Handbook-Welding Ferrous Metals

4 Galvanized Steel Galvanized steel (frequently called ”galvanized iron” ) is steel which has been coated with zinc to protect it against corrosion. Most coating is done by immersing the steel sheet, pipe, or wire in a bath of molten zinc. The thickness of such hot-dip coating ranges from about 0.025 mm (0.001 in.) to 0.125 mm (0.005 in.) Galvanizing can also be done by electroplating; the thickness of the zinc coating on electroplated material will often be less than 0.025 mm (0.001 in.) AVOID INHALING ZINC FUMES! Zinc has a low melting point, about 420⁰C, and vaporizes (become gas) at a temperature (900⁰C) far below the melting point of steel. As it vaporizes, it reacts with oxygen to form fumes of white zinc oxide. If you inhale many of these fumes, you are likely to feel sick. While the sickness will pass, leaving no known lasting after-effects, it can be quite unpleasant. Therefore, when you weld galvanized steel, do it only in a well-ventilated location. If good ventilation cannot be assured, wear a respirator. Fusion Welding. Fusion weld galvanized steel exactly as you would ungalvanized steel. Be sure to clean the surfaces thoroughly. If beveling is necessary, do not hesitate to use the cutting torch, since that will remove no more zinc than will the welding operation.