Ni-P/Ni-W-P double-layer coating with Ni-P coating as the bottom layer,Ni-W-P coating as the outer layer was prepared on 45# steel substrate by chemical deposition method.The surface morphology,composition,microstructure and corrosion resistance of double-layer coating were characterized by scanning electron microscope,X-ray diffraction and electrochemical workstation respectively.The results showed that double-layer coating had an amorphous structure with a small amount of microcrystalline structure,its porosity was only 1.94% and the surface compactness was better than that of Ni-P single-layer coating.The corrosion current density of double-layer coating without immersion was 8.58×10-7A·cm-2,which was two orders of magnitude lower than that of 45# steel substrate.The corrosion rate of double-layer coating was only 0.050 g·(cm2·a)-1,which was lower than that of 45# steel substrate.After immersion in 3.5% sodium chloride solution for 10 d,the corrosion degree of double-layer coating was very light,and the corrosion current density increased very slowly,indicating that the corrosion resistance of double-layer coating was better than that of single-layer coating,which provided better protection for 45# steel substrate.
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