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In this work, Ni-P coatings are deposited on the steel substrate by electrodeposition from a solution containing nickel sulfate and sodium hypophosphite (NaH 2 PO 2 ). The effect of the current density on the morphology, phase structure, microhardness, and corrosion performance of the Ni-P coatings are studied. Scanning electron microscopy and energy dispersive X-ray analysis and X-ray diffraction are used to study the morphological, composition and phase structure. The corrosion performance of the coatings is evaluated by weight loss, electrochemical impedance spectroscopy and Tafel polarization. Results showed that the morphology of the electrodeposited Ni-P alloys coatings has spherical grains for all the samples, and the Ni 3 P phases are formed all over the microstructure of the coatings. It is observed that the phosphorus content and microhardness are dependent on the current density. The corrosion tests show that 5 A⋅dm −2 current density is the optimal value which gives the best protective coating against corrosion. It also exhibits superior microhardness originated from the higher Ni 3 P amount.

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