Hot-dip technology overview
Publication Date:
2017-08-08 00:00
Hot-dip coating, also known as hot dipping, involves coating a metallic material by immersing it into a lower melting point liquid metal or alloy. The main characteristic of this method is the formation of an alloy layer between the base metal and the coating metal. Therefore, hot-dip coating is made of fused metal and metallized metal. Metallized metallic materials are typically steel, cast iron, and stainless steel. The low-melting-point metal used for hot dipping includes zinc, aluminum, tin, and their alloys.
The hot-dip process is categorized into flux and hydrogen reduction methods. Among them, the hydrogen reduction method for continuous hot-dip coating of steel strip, a typical Sendzimir method and the United States method, belongs to this process. The flux method is for steel and steel structure coating. In this method, before immersion, the steel part is first cleaned and its surface is covered with a layer of flux. In the immersion area, the flux layer thermally decomposes or evaporates, allowing the fresh steel surface and molten metal to come into direct contact, resulting in a reaction and diffusion to form the coating.
The flux method includes wet and dry processes. The wet method is an earlier application. It involves immersing the cleaned steel into a flux without drying, directly into the molten metal in a hot state, but with the molten metal surface covered by a layer of molten flux. The dry process involves immersing the flux after drying and removing moisture. Because the dry process is simple and produces high-quality coatings, most hot-dip galvanized steel production uses the dry method, while the wet method is less common.