The electrodeposition of tin and lead-tin based alloys

A summary of the conditions for alloy electrodeposition follows a brief introduction which includes the history and the scope of the tin and lead-tin alloy coating industry. The roles of the different variables in the electrodeposition of alloys have been briefly described. A detailed review of the different types of solutions which have been used in tin and lead-tin based alloy electroplating introduces the main industrial applications of such alloys. A detailed study, including the investigation of many methods of preparing a tin sulphamate solution for tin-plating, has been carried out. The optimum conditions for such a solution have been defined following detailed experiments concerning the effect of the different parameters (polarization, current density, additives, etc). Some additives have been studied in detail to secure stability for the solution. A sulphamate electrolyte for lead-tin alloy plating has been proposed as a combination of the already developed tin solution and a lead sulphamate solution developed previously (see MSc dissertation, 1981). This solution has been used to electrodeposit four types of alloys of composition 90, 80, 70 and 40% lead (remainder tin). The effects of the more important parameters for the alloy solutions have been investigated to achieve the optimum condition for alloy electrodeposition. As an application of the alloy of composition 90% lead (remainder tin), a set of bearings of a motor car engine has been plated for the purpose of examining the suitability of the alloy for such applications. Preliminary indications are of general acceptance.