The principle of hot-dip galvanized steel pipe and the application of galvanized steel pipe. Hot-dip galvanized steel pipe, in order to improve the corrosion resistance of steel pipe, general steel pipe is galvanized. Galvanized steel pipe is divided into two types: hot-dip galvanized and electro-galvanized. The hot-dip galvanized galvanized layer is thick, the cost of electro-galvanized is low, and the surface is not very smooth. At present, the most used are hot-dip galvanized steel pipe and hot-dip galvanized pipe.
Hot-dip galvanizing is also called hot-dip galvanizing and hot-dip galvanizing: it is an effective method of metal anti-corrosion and is mainly used in metal structural facilities in various industries. It is to immerse the rust-removed steel parts in a molten zinc solution at about 500 ° C, so that the surface of the steel parts adheres to the zinc layer, so as to achieve the purpose of anti-corrosion. Process flow of hot-dip galvanizing: pickling of finished products - washing - adding plating solution - drying - rack plating - cooling - chemical treatment - cleaning - grinding - hot-dip galvanizing is completed. So what is the principle of hot-dip galvanized steel pipe?
Principle: The hot-dip galvanized layer is formed by zinc in a high temperature liquid state in three steps:
1. The iron-based surface is dissolved by the zinc solution to form a zinc-iron alloy phase layer;
2. The zinc ions in the alloy layer further diffuse into the matrix to form a zinc-iron mutual solubility layer;
3. The surface of the alloy layer is surrounded by a zinc layer.
The hot-dip galvanized steel pipe has a thick and dense layer of pure zinc covering the surface of the steel, which can avoid the contact between the steel matrix and any corrosive solution and protect the steel matrix from corrosion. In the general atmosphere, a very thin and dense zinc oxide layer is formed on the surface of the zinc layer, which is difficult to dissolve in water, so it plays a certain protective role on the steel substrate. If zinc oxide and other components in the atmosphere form insoluble zinc salts, the anti-corrosion effect is more ideal.
The hot-dip galvanized pipe is to make the molten metal react with the iron matrix to produce an alloy layer, so that the matrix and the coating are combined. Hot-dip galvanizing is to pickle the steel pipe first. In order to remove the iron oxide on the surface of the steel pipe, after pickling, it is cleaned in the tank of ammonium chloride or zinc chloride aqueous solution or mixed aqueous solution of ammonium chloride and zinc chloride, and then sent to the in the hot dip bath. Hot-dip galvanizing has the advantages of uniform coating, strong adhesion and long service life. The matrix of the hot-dip galvanized steel pipe and the molten plating solution undergo complex physical and chemical anti-galvanizing reactions to form a corrosion-resistant zinc-iron alloy layer with a compact structure. The alloy layer is integrated with the pure zinc layer and the steel tube substrate. Therefore, it has strong corrosion resistance.
Scope of application of hot-dip galvanized pipe:
The application of hot-dip galvanizing has also expanded with the development of industry and agriculture. Therefore, hot-dip galvanized products are used in industry (such as chemical equipment, petroleum processing, marine exploration, metal structures, power transmission, shipbuilding, etc.), agriculture (such as sprinkler irrigation, heating houses), construction (such as water and gas transmission, wire sleeves, etc.) Pipes, scaffolding, houses, etc.), bridges, transportation, etc., have been widely used in recent years. Because hot-dip galvanized products have the characteristics of beautiful appearance and good corrosion resistance, their application scope is more and more extensive.