What is hot-dip galvanized pipe?

Hot-dip galvanized pipe is a special steel pipe, its surface is covered with a layer of galvanized layer, which is mainly to improve the corrosion resistance of the steel pipe. This steel pipe is mainly divided into two types: hot dip galvanized and electric galvanized. Among them, the coating of hot galvanizing is thicker, and the cost of electric galvanizing is lower, but the surface may not be as smooth as hot galvanizing.

The production process of hot-dip galvanized pipe involves the reaction of molten metal with iron matrix to form an alloy layer. In this way, the substrate and the coating can be tightly bonded together. Specifically, the process of hot dip galvanizing begins with pickling the steel pipe to remove the iron oxide on the surface of the steel pipe. After pickling, the steel pipe is washed in an aqueous solution containing ammonium chloride or zinc chloride before being fed into a hot dip bath. The advantages of hot dip galvanizing lie in its uniform coating, strong adhesion and long service life. In this process, the steel tube matrix and the molten bath will undergo complex physical and chemical reactions to form a corrosion-resistant zinc-iron alloy layer. This alloy layer is closely combined with the pure zinc layer and the steel tube matrix, and therefore has strong corrosion resistance.

In practical applications, the iron pipes commonly used in gas, greenhouses and heating systems are also galvanized. However, when the galvanized pipe is used as a water pipe, a large amount of rust and scale may be produced in the pipe. This will not only contaminate the sanitary ware, but also may breed bacteria because the tube walls are not smooth. In addition, rust may also lead to high levels of heavy metals in water, posing a serious threat to human health. Therefore, from the 1960s and 1970s, developed countries in the world began to develop new pipes and gradually banned the use of galvanized pipes. China's Ministry of Construction and other relevant departments also issued a clear document in 2000, prohibiting the use of galvanized pipes. Now, the cold water pipe in the new community has rarely used galvanized pipe, but the hot water pipe in some communities still uses galvanized pipe.