunities for improved materials conservation through dematerialization, durability, design for second life, and diversion of waste streams through industrial symbiosis.

Molecular Modeling of Corrosion Processes: Scientific Development and Engineering Applications

ECS / Wiley

This book demonstrates how molecular modeling has the potential to yield unique and unprecedented insights into the multitude of interconnected and complex processes that comprise corrosion of metals. In any given environment, numerous competing mechanisms can lead to corrosion. These include competitive surface adsorption, electron transfer via cathodic and anodic processes, dissolution of metals and dealloying, the formation of pre-passive oxide films, localized corrosion and passivity breakdown, the adsorption of inhibitors, and hydrogen embrittlement. This book therefore explains via molecular modeling how these pathways can be individually assessed and compared to one another. The book describes both the strengths and limitations of the current molecular and atomistic modelling toolkit so that the professional interested in using these techniques can determine whether or not a given tool is appropriate for simulating the corrosion phenomenon at hand. The book also can serve as a reference for researchers seeking to build new research programs that will extend the current molecular modelling toolkit into exciting new directions.

Corrosion Management for a Sustainable Concrete Infrastructure

Materials Performance (NACE)

Analysis of materials flows through society reveals that infrastructure construction is one of the most significant contributors to global materials consumption, as well as other sustainability impacts such as energy and water consumption and carbon dioxide (CO2) generation. Furthermore, due to degradation these lifecycle costs may recur within one to two generations. Effective corrosion control through understanding the degradation of reinforced concrete, optimizing concrete composition, and implementing corrosion protection can extend the lifetime of existing structures and decrease net CO2 emissions.

Computational Investigation of Technetium(IV) Incorporation into Inverse Spinels: Magnetite (Fe3O4) and Trevorite (NiFe2O4)

Environmental Science and Technology

Iron oxides and oxyhydroxides play an important role in minimizing the mobility of redox-sensitive elements in engineered and natural environments. For the radionuclide technetium-99 (Tc), these phases hold promise as primary hosts for increasing Tc loading into glass waste form matrices, or as secondary sinks during the long-term storage of nuclear materials. Recent experiments show that the inverse spinel, magnetite [Fe(II)Fe(III)2O4], can incorporate Tc(IV) into its octahedral sub-lattice. In that same class of materials, trevorite [Ni(II)Fe(III)2O4] is also being investigated for its ability to host Tc(IV). However, questions remain regarding the most energetically favorable charge-compensation mechanism for Tc(IV) incorporation in each structure, which will affect Tc behavior under changing waste processing or storage conditions. Here, quantum-mechanical methods were used to evaluate incorporation energies and optimized lattice bonding environments for three different, charge-balanced Tc(IV) incorporation mechanisms in magnetite and trevorite (~5 wt% Tc). For both phases, the removal of two octahedral Fe(II) or Ni(II) ions upon the addition of Tc(IV) in an octahedral site is the most stable mechanism, relative to the creation of octahedral Fe(III) defects or increasing octahedral Fe(II) content. Following hydration-energy corrections, Tc(IV) incorporation into magnetite is energetically favorable while an energy barrier exists for trevorite.

Design and Prediction of Corrosion Inhibitors from Quantum Chemistry II. A General Framework for Prediction of Effective Oil/Water Partition Coefficients and Speciation from Quantum Chemistry

Journal of the Electrochemical Society

Quantum chemistry is a powerful tool for computing the properties of molecules and their interactions with one another in a variety of environments. In this second paper of a two-part series, the technique is applied in this work to calculate fundamental properties of inhibitor molecules important to the overall corrosion inhibitor performance. The study focuses on the issue of oil/water partitioning as quantified by the partition coefficient (log P) and the important issue of inhibitor speciation according to the acid dissociation constant (pKa). pKa and log P values are then calculated from first-principles for a series of imidazole derivatives and integrated into a model for inhibitor availability as a function of the water cut. Applications to lifetime prediction and inhibitor design are then discussed.

A First-Principles Surface Reaction Kinetic Model for Hydrogen Evolution under Cathodic and Anodic Conditions on Magnesium

Journal of the Electrochemical Society

A surface kinetic model is developed using a proposed mechanism for the anodic and cathodic branches of the hydrogen evolution observed over magnesium (i.e. the negative difference effect). The key element to the model is that hydrogen evolution requires the removal of adsorbed OH from the surface. This step is achieved in the cathodic branch by reductive desorption of OH to form OH− from the surface, and in the anodic branch by the dissolution of both adsorbed OH along with the Mg atom to which it is attached (thus combined desorption of OH− alongside dissolution of Mg2+). Steady state theory is applied to derive expressions for the hydrogen evolution rate as a function of potential. First-principles parameters obtained from the literature are used to compute the rate constants for the individual mechanistic steps, where available, and reasonable values based on cohesive energies are used to estimate the remaining parameters where first-principles information is not available. These rate constants are then applied to the surface kinetic model to show that the model provides reasonable agreement with the observed phenomenology for hydrogen evolution over magnesium, both in terms of the shape and order of magnitude of hydrogen evolved, and the transition potential (i.e. the open circuit potential) between the anodic and cathodic hydrogen evolution branches.

