The so-called Hot-Dip Galvanizing treatment is carried out on the surface of steel fabrications which need strong and effective protection against corrosion.
Unlike the traditional anticorrosive coatings which only cover the metal surface by passive protection, hot-dip galvanizing is carried out by dipping steel products into a molten zinc bath at 440° C, which causes a metallurgic fusion between steel and zinc, able to resist to corrosion and to mechanical stresses for a long time. The process takes place following clearly defined operational steps, as described below:
The steel materials are hung by wire and/or chains and/or tackles to the holder-girder, in order to allow their handling along all the production process.
It consists in removing oil and grease from the surface of the steel fabrication through dipping it in acidic degreasing solution with added surfactants.
it allows removing rust, calamine, processing residues, water-based paints, through dipping in aqueous solution of hydrochloric acid (HCI).
after pickling, it allows to remove all acidic residuals from the previous processes, by dipping and rinsing in water.
it is the dipping of the steel fabrications in an aqueous solution of zinc chloride and ammonium chloride.
In order to reduce the thermal shock due to dipping in the galvanizing bath, and to allow drying the flushing salts film, the steel fabrication is heated in a preheating oven at about 110°-120°C.
It consists in dipping the steel fabrication in a molten zinc bath at a controlled temperature of 440°-450° C.
It is the natural cooling in air at room temperature or in water by immersion in a separate tank.