Characterisation and Corrosion Performance of MultilayerNano Nickel Coatings on AZ31 Magnesium Alloy

Ni-P and Ni layers multilayer coatings were applied to AZ31 magnesium alloy utilizing electroless and electrodeposition procedures. The aim of the project was to decrease cracks and increase corrosion resistance of the coatings. In order to compare the coatings, the effect of single layer electroless Ni-P coatings with different thicknesses was also investigated. The microstructure and phase composition of the coatings were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The results showed that increase in the thickness of the single layer coatings was not an effective solution to inhibit the reaction of magnesium with plating bath during electroless process. In this regard, magnesium was detected on the surface of the single layer coatings. The application of a thin electroplated Ni layer between two electroless layers could inhibit the reaction of magnesium with plating bath during electroless process, which resulted in improving the corrosion resistance of the coatings.