Hot deep galvanizing consists in immersing steel objects in a bath of molten zinc, kept at an average temperature of 450 °C, that coats the steel with a thin and resistant zinc layer. Thanks to the pre-treatment in a bath of molten salts of zinc chloride and ammonium chloride, the steel binds to the zinc, conferring a much higher resistance to corrosion compared to electro galvanizing. This greater mechanical resistance is also effective against salt and galvanic currents. Pursuant to UNI EN ISO 1461 standard, the process consists of the following phases:
1) degreasing and pickling, using surface-active agents and hydrochloric acid;
2) fluxing by immersion in ammonium chloride and zinc chloride solution;
3) galvanization through immersion, after pre-heating at 100°C, in molten zinc vat at 450°C, for the time required for the steel to reach the same temperature of the zinc;
4) cooling in air or water, followed by an eventual passivation treatment.
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