What is the impact of magnesium in molten zinc on hot-dip galvanizing?

Magnesium (Mg), which has a silvery-white color and belongs to the hexagonal crystal system, has a relative atomic mass of 24.32, a melting point of 650°C, and a boiling point of 1120°C. The addition of magnesium to zinc improves corrosion resistance, even at concentrations of a few thousandths or even ten thousandths. The corrosion resistance is optimal when the magnesium content is between 0.024-0.084%. However, when the magnesium content reaches 0.3-0.5%, the galvanized layer's surface structure becomes thicker and rougher, the appearance turns milky white, and the hardness increases, resulting in poorer adhesion. But once the magnesium content exceeds 0.6%, the galvanized layer becomes thinner again. The addition of magnesium leads to intermediate reactions during the oxidation process of zinc, first forming magnesium oxide, which transfers oxygen to zinc more easily than if zinc directly took oxygen from the air. Generally, magnesium is not added in the production of galvanized steel pipes for water and gas transmission, unless used in special occasions.