Determination of cathodic and anodic charge from operando x-ray tomography observation of galvanic corrosion of aluminum alloy 7050-T7451 and 304 stainless steel in a simulated fastener

Operando x-ray computed tomography (XCT) was used to observe the hidden corrosion damage in a simulated fastener of aluminum alloy (AA) 7050-T7451 coupled to 304 stainless steel under a droplet of NaCl at 97% relative humidity. Four fissures grew during the exposure in the aluminum alloy. The volume of corrosion damage was monitored over time and the anodic charge was determined from XCT slice voxel analysis. The maximum theoretical cathodic charge available for the cathodic reactions on the stainless steel and other sources (intermetallic particles and copper replating in the AA7050) could support the growth of multiple fissures.