Deposition Current Density Induced Alterations in Texture and Grain Boundary Constitution of Electrodeposited Zinc Coatings for Enhanced Corrosion Resistance Performance

Zinc coatings were electrodeposited at different current densities, i.e., 30, 40, 50, 60, and 70 mA/cm². All the coatings exhibited compact and crack-free morphology. The coating electrodeposited at 50 and 30 mA/cm² current density showed the highest and lowest corrosion resistance, respectively. Corrosion current density (i_corr) and polarization resistance (R_p) values for the 50 mA/cm² deposited coating were 0.995 µA/cm² and 5268.62 Ω cm², respectively. i_corr and R_p values for 30 mA/cm² electrodeposited coating were 64.63 µA/cm² and 627.51 Ω cm², respectively. Electron backscatter diffraction analysis showed a direct correlation between the coating micro-texture and its corrosion behavior. The high corrosion resistance of coating electrodeposited at 50 mA/cm² current density was due to the presence of dominant basal plane surface texture and a higher fraction of low-energy grain boundaries. The high corrosion rate of coating deposited at 30 mA/cm² current density was due to the presence of high energy texture and large angle boundaries, which promoted corrosive media penetration through grains and grain boundaries, resulting in a higher dissolution rate.