Ni-P and its nano-CeO2 doped coating were electrolessly prepared in acidic condition,and their microstructure and anti-corrosion property were studied and compared.Scanning electronic microscopy（SEM）,transmission electronic microscopy（TEM）,X-ray diffraction spectrometer（XRD）and differential scanning calorimeter（DSC）were used to examine surface morphology and microstructure of coatings.The results showed that Ni-P coating had partial amorphous structure mixed with nano-crystals,while the Ni-P/CeO2 coating had perfect amorphous structure.Upon heating,Ni3P precipitation and Ni crystallization took place in both coatings but at different temperatures of phase change.In addition,the Ni-P/CeO2 coating had sintered phase of NiCe2O4 spinels.The anti-corrosion property and passivity were improved in the CeO2-doped coating because it was less liable to undergo localized corrosion and had a slower corroding rate than its CeO2-free counterpart.During the co-deposition process,some Cen+（n=3,4）ions might be adsorbed to the metal/solution electrical double layer and hinder nickel deposition.Ni-P/CeO2 coating’s perfect amorphous structure was probably due to the hindered crystal-typed deposition of nickel and the promoted deposition of phosphorous.
The isothermal and cyclic oxidation behaviors of bulk pure nickel and its magnetically sputtered Ni 0 5Y micro crystal coating were studied at 1?000?℃ in air. Scanning electronic microscopy (SEM) and transmission electronic microscopy (TEM) were used to examine structures of the coating and the NiO oxide films. Laser Raman spectrum was also used to measure the stress level in NiO films formed on bulk nickel and the coating. It was found that Ni 0 5Y micro crystal coating had lower oxidation rate, and the grain size of NiO formed on Ni 0 5Y coating was also relatively smaller than that formed on bulk nickel. Meanwhile, the compressive stress level of oxide film formed on Ni 0 5Y coating was lower than that formed on bulk nickel, and the oxide film’s high temperature plasticity was improved in the coating case. The improvements of anti oxidation properties of the sputtered Ni 0 5Y coating were due to the micro crystal structure and the rare earth element Y.
