Silicon nitride nanoparticles reinforced the corrosion resistance of Ni-Cu composite coating in simulated seawater solution

A new type of Ni-Cu/Si3N4 nanocomposites was prepared by pulse electrodeposition technology, which can be used for corrosion protection in seawater environment. XRD, SEM, AFM, EDS and XPS were used to study the structure, morphology, and surface composition of the deposited layers. The hardness and anti-corrosion performance of the deposits were evaluated using a microhardness tester and an electrochemical workstation. Meanwhile, the samples were characterized by EIS, SEM, EDS and XPS after immersion in simulated seawater for 7 days, 14 days, and 28 days. The results show that the average crystallite size of the nanocomposite with face-centered cubic structure is 13.2 nm, and has a dense granular nodular structure without obvious defects. EDS and XPS demonstrated the successful embedding of Si3N4 nanoparticles with uniform distribution in the coating. Besides, it was found that embedding Si3N4 particles in Ni-Cu alloy coatings can significantly strengthen the microhardness and anti-corrosion performance of the material. Furthermore, the Ni-Cu-Si3N4 (0.7 g·L−1) nanocomposite exhibited excellent corrosion resistance even after immersion in simulated seawater medium for 28 days.