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

Abstract

© The Author(s) 2016. Published by ECS. All rights reserved. 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 (Na 2 Zn 3 (CO 3 ) 4 .3H 2 O) is the dominant corrosion product at low temperature, together with Na 2 ZnCl 4 · 3H 2 O and sweetite (Zn(OH) 2 ). The results are interpreted in terms of two distinct corrosion modes prevailing at "high" and "low" temperature, respectively.