Corrosion and corrosion products of hot dipped galvanized steel during long term atmospheric exposure at different sites world-wide

The atmospheric corrosion of hot dipped galvanized steel was studied in a wide-world exposure in Europe, East Asia and USA. The corrosion product composition, morphology and surface distribution was investigated after 0.5, 1 and 2 years exposure. The corrosion was localized for all exposure conditions with sulfate and chloride containing corrosion products(Zn(OH)2)3·ZnSO4·nH2O,NaZn4(SO4)(OH)6Cl·6H2O and Zn5(OH)8Cl2·H2O formed at the anodic sites in corrosion pits and Zn5(OH)6(CO3)2 mainly in the outer parts of the corrosion products and cathodic areas outside the pits. The content of the sulfate containing corrosion products increased in the order marine < marine/urban, marine/industrial < industrial/urban.