Evidence for an Unusual Temperature Dependence of the Atmospheric Corrosion of Zinc

M Esmaily,N Mortazavi,J E Svensson,L G Johansson

doi:10.1149/2.0751614jes

M Esmaily, N Mortazavi + Show 2 more

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https://doi.org/10.1149/2.0751614jes

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Abstract

The atmospheric corrosion behavior of zinc in the presence of NaCl has been investigated using well-controlled laboratory exposures in 95% RH air at ten different temperatures in the range −4 to 22°C. Results show that a critical temperature (∼ −0.5°C) exists in zinc corrosion above which the rate of corrosion is constant/independent of temperature, and, below which there is a positive correlation between temperature and corrosion rate. The corrosion products formed above and below −0.5°C are also entirely different. While simonkolleite, hydrozincite and zinc carbonate hydroxide are the main corrosion products at T ≥ −0.5°C, the same compounds are absent at T < −0.5°C. Instead, sodium zinc carbonate (Na2Zn3(CO3)4.3H2O) is the dominant corrosion product at low temperature, together with Na2ZnCl4·3H2O and sweetite (Zn(OH)2). The results are interpreted in terms of two distinct corrosion modes prevailing at “high” and “low” temperature, respectively.

Highlights

Zn) have numerous applications in e.g., infrastructure and engineering sectors,[1,2,3,4] where environmental degradation is often an issue
The present results show that the rate of NaCl-induced corrosion of Zn in the presence of CO2 is independent of temperature in the range −0.5–22◦C
We studied the NaCl-induced atmospheric corrosion of Zn at different temperatures in the range −4 to 22◦C

Summary

Introduction

Zn) have numerous applications in e.g., infrastructure and engineering sectors,[1,2,3,4] where environmental degradation is often an issue. Because the anodic and cathodic reactions and electrolytic conductivity are all thermally activated processes,[31,32,33] the rate of electrochemical corrosion usually increases with temperature. Gases that are adsorbed on surfaces or dissolved in the surface electrolyte play important roles, i.e., as oxidants (O2) or by reacting with the surface film (SO2, CO2). Because gas adsorption and gas dissolution are exothermic processes, the equilibrium concentration of dissolved and adsorbed gases increases with decreasing temperature. This may cause an inverse dependence of the rate of atmospheric corrosion on temperature in some cases. There is no systematic study of Zn corrosion at temperatures

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