Hot-Dip Galvanization
Hot-dip galvanization is a corrosion-resistant treatment for steel, applied by immersing pre-treated items into a bath of molten zinc.
The purpose of this process is to provide the product with highly effective protection, significantly slowing down the corrosion process and ensuring long-term integrity.
It is important to emphasize that galvanization, by multiplying the useful life of a product several times, effectively reduces the environmental impact.
With the hot-dip galvanization process, the zinc coating that covers the steel is not just a simple protective film. During immersion in molten zinc, a true iron-zinc alloy is formed, which is strongly bonded to the steel and can only be removed by robust mechanical action or highly acidic solutions.
Hot-dip galvanization protects steel structures for a period that often exceeds the useful life cycle of the structures themselves; it also plays a positive role in reducing the environmental load over time and is eco-friendly. By protecting the steel from corrosion, it preserves the design characteristics of a structure, increasing its safety; it has a low initial cost compared to other anti-corrosion systems and does not require maintenance for decades, thus significantly reducing the overall cost of the structure over time.
The hot-dip galvanization treatment consists of the following phases:
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1. Identification and Hooking of Material
Incoming material is identified by assigning a batch number. Each batch is hooked using wire or special equipment to numbered balancing devices, which transport the material through the entire process.
2. Chemical Treatment:
Degreasing
The steel items are immersed in tanks containing aqueous solutions of surfactants at a concentration of approximately 10%. The purpose of this phase is to remove oils and greases left from previous mechanical processes. The solution is replenished with water and surfactants.
Pickling
The steel items are immersed in tanks containing aqueous hydrochloric acid solutions. The purpose of this phase is to remove iron oxides from the surface of the parts, which are generated during the production and processing of steel.
The solution is replenished with water, commercial hydrochloric acid, and corrosion inhibitors.
Washing
The steel items are immersed in tanks containing water. The purpose of this phase is to remove residual pickling solution to reduce the carryover of ferrous chloride, a byproduct of iron oxide dissolution, into the fluxing phase. Solutions are periodically corrected by adding water.
Fluxing
The steel items are immersed in a tank containing an aqueous solution enriched with zinc chloride and ammonium chloride salts.
This phase coats the surface of the pieces with a protective salt film, preventing any oxidation that would hinder the galvanization process.
The solution is replenished with water and zinc chloride and ammonium chloride salts.
3. Preheating Furnace
After fluxing, the parts are placed in a ventilated chamber where the material is heated before being galvanized.
4. Hot-Dip Galvanization
This process involves immersing steel items in a bath containing molten zinc.
The indicative temperature of the zinc is 450°C.
The zinc bath level is adjusted daily by adding zinc and alloys in accordance with UNI EN ISO 1461 and its related references.
Unless otherwise agreed with the customer, the coating thickness is applied in accordance with UNI EN ISO 1461:2022.