Long‐term atmospheric corrosion rates of Zn55Al‐coated steel

Hot‐dip Zn55Al‐coated steel samples have been exposed for up to 6 years at 11 different weathering sites, including marine, marine‐industrial, acid‐rain and dry atmospheres. From the mass loss measurements, Zn55Al metallic coating showed globally long‐term good corrosion resistance in all weathering...

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Bibliographic Details
Published in:Materials and corrosion 2024-06, Vol.75 (6), p.694-704
Main Authors: Thierry, Dominique, Persson, Dan, LeBozec, Nathalie
Format: Article
Language:English
Subjects:
Acid rain
Aluminum alloys
Aluminum coated steel
Aluminum coatings
Aluminum corrosion
Aluminum sulfate
Atmospheric corrosion
Atmospheric corrosion rates
Binary alloys
Coated steel
Corrosion products
Corrosion rate
Corrosion resistance
Corrosion resistant coatings
Corrosion resistant steels
Dry atmospheres
Hot dips
hot-dip zinc-coated steel
Hot-dip zincs
Immersion coating
Mass-loss measurement
Seawater
Seawater corrosion
Steel corrosion
Steel samples
Sulfur compounds
Weathering
Zinc
Zinc alloys
zinc aluminium
Zinc coatings
Zinc-coated steel
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Summary:Hot‐dip Zn55Al‐coated steel samples have been exposed for up to 6 years at 11 different weathering sites, including marine, marine‐industrial, acid‐rain and dry atmospheres. From the mass loss measurements, Zn55Al metallic coating showed globally long‐term good corrosion resistance in all weathering conditions compared with hot‐dip Zn‐0.2Al‐coated steel (Z). Yet, weaker performance was observed on Zn55Al in high SO2 polluted atmosphere, particularly when combined with seawater aerosols. This is explained by a more acidic surface condition linked to high SO2. Although the extent of corrosion in this phase was different at the different sites, the final corrosion products formed after 6 years were rather similar at all sites. This consists of hydrous aluminium sulphate or hydrous aluminium hydroxy sulphate and, probably also a smaller amount of sulphate‐containing zinc corrosion products or Al/Zn products. The scanning electron microscopy‐energy dispersive X‐ray spectroscopy (SEM‐EDS) cross‐section observation of Zn55Al‐coated steel exposed in Qingdao (China) shows that zinc‐rich phases are preferentially attacked with the formation of sulphur‐containing corrosion products.
ISSN:0947-5117
1521-4176
1521-4176
DOI:10.1002/maco.202314209