Flux compositions for steel galvanization

This invention relates to a flux composition for treating a metal surface prior to batch hot galvanizing in molten zinc-based alloys. The composition comprises (a) more than 40 and less than 70 wt.% zinc chloride, (b) 10 to 30 wt.% ammonium chloride, (c) more than 6 and less than 30 wt.% of a set of at least two alkali or alkaline earth metal halides, (d) from 0.1 to 2 wt.% lead chloride, and (e) from 2 to 15 wt.% tin chloride, provided that the combined amounts of lead chloride and tin chloride represent at least 2.5 wt.% of said composition. The invention further relates to a fluxing bath comprising this flux composition dissolved in water for use in galvanizing processes, by batch or continuously, of metal articles such as iron or steel long products and flat products, thus affording a protective coating layer with a thickness ranging from 5 to 30 µm.