Ferrous product having an alloy coating thereon of aluminium-zinc-magnesium-silicon, and method.

摘要

A coated ferrous article with improved properties, e.g., improved overall corrosion resistance and good appearance has a ferrous substrate and a ductile, adherent, corrosion resistant alloy coating metallurgically bonded to the substrate. The alloy coating has a thin intermetallic alloy layer intermediate the substrate and an alloy overlay. The alloy overlay consists essentially of, by weight, magnesium from 3% to 20%, silicon from 3% to 15%, balance aluminum and zinc, where the is between 1 and 1.5. The metallurgical structure of the overlay is a mixture of (1) cored aluminum-rich dendrites having dendrite arm spacings (DAS) of less than 10 µm, (2) zinc-rich interdendritic regions, and (3) intermetallic phases of zinc, aluminum, magnesium and silicon. The article may be produced by hot dip coating a ferrous substrate in a molten metal bath of the above composition.