By first fluxing a steel long product with novel specific flux compositions, it is possible to continuously produce, more uniform, smoother and void-free galvanized coatings on such steel long products in a single hot dip galvanization step making use of zinc-aluminum alloys or zinc-aluminum-magnesium alloys with less than 95 wt. % zinc. This is achieved by providing potassium and sodium chlorides in a KCl/NaCl weight ratio of at least 2.0 in a flux composition comprising (a) more than 40 and less than 70 weight % zinc chloride, (b) from 10 to 30 weight % ammonium chloride, (c) more than 6 and less than 30 weight % of a set of at least two alkali metal chlorides.