Acidic Bath for Tin Electrodeposition Containing Cationic Surfactant

An acidic bath of simple electrolyte composition for electrolytic refining of tin was investigated with the object of obtaining a tin deposit of good adhesion. The effects of the addition of cationic surfactants to the bath was studied and the behavior of these additives was discussed. The results obtained were summarized as follows. (1) A tin deposit of good adhesion was obtained from the bath composition of 0.1mol/l SnCl2 and 0.25N HCl at 60°C. However, the optimum current density was very low as 0.16amp./dm2. (2) When 0.5g/l dodecylpyridinium chloride was added to the bath of 0.1mol/l SnCl2 and 0.5N HCl at 60°C, a tin deposit of good adhesion was obtained under high current density (2.4amp./dm2) and at high current efficincy (99%), (3) As the results of the studies on the effects of dodecylpyridinium chloride on the tin electrodeposition, the following conclusion was drawn. (a) The additive is strongly polarized as CH3(CH2)11-N⊕ and has no secondary substituent. (b) Adsorbed atom N is positioned in 6-member ring of plane structure.