摘要
The effect of Zn-Si3 N4 deposition prepared via direct electrolytic co-deposition on mild steel was studied as a result its inherent vulnerability to corrosion in an aggressive environment and failure on the application of load.The experiment was conducted varying the mass concentration of silicon nitride(Si3 N4)between 7 and 13 gat cell voltage of 0.3 and 0.5 V,at constant temperature of 45℃.The morphologies of the coated surfaces were characterized using high resolution Nikon Optical Microscope and Scanning Electron Microscope(SEM)revealing that the particles of the Zn-Si3 N4 were homogeneously dispersed.The corrosion behaviour was studied using potentiodynamic polarization technique in 3.65%NaCl solution and the microhardness was examined using Brinell hardness testing technique.The result of the corrosion experiment confirmed an improved corrosion resistance with a reduction in corrosion rate from 9.7425 mm/year to 0.10847 mm/year,maximum coating efficiency of 98.9%,maximum polarization resistance of 1555.3 Ω and a very low current density of 9.33 × 10-6A/cm2.The negative shift in the Ecorr revealed the cathodic protective nature of the coating.The microhardness was also found to have increased from 137.9 HBN for the unmodified steel to a maximum value of 263.3 HBN for the0.5 Zn-13 Si3 N4 coated steel representing 90.9% increment in hardness as a result of the matrix grain refining and dispersion-strengthening ability of the incorporated Si3 N4 particles.
The effect of Zn-Si3 N4 deposition prepared via direct electrolytic co-deposition on mild steel was studied as a result its inherent vulnerability to corrosion in an aggressive environment and failure on the application of load.The experiment was conducted varying the mass concentration of silicon nitride（Si3 N4）between 7 and 13 gat cell voltage of 0.3 and 0.5 V,at constant temperature of 45℃.The morphologies of the coated surfaces were characterized using high resolution Nikon Optical Microscope and Scanning Electron Microscope（SEM）revealing that the particles of the Zn-Si3 N4 were homogeneously dispersed.The corrosion behaviour was studied using potentiodynamic polarization technique in 3.65%NaCl solution and the microhardness was examined using Brinell hardness testing technique.The result of the corrosion experiment confirmed an improved corrosion resistance with a reduction in corrosion rate from 9.7425 mm/year to 0.10847 mm/year,maximum coating efficiency of 98.9%,maximum polarization resistance of 1555.3 Ω and a very low current density of 9.33 × 10-6A/cm2.The negative shift in the Ecorr revealed the cathodic protective nature of the coating.The microhardness was also found to have increased from 137.9 HBN for the unmodified steel to a maximum value of 263.3 HBN for the0.5 Zn-13 Si3 N4 coated steel representing 90.9% increment in hardness as a result of the matrix grain refining and dispersion-strengthening ability of the incorporated Si3 N4 particles.
