Dissolution of tin in the presence of Cl? ions at pH 4

Abstract

The anodic dissolution of tin, investigated in an acidic solution at pH 4 containing 0.1–1 M NaCl at 25°C, displays Tafel behavior as long as the electrode surface is bare (E≤−0.5 V vs SCE). The main characteristics can be derived from the proposed dissolution mechanism, i.e $$(\partial E/\partial \log i)_{a_{Cl} } = 40 mV/d.c., (\partial log i/\partial a_{Cl^ - } )_E \approx 1$$ and $$(\partial i/\partial \omega )_{E, a_{Cl^ - } } \approx 0$$ . The mechanism involves two consecutive steps, each corresponding to the transfer of one electron, the second step being rate determining. ForE values anodic to ∼−0.5V vs SCE partial coverage of the surface by a corrosion product is observed and the behavior is no longer Tafelian. From 0.4 to 1V vs SCE, a plateau current is observed on logi vsE curves and the anode is completely covdered by a corrosion product. Results obtained with a rotating disc electrode suggest that the rate-determining step of the dissolution process in this region of potential is the diffusion of an ionic species into the solution.