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

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) (-864mV SCE, 0.60μA/cm 2) during polarization and lower weight loss during IGC when compared with CG alloy (-902mV SCE, 4.9μA/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. © 2012 Elsevier Ltd.