Study of the composition and morphology of initial stages of corrosion products formed on Zn plates exposed to the atmosphere of southeast Mexico

A year-long study of the composition and morphology of the corrosion products formed on zinc plates, using XRD (with Bragg-Brentano and grazing incidence geometry) and SEM techniques, was carried out in marine and rural atmospheres with a humid tropical climate in southeast of Mexico. These samples were analyzed after 1, 3, 6, 9, and 12 month exposures, for two different angles to the horizontal, 22° and 45°. The main phases determined were: zincite, ZnO; simonkolleite, Zn5(OH)8Cl2H2O; zinc hydroxychlorosulfate, Zn12(OH)15Cl3(SO4)3H2O and zinc sulfate hydroxide hydrate, Zn4SO4(OH)65H2O. The differences in the development and morphology of the phases formed, on the skyward and groundward faces, are analyzed. The film of the corrosion products is very sensitive to the environmental conditions, as rainy and dry seasons and the level of contaminants.