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In order to improve the poor corrosion resistance of Mg and its alloys,Ni-Co-P alloy coating is tried to deposit on AZ31 magnesium alloys by electroless plating in present paper.The microstructure,surface morphology and composition of the formed coating are analyzed by X-ray diffraction(XRD),scanning electron microscopy(SEM) and energy dispersive spectrometer(EDS),respectively,and the corrosion resistance of the coating is measured briefly by drip drops of the solution of KMnO4 and HNO3 and by Tafel curves precisely.Drip drops test and electrochemical polarization measurement shows that the corrosion resistance of the formed Ni-Co-P coating is good.The effect of the concentration of NiSO4,CoSO4,NaH2PO2 and deposition temperature on the films corrosion resistance was studied by an orthogonal experiment,it is found that appropriate concentration of NiSO4,CoSO4 and NaH2PO2 and proper deposition temperature can enhance the coatings corrosion resistance.Then the optimal process parameters to obtain a coating with good corrosion resistance were suggested.Furthermore,Ni-Co-P coating is fabricated on AZ91 magnesium alloys and compared with that on AZ31.