Kuumalämpögalvanointi

Kuumalämpögalvanointi, also known as hot-dip galvanizing, is a corrosion protection process for steel and iron. It involves immersing a fabricated steel item into a bath of molten zinc. Before the immersion, the steel undergoes a series of cleaning steps, typically including degreasing, pickling in acid to remove mill scale and rust, and a fluxing step to ensure proper wetting by the molten zinc.

During the immersion in the molten zinc bath, which is usually around 450 degrees Celsius (840 degrees Fahrenheit), a metallurgical reaction occurs between the iron in the steel and the molten zinc. This reaction forms a series of zinc-iron alloy layers bonded to the steel substrate, with a pure zinc outer layer. This creates a robust, abrasion-resistant coating that offers excellent protection against corrosion.

The galvanizing process provides both barrier protection, physically separating the steel from the corrosive environment, and sacrificial protection. If the coating is scratched or damaged, the zinc will corrode preferentially to the steel, protecting it from rust. The thickness and uniformity of the coating depend on factors such as the steel's surface condition, the zinc bath temperature, and the immersion time. Kuumalämpögalvanointi is widely used for structural steel, fasteners, automotive parts, and many other applications where long-term corrosion resistance is required.