Technetium Incorporation into Goethite (α-FeOOH): An Atomic-Scale Investigation

Environmental Science & Technology

During the processing of low-activity radioactive waste to generate solid waste forms (e.g., glass), technetium-99 (Tc) is of concern because of its volatility. A variety of materials are under consideration to capture Tc from waste streams, including the iron oxyhydroxide, goethite (α-FeOOH), which was experimentally shown to sequester Tc(IV). This material could ultimately be incorporated into glass or alternative low-temperature waste form matrices. However, questions remain regarding the incorporation mechanism for Tc(IV) in goethite, which has implications for predicting the long-term stability of Tc in waste forms under changing conditions. Here, quantum-mechanical calculations were used to evaluate the energy of five different charge-compensated Tc(IV) incorporation scenarios in goethite. The two most stable incorporation mechanisms involve direct substitution of Tc(IV) onto Fe(III) lattice sites and charge balancing either by removing one nearby H+ (i.e., within 5 Å) or by creating an Fe(III) vacancy when substituting 3 Tc(IV) for 4 Fe(III), with the former being preferred over the latter relative to gas-phase ions. When corrections for hydrated references phases are applied, the Fe(III)-vacancy mechanism becomes more energetically competitive. Calculated incorporation energies and optimized bond lengths are presented. Proton movement is observed to satisfy undercoordinated bonds surrounding Fe(III)-vacancies in the goethite structure.

A Multiphysics Perspective on Mechanistic Models for Chemical Corrosion Inhibitor Performance

Journal of the Electrochemical Society

The emergence of multiphysics modeling tools that span molecular interactions, solid-state physics, and materials microstructure through to thermodynamics, fluid mechanics and electrochemical kinetics provides new opportunities for the construction of predictive modeling tools for corrosion science and engineering. One particular field in which models have been actively developed from the atomistic to macroscopic levels includes the problem of the prediction of performance and the molecular design of chemical corrosion inhibitors. Herein we provide a concise review of these historical and contemporary approaches. Afterwards, a general outline for a multiphysics model is presented for the prediction of corrosion inhibitor efficiency (i.e. % reduction in corrosion rate) as a function of environment, material, inhibitor concentration, and the molecular identity of the inhibitor. Applications to experimental design and analysis, lifetime prediction and inhibitor design are then discussed.

Multiphysics Modeling of the Role of Iodine in Environmentally Assisted Cracking of Zirconium via Pellet-Clad Interaction

Corrosion Journal (NACE)

This paper reviews the development of a multiphysics approach to studying the environmentally assisted cracking of zirconium as induced by iodine, a failure mechanism pertinent to the degradation of clad materials encasing nuclear fuel rod assemblies. The phenomenological model of Lewis is reviewed, along with atomistic modeling of surface and grain boundary effects. The paper then surveys the modeling work performed in the authors’ own research group to model the physical and chemical effects surrounding Lewis’ phenomenological model, culminating in a molecular dynamics simulation of intergranular failure. Then, recent trends in modeling are surveyed that will lead to the next steps in the multiphysics simulation of iodine-induced stress corrosion cracking of zirconium and Zircaloy materials, and potentially other systems in which intergranular corrosion cracking is a key mechanism.

Towards Materials Sustainability through Materials Stewardship

Sustainability

Materials sustainability requires a concerted change in philosophy across the entire materials lifecycle, orienting around the theme of materials stewardship. In this paper, we address the opportunities for improved materials conservation through dematerialization, durability, design for second life, and diversion of waste streams through industrial symbiosis.

Molecular Modeling of Corrosion Processes: Scientific Development and Engineering Applications

ECS / Wiley

This book demonstrates how molecular modeling has the potential to yield unique and unprecedented insights into the multitude of interconnected and complex processes that comprise corrosion of metals. In any given environment, numerous competing mechanisms can lead to corrosion. These include competitive surface adsorption, electron transfer via cathodic and anodic processes, dissolution of metals and dealloying, the formation of pre-passive oxide films, localized corrosion and passivity breakdown, the adsorption of inhibitors, and hydrogen embrittlement. This book therefore explains via molecular modeling how these pathways can be individually assessed and compared to one another. The book describes both the strengths and limitations of the current molecular and atomistic modelling toolkit so that the professional interested in using these techniques can determine whether or not a given tool is appropriate for simulating the corrosion phenomenon at hand. The book also can serve as a reference for researchers seeking to build new research programs that will extend the current molecular modelling toolkit into exciting new directions.

