What impact does zinc dross have on the galvanized layer of galvanized steel pipes?

During hot-dip galvanizing, zinc dross in molten zinc is mixed within the zinc bath and becomes embedded in the galvanized layer after coating the steel pipe. Surrounded by pure zinc, these zinc dross particles adhere to the pure zinc layer. Additionally, the increased iron content in the molten zinc reduces its wettability to the surface of the steel pipe billet, resulting in uneven distribution of the galvanized layer. Consequently, the galvanized layer surface becomes rough and uneven, with the appearance of dull spots, and in severe cases, large and small zinc tumors may form. Zinc dross increases the brittleness of the pure zinc layer, causing the galvanized layer to peel off when bent; it also leads to false termination points during copper sulfate testing. We know that the more impurities in the pure zinc layer, the less corrosion-resistant it becomes. Similarly, zinc dross included in the pure zinc layer can produce a micro-galvanic effect, corroding the surrounding pure zinc layer first. An increase in the amount of zinc dross results in a thicker galvanized layer, thereby increasing zinc consumption. For example, when the immersion time is 30 seconds and the molten zinc temperature is 450°C, the weight of the galvanized layer on the steel pipe is 330 grams per cubic meter when the iron content in the molten zinc is 0.06%; when the iron content in the molten zinc increases to 0.25%, the weight of the galvanized layer on the steel pipe increases to 450 grams per cubic meter.