Tin-Cobalt Alloy Plating in a Pyrophosphate Bath

摘要

We examined bath composition, plating condition and plating process of tin-cobalt alloy deposits substituting chromium plating. It has been also investigated and reviewed surface characteristics, corrosion resistance, impurity influence, and abrasion utilizing pilot plant after investigating reviewing cathodic polarization curve, corrosion resistance and SEM through Hull-cell and beaker test. As a result, it was found that basic bath composition of tin-cobalt alloy plating is SnCl_2·2H_2O (0.03M), CoSO_4·7H_2O (0.05M), K_4P_2O_7 (0.7M). It has been also found that surface of plating is best when plating condition is current density (1A/dm2), solution temperature (50℃), pH8 with current efficiency of 70 ～ 73% and plating rate of 0.2μm/min. Tin-cobalt alloy plating is at least equal to. or better than chromium plating in adhesion and tarnish test, while chromium plating is better than tin-cobalt alloy plating in corrosion resistance and abrasion test.