Corrosion Management for a Sustainable Concrete Infrastructure

Materials Performance (NACE)

Analysis of materials flows through society reveals that infrastructure construction is one of the most significant contributors to global materials consumption, as well as other sustainability impacts such as energy and water consumption and carbon dioxide (CO2) generation. Furthermore, due to degradation these lifecycle costs may recur within one to two generations. Effective corrosion control through understanding the degradation of reinforced concrete, optimizing concrete composition, and implementing corrosion protection can extend the lifetime of existing structures and decrease net CO2 emissions.

Computational Investigation of Technetium(IV) Incorporation into Inverse Spinels: Magnetite (Fe3O4) and Trevorite (NiFe2O4)

Environmental Science and Technology

Iron oxides and oxyhydroxides play an important role in minimizing the mobility of redox-sensitive elements in engineered and natural environments. For the radionuclide technetium-99 (Tc), these phases hold promise as primary hosts for increasing Tc loading into glass waste form matrices, or as secondary sinks during the long-term storage of nuclear materials. Recent experiments show that the inverse spinel, magnetite [Fe(II)Fe(III)2O4], can incorporate Tc(IV) into its octahedral sub-lattice. In that same class of materials, trevorite [Ni(II)Fe(III)2O4] is also being investigated for its ability to host Tc(IV). However, questions remain regarding the most energetically favorable charge-compensation mechanism for Tc(IV) incorporation in each structure, which will affect Tc behavior under changing waste processing or storage conditions. Here, quantum-mechanical methods were used to evaluate incorporation energies and optimized lattice bonding environments for three different, charge-balanced Tc(IV) incorporation mechanisms in magnetite and trevorite (~5 wt% Tc). For both phases, the removal of two octahedral Fe(II) or Ni(II) ions upon the addition of Tc(IV) in an octahedral site is the most stable mechanism, relative to the creation of octahedral Fe(III) defects or increasing octahedral Fe(II) content. Following hydration-energy corrections, Tc(IV) incorporation into magnetite is energetically favorable while an energy barrier exists for trevorite.

Design and Prediction of Corrosion Inhibitors from Quantum Chemistry II. A General Framework for Prediction of Effective Oil/Water Partition Coefficients and Speciation from Quantum Chemistry

Journal of the Electrochemical Society

Quantum chemistry is a powerful tool for computing the properties of molecules and their interactions with one another in a variety of environments. In this second paper of a two-part series, the technique is applied in this work to calculate fundamental properties of inhibitor molecules important to the overall corrosion inhibitor performance. The study focuses on the issue of oil/water partitioning as quantified by the partition coefficient (log P) and the important issue of inhibitor speciation according to the acid dissociation constant (pKa). pKa and log P values are then calculated from first-principles for a series of imidazole derivatives and integrated into a model for inhibitor availability as a function of the water cut. Applications to lifetime prediction and inhibitor design are then discussed.

A First-Principles Surface Reaction Kinetic Model for Hydrogen Evolution under Cathodic and Anodic Conditions on Magnesium

Journal of the Electrochemical Society

A surface kinetic model is developed using a proposed mechanism for the anodic and cathodic branches of the hydrogen evolution observed over magnesium (i.e. the negative difference effect). The key element to the model is that hydrogen evolution requires the removal of adsorbed OH from the surface. This step is achieved in the cathodic branch by reductive desorption of OH to form OH− from the surface, and in the anodic branch by the dissolution of both adsorbed OH along with the Mg atom to which it is attached (thus combined desorption of OH− alongside dissolution of Mg2+). Steady state theory is applied to derive expressions for the hydrogen evolution rate as a function of potential. First-principles parameters obtained from the literature are used to compute the rate constants for the individual mechanistic steps, where available, and reasonable values based on cohesive energies are used to estimate the remaining parameters where first-principles information is not available. These rate constants are then applied to the surface kinetic model to show that the model provides reasonable agreement with the observed phenomenology for hydrogen evolution over magnesium, both in terms of the shape and order of magnitude of hydrogen evolved, and the transition potential (i.e. the open circuit potential) between the anodic and cathodic hydrogen evolution branches.

