Mechanisms of Atmospheric Corrosion of ZnMgAl Coated Steel in Chloride and Sulphur Dioxide Containing Environments

摘要

Zinc-based coatings alloyed with small amount of magnesium and aluminium show superior corrosion resistance compared to conventional zinc coated steel under some conditions. Application of the new coatings in a wider range of environments requires a better understanding of the corrosion behaviour and corrosion mechanisms in environments containing different corrosion stimulating species, such as chloride and sulphur dioxide SO_2. In this work, the atmospheric corrosion of ZnMgAl coated steel was studied upon exposure to humid air containing chloride or SO_2 with addition of NO_2. The corrosion products formation on ZnMgAl surfaces with and without pre-deposited NaCl was investigated with in situ Infrared Reflection Absorption Spectroscopy (IRRAS), and complementaryex situ analysis was performed by X-ray diffraction and SEM/EDS. The results are compared to that obtained on conventional hot-dip galvanised steel and/or electro-galvanised steel.