Phase structure of galvanized zinc on sheet steel

A. Do you mean zinc-coated sheet steel? Formulas and thicknesses of layers make sense for galvanized steel produced by hot-dipping in molten zinc. The liquid zinc alloys with the steel (iron) to form the phases of the Fe-Zn phase diagram: Fe (containing up to 6.3 wt% Zn at its surface), Gamma (20.5-28 wt% Fe), delta (7-10% Fe), zeta-FeZn13 (6-6.2% Fe) and Zn.

The Gamma layer comprises about 1% of the coating thickness, delta about 5%, zeta about 40%, and the Zn surface layer being the remainder. There is some intermixing of the zeta and zinc phases.

A common galvanized coating specification (U. S. and EN ISO 1461) is 2 oz/square foot (600 g/sq.meter) by weight, or 0.0033 inch (85 microns) by thickness.

The American Galvanizers Association publication "Zinc Coatings" shows cross-sectional microstructures of zinc coatings: https://www.galvanizeit.org/resources/files/AGA%20PDFs/T_ZC_00.pdf

Updated URL, June 2013:
https://www.galvanizeit.org/about-hot-dip-galvanizing/what-is-hot-dip-galvanizing/the-hdg-coating/zinc-coating/

The European Galvanizers has a product fact file showing a similar Fe-Zn galvanize microstructure, with text available in 5 languages, e.g., the Spanish version at http://www.egga.com/fact/spanish/02/industry.htm

Ken Vlach [deceased]
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