Effect of Polyethyleneimine Cationic Surfactant on Morphology and Corrosion Resistance of Electrodeposited Ni-Co-SiC Composite Coatings

Ni-Co-SiC composite coatings were prepared by modified watt-type plating solution with 40 nm SiC particles. The effects of polyethyleneimine (PEI) on the dispersion of SiC nanoparticles and the hardness and corrosion resistance of Ni-Co-SiC coatings were studied. The electrode reaction process was measured by cyclic voltammetry. The results showed that when the PEI concentration was 0.06 g/L, the peak current was the highest. SiC distribution in Ni-Co-SiC coatings was relatively uniform and the coating was flat and dense. With the increase in PEI concentration, the hardness and corrosion resistance showed a trend of increasing first and then decreasing. The hardness and corrosion resistance were at their best with 0.06 g/L PEI. Pretreatment effectively avoided the competitive adsorption of surfactant and other additives on the surface of SiC particles. PEI was preferentially adsorbed on the surface of SiC particles by pretreatment. Steric resistance was formed, which inhibited the agglomeration of nanoparticles and make SiC particles more evenly dispersed into the coating. The hardness was significantly increased by 119.26 Hv, and the corrosion resistance improved accordingly.