The humid tropical climate parameters and airborne salinity are generally considered important factors affecting detrimental corrosion of zinc and its alloy coatings. To more thoroughly understand their corrosion performances, the five years weathering tests for zinc and Zn-Al galvanized steels in rural and coastal humid tropical areas were conducted. Corrosion rates and other performance characteristics of zinc and Zn-Al coated samples were determined and discussed in relation with climatic and environmental parameters. Behavior of the coatings in rural and coastal tropical conditions revealed a strong influence of time of wetness (TOW) and airborne salinity on corrosion rates. In both test conditions, the dependence of coating’s mass loss on exposure time shows that the corrosion process of zinc coatings mostly obeys the law of power model M = Atn. Corrosion is recorded considerably stronger in the coastal atmosphere containing higher chlorides. The laboratory observation in cut-edge area of zinc alloys coated steel was also conducted and their corrosion behavior was detailed in condition of chloride ions attack.
UNDERSTANDING CORROSION BEHAVIOR OF Zn AND Zn ALLOY GALVANIZED STEELS IN HUMID TROPICAL CLIMATE