Exploring Galvanic Coupling of SS/Al in Fastener Configurations with Finite Element Modeling

Finite Element Modeling (FEM) of Galvanic Coupling

Sponsor: Office of Naval Research

Gradute Students Involved: Rebecca Marshall

The overall goals of this project are to develop a quantitative scientific understanding of the effects of important external variables on the electrochemical potential and current distributions that develop in fastener hole configurations involving a realistic thin film/galvanic couple configuration between a 7050- T7451 component and a CRES 316 fastener, and investigate how these potential and current distributions correlate potential local damages on the metal surfaces in the galvanic coupling. A combination of experimental and modeling approaches are being used to characterize key processes and important external factors in atmospheric localized corrosion. The Laplace equation is used to model steady state potential and current distributions under thin film electrolyte conditions, ignoring ion species diffusion and changes in solution chemistry. The use of the Laplace equation relies on a knowledge or estimation of the electrolyte characteristics (primary conductivity) and its dependence on position and other experimental variables. FEM modeling is applied to numerically determine the potential and current distributions in the thin film at steady state for the range of geometries and environments. To accomplish this objective, a series of appreciate electrochemical kinetics for the CRES 316 and 7050-T7451 alloys were determined experimentally and then served as boundary conditions in the modeling. These kinetics were developed in solutions designed to mimic the chemistry of the cathodic and anodic areas.

Associated Publications: 

R. Marshall, R. Kelly, A. Goff, C. Sprinkle, Galvanic Corrosion Between Coated Al Alloy Plate and Stainless Steel Fasteners, Part 1: FEM Model Development and Validation, Corrosion. 75 (2019) 1461–1473. https://doi.org/10.5006/3308.

R.S. Marshall, A. Goff, C. Sprinkle, A. Britos, R.G. Kelly, Estimating the Throwing Power of SS316 when Coupled with AA7075 Through Finite Element Modeling, Corrosion. 76 (2020) 476–484. https://doi.org/10.5006/3438.