This paper reports a phenomenon of spontaneous periodical current oscillation during electrochemical anodization of tin in alkaline electrolytes. Such phenomenon has been reported in the literature. Attempts have been made to explain this phenomenon on the basis of oxide film lift-off and electrolyte diffusion. This investigation demonstrates that the current oscillation is caused by oxygen generation and release on the tin anode, causing periodic redistribution of ion concentration in the electrolyte. The analysis also enables determination of the contributions of the two anodic reactions of Sn oxidation and oxygen generation to the total anodic current. (C) 2011 Elsevier Ltd. All rights reserved.