Investigation of electrochemical reduction of Sn(II) ions in acidic (pH 1) sulphamate-fluoride solutions

The electrochemical reduction of Sn(II) ions in acidic (pH 1) sulphamate and sulphamate-fluoride solutions was investigated using voltammetric, chronopotentiometric, and rotating disc electrode techniques. In both solutions, the process of Sn(II) reduction was found to be reversible and mostly diffusion-controlled. The Sn(II) ion diffusion coefficient was D = 6.1 . 10(-6) cm(2)/s. In acidic sulphamate-fluoride solutions, the decomposition of Sn-fluoride complexes into Sn(II) ions and F- ions precedes by the electrochemical reduction step. The transfer reaction in acidic tin sulphamate and sulphamate-fluoride solutions proceeds in one step: Sn2+ + 2e(-) reversible arrow The determined kinetic parameters of the ionization-reduction reaction in Sn(II) solutions (concentration 0.01 M-0.1 M) were: exchange current i(0) = 0.0055-0.0100 A/cm(2), cathodic and anodic transfer coefficients alpha approximate to beta approximate to 0.5, and the reaction rate constant k(s) = (1 . 10(-6)-10 . 10(-6)) cm/s. In both sulphamate and sulphamate-fluoride solutions, the electrochemical reduction of Sn(II) ions follows the same pattern which determines the identical properties of deposited Sn coatings.