Electroless nickel-plating on AZ91D magnesium alloy by using NiSO4·6H2O as main salt was described.Permanganate and phosphate chemical conversion films were proposed as the chrome-free pretreatment layer between electroless nickel-plating and AZ91D magnesium alloy substrate.Morphology

composition and corrosion resistance of the chemical conversion film and electroless nickel-plating layer in 3.5%NaCl solution were determined by SEM

EDX

XRD and polarization curve.The results show that the electroless nickel-plating coating after permanganate pretreatment exhibits cell structure with sound to some extent and micro-crack

while one after phosphate pretreatment also exhibits cell structure with uneven grain size and micro-crack free

and plating coating shows uniform thickness with compact structure and pore-free.Corrosion resistance is slightly improved by chemical conversion treatment compared with that of magnesium substrate

and corrosion potential of electroless nickel-plating coating after permanganate pretreatment and phosphate pretreatment reach-0.48Vsce and-1.12Vsce

respectively

in 3.5%NaCl solution by polarization curves.Corrosion resistance of AZ91D magnesium alloy is improved by electroless nickel-plating layers after phosphate pretreatment with NiSO4·6H2O as main salt.