What is the inherent difference between electro-galvanizing and hot-dip galvanizing (hot-dip galvanizing)?

Electro-galvanized

　　 Steel is easy to rust in the air, water or soil, and even completely damaged. The annual steel loss due to corrosion accounts for about 1/10 of the entire steel output. On the other hand, in order to make the surface of steel products and parts have a certain special function, and at the same time give them a decorative appearance, electrogalvanized steel is generally used. Way to deal with it.

1. Principle:

　 Because zinc is not easy to change in dry air, and in humid air, a very dense basic zinc carbonate film can be formed on the surface, which can effectively protect the interior from corrosion. And when for some reason, the plating layer is destroyed and the steel substrate is not too large to be exposed, the zinc and the steel substrate form a micro-battery, and the steel substrate becomes the cathode and is protected.

Two, performance characteristics:

　1. The zinc coating is thick, with fine crystals, uniformity and no porosity, and good corrosion resistance;

　2. The zinc layer obtained by electroplating is relatively pure, and corrodes slowly in the mist of acid, alkali, etc., and can effectively protect the steel substrate;

　3. The zinc coating is passivated by chromic acid to form white, colorful, military green, etc., which is beautiful and decorative;

　4. Because the zinc coating has good ductility, it can be cold stamped, rolled, bent and other forming without damaging the coating.

3. Application range: (Guide: Hardware knowledge: Introduction to basic knowledge of aluminum)

　　 With the development of scientific and technological production, the electroplating industry involves more and more fields. At present, the application of electro-galvanization has spread to various production and research departments of the national economy. For example, machine manufacturing, electronics, precision instruments, chemicals, light industry, transportation, weapons, aerospace, atomic energy, etc., are of great significance in the national economy.

Hot-dip galvanizing:

1. Overview:

　　 Among various coating methods for protecting steel substrates, hot-dip galvanizing is a very good one. It is when the zinc is in a liquid state, after quite complex physical and chemical actions, not only a thicker pure zinc layer is plated on the steel, but also a zinc-iron alloy layer is formed. This plating method not only has the corrosion resistance characteristics of electro-galvanization, but also has a zinc-iron alloy layer. It also has strong corrosion resistance unmatched by electro-galvanizing. Therefore, this plating method is particularly suitable for a variety of strong acid, alkali mist and other strong corrosive environments.

2. Principle: The hot-dip galvanizing layer is formed by zinc in a high temperature liquid state in three steps:

1. The surface of the iron base is dissolved by the zinc solution to form a zinc-iron alloy phase layer;

2. The zinc ions in the alloy layer further diffuse to the substrate to form a zinc-iron mutual dissolving layer;

3. The surface of the alloy layer is surrounded by a zinc layer.

Three, performance characteristics:

(1) With a thick and dense pure zinc layer covering the surface of the steel, it can avoid the contact of the steel substrate with any corrosive solution and protect the steel substrate 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 has a certain protective effect on the steel substrate. If zinc oxide and other components in the atmosphere form insoluble zinc salt, the corrosion protection effect is more ideal.

(2) With iron-zinc alloy layer, combined with compactness, it exhibits unique corrosion resistance in marine salt spray atmosphere and industrial atmosphere;

(3) Because of the firm bonding, zinc and iron are mutually soluble, and have strong wear resistance;

(4) Because zinc has good ductility and its alloy layer is firmly attached to the steel base, hot-dip galvanized parts can be formed by cold punching, rolling, wire drawing, and bending without damaging the coating;

(5) After hot-dip galvanizing of steel structural parts, it is equivalent to one annealing treatment, which can effectively improve the mechanical properties of the steel matrix, eliminate the stress during forming and welding of steel parts, and is beneficial to turning the steel structural parts.

(6) The surface of the parts after hot-dip galvanizing is bright and beautiful.

(7) The pure zinc layer is the most plastic galvanized layer in hot-dip galvanizing. Its properties are basically close to pure zinc, and it has ductility, so it is rich in flexibility.

Four, the scope of application:

　　The application of hot-dip galvanizing has expanded with the development of industry and agriculture. Therefore, hot-dip galvanized products are used in industries (such as chemical equipment, petroleum processing, ocean exploration, metal structures, power transmission, shipbuilding, etc.), agriculture (such as sprinkler irrigation, warm rooms), construction (such as water and gas transmission, wire sets) Pipes, scaffolding, houses, etc.), bridges, transportation, etc., have been widely used in recent years. As hot-dip galvanized products have the characteristics of beautiful appearance and good corrosion resistance, their application scope is becoming more and more extensive.

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