The corrosion behavior of ZnAlMg alloys in maritime environments

Steel strip with a ZnAlMg coating presents an interesting alternative for use in construction applications in highly corrosive environments. Two ZnAlMg alloys were exposed to the atmosphere in maritime environments in Mexico, China, and Sweden for periods of up to 3 years. The exposure program included specimens fully exposed to the weather at a 45° angle and specimens under shelter at 5°. Parallel to the field exposure a cyclic corrosion test (ISO 16701) was done. After exposure, the specimens were subjected to metallographic (SEM) examination. After 1 year, the rates of corrosion were determined gravimetrically by using a pickling process to remove the products of corrosion. ZnAlMg coatings show a selective corrosion mechanism and improved corrosion resistance compared to pure Zn coatings in every investigated environment.