Technetium Incorporation into Goethite (α-FeOOH): An Atomic-Scale Investigation

Environmental Science & Technology

During the processing of low-activity radioactive waste to generate solid waste forms (e.g., glass), technetium-99 (Tc) is of concern because of its volatility. A variety of materials are under consideration to capture Tc from waste streams, including the iron oxyhydroxide, goethite (α-FeOOH), which was experimentally shown to sequester Tc(IV). This material could ultimately be incorporated into glass or alternative low-temperature waste form matrices. However, questions remain regarding the incorporation mechanism for Tc(IV) in goethite, which has implications for predicting the long-term stability of Tc in waste forms under changing conditions. Here, quantum-mechanical calculations were used to evaluate the energy of five different charge-compensated Tc(IV) incorporation scenarios in goethite. The two most stable incorporation mechanisms involve direct substitution of Tc(IV) onto Fe(III) lattice sites and charge balancing either by removing one nearby H+ (i.e., within 5 Å) or by creating an Fe(III) vacancy when substituting 3 Tc(IV) for 4 Fe(III), with the former being preferred over the latter relative to gas-phase ions. When corrections for hydrated references phases are applied, the Fe(III)-vacancy mechanism becomes more energetically competitive. Calculated incorporation energies and optimized bond lengths are presented. Proton movement is observed to satisfy undercoordinated bonds surrounding Fe(III)-vacancies in the goethite structure.

A Multiphysics Perspective on Mechanistic Models for Chemical Corrosion Inhibitor Performance

Journal of the Electrochemical Society

The emergence of multiphysics modeling tools that span molecular interactions, solid-state physics, and materials microstructure through to thermodynamics, fluid mechanics and electrochemical kinetics provides new opportunities for the construction of predictive modeling tools for corrosion science and engineering. One particular field in which models have been actively developed from the atomistic to macroscopic levels includes the problem of the prediction of performance and the molecular design of chemical corrosion inhibitors. Herein we provide a concise review of these historical and contemporary approaches. Afterwards, a general outline for a multiphysics model is presented for the prediction of corrosion inhibitor efficiency (i.e. % reduction in corrosion rate) as a function of environment, material, inhibitor concentration, and the molecular identity of the inhibitor. Applications to experimental design and analysis, lifetime prediction and inhibitor design are then discussed.

Multiphysics Modeling of the Role of Iodine in Environmentally Assisted Cracking of Zirconium via Pellet-Clad Interaction

Corrosion Journal (NACE)

This paper reviews the development of a multiphysics approach to studying the environmentally assisted cracking of zirconium as induced by iodine, a failure mechanism pertinent to the degradation of clad materials encasing nuclear fuel rod assemblies. The phenomenological model of Lewis is reviewed, along with atomistic modeling of surface and grain boundary effects. The paper then surveys the modeling work performed in the authors’ own research group to model the physical and chemical effects surrounding Lewis’ phenomenological model, culminating in a molecular dynamics simulation of intergranular failure. Then, recent trends in modeling are surveyed that will lead to the next steps in the multiphysics simulation of iodine-induced stress corrosion cracking of zirconium and Zircaloy materials, and potentially other systems in which intergranular corrosion cracking is a key mechanism.

Design and Prediction of Corrosion Inhibitors from Quantum Chemistry I. Can Effective Partition Coefficients for Organic Corrosion Inhibitors be Determined from First-Principles?

Journal of the Electrochemical Society

Quantum chemistry is a powerful tool for computing the properties of molecules and their interactions with one another in a variety of environments. In this first paper of a two-part series, the technique is applied to investigate the capabilities for different quantum chemical techniques to compute the partition coefficients for chemical inhibitors relevant to corrosion management from first-principles. Density functional theory calculations using the exchange-correlation functionals B3LYP and M05-2X, with either 6-31+g(d,p) or the pc-3 basis set, as well as the semi-empirical AM1 method and two separate solvation methods (PCM and SMD) were used to calculate the effective partition coefficients for benzimidazole and 1,2-dimethylimidazole for the n-octanol/water system. The equation for the effective partition coefficient (log P) was developed taking into account the possible protonation of the solute molecules, according to the computed acid dissociation constant (pKa) obtained using the isodesmic method with ethylamine as a reference. The variation in log P computed using the different theoretical methods was presented along with a discussion of how to apply theoretical calculations of observable quantities, such as the partition coefficient, in an engineering context.

Towards Materials Sustainability through Materials Stewardship

Sustainability

Materials sustainability requires a concerted change in philosophy across the entire materials lifecycle, orienting around the theme of materials stewardship. In this paper, we address the opportunities for improved materials conservation through dematerialization, durability, design for second life, and diversion of waste streams through industrial symbiosis.

