Effect of chloride concentration on the corrosion resistance of pure Zn metal in a 0.0626 M H2SO4 solution

The aftermath of Cl anion concentration reactions on the corrosion resistance of pure Zn metal in 0.0625 M H SO was examined by potentiodynamic polarization, optical representations, scanning electron image analysis, energy dispersive X-ray (EDX) spectroscopy, open-circuit potential analysis, X-ray diffractometry, weight loss method and X-ray fluorescence. The results show that the degradation of Zn increased with an increase in the chloride concentration from 4.089 and 0.218 mm/year to 10.085 and 4.015 mm/year (polarization and weight loss). The corrosion potential at 0.0625 M H SO to 0.0625 M H SO /0.5% NaCl concentration displayed minimal variation (−1.535 to −1.519 V), whereas a significant shift was observed for the plots at 0.0625 M H SO /1% NaCl and 0.0625 M H SO /2% NaCl (−1.384 and −0.932 V). The weight loss plot at all Cl anion concentrations displayed an ordered decrease in the corrosion rate analogous to exposure times. The scanning electron microscopic images of Zn in 0.0625 M H SO /2% NaCl solution showed significant deterioration and corrosion pits. The image at 0.0625 M H SO solution revealed limited localized and general surface deterioration, while the corresponding EDX data depict the presence of S. The Zn open-circuit potential plot from a 0.0625 M H SO solution was relatively electropositive compared to the plot from a 0.0625 M H SO /2% NaCl solution. Both plots exhibited limited reactive-inert transition properties and attained relative thermodynamic equilibrium after 600 s of exposure with final corrosion potentials of −0.91 and −0.97 V at 7,200 s. Zn was the only crystallographic phase identified on its surface before corrosion, whereas ZnS, ZnFes, ZnMnS, ZnMnFeS, and ZnMg4 corrosion products were identified after corrosion.