Corrosion behaviour of stainless steel-titanium alloy linear friction welded joints: Galvanic coupling

Linear friction welding may be used to join titanium alloys to stainless steel for a variety of applications. After welding, a crevice is often observed close to the edges and, in aqueous wet environments, a galvanic couple is formed between the two materials. If corrosion resistance is a requirement, the combined presence of a crevice and a galvanic couple is a concern. In this study, the behaviour of galvanically coupled titanium alloy and stainless steel has been investigated, both for planar electrodes and under simulated crevice conditions. In both cases, it was found that a significant driving force between the two materials develops over time to progress corrosion on the stainless steel, but the high specific impedance of the titanium surface limits the current flow. Consequently, it is concluded that galvanic coupling between titanium and stainless steel is only of concern if the area of the titanium largely exceeds the area of the steel, and only under complete immersion conditions in a sufficiently conductive electrolyte.