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 cm²/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⁺ + 2^e– ↔ Sn.
The determined kinetic parameters of the ionization-reduction reaction in Sn(II) solutions (concentration 0.01 M–0.1 M) were: exchange current i₀ = 0.0055–0.0100 A/cm², cathodic and anodic transfer coefficients α ≈ β ≈ 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.

Keywords: sulphamate solution, Sn(II) ions, Sn(II) fluoride, diffusion, exchange current, polarization