Corrosion Studies on AA7075-T7352 Alloys Under Adverse Environments

The stress corrosion cracking (SCC) resistance of AA7075-T7352 aluminum alloy is critically examined in this study to analyze its failure under corrosive environments. The above class of alloy which had a dendritic coring was subjected to corrosion and stress corrosion cracking tests in sodium chloride solution to check the effect of such coring on its corrosion behavior. Microstructural analysis of the material was carried out in all three grain orientations to observe the cast structure which can influence its corrosion characteristics. Potentiodynamic polarization study was carried out to find the resistance of the alloy against induced corrosion. Similarly, analysis of corrosion morphology and SCC was carried using scanning electron microscopy (SEM) and slow strain rate test (SSRT). Fracture morphology was studied using SEM to investigate the mechanism of fracture. The results thus obtained realizes that, the presence of dendritic coring resulted in severe localized corrosion of the alloy. This heterogeneous microstructure increased the corrosion initiation at a faster rate during the SCC test. The formation of localized corrosion pits increased the stress intensity causing sudden mechanical failure during SSRT. The present study emphasizes the importance of analyzing microstructure during forging operations which can affect the localized corrosion resistance of the alloy and indirectly affects its mechanical behavior when exposed to corrosive environment.