An Investigation on the effect of adding copper sulfate on the properties and corrosion resistance of electroless nickel-phosphorus coating

In this study, the effects of adding copper sulfate on the properties and corrosion resistance of electroless coating of nickel - phosphorus on aluminum substrates has been investigated. Samples after surface preparation were coated with adding different concentrations of copper sulfate (0.2 to 1 gram per liter) in nickel-phosphorus electroless baths. To examine the coating structure changes with different concentrations of copper sulfate, X-ray diffraction(XRD) was used. In order to evaluate the morphology of the surface , the optical microscope was used and to study the chemical composition and cross-section, the scanning electron microscope equipped with EDS analyzer was used. Vickers hardness was measured using the micro-scale. The corrosion resistance studies were carried out using Tafel polarization test in a solution of % 3/5 NaCl. Test results showed that increasing the amount of copper sulfate in electroless nickel-phosphorus plating bath increases the bath stability and reduce the deposition rate, morphology changes and crystallization of coverage and significant reduction in hardnes were resulted.also corrosion resistance of Electroless nickel-phosphorus coating significantly increased In the presence of copper , due to Reduce porosity and the passire state which was resulted.