Electrochemical behaviour of tin in alkaline electrolyte

• Potential regions of Sn oxidation to Sn(II) and Sn(IV) identified by means of RRDE
• Imaginary impedance changes when anodic reactivation of passivated Sn takes place.
• Sn reactivation is accompanied by oxidation of metallic Sn to soluble Sn(II) species.

The electrochemical behaviour of two types of tin electrodes, Sn rod and electrodeposited Sn is investigated in 0.1 M KOHaq in order to evaluate processes related to anodic Sn dissolution. Potential regions of formation of soluble Sn(II) and Sn(IV) are identified by means of a rotating ring disk electrode. An anodic reactivation peak observed for cathodic potential scans for partially passivated electrodes is accompanied by formation of soluble Sn(II) species and a minimum in the imaginary part of the impedance. This confirms that the reactivation peak is due to active dissolution of metallic Sn exposed to the electrolyte during rupture of the oxidised layer.