Molecular Modeling of Corrosion Processes: Scientific Development and Engineering Applications

ECS / Wiley

This book demonstrates how molecular modeling has the potential to yield unique and unprecedented insights into the multitude of interconnected and complex processes that comprise corrosion of metals. In any given environment, numerous competing mechanisms can lead to corrosion. These include competitive surface adsorption, electron transfer via cathodic and anodic processes, dissolution of metals and dealloying, the formation of pre-passive oxide films, localized corrosion and passivity breakdown, the adsorption of inhibitors, and hydrogen embrittlement. This book therefore explains via molecular modeling how these pathways can be individually assessed and compared to one another. The book describes both the strengths and limitations of the current molecular and atomistic modelling toolkit so that the professional interested in using these techniques can determine whether or not a given tool is appropriate for simulating the corrosion phenomenon at hand. The book also can serve as a reference for researchers seeking to build new research programs that will extend the current molecular modelling toolkit into exciting new directions.

Corrosion Management for a Sustainable Concrete Infrastructure

Materials Performance (NACE)

Analysis of materials flows through society reveals that infrastructure construction is one of the most significant contributors to global materials consumption, as well as other sustainability impacts such as energy and water consumption and carbon dioxide (CO2) generation. Furthermore, due to degradation these lifecycle costs may recur within one to two generations. Effective corrosion control through understanding the degradation of reinforced concrete, optimizing concrete composition, and implementing corrosion protection can extend the lifetime of existing structures and decrease net CO2 emissions.

Computational Investigation of Technetium(IV) Incorporation into Inverse Spinels: Magnetite (Fe3O4) and Trevorite (NiFe2O4)

Environmental Science and Technology

Iron oxides and oxyhydroxides play an important role in minimizing the mobility of redox-sensitive elements in engineered and natural environments. For the radionuclide technetium-99 (Tc), these phases hold promise as primary hosts for increasing Tc loading into glass waste form matrices, or as secondary sinks during the long-term storage of nuclear materials. Recent experiments show that the inverse spinel, magnetite [Fe(II)Fe(III)2O4], can incorporate Tc(IV) into its octahedral sub-lattice. In that same class of materials, trevorite [Ni(II)Fe(III)2O4] is also being investigated for its ability to host Tc(IV). However, questions remain regarding the most energetically favorable charge-compensation mechanism for Tc(IV) incorporation in each structure, which will affect Tc behavior under changing waste processing or storage conditions. Here, quantum-mechanical methods were used to evaluate incorporation energies and optimized lattice bonding environments for three different, charge-balanced Tc(IV) incorporation mechanisms in magnetite and trevorite (~5 wt% Tc). For both phases, the removal of two octahedral Fe(II) or Ni(II) ions upon the addition of Tc(IV) in an octahedral site is the most stable mechanism, relative to the creation of octahedral Fe(III) defects or increasing octahedral Fe(II) content. Following hydration-energy corrections, Tc(IV) incorporation into magnetite is energetically favorable while an energy barrier exists for trevorite.

Design and Prediction of Corrosion Inhibitors from Quantum Chemistry II. A General Framework for Prediction of Effective Oil/Water Partition Coefficients and Speciation from Quantum Chemistry

Journal of the Electrochemical Society

Quantum chemistry is a powerful tool for computing the properties of molecules and their interactions with one another in a variety of environments. In this second paper of a two-part series, the technique is applied in this work to calculate fundamental properties of inhibitor molecules important to the overall corrosion inhibitor performance. The study focuses on the issue of oil/water partitioning as quantified by the partition coefficient (log P) and the important issue of inhibitor speciation according to the acid dissociation constant (pKa). pKa and log P values are then calculated from first-principles for a series of imidazole derivatives and integrated into a model for inhibitor availability as a function of the water cut. Applications to lifetime prediction and inhibitor design are then discussed.

A First-Principles Surface Reaction Kinetic Model for Hydrogen Evolution under Cathodic and Anodic Conditions on Magnesium

Journal of the Electrochemical Society

A surface kinetic model is developed using a proposed mechanism for the anodic and cathodic branches of the hydrogen evolution observed over magnesium (i.e. the negative difference effect). The key element to the model is that hydrogen evolution requires the removal of adsorbed OH from the surface. This step is achieved in the cathodic branch by reductive desorption of OH to form OH− from the surface, and in the anodic branch by the dissolution of both adsorbed OH along with the Mg atom to which it is attached (thus combined desorption of OH− alongside dissolution of Mg2+). Steady state theory is applied to derive expressions for the hydrogen evolution rate as a function of potential. First-principles parameters obtained from the literature are used to compute the rate constants for the individual mechanistic steps, where available, and reasonable values based on cohesive energies are used to estimate the remaining parameters where first-principles information is not available. These rate constants are then applied to the surface kinetic model to show that the model provides reasonable agreement with the observed phenomenology for hydrogen evolution over magnesium, both in terms of the shape and order of magnitude of hydrogen evolved, and the transition potential (i.e. the open circuit potential) between the anodic and cathodic hydrogen evolution branches.

