Cobalt tungsten alloy-electrodeposition and characterisation

513-518Bright Co-W alloy on steel is obtained from the optimised bath with the operating conditions of cobalt sulphate 0.15 M sodium tungstate 24 gpl, ammonium chloride 0.2 M, sodium citrate 0.2 M, dimethyl sulphoxide 0.06 M, pH 8 at 4 Adm-2. The hardness of the alloy deposit is two times that of cobalt deposit. The corrosion resistance in 1.0 M acidic solutions for Co-20% W alloy is in the order of HCl > H2SO4 > HClO4. The deposition of cobalt on platinum takes place from cobalt citrate complex. This citrate complex undergoes successive electron transfer. During the Co-W alloy deposition on platinum, cobalt tungstate complex undergoes reduction to form an alloy. The dissolution of Co-W alloy film occurs from Co-W intermediate phase.<span style="mso-bidi-font-weight: bold">