Selective corrosion of ?-Sn and intermetallic compounds in an Ag-Sn alloy at different potentials in NaCl and Na₂SO₄ solutions

The corrosion behavior of beta-Sn and intermetallic compounds in Ag-28Sn alloy was investigated by potentio-dynamic polarization and bipolar electrochemistry tests. The potential distribution along the bipolar electrode was measured. The results show that the potential distribution is linear along the center of the bipolar electrode. In the Na2SO4 solution Ag4Sn intermetallic compounds preferentially corrode at high potential and beta-Sn at low potential; in the NaCl solution, beta-Sn preferentially corrodes at both high and low potential. Based on the potential-pH diagram, the selective corrosion mechanism of the Ag-Sn alloy is elucidated.