CORROSION BEHAVIOUR OF NANOSTRUCTURED ALUMINIUM ALLOYS PROCESSED BY CRYO-ROLLING

Abstract

The present work is envisaged to study the corrosion behavior of ultrafine grained aluminium alloys processed by cryo-rolling. The chemical compositions of this alloy by weight % are 0.45% Si, 0.3% Mg, 0.05%Cu, 0.013% Mn, 0.048 %Fe, 0.22% Zn, 0.022% Cr and the remaining are aluminium in wet environments. Five different thickness of cryo-rolled aluminium alloy samples of three sets each were subjected to salt spray corrosion tests (ASTM-B 117 standard) for 24 hours, 48 hours, and 72 hours respectively. Three different thickness of cryo-rolled aluminium alloys were also subjected to immersion tests. The weight loss kinetics curves of the alloys, in 3.5% NaCI environment, were measured. The surface morphology of the corroded alloys was characterized by Flt-SEM. Upon exposed to the corrosive environment, a localized type of attack occurs on the samples and showed the presence of A1203, MgO, ZnO, Cr203,Cu2o,Fe2O3, Na2O,SiO2. However, the dominant phase was aluminium oxide for all thickness samples. From the surface morphology of the corroded samples, we found that a less thickness sample undergo corrosion at a relatively faster rate when compared to larger thickness sample.