Direct electroless nickel–boron plating on AZ91D magnesium alloy

A Ni–B coating was electroless-deposited directly on acetic acid pickled AZ91D. The plating rate was found to be influenced by pH, temperature, and bath composition. The electroless Ni–B plating exhibits a uniform surface and an amorphous structure. Polarization curve and 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. It is proposed that different deposition reactions dominate in different stages of the plating process.

► A paper on an innovative direct electroless Ni–B plating for Mg alloys. ► The Ni–B plating exhibits superior corrosion resistance in a NaCl solution. ► The effect of plating bath and plating conditions on plating rate are studied. ► The composition and microstructure of the Ni–B coating are analyzed. ► Ni nucleation, Ni–B plating mechanisms and substrate effect are discussed.