Erosion–corrosion resistance of Ni composite coatings with embedded SiC nanoparticles

Abstract

This study assessed the erosion–corrosion behavior of pure Ni and Ni–SiC composite coatings evaluated in a corrosive environment using in situ potentiondynamic polarization and electrochemical impedance. Coatings were obtained from a Watts classical solution in which SiC nanoparticles were added. Coatings were galvanostatically deposited on carbon steel on a rotating disk electrode. The hydrodynamic conditions of the bath and the content of SiC in the electrolyte were varied. The morphology, structure and properties of the coatings were evaluated in relation to the electro-synthesis conditions. It was found that incorporation of SiC nanoparticles into the metal matrix produces morphological changes in the deposit. These are responsible for increases in the microhardness of the composite coatings and a better resistance against erosion–corrosion compared with pure nickel coatings. The increases in SiC nanoparticle content in the coating and the hydrodynamic conditions in the electroplating process cause grain refining and changes in the crystal growth of the nickel grains in the Ni deposit. As consequence of structural modification in the crystalline orientation of the Ni deposit, grain refining and strain occurred in the nickel lattice. These structural changes in the nickel deposit led to enhanced performance of the Ni–Sic composite coating in the erosion–corrosion test. Additionally, the presence of inert particles of SiC in the conductive matrix coating may have blocked the passage of the anodic Faradaic current, diminishing the corrosion rate of the coating.