Effect of Nanodiamond Content in the Plating Solution on the Corrosion Resistance of Nickel–Nanodiamond Composite Coatings Prepared on Annealed 45 Carbon Steel

A nickel-nanodiamond composite coating was prepared on the surface of annealed 45 carbon steel by double-pulse electrodeposition. The effect of nanodiamond particle content on the surface morphology, grain size and wear and corrosion resistance of the composite coating were investigated. According to the analysis of the test results of X-ray diffractometry and scanning electron microscopy, it was found that the cathodic polarization of the electrodeposition process was enhanced after the addition of nanodiamond particles to the Watts nickel plating solution. The positively charged nanodiamond particles on the surface facilitate the reduction reaction at the cathode. Nanodiamond particles provide crystalline growth sites for the non-spontaneous nucleation of nickel atoms. As the addition of nanodiamond particles increases, the diffusely distributed nanodiamond particles are able to attract more nickel ions to deposit nuclei, and its fine crystallization effect increases, resulting in improved wear resistance and corrosion resistance of the composite plating. Among the results, the polarization potential was the smallest when the nanodiamond content in the plating solution was 10 g/L. The surface of the prepared nickel-nanodiamond composite coating was relatively flat and smooth, with good density and a uniform grain size distribution, and the content of element C on the surface of the composite coating was the largest, reaching 1.99%.