Atmospheric corrosion of zinc in coastal atmospheres

The atmospheric corrosion of zinc in pure marine coastal atmospheres has not been extensively studied. This paper presents the results obtained in six pure marine atmospheres located at different distances from the seashore in the same coastal area with annual chloride deposition rates of between 47 and 1142 mg · m−2 · day−1. Zinc specimens were exposed for 3, 6, 9, and 12 months in two annual exposure sequences starting 6 months apart. Tests were performed to determine the corrosion rate and its evolution with exposure time. Quantitative (Rietveld) grazing X‐ray diffraction and X‐ray photoelectron spectroscopy (C 1s) were applied to analyze the corrosion products formed. Scanning electron microscopy/energy dispersive X‐ray spectrometry were employed to study the morphology of the corrosion layers. The most relevant findings of this study are: (a) the presence of hydrozincite [Zn5(CO3)2(OH)6]; (b) the aqueous precipitation can be a major controlling factor of the atmospheric corrosion of zinc in atmospheres with low chloride deposition rates (30–50 mg · m−2 · day−1); and (c) the formation of zinc hydroxysulfates also takes place due to the presence of sulfate ions in the marine aerosol.