Atmospheric corrosion of ZnAlMg coated steel during long term atmospheric weathering at different worldwide exposure sites

摘要

The atmospheric corrosion of zinc aluminium magnesium (ZnAlMg) coated steel was studied in a worldwide exposure in Europe, East Asia and USA. The mass loss of ZnAlMg coated steel was about 2-3 times lower compared to hot dipped galvanised steel (HDG) after 4 years exposure. The corrosion of ZnAlMg coated steel was highly localised with selective corrosion attacks in the eutectic phases of the coating. Sulfate and chloride containing corrosion products were formed in the corrosion pits while zinc hydroxy carbonate and carbonate containing layered doubly hydroxides (LDH) formed mainly in the outer parts of corrosion attacks.