TIGGalvanized and coated steels are frequently welded and the TIG process may be used for this, particularly for welding thin sheet. Standard TIG equipment is suitable and DCEN would be the preferred polarity and argon the preferred shielding gas. A mild steel filler rod closely matching the parent steel plate would normally be selected. However, TIG welding galvanized steel and coated steels presents problems. With galvanizing porosity is a major problem, especially in fillet welds, spatter particles can contaminate the tungsten electrode, and the zinc boils off giving zinc oxide fume. Similar problems are also present when welding over other coatings, and some of the fume emitted can be very toxic. Many of the problems can be overcome by removing the coating from the area of the weld before welding, and then re-coating after welding to restore the corrosion resistance. Without such practices TIG welding over coatings can be very difficult. The main safety issues are potentially toxic fume, electrical, radiation, spatter, and compressed, inert, gas.
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