Investigation of the exfoliation-like attack mechanism in relation to Al–Mg–Si alloy microstructure

A directed attack, denominated as exfoliation-like attack (ELA), is observed in Al–Mg–Si alloy AA6016 exposed to aggressive electrolyte conditions. This localized corrosion propagates restricted to a specific plane. Immersion experiments combined with in situ microtomography and SEM/EBSD characterization showed that the ELA path does not follow aligned intermetallic phases, texture or grain boundaries. Si concentration variation in solid solution is one factor which correlates with the propagation of this attack. In a model alloy, the influence of Si composition gradients on corrosion susceptibility was demonstrated in mild neutral electrolytes (oxide layer influence) and in aggressive acidic conditions (active dissolution rates).