Localized corrosion of an ultrafine grained Al–4Zn–2Mg alloy produced by cryorolling

Abstract The effect of microstructure on corrosion behaviour of an ultrafine grained (UFG) Al–4Zn–2Mg alloy produced by cryorolling was investigated. Both UFG and coarse grained (CG) alloys in peak-aged condition were subjected to potentiodynamic polarization and intergranular corrosion (IGC) tests in chloride solutions. UFG alloy exhibited increased corrosion potential ( E corr ), decreased corrosion current density ( i corr ) (−864 mV SCE , 0.60 μA/cm 2 ) during polarization and lower weight loss during IGC when compared with CG alloy (−902 mV SCE , 4.9 μA/cm 2 ). Improved corrosion resistance of UFG alloy is mainly attributed to sub-micrometer grains, absence of coarse MgZn 2 anodic precipitates and precipitate-free zones along the grain boundaries.