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 H2SO4 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 H2SO4 to 0.0625 M H2SO4/0.5% NaCl concentration displayed minimal variation (-1.535 to -1.519 V), whereas a significant shift was observed for the plots at 0.0625 M H2SO4/1% NaCl and 0.0625 M H2SO4/2% 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 H2SO4/2% NaCl solution showed significant deterioration and corrosion pits. The image at 0.0625 M H2SO4 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 H2SO4 solution was relatively electropositive compared to the plot from a 0.0625 M H2SO4/2% 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.