Specific metallurgical aspects when welding steels protected by hot-dip galvanizing

Hot-dip galvanizing is the most effective method of anti-corrosion protection of steel structures, achieved by the diffusion of zinc into the base steel during immersion in a molten zinc bath. The predictability and sustainability qualities brought by hot dip galvanizing together with the assertion that almost all the con- struction of steel structures that reach the galvanizing sections includes welding joints are emphasized, too. It is shown through the equilibrium diagrams (Fe-C and Fe-Zn) and the annealing graphs the way the working temperature for hot-dip galvanizing process interferes with the stability and mechanical properties of the steel. The existence of variations of zinc layers thicknesses that occur between the base material (the used steel for construction) and the added material used for welding is identified. The relationship between the holding time in the molten zinc bath, the silicon concentration contained in the added welding material and the layers thickness in the welded seam area is graphically presented. As additions, are presented data regarding the importance of proper welding, the adhesion of the zinc layer and the appearance of the surface after galvanizing.