The influence of the surface distribution of Al6(MnFe) intermetallic on the electrochemical response of AA5083 aluminium alloy in NaCl solutions

In this paper the behaviour against pitting corrosion of different samples of AA5083 aluminium alloy has been studied. A correlation between the microstructure of the samples and their susceptibility to pitting has been established. Metallographic analysis combined with SEM and EDS techniques have allowed us to detect three intermetallic compounds in the samples. The particle size distribution and surface density of each intermetallic phase have been evaluated for the three AA5083 alloy samples coming from different suppliers. Significant differences in the microstructure of the three samples have been found. Full immersion test carried out in 3.5% aerated aqueous solutions showed that pitting starts at the locations of the Al-6(MnFe) intermetallic particles. As a consequence of this, the samples with higher Al-6(MnFe) content showed a higher pit density on its surface. The results of cyclic polarisation tests showed also a good correlation with the microstructural parameters.