Technetium Incorporation into Goethite (α-FeOOH): An Atomic-Scale Investigation

Environmental Science & Technology

During the processing of low-activity radioactive waste to generate solid waste forms (e.g., glass), technetium-99 (Tc) is of concern because of its volatility. A variety of materials are under consideration to capture Tc from waste streams, including the iron oxyhydroxide, goethite (α-FeOOH), which was experimentally shown to sequester Tc(IV). This material could ultimately be incorporated into glass or alternative low-temperature waste form matrices. However, questions remain regarding the incorporation mechanism for Tc(IV) in goethite, which has implications for predicting the long-term stability of Tc in waste forms under changing conditions. Here, quantum-mechanical calculations were used to evaluate the energy of five different charge-compensated Tc(IV) incorporation scenarios in goethite. The two most stable incorporation mechanisms involve direct substitution of Tc(IV) onto Fe(III) lattice sites and charge balancing either by removing one nearby H+ (i.e., within 5 Å) or by creating an Fe(III) vacancy when substituting 3 Tc(IV) for 4 Fe(III), with the former being preferred over the latter relative to gas-phase ions. When corrections for hydrated references phases are applied, the Fe(III)-vacancy mechanism becomes more energetically competitive. Calculated incorporation energies and optimized bond lengths are presented. Proton movement is observed to satisfy undercoordinated bonds surrounding Fe(III)-vacancies in the goethite structure.

A Multiphysics Perspective on Mechanistic Models for Chemical Corrosion Inhibitor Performance

Journal of the Electrochemical Society

The emergence of multiphysics modeling tools that span molecular interactions, solid-state physics, and materials microstructure through to thermodynamics, fluid mechanics and electrochemical kinetics provides new opportunities for the construction of predictive modeling tools for corrosion science and engineering. One particular field in which models have been actively developed from the atomistic to macroscopic levels includes the problem of the prediction of performance and the molecular design of chemical corrosion inhibitors. Herein we provide a concise review of these historical and contemporary approaches. Afterwards, a general outline for a multiphysics model is presented for the prediction of corrosion inhibitor efficiency (i.e. % reduction in corrosion rate) as a function of environment, material, inhibitor concentration, and the molecular identity of the inhibitor. Applications to experimental design and analysis, lifetime prediction and inhibitor design are then discussed.

Multiphysics Modeling of the Role of Iodine in Environmentally Assisted Cracking of Zirconium via Pellet-Clad Interaction

Corrosion Journal (NACE)

This paper reviews the development of a multiphysics approach to studying the environmentally assisted cracking of zirconium as induced by iodine, a failure mechanism pertinent to the degradation of clad materials encasing nuclear fuel rod assemblies. The phenomenological model of Lewis is reviewed, along with atomistic modeling of surface and grain boundary effects. The paper then surveys the modeling work performed in the authors’ own research group to model the physical and chemical effects surrounding Lewis’ phenomenological model, culminating in a molecular dynamics simulation of intergranular failure. Then, recent trends in modeling are surveyed that will lead to the next steps in the multiphysics simulation of iodine-induced stress corrosion cracking of zirconium and Zircaloy materials, and potentially other systems in which intergranular corrosion cracking is a key mechanism.

Design and Prediction of Corrosion Inhibitors from Quantum Chemistry I. Can Effective Partition Coefficients for Organic Corrosion Inhibitors be Determined from First-Principles?

Journal of the Electrochemical Society

Quantum chemistry is a powerful tool for computing the properties of molecules and their interactions with one another in a variety of environments. In this first paper of a two-part series, the technique is applied to investigate the capabilities for different quantum chemical techniques to compute the partition coefficients for chemical inhibitors relevant to corrosion management from first-principles. Density functional theory calculations using the exchange-correlation functionals B3LYP and M05-2X, with either 6-31+g(d,p) or the pc-3 basis set, as well as the semi-empirical AM1 method and two separate solvation methods (PCM and SMD) were used to calculate the effective partition coefficients for benzimidazole and 1,2-dimethylimidazole for the n-octanol/water system. The equation for the effective partition coefficient (log P) was developed taking into account the possible protonation of the solute molecules, according to the computed acid dissociation constant (pKa) obtained using the isodesmic method with ethylamine as a reference. The variation in log P computed using the different theoretical methods was presented along with a discussion of how to apply theoretical calculations of observable quantities, such as the partition coefficient, in an engineering context.

Towards Materials Sustainability through Materials Stewardship

Sustainability

Materials sustainability requires a concerted change in philosophy across the entire materials lifecycle, orienting around the theme of materials stewardship. In this paper, we address the opportunities for improved materials conservation through dematerialization, durability, design for second life, and diversion of waste streams through industrial symbiosis.

