Evidence for an unusual temperature dependence of the atmospheric corrosion of zinc
Journal article, 2016
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.