To inhibit the corrosion of magnesium alloy in electroless nickel plating bath, nickelous
hydroxide and phytic acid were used as main salt and corrosion inhibitor to inhibit the dissolution
of substrate during the nickel deposition process. Effects of nickel ion and phytic acid
concentration on plating rate and porosity were studied by single-factor experiment, and the
optimum concentrations were obtained at 8.8 g/L and 4 ml/L, respectively. Deposition process of
nickel phosphorus (Ni-P) coating was observed by using scanning electron microscope (SEM) and
activation energy of Ni deposition process was estimated by Arrhenius equation. SEM observation
showed that Ni deposition process could be divided into two stages, the first stage was Ni
replacement reaction competition with corrosion inhibition reaction of substrate, the second stage
was Ni autocatalysis reduction process. Potentiodynamic polarization curve revealed that Ni-P
coating exhibited good corrosion resistance in protecting magnesium alloy. Scratch and thermal
shock tests showed excellent adhesion between the Ni-P coating and magnesium alloy substrate.