Abstract: The NiCrBSi alloy powder was sprayed to a steel sub-strate using high velocity oxyfuel(HVOF) and the corrosion fM lure process of the coating in 3.5% NaCl aqueous solution was investigated u-sing electrochemical impedance spectroscopy.Preferential corrosion hap.pened in the corrosion process of steel coated by HVOF coating.Firsdy,because the defects such as porosities were harmful to the uniformitv of electrochemical behavior and local corrosion occurred in these sDots.And then,the steel substrate was preferentially corroded after the solution penetratiag into the interface between the coating and the steel.The corrosion resistance of the coating fell sharply at the early stage,and then increased because corrosion products had blocked some corrosion paths.The COrro-sion resistance of the steel substrate coated by NiCrBSi coating fell contin-uously after the steel taking part in the electrochemical reaction.