Abstract
Connections between components made from corrosion prone alloys (e.g., precipitation hardened aluminum (Al) alloys) and stainless steel (SS) fasteners are frequently encountered in airframes exposed to an atmospheric marine environment. This exposure results in the formation of thin electrolytes containing chloride species on the materials surface. The thin film electrolyte can wick into the tight crevice formed between the Al alloy component and the SS fastener when breakdown of corrosion protection coating happens. As a result, an electrochemical cell is established due to this galvanic coupling, and localized corrosion is likely aggravated in the crevice that forms. Electrolyte layer thickness is one of the most important environmental variables impacting the degree of atmospheric corrosion. In this study, a combined experimental and modeling approach was used to characterize the effect of electrolyte layer thickness on electrochemical and localized corrosion distributions in the crevice between SS fastener and Al alloy component. Experimentally determined electrochemical kinetics in thin film electrolytes were used as boundary conditions in modeling work. It was shown that that localized corrosion was more focused at crevice mouth regime in the galvanic coupling for thinner electrolyte layer thickness above the crevice than was the case for larger electrolyte layer thickness.
