Effect of Fe and Mn on Corrosion Resistance of Recycled Self-hardening AlZn10Si8Mg Alloy

Recycled aluminium alloys are a highly valued alternative for manufacturers, particularly in the automotive and aerospace industries, due to increasing demands on the environmental performance and sustainability of the industry. Self-hardening aluminium alloys, which achieve the required mechanical properties without heat treatment, enable the emissions generated by production to be reduced even further. In addition to an advantageous strength-to-weight ratio and excellent machinability, corrosion resistance in a variety of environments is also important in most applications of aluminium alloys. Repeated recycling cycles negatively influence the quality of aluminium because of an increase in iron content, which is considered an impurity. This is due to the formation of intermetallic phases which negatively affect the mechanical, fatigue and corrosion properties. In this paper, the effect of Fe and Mn on the microstructure and corrosion resistance of self-hardening recycled AlZn10Si8Mg alloy was investigated using the AUDI test, atmospheric long-terming test and 3.5% NaCl solution test. The corrosion mechanism was subsequently determined by sectioning the samples. Alloy A with the lowest iron content exhibited the best corrosion behaviour, as it was subjected to only localised forms of corrosion even in the aggressive environment of the AUDI test. In this environment, the other alloys were attacked by general corrosion of the entire surface. Manganese alloying caused a subtle improvement in the corrosion resistance of alloy D but was limited by the high porosity. The eutectic and intermetallic phases corroded the most, while the alpha phase was more resistant.