Characterization of electroless Ni-P coating prepared on a wrought ZE10 magnesium alloy

Abstract

Electroless low-phosphorus Ni-P coating was deposited on a wrought ZE10 magnesium alloy including an advanced pre-treatment of the material surface before deposition. Uniform Ni-P coating with an average thickness of 10 μm was formed by 95.6 wt % Ni and 4.4 wt % P. The content of Ni and P was homogeneous in the entire cross-section of the coating. Applying the Ni-P coating to the magnesium substrate, the surface microhardness increased from 60 ± 4 HV 0.025 to 690 ± 30 HV 0.025. Using the scratch test, it was determined that deposited Ni-P coating exhibits a high degree of adhesion to the magnesium substrate. Electrochemical corrosion properties of Ni-P coating were analyzed using the polarization tests in 0.1 M NaCl, while the deposited Ni-P coating showed an improvement of the corrosion resistance when compared to the ZE10 magnesium alloy. Using the scanning electron microscopy analysis, it was determined that the fine morphology of the deposited Ni-P coating did not contain visible microcavities. The absence of macrodefects due to the adequate pre-treatment before coating was reflected on the mechanism of the coated ZE10 degradation in a 0.1 M NaCl solution.