Effect of Gd element on the corrosion resistance of Al–9Si–0.4Mg–0.025Sr alloy

This study systematically investigated the impact of Gd on the corrosion resistance of the Al–9Si–0.4Mg–0.025Sr alloy in a 3.5 wt-% NaCl solution using electrochemical tests and immersion corrosion analysis. The results show that the AS2 alloy containing 0.4 wt-% Gd exhibited the best corrosion resistance. Electrochemical tests show that AS2 has the highest corrosion potential and the smallest capacitive arc radius, demonstrating its superior resistance to corrosion initiation and propagation. Immersion corrosion morphology analysis revealed that minimal corrosion pit formation and a slower corrosion rate occurred in AS2 compared to other alloys. Microstructural analysis showed that Gd promoted the formation of protective Al 3 Gd phases on eutectic Si particles and in the matrix, thereby enhancing passivation and inhibiting corrosion propagation. Furthermore, galvanic coupling between eutectic Si and the Al matrix accelerated localised dissolution, while Gd mitigated this effect by stabilising the oxide films and decreasing the cathodic activity.