Effect of current density on corrosion and mechanical properties of Zn-SiC composite coating

Abstract

Abstract The Zn-SiC composite coating is an effective protection measure for steel structures. Incorporation of SiC particles within zinc matrix and well dispersion of these particles through coating thickness are found a practical problems. In order to get uniform and dense Zn-SiC composite coating using electrodeposition process, operating parameters should be well controlled. Current density is one of important electrodeposition parameter that effects formation of Zn-SiC composite coating and hence could influence the mechanical and corrosion properties of composite coating. The main objective of this study was to investigate the effect of current density on the deposition of Zn-SiC composite coating. The deposition of zinc with SiC particles was conducted by electrodeposition process and using zinc sulfate bath containing 20 g/L of 2 micron of SiC particles. The stirring speed of 600 rpm and current density over range of 20, 30, 40 and 50 mA/cm2 were used to obtain Zn-SiC composite coatings. Morphology and microstructure of composite coating were observed using scanning electron microscopy. Corrosion behavior of Zn-SiC composite coating was investigated by potentiodynamic polarization analysis while microhardness was studied using Vickers hardness method. The incorporation of SiC particles along zinc coating layer was confirmed using SEM and EDS study. Significant reduction in corrosion rate of Zn-SiC composite coating was observed with 3.0 x 10-1 mm/yr for Zn-SiC composite coating deposited at current density of 40 mA/cm2. An improvement in microhardnesss due to incorporation of SiC particles into zinc matrix was noted. Microhardness of 166 Hv was obtained at current density of 40 mA/cm2. An average coating thickness of Zn-SiC composite coatings were measured and found 20 microns. Microhardness and corrosion properties of Zn-SiC composite coatings were improved further due to incorporation of SiC particles into zinc matrix under the optimum value of current density of 40 mA/cm2.