Effect of chloride concentration on the corrosion resistance of pure Zn metal in a 0.0626 M H2SO4 solution
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DE GRUYTER
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The aftermath of Cl− anion concentration reactions
on the corrosion resistance of pure Zn metal in 0.0625M
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 0.218mm/year to 10.085 and
4.015mm/year (polarization and weight loss). The corrosion
potential at 0.0625M H2SO4 to 0.0625M H2SO4/0.5% NaCl
concentration displayed minimal variation (−1.535 to −1.519 V),
whereas a significant shift was observed for the plots at
0.0625M H2SO4/1% NaCl and 0.0625M 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 0.0625M H2SO4/2% NaCl solution
showed significant deterioration and corrosion pits. The
image at 0.0625M 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 0.0625M H2SO4 solution was relatively
electropositive compared to the plot from a 0.0625M 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.
Keywords
TJ Mechanical engineering and machinery, TP Chemical technology