Application of Finite Element Modeling to Macro-Galvanic Coupling of AA7050 and SS316: Validation Using the Scanning Vibrating Electrode Technique

Abstract

The scanning vibrating electrode technique (SVET) was utilized to experimentally validate the applicability of finite element modeling (FEM) in simulating macro-galvanic-induced corrosion of AA7050 coupled to SS316, in environments representative of the boldly exposed surface of an actual fastener couple. The FEM boundary conditions were modified from the SVET environments in which the AA7050-SS316 couple sample was initially exposed, in order to better represent the steady-state corroding surface of the localized corrosion-prone AA7050. Better agreements between the SVET-derived data and the model in the case of macro-galvanic coupling behavior were achieved for near-neutral conditions, compared to acidic conditions. The current density at the electrode/electrolyte interface was determined with the validated model. In addition, the percent difference between the measured current density at the SVET probe height and that at the electrode surface was observed to scale with the magnitude of current density at the electrode surface, with the largest discrepancy seen at the galvanic couple interface. Plausible reasons for the deviation of the model predictions from the SVET-derived data are discussed.