Steel can easily rust in air, water or soil, or even be completely damaged. The annual loss of steel 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 the surface a decorative appearance, electro-galvanized steel is generally used. way to deal with it.
Frist, principle:
Since 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 coating is damaged and the steel base that is not too large is exposed, the zinc and the steel base form a micro-battery, and the steel base becomes a cathode and is protected.
Second, the performance characteristics:
1. The zinc coating is thick, the crystals are fine, uniform and no pores, and the corrosion resistance is good;
2. The zinc layer obtained by electroplating is relatively pure, and corrodes slowly in the mist such as acid and alkali, which 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 has a certain decorative effect;
4. Due to the good ductility of the zinc coating, various forming such as cold punching