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 p roducts formed on zinc plates, using XRD (with Bragg-Brentano and graz ing incidence geometry) and SEM techniques, was carried out in marine and rural atmospheres with a humid tropical climate in southeast of Me xico. These samples were analyzed after 1, 3, 6, 9, and 12 month expos ures, for two different angles to the horizontal, 22 degrees and 45 de grees. The main phases determined were: zincite, ZnO; simonkolleite, Z n-5(OH)(8)Cl2H2O; zinc hydroxychlorosulfate, Zn-12(OH)(15)Cl-3(SO4)(3) H2O and zinc sulfate hydroxide hydrate, Zn4SO4(OH)(6)5H(2)O. The diffe rences 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 a nd dry seasons and the level of contaminants.