Dislocation-assisted localised pitting corrosion behaviour of Al Si Mg Cu Mn alloy

The effects of the electrochemical nature of intermetallic particles (IMPs) and dislocation density on the localised pitting corrosion behaviour of AlSiMgCuMn alloy was investigated. The Cu-rich Q-phase and Mn-rich α-AlFeMnSi particles cause the anodic dissolution of adjacent Al, leading to localised pitting. Kelvin-probe atomic force microscopy studies revealed that the high potential of Q-phase and α-AlFeMnSi particles renders them cathodic. Therefore, micro-galvanic coupling arises between these IMPs and the surrounding Al. High dislocation densities in Al regions adjacent to the IMPs exacerbated localised pitting, which causes stress localisation and deteriorates the overall corrosion resistance of the alloy.