The Impact of Magnesium in Molten Zinc on Hot-Dip Galvanizing

Magnesium (Mg) is silvery-white in color and belongs to the hexagonal crystal system, with 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 particularly optimal when the magnesium content is between 0.024% and 0.084%. However, when the magnesium content reaches 0.3-0.5%, it causes the galvanized layer to become thicker and rougher, changing its appearance to a milky white color and increasing its brittleness, while also deteriorating its adhesion. 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 took oxygen directly from the air. Generally, magnesium is not added when producing galvanized steel pipes for water and gas transmission, unless in special circumstances.