Antifriction coatings of Pb–Sn–Cu alloy electro-deposited from methanesulphonate bath

Electrodeposition of antifriction Pb–Sn–Cu coatings from a bath based on methanesulphonic acid (MSA) has been investigated. The bath contains two specially selected organic additives which modify both the structure and the appearance of deposits, prevent the oxidisation of Sn(II) ions and allow the increase of tin content in deposits. The antifriction lead (∼90%)–tin (∼8%)–copper (∼2%) films are deposited from the MSA-electrolyte at a current density of 4 A dm−2 and a bath temperature of about 20–25°C. Inhibition of the Sn2+ ions discharge reaction is observed when the ternary alloy is deposited on the cathode. The Cu2+ ions discharge proceeds at a diffusion limiting current. Simultaneous co-deposition of copper has no effect on the kinetics of both lead and tin electrodeposition. Wear characteristics of the deposits from the methanesulphonate bath do not differ from those obtained from the usual fluoroborate bath.