Deconvoluting the Surface Area and Geometric Effects of Fastener Heads on Galvanic Corrosion Prediction through FEM Modelling

Abstract

Galvanic couples are common in commercial and military aerospace applications and arise from a difference in the substrate and fastener materials. These couples are often formed between aluminum alloys (e.g., AA7075-T6) with stainless steels (e.g., SS316L) or Ti-6Al-4V and can cause extensive corrosion damage to occur. This work uses laboratory techniques, including polarization curves and rotating disk electrode testing, to determine the kinetics of the electrochemical reactions. Collecting over a range of revolution rates on the RDE allows for the determination of the dependence of limiting current density due to oxygen diffusion at variable water layer thicknesses. Constructing geometries in commercial software that will be comparable to aerospace structures, coupled with experimentally-determined boundary conditions, allows for quantification and prediction of galvanic corrosion in aerospace applications. With the wide array of fasteners used, many material and geometric combinations are possible. This work focuses on the deconvolution of the impact of surface area and geometry on the prediction of the galvanic corrosion through the FEM software to better understand their effects.