Molecular Modeling of Corrosion Processes: Scientific Development and Engineering Applications

ECS / Wiley

This book demonstrates how molecular modeling has the potential to yield unique and unprecedented insights into the multitude of interconnected and complex processes that comprise corrosion of metals. In any given environment, numerous competing mechanisms can lead to corrosion. These include competitive surface adsorption, electron transfer via cathodic and anodic processes, dissolution of metals and dealloying, the formation of pre-passive oxide films, localized corrosion and passivity breakdown, the adsorption of inhibitors, and hydrogen embrittlement. This book therefore explains via molecular modeling how these pathways can be individually assessed and compared to one another. The book describes both the strengths and limitations of the current molecular and atomistic modelling toolkit so that the professional interested in using these techniques can determine whether or not a given tool is appropriate for simulating the corrosion phenomenon at hand. The book also can serve as a reference for researchers seeking to build new research programs that will extend the current molecular modelling toolkit into exciting new directions.

Corrosion Management for a Sustainable Concrete Infrastructure

Materials Performance (NACE)

Analysis of materials flows through society reveals that infrastructure construction is one of the most significant contributors to global materials consumption, as well as other sustainability impacts such as energy and water consumption and carbon dioxide (CO2) generation. Furthermore, due to degradation these lifecycle costs may recur within one to two generations. Effective corrosion control through understanding the degradation of reinforced concrete, optimizing concrete composition, and implementing corrosion protection can extend the lifetime of existing structures and decrease net CO2 emissions.

Computational Investigation of Technetium(IV) Incorporation into Inverse Spinels: Magnetite (Fe3O4) and Trevorite (NiFe2O4)

Environmental Science and Technology

Iron oxides and oxyhydroxides play an important role in minimizing the mobility of redox-sensitive elements in engineered and natural environments. For the radionuclide technetium-99 (Tc), these phases hold promise as primary hosts for increasing Tc loading into glass waste form matrices, or as secondary sinks during the long-term storage of nuclear materials. Recent experiments show that the inverse spinel, magnetite [Fe(II)Fe(III)2O4], can incorporate Tc(IV) into its octahedral sub-lattice. In that same class of materials, trevorite [Ni(II)Fe(III)2O4] is also being investigated for its ability to host Tc(IV). However, questions remain regarding the most energetically favorable charge-compensation mechanism for Tc(IV) incorporation in each structure, which will affect Tc behavior under changing waste processing or storage conditions. Here, quantum-mechanical methods were used to evaluate incorporation energies and optimized lattice bonding environments for three different, charge-balanced Tc(IV) incorporation mechanisms in magnetite and trevorite (~5 wt% Tc). For both phases, the removal of two octahedral Fe(II) or Ni(II) ions upon the addition of Tc(IV) in an octahedral site is the most stable mechanism, relative to the creation of octahedral Fe(III) defects or increasing octahedral Fe(II) content. Following hydration-energy corrections, Tc(IV) incorporation into magnetite is energetically favorable while an energy barrier exists for trevorite.

Design and Prediction of Corrosion Inhibitors from Quantum Chemistry II. A General Framework for Prediction of Effective Oil/Water Partition Coefficients and Speciation from Quantum Chemistry

Journal of the Electrochemical Society

Quantum chemistry is a powerful tool for computing the properties of molecules and their interactions with one another in a variety of environments. In this second paper of a two-part series, the technique is applied in this work to calculate fundamental properties of inhibitor molecules important to the overall corrosion inhibitor performance. The study focuses on the issue of oil/water partitioning as quantified by the partition coefficient (log P) and the important issue of inhibitor speciation according to the acid dissociation constant (pKa). pKa and log P values are then calculated from first-principles for a series of imidazole derivatives and integrated into a model for inhibitor availability as a function of the water cut. Applications to lifetime prediction and inhibitor design are then discussed.

A First-Principles Surface Reaction Kinetic Model for Hydrogen Evolution under Cathodic and Anodic Conditions on Magnesium

Journal of the Electrochemical Society

A surface kinetic model is developed using a proposed mechanism for the anodic and cathodic branches of the hydrogen evolution observed over magnesium (i.e. the negative difference effect). The key element to the model is that hydrogen evolution requires the removal of adsorbed OH from the surface. This step is achieved in the cathodic branch by reductive desorption of OH to form OH− from the surface, and in the anodic branch by the dissolution of both adsorbed OH along with the Mg atom to which it is attached (thus combined desorption of OH− alongside dissolution of Mg2+). Steady state theory is applied to derive expressions for the hydrogen evolution rate as a function of potential. First-principles parameters obtained from the literature are used to compute the rate constants for the individual mechanistic steps, where available, and reasonable values based on cohesive energies are used to estimate the remaining parameters where first-principles information is not available. These rate constants are then applied to the surface kinetic model to show that the model provides reasonable agreement with the observed phenomenology for hydrogen evolution over magnesium, both in terms of the shape and order of magnitude of hydrogen evolved, and the transition potential (i.e. the open circuit potential) between the anodic and cathodic hydrogen evolution branches.

Technetium Incorporation into Goethite (α-FeOOH): An Atomic-Scale Investigation

Environmental Science & Technology

During the processing of low-activity radioactive waste to generate solid waste forms (e.g., glass), technetium-99 (Tc) is of concern because of its volatility. A variety of materials are under consideration to capture Tc from waste streams, including the iron oxyhydroxide, goethite (α-FeOOH), which was experimentally shown to sequester Tc(IV). This material could ultimately be incorporated into glass or alternative low-temperature waste form matrices. However, questions remain regarding the incorporation mechanism for Tc(IV) in goethite, which has implications for predicting the long-term stability of Tc in waste forms under changing conditions. Here, quantum-mechanical calculations were used to evaluate the energy of five different charge-compensated Tc(IV) incorporation scenarios in goethite. The two most stable incorporation mechanisms involve direct substitution of Tc(IV) onto Fe(III) lattice sites and charge balancing either by removing one nearby H+ (i.e., within 5 Å) or by creating an Fe(III) vacancy when substituting 3 Tc(IV) for 4 Fe(III), with the former being preferred over the latter relative to gas-phase ions. When corrections for hydrated references phases are applied, the Fe(III)-vacancy mechanism becomes more energetically competitive. Calculated incorporation energies and optimized bond lengths are presented. Proton movement is observed to satisfy undercoordinated bonds surrounding Fe(III)-vacancies in the goethite structure.

A Multiphysics Perspective on Mechanistic Models for Chemical Corrosion Inhibitor Performance

Journal of the Electrochemical Society

The emergence of multiphysics modeling tools that span molecular interactions, solid-state physics, and materials microstructure through to thermodynamics, fluid mechanics and electrochemical kinetics provides new opportunities for the construction of predictive modeling tools for corrosion science and engineering. One particular field in which models have been actively developed from the atomistic to macroscopic levels includes the problem of the prediction of performance and the molecular design of chemical corrosion inhibitors. Herein we provide a concise review of these historical and contemporary approaches. Afterwards, a general outline for a multiphysics model is presented for the prediction of corrosion inhibitor efficiency (i.e. % reduction in corrosion rate) as a function of environment, material, inhibitor concentration, and the molecular identity of the inhibitor. Applications to experimental design and analysis, lifetime prediction and inhibitor design are then discussed.

Multiphysics Modeling of the Role of Iodine in Environmentally Assisted Cracking of Zirconium via Pellet-Clad Interaction

Corrosion Journal (NACE)

This paper reviews the development of a multiphysics approach to studying the environmentally assisted cracking of zirconium as induced by iodine, a failure mechanism pertinent to the degradation of clad materials encasing nuclear fuel rod assemblies. The phenomenological model of Lewis is reviewed, along with atomistic modeling of surface and grain boundary effects. The paper then surveys the modeling work performed in the authors’ own research group to model the physical and chemical effects surrounding Lewis’ phenomenological model, culminating in a molecular dynamics simulation of intergranular failure. Then, recent trends in modeling are surveyed that will lead to the next steps in the multiphysics simulation of iodine-induced stress corrosion cracking of zirconium and Zircaloy materials, and potentially other systems in which intergranular corrosion cracking is a key mechanism.

Design and Prediction of Corrosion Inhibitors from Quantum Chemistry I. Can Effective Partition Coefficients for Organic Corrosion Inhibitors be Determined from First-Principles?

Journal of the Electrochemical Society

Quantum chemistry is a powerful tool for computing the properties of molecules and their interactions with one another in a variety of environments. In this first paper of a two-part series, the technique is applied to investigate the capabilities for different quantum chemical techniques to compute the partition coefficients for chemical inhibitors relevant to corrosion management from first-principles. Density functional theory calculations using the exchange-correlation functionals B3LYP and M05-2X, with either 6-31+g(d,p) or the pc-3 basis set, as well as the semi-empirical AM1 method and two separate solvation methods (PCM and SMD) were used to calculate the effective partition coefficients for benzimidazole and 1,2-dimethylimidazole for the n-octanol/water system. The equation for the effective partition coefficient (log P) was developed taking into account the possible protonation of the solute molecules, according to the computed acid dissociation constant (pKa) obtained using the isodesmic method with ethylamine as a reference. The variation in log P computed using the different theoretical methods was presented along with a discussion of how to apply theoretical calculations of observable quantities, such as the partition coefficient, in an engineering context.