Electroless Plating of Ni-B Composite Coating on AZ31 Mg alloy

A Ni–B coating was electroless-deposited directly on H 3 PO 4 /HF pickled AZ31. The thickness of the plating layer was estimated through weight gain measurements and was affected by temperature, time and bath composition. The highest thickness was obtained at 6 g/L of NaHB 4 at 85 o C.  An adherent compact layer of Ni-B was obtained. Electrochemical impedance spectroscopy measurements in 3.5 wt.% sodium chloride aqueous solution suggest that the plating can protect the magnesium alloy substrate from corrosion attack.