Macro-galvanic effect and its influence on corrosion behaviors of friction stir welding joint of 7050-T76 Al alloy

The corrosion behavior of various zones of the 7050-T76 aluminum alloy friction stir welding (FSW) joint and their interaction were studied. The wire beam electrode (WBE) analysis reveals that heat-affected zone (HAZ) adjacent to nugget zone (NZ) receives the most intense negative current and thus presents the intensified susceptibility to corrosion. Both pitting and intergranular corrosion are aggravated greatly in HAZ while suppressed in base material (BM) when the whole FSW joint was put into NaCl solution, indicating the dominating influence from macro-galvanic effect. The coupling relationship between macro-galvanic and micro-galvanic effects is revealed based on the electrochemical analysis.