In this paper, the preparation and characterization of as-deposited and heat-treated low phosphorus Ni-P coatings on AZ91 magnesium was performed. Heat-treated Ni-P coatings reached the higher microhardness of 1030 ± 20 HV 0.025 when compared to as-deposited Ni-P coatings (560 ± 20 HV 0.025). Using the scanning electron microscopy, the microstructure and surface morphology of Ni-P coatings was observed. Heat-treated coatings were formed by cracks network on their surface due to their crystallization during the heat-treatment. These cracks negatively affected the electrochemical and corrosion properties. However, as-deposited Ni-P coatings improved the electrochemical corrosion properties when compared to AZ91 alloy. The corrosion potential increased to -0.59 ± 0.02 V and the corrosion current density decreased to 1.4 ± 0.3 µA∙cm-2.Keywords: Electroless Ni-P coating, AZ91, magnesium alloy, heat treatment, potentiodynamic polarization test
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