The hot-dip galvanizing process is based on careful and thorough chemical preparation of steel parts. Chemical cleaning of steel is a multi-stage process and has the aim of completely removing all contaminants from the surface of an oxidized and dirty part. After the surface has been prepared thoroughly, the steel permanently binds with molten zinc, forming a protective coating.
Steel products improperly protected against the action of external factors are characterized by a reduced lifetime. Among all known methods of corrosion prevention, hot-dip galvanization is considered to be the best. It is a particularly effective, durable, and the most economical method of anti-corrosion protection. Corrosion, that is, the oxidation of the iron in steel, is the phenomenon of unintended destruction of a material as a result of its reaction with the surrounding environment. Hot-dip galvanization involved immersing a properly prepared steel part in molten zinc. The temperature of the hot-dip galvanizing process is 450-460°C. At this temperature, zinc particles diffuse into the exterior layer of steel, as a result of which a strong intermolecular Fe-Zn bond is formed. Several alloy layers are formed during the process, and they are responsible for the zinc coating’s very good adhesion to the steel substrate. The exterior surface of the alloy is a coat of pure zinc. The total thickness of the coating depends on the thickness of the steel part’s material, and ranges from 45 to 280 µm. The lifetime of the zinc coat depends on factors such as: acidity of precipitation, mechanical erosion, aggression of the environment in which the galvanized structure is located, and the thickness of the zinc coat. In the case of normal, urban conditions, zinc loss is approx. 3 µm per year. The effectiveness of anti-corrosion protection under conditions of low aggression is 30 to 50 years. Advantages of hot-dip galvanization: possibility of applying zinc coat in closed spaces (e.g. pipe, tank interiors); prevention of subsurface corrosion; guarantee of high-quality appearance of the steel structure; precise and uniform coating with a layer of zinc, which can reach all hard-to-reach places; thoroughness of surface preparation for the anti-corrosion protection process thanks to complex chemical processes; decidedly greater coating thickness than in the case of other zinc coating methods, thanks to which the duration of steel’s protection against corrosion is extended many-fold; absence of the negative influence of strong impacts on steel, since the alloy layers are several times harder than it; absorption of energy from undesired impacts (zinc is a soft metal).
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