Zn-Ni alloy coatings pulse-plated on magnesium alloy

Zn-Ni alloy coatings are plated on AZ91 magnesium alloy using a pulse potential after an appropriate pretreatment. The current density, frequency, ton/toff and time have effects on thickness, morphology, Ni content, microhardness and anticorrosion of Zn-Ni coatings. Corrosion can reach above 200 h in salt spray test according to ASTM B117; the corrosion behavior of coatings is interfacial corrosion of particles and results in particle degradation as observed by scanning electron microscopy. Weight loss method and polarization curves are also used to investigate anticorrosion properties. Bonding strength is above 14.8 MPa in adhesive tensile tests.