Effect of Ag addition on the microstructure and corrosion properties of Sn–9Zn lead-free solder
Cunji Pu, Caiju Li, Tinghao Dong, Yingde Miao, Peng Gao, Xin Zhang, Jubo Peng, Jianhong Yi
Abstract
The effects of Ag addition on the microstructure of Sn–9Zn alloy and its corrosion behaviour in neutral and static 3.5 wt% NaCl solutions were investigated using surface characterization techniques and electrochemical techniques. The results show that in Sn–9Zn-xAg alloys, Ag reacts with Zn to form AgZn3 intermetallic compounds (IMCs), which refined the microstructure of the alloys and changed the corrosion mode of the alloy surfaces from pitting corrosion to surface corrosion. The addition of Ag effectively improved the corrosion passivation film structure and electron transfer characteristics of the alloy, increased the self-corrosion potential (Ecorr) and reduced the self-corrosion current (Icorr), thus improving the corrosion resistance of the alloy. The study explained and verified the corrosion mechanism of the alloy from both experimental and theoretical perspectives. It is concluded that Sn–9Zn-0.4Ag alloy shows relatively the best corrosion resistance.