Effect of Si addition on corrosion behaviors of Cu/Al dissimilar joint brazed with novel Zn-Al-xSi filler metals

Novel Zn-Al-Si filler metals were used to enhance the corrosion resistance of Cu/Al brazed joint. The corrosion behaviors of the joint were investigated by neutral salt spray test. The effect of Si addition on the corrosion behaviors of the joint was discussed, and the corrosion resistance was evaluated for the first time. The results showed that the thickness of the diffusion layer on Al side was remarkably reduced with the addition of Si. Meanwhile, the Zn element aggregation degree was alleviated because the Zn-Al eutectic was divided into narrow strips by scattered fine CuAl2 phases, especially the Zn-rich Zn-Al eutectic. Thinner diffusion layer suppressed the initiation and propagation of the stress corrosion crack, while the alleviated degree of Zn aggregation significantly slowed down the deepening and expansion rate of the corrosion pit. After 36 h salt spray test, Zn-22Al-1.5Si joints turned out to possess the best corrosion resistance.