Cobalt tungsten alloy-electrodeposition and characterisation

Abstract

Bright Co-W alloy on steel is obtained from the optimised bath with the operating conditions of cobalt sulphate 0.15 <i>M</i> sodium tungstate 24 gpl, ammonium chloride 0.2 <i>M</i>, sodium citrate 0.2 <i>M</i>, dimethyl sulphoxide 0.06 <i>M</i>, <i>p</i>H 8 at 4 Adm^-2. The hardness of the alloy deposit is two times that of cobalt deposit. The corrosion resistance in 1.0 <i>M</i> 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">

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