The Corrosion Behavior of 5xxx and 6xxx Aluminum Alloys with Trace Calcium

The aluminum alloys containing magnesium and silicon as main alloying elements have been found to be amenable to recycling. During the recycling process, calcium is found as a trace element or through deliberate addition. The addition of calcium may influence the corrosion properties of the alloy via changes like microstructure and compositional chemistry. This study investigates the potential effects of added calcium, heat treatment, and deformation on the corrosion behavior of 5xxx and 6xxx alloys using standard corrosion evaluation techniques, like Tafel, linear and cyclic polarization. The addition of trace calcium has affected the microstructure of 6xxx alloy, but it does not show significant changes to corrosion behavior and repassivation behavior of both alloys. The change in microstructure has altered the pit forming mechanism in both, but it is predominantly shown in 6xxx alloy. Although the 5xxx alloy shows decreased corrosion potential and increased sensitization time the corrosion rates are comparable.