Kuumakastelumenetelmä

Kuumakastelumenetelmä, also known as hot dip galvanizing, is a process used to provide corrosion protection for steel and iron by immersing the base metal in a molten zinc bath. This method creates a metallurgical bond between the zinc and the steel, forming a durable, multi-layered coating. The process typically involves several steps. First, the steel or iron components are thoroughly cleaned to remove any mill scale, rust, or contaminants. This is usually achieved through degreasing and pickling in acid solutions. After cleaning, the items are fluxed, often by immersing them in an ammonium chloride or zinc ammonium chloride solution, to ensure a clean surface for zinc adhesion.

The cleaned and fluxed articles are then dipped into a bath of molten zinc, which is maintained at a specific temperature, typically around 450 degrees Celsius (842 degrees Fahrenheit). During immersion, a reaction occurs between the molten zinc and the iron, forming a series of zinc-iron alloy layers. As the article is withdrawn from the bath, a final layer of pure zinc solidifies on top of the alloy layers, creating the characteristic bright, metallic finish. This outer layer provides sacrificial protection, meaning it will corrode preferentially before the underlying steel, thus extending the life of the component. Kuumakastelumenetelmä is widely used for items such as structural steel, guardrails, pipes, and fasteners due to its effectiveness and cost-efficiency in providing long-term corrosion resistance, especially in outdoor or harsh environments. The thickness and uniformity of the coating can be influenced by factors like the steel's composition and the immersion time.