Crevice corrosion occurs in metallic system in which anodic and cathodic regions appear, generating an electric current in the surrounding electrolyte. The corrosion process is highly dependent upon operating conditions – the metals or alloys involved, the chemical species found in the electrolyte, the geometric configuration and the applied potential.
FY11 UCC4A, 4B and 4C: Crevice Corrosion Damage Evolution Modeling and Computational Simulation
The FY11 work comprises the following projects:
FY 11-Task 4A Model for Crevice Corrosion Damage Evolution for Fe-Cr-Ni-Mo alloys led by G. Young
FY 11-Task 4B Determination of Crevice Corrosion Damage Evolution for Fe-Cr-Ni-Mo alloys led by S. Lillard and J. Payer
FY 11-Task 4C Validation of Model for Crevice Corrosion of Pure Metal led by H. Castenada
The goal of this project is to formulate, analyze and solve mathematical models for crevice corrosion damage evolution. The knowledge gained through mathematical modeling and simulation coupled with an experimental plan of investigation provides insight into the fundamental mechanisms underlying crevice corrosion and means to prevent it, and improve our ability to predict metal component performance assessment and life. This work initiated with FY10 funds and continues with FY11 funds.
The models receive input from and validation by laboratory experiments that measure different stages of the corrosion process, such as initiation, propagation, stifling (corrosion slows) and arrest (corrosion stops). Experiments provide direct measurement of corrosion rates, characterization of interface processes, electrochemical tests for dissolution evolution, and supplemental tests to determine properties of solutions and deposits that affect active and passive states. In turn the models identify material parameters, environmental and system variables that need to be measured.
Key objectives are to:
Three models (identified as as α1, α2 and α3) are being developed (FY10) to investigate the corrosion in a thin crevice established between a metal surface and the crevice former. In models α1 and α2 the domain outside the crevice is a thin electrolyte film. In model α3 the crevice former is completely immersed in liquid.
α Models (FY10)
α1 Model. This initial model focuses on the scenario in which the only reaction is for the anodic dissolution of a pure metal substrate.
α2 Model. This model investigates the same geometry as the α1 model. However, reactions for the anodic dissolution of the metal substrate, the hydrolysis of the metal cations, dissociation of water, and cathodic reduction of oxygen, hydrogen ions and water are included.
α3 Model. This model investigates the same species and reactions as the α2 model. However, the crevice former is completely immersed in liquid for this case.
β Models (FY11): While the α models focus on pure metal systems, the β models focus on alloys of iron-chromium-nickel-molybdenum, i.e. stainless steels and higher corrosion resistant alloys. Similar reactive, transport and solution methodologies as the α models are used.
The FY11 work builds on and extends FY10 work and comprises the following:
Task 1: Conceptual formulation of an enhanced damage evolution model (β1), including oxygen and multiple ionic species, for an alloy system in a thin electrolyte film environment outside the crevice – to be started July 2011.
Task 2: Conceptual formulation of an enhanced damage evolution model (β2), including oxygen and multiple ionic species, for an alloy system in a fully immersed environment outside the crevice – to be started Sept 2011.
Task 3: Solution of the models will begin after completion of the simplified α2 model. The α models are providing the framework for the solution procedure – to be started in Dec 2011.
Task 4; Comparison with experiments, β model validation and model refinement – to be started in Mar 2012.
Task 5: Validation of model for pure metals in June 2012.
Task 6: Compilation of data for model inputs (continuing).
Task 7: Compilation of experimental results for model inputs and validation (continuing).
Task 8: Technical assessment of findings and recommendations for continued development in Dec 2012.
Product Deliverables [FY11 Funds]
The knowledge gained through mathematical modeling and simulation coupled with an experimental plan of investigation provides insight into the fundamental mechanisms underlying crevice corrosion and means to prevent it, and improve our ability to predict metal component performance assessment and life. Hence, outcomes of the research are:
Relevance and Cost of Corrosion Relationship
Crevice corrosion is difficult to detect because it develops in narrow gaps formed by bolt heads and lap joints, for example, with a metal surface. Materials (stainless steels, titanium and aluminum) that usually do not corrode under normal circumstances can be damaged in a crevice corrosion environment. Catastrophic structural failure can occur in situations where corrosion is unexpected or undetected. While much progress has been made in understanding crevice corrosion initiation, propagation (damage evolution of the metal surface) is less characterized. Only limited progress has been made for quantitative descriptions of damage evolution (shape and depth of corrosion), and this information is required for enhanced performance assessment, structural analysis and risk management.
Personnel and Schedule
Dr. Gerald Young, Dept of Mathematics – Co-PI, Modeling and Simulation
Dr. Curtis Clemons, Dept of Mathematics – Researcher, Modeling and Simulation
Dr. Dmitry Golovaty, Dept of Mathematics – Researcher, Modeling and Simulation
Dr. Kevin Kreider, Dept of Mathematics – Researcher, Modeling and Simulation
Corrosion and Reliability Engineering
Dr. Scott Lillard -- Dept of Chemical and Biomolecular Eng – Co-PI, Advanced Electrochemical and Characterization Experiments, Modeling and Validation
Dr. Joe Payer, Corrosion Reliability and Eng–Co-PI, Experiments, Modeling and Simulation
Dr. Homero Castaneda, Dept of Chemical and Biomolecular Eng – Co-PI, Advanced Electrochemical and Characterization Experiments, Modeling and Validation
The work on the α models is underway [FY10 funds]. This proposal focuses on the β models [FY11 funds], and the FY11work is scheduled to be completed in Dec 2012. Additional work in this area is anticipated based on available funding.