Influence of Mg Content on the Sensitization and Corrosion of Al-xMg(-Mn) Alloys

The influence of Mg content on the degree of sensitization (DoS) of Al-xMg-0.5Mn (wt%) alloys (where x varies from 3.36 wt% to 8.85 wt%) was investigated via the nitric acid mass loss test (NAMLT). NAMLT upon sensitized specimens revealed that mass loss was negligible below ~4.01 wt% Mg, while for Mg content ≥4.01 wt%, mass loss increased monotonically. The calculated equilibrium β-phase fractions were contrast with the DoS values. Additionally, the influence of the Mg content on corrosion was investigated via potentiodynamic polarization testing, in conjunction with microhardness measurements. We found that Mg additions lead to an increase in hardness without causing any significant impact on electrochemically determined corrosion current density; however, Mg content has a major impact on intergranular corrosion as determined from NAMLT.