Effect Of Operational Parameters On Continuous- Current Electrodeposition Of Ni-Co Alloys

Abstract

Ni-Co coatings on carbon steel substrate were prepared by conventional continuous-current electrodeposition in watt's bath at 40 and 50^oC. The deposition process was done without electrolyte agitation at different current densities. The dependence of coating properties on type of anode, pH and current density was investigated. The deposition efficiency was evaluated in relation to current density with use of soluble and insoluble anodes. It was found that using the insoluble anode material has led to a gradual decrease in the pH of the deposition bath down to very acidic values. This was affected by the oxidation of water molecules at the anode surface. However, using the soluble Ni-anode gave good control over the pH of deposition bath due to compensation for the loss of consumed Ni-ions in solution. Under both of test regimes, i.e., with use of soluble and insoluble anodes, increasing current density has improved the amount of electrodeposited Nickel; which led to increased thickness of electrodeposited layer.

Based on x-ray diffraction data, the recoded diffraction pattern has proved the crystalline nature of the electrodeposited Ni-Co alloy. Moreover, electrochemical measurement using a modern electrochemical system showed that coating with Ni-Co alloy has shifted the corrosion potential of steel substrate (in 3% NaCl solution) by more than 400 mV in the noble direction; which means a high degree of protection against corrosion has been achieved.