Effect of In on Corrosion Performance of Zn-15Al-5Cu-xIn Solders

The salt spray test has been used to study the effect of adding In on the corrosion performance of Zn-15Al-5Cu-xIn (x = 0, 1, 3, and 5, where x is the mass percentage) solder alloys. The focus was on the microstructure and corrosion properties of the alloy. The results of scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), x-ray diffraction (XRD) analysis, and differential scanning calorimetry (DSC) revealed the distributed formation of In-based solid solution. Corrosion performance tests on the Zn-15Al-5Cu-xIn solders revealed the influence of In on the corrosion performance; addition of 3% In resulted in the solder with the highest corrosion potential and slowest corrosion rate. The main reason is that more γ (CuZn₄) phase with strong corrosion resistance was dispersed and distributed in the solder. Remarkably, when the In content exceeded 3%, it could enrich the dendritic zone of the grains, which could reduce the corrosion resistance of the solder alloy. It is thus concluded that the optimal In content in this alloy system is 3%.