Galvanizing process
Preparation
Initial phase of the process in which the steel products are hung on special equipment by means of iron wire and then continue with the production cycle and be galvanized.
Degreasing - Pickling - Flushing
The material is cleaned of carpentry oils and greases and subsequently pickled. The first operation to be carried out is degreasing which consists in immersing the products in an acid solution at high temperatures of about 60 ° / 70 °, for the elimination of oils and fats.
After this phase lasting about two hours, the material removed from the tank and allowed to drain, is then immersed in water for a rinse and then proceeds with immersion in pickling tanks, composed of hydrochloric acid and water (HCL-H2O ). This step can last from two to four hours and is the most important operation where the surface of the steel product is freed from oxides, rust and residual calamine from the translation and rolling processes.
After a further washing in water, we proceed with the last procedure: flushing. By immersing the material in a solution composed of zinc salts and ammonium salts at about 50 °, a uniform film is formed that prevents oxidation until the moment of immersion in the molten zinc and improves the zinc-iron reaction.
Drying
The drying of the pieces in a special oven at about 70 ° / 80 °, before galvanizing, causes a lowering of the thermal inertia which improves the Zn-Fe reaction allowing to reduce the immersion times in the molten zinc.
Galvanizing
Most delicate phase of the whole hot dip galvanizing cycle.
The objects to be galvanized are immersed in molten zinc at a temperature ranging from about 440 ° to 460 °, with a zinc purity that never falls below the threshold set by the UNI EN ISO 1179 standard.
The immersion speed is also different, in relation to the size and shape of the pieces and as this operation proceeds, the zinc and ammonium salts perform a final pickling action.
Cooling and controls
The hot dip galvanizing cycle ends immediately after the extraction, with the cooling in air or in water of the steel products.
We then proceed with a visual check of the material and a mechanical check with a device (thickness gauge) to check the thickness of the zinc, which can vary according to the thickness of the object.
Once all the checks have been carried out and the material has been packed, the products are ready for delivery.