Investigation on corrosion resistance of electroless Ni-W-P coatings co-deposited with SiO2 nanoparticles

Abstract

The corrosion of materials in sea environment are generally caused by salt spray, tidal action and adhesion of marine organisms. It is necessary to ensure the materials possess the required strength and good corrosion resistance during operation. Although the existing Ni-W-P electroless plating can provide a certain degree of corrosion protection, its corrosion resistance is still limited under harsh marine condition. SiO2 nanoparticles have received extensive concern due to their excellent corrosion resistance, which has been considered as potential candidates for enhancing corrosion resistance in multicomponent electroless coatings. In this study, the electroless Ni-W-P coatings with SiO2 nanoparticles co-deposition on the Q235 substrate was prepared. The coating was characterized through scanning electron microscopy (SEM), x-ray diffraction (XRD), polarization techniques, and electrochemical impedance spectroscopy (EIS). As a result, the Ni-W-P coating co-deposited with SiO2 nanoparticles demonstrates superior corrosion resistance compared to the pure Ni-W-P coating. The surface of SiO2 nanoparticles contain three distinct bonded hydroxyl functional groups, which can influence the ionic reaction in the plating solution and the deposition of elements in the coating. After modified by PVA, it can be uniformly dispersed in the coating, and the composite coating with SiO2 nanoparticles co-deposited is transformed into a nanocrystalline structure. The even distribution of SiO2 nanoparticles fill the defects within the coating, leading to a reduction in porosity, permeability, and susceptibility to penetration of corrosive media. Concurrently, the nanoparticles facilitate surface passivation, forming a stable interface with substrate and coating that inhibits electrochemical reactions and diminishes the rate of self-corrosion reactions. The good and stable corrosion resistance is achieved at the SiO2 concentration of 9 g l−1 and PVA concentration of 1.08 g l−1. These findings offer valuable insights for addressing corrosion challenges in the field of marine engineering.