Principle of hot-dip galvanized pipe

Hot-dip galvanizing is the reaction of a molten metal with an iron matrix to produce an alloy layer, thereby combining the substrate and the plating. Hot-dip galvanizing is the first step of pickling steel parts in order to remove iron oxide on the surface of steel parts. After pickling, it is cleaned by ammonium chloride or zinc chloride aqueous solution or mixed solution of ammonium chloride and zinc chloride. And then sent to the hot dip plating tank. Hot-dip galvanizing has the advantages of uniform plating, strong adhesion and long service life.

Hot dip zinc:
I. Overview:
Hot dip galvanizing is a very excellent one in various coating methods for protecting steel substrates. It is not only plated with a thick layer of pure zinc on the steel, but also a layer of zinc-iron alloy after a relatively complicated physical and chemical action in the state of zinc being liquid. This plating method not only has the corrosion resistance characteristics of electrogalvanizing, but also has a zinc-iron alloy layer. It also has strong corrosion resistance that cannot be compared with electrogalvanized. Therefore, this plating method is particularly suitable for use in various strong corrosive environments such as strong acid and alkali mist.
Second, the principle: the hot-dip galvanizing layer is formed in three steps under high temperature liquid state:
1. The iron-based surface is dissolved by the zinc liquid 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 solution layer;
3. The surface of the alloy layer is covered with a zinc layer.

Third, the performance characteristics:
(1) A thick, dense layer of pure zinc is applied over the surface of the steel to prevent contact of the steel substrate with any corrosive solution and to protect the steel substrate from corrosion. In the general atmosphere, the surface of the zinc layer forms a very thin and dense surface of the zinc oxide layer, which is difficult to dissolve in water, so it plays a protective role on the steel substrate. If zinc oxide forms an insoluble zinc salt with other components in the atmosphere, the corrosion resistance is more desirable.
(2) It has an iron-zinc alloy layer, which combines compactness and exhibits special corrosion resistance in marine salt spray atmosphere and industrial atmosphere;
(3) Due to the strong bonding, zinc-iron is mutually soluble and has strong wear resistance;
(4) Since zinc has good ductility, its alloy layer adheres firmly to the steel base, so the hot-dip parts can be cold-drawn, rolled, drawn, bent, etc. without damaging the plating;
(5) After hot-dip galvanizing of steel structural parts, it is equivalent to one-time annealing treatment, which can effectively improve the mechanical properties of the steel matrix, eliminate the stress during the forming and welding of steel parts, and facilitate the turning of steel structural parts.
(6) The surface of the hot-dip galvanized part is bright and beautiful.
(7) The pure zinc layer is the most plasticized galvanized layer in hot-dip galvanizing. Its properties are basically close to pure zinc and it is malleable, so it is flexible.

Fourth, the scope of application:
The application of hot-dip galvanizing has also expanded correspondingly 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 (eg sprinkler irrigation, boudoir), construction (eg water and gas transportation, wire sets) Pipes, scaffolding, houses, etc., bridges, transportation, etc. have been widely adopted in recent years. Since the hot-dip galvanized products have the characteristics of beautiful appearance and good corrosion resistance, the application range thereof is more and more extensive.