Corrosion of Linear-Friction-Welded AZ91 and AZX912 Mg-Al Alloys

Abstract

The corrosion performance of the AZ91 and AZ91 + 2%Ca (AZX912) magnesium alloys joined using linear friction welding was investigated. For similar and dissimilar metal combinations—namely AZ91/AZ91, AZX912/AZX912, and AZ91/AZX912, the performance was evaluated by mass loss analysis and the scanning vibrating electrode technique in 1 wt% NaCl solution. Galvanic behavior between AZ91 and AZX912 was examined by potentiostatic polarization and galvanic current measurements. Approximately 0.3–0.6 mm thick seamless weld zones were generated in all of the welds, which did not show any appreciable changes in the surface profiles acquired after the corrosion test. The corrosion-induced mass loss rate of the AZ91/AZX912 dissimilar weld was 10% higher than those of the AZ91/AZ91 and AZX912/AZX912 similar welds. The galvanic test indicated that AZ91 and AZX912 were the anodic and cathodic regions, respectively, with a difference in the corrosion potential of 20–30 mV. The corrosion of the AZ91/AZX912 weld was presumed to proceed via a macro-galvanic cell between the base alloys, whereas the weld acted as a bridge and did not influence the corrosion.