Long-term atmospheric corrosion rates of hot dip galvanised steel and zinc-aluminium-magnesium coated steel

• Zn coated steel (Z) and ZnAlMg coated steel (ZM3.7/3 = Zn–Al (3.7 wt.%)-Mg (3.0 wt.%)) have been exposed for 6 years at twelve different weathering sites world wide. The mass loss of the coatings have been measured after 1, 2, 4, and 6 years exposure. From the results, it is shown that ZM3.7/3 had always a better corrosion performance compared to Z. The ratio of performance after 6 years of exposure varied from about 1.4 to 4.4 with a mean value of 2.8. At temperate marine sites (e.g., temperature between 9–20°C) with low to moderate SO 2 pollution a good relationship was observed between the relative performance of ZM3.7/3 and the corrosion rate of Z. It was thus concluded that ZM3.7/3 has a better relative performance in harsh environments. The corrosion performance of ZM3.7/3 was shown to be connected to the formation of protective corrosion products.

Nyckelord

atmospheric corrosion

hot dip galvanized steel

zinc

zinc aluminium magnesium

Aluminum alloys

Aluminum coated steel

Aluminum coatings

Aluminum corrosion

Corrosion protection

Corrosion rate

Galvanizing

Magnesium alloys

Marine pollution

Pollution induced corrosion

Seawater corrosion

Weathering steel

Coated steel

Corrosion performance

Corrosion products

Galvanised steel

Harsh environment

Hot dip galvanized steels

Relative performance

Zinc aluminiums

Steel corrosion

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