In situ study of the electrochemical migration of tin in the presence of H₂S

The electrochemical migration of tin in the presence of H₂S was in situ investigated using optical and electrochemical techniques. The results show that dendrites co-exist with precipitates at H₂S concentration range from 0 to 1000 ppm_v; furthermore, the time to short circuit decreases with increasing H₂S concentration. The essential reason is that higher H₂S concentration increases the conductivity of electrolyte, resulting in a higher growth rate of dendrite. As the H₂S concentration further increases up to 10,000 ppm_v or 100,000 ppm_v, no dendrites but precipitates can be observed. This can be attributed to that large amount of tin hydroxides and tin sulfides are produced quickly at the beginning of electrochemical migration test, which act as a barrier to hinder the arrival of Sn²⁺/Sn⁴⁺ to the cathode. Thus, no dendrites but precipitates can be found. Under square wave electric field with a time period of 1 s, it is observed that there are no dendrites but some precipitates. This is because there is a circulation between metal tin deposition during the first 0.5 s and its dissolution in the next 0.5 s. Therefore, the occurrence of short circuit in the presence of H₂S is semi-cycle dependent.