Effect of a polyethoxylate surfactant on the electrodeposition of tin

The electrodeposition of tin in the presence of polyethoxylated additive TX-102 has been investigated in acid medium. The additive causes a substantial increase in the overpotential for the discharge of Sn²⁺ ions. Below 0.12 g dm^–3 the additive has little effect on the quality of the tin deposits. Periodic oscillations in the voltage of the cell are observed, which are associated with the initial growth of whiskers. For higher concentrations of additive, the deposits are smooth and homogeneous, and no growth of whiskers and no voltage oscillations are observed. The effect of TX-102 for concentrations below the CMC has been interpreted in terms of blockage of high energy sites of preferential growth on the tin surface. For additive concentrations above the CMC, micelles are formed. These high molecular weight aggregates also block the surface, hindering the mass transport of Sn²⁺ through a membrane-like layer that forms on the tin.