Chemistry of corrosion products on Zn–Al–Mg alloy coated steel

• Published in: Corrosion science Vol. 52; no. 10; pp. 3271 - 3279
• Main Authors: Schürz, S., Luckeneder, G.H., Fleischanderl, M., Mack, P., Gsaller, H., Kneissl, A.C., Mori, G.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01-10-2010; Elsevier
• Subjects: A. Alloy; A. Magnesium; A. Metal coatings; A. Zinc; Alloy steels; Applied sciences; B. XPS; Carbonates; Coating; Corrosion; Corrosion environments; Corrosion products; Exact sciences and technology; Magnesium; Metallic coatings; Metals. Metallurgy; Production techniques; Protective coatings; Steels; Surface treatment; Zinc; Zinc base alloys; B. XPS; A. Magnesium; A. Metal coatings; A. Alloy; A. Zinc; Zinc base alloys; Aluminium base alloys; Aluminium alloy; Corrosion product; Surface treatment; Metal coating; Corrosion; Magnesium alloy; Photoelectron spectrometry
• ISSN: 0010-938X; 1879-0496
• DOI: 10.1016/j.corsci.2010.05.044

Zn–Al–Mg alloy (ZM) coating provides a decisively enhanced corrosion resistance in a salt spray test according to DIN EN ISO 9227 (NSS) compared to conventional hot-dip galvanised zinc (Z) coating because of its ability to form a very stable, well adherent protecting layer of zinc aluminium carbonate hydroxide, Zn
6Al
2(CO
3)(OH)
16·4H
2O on the steel substrate. This protecting layer is the main reason for the enhanced corrosion resistance of the ZM coating. Surface corrosion products on ZM coated steel consist mainly of Zn
5(OH)
6(CO
3)
2, ZnCO
3 and Zn(OH)
2 with additions of Zn
5(OH)
8Cl
2
·
H
2O and a carbonate-containing magnesium species.