Atmospheric Corrosion of Hot Dip Zinc Coated Steel in Coastal and Rural Areas of Vietnam

Abstract

The comparative results of corrosion testing in humid tropical atmosphere in rural and coastal areas forhot dipped zinc coatings are presented below. The test was conducted in outdoor conditions over a periodof five years. The mass loss and other performance characteristics of two types of zinc coatings were evaluated,analysed and discussed in relation to the climatic and environmental parameters. The corrosion rates ofthe coatings exposed to coastal conditions were about three times higher than the corrosion rates appreciatedin rural conditions. The data demonstrates that the corrosion process obeys an equation of the form M=Atn,where M is the loss of metal and t is the time of exposure. A and n are constants which values dependon the environmental characteristics and the physicochemical behavior of the corrosion products respectively. Corrosion is strongly influenced by atmospheric time of wetness (TOW) and airborne salinity. The natureand composition of corrosion products are also considered. Simonkolleite, a major crystalline phase, wasfound in the zinc corrosion products exposed to coastal conditions, while zinc hydroxide and zinc hydrosulfateare easily found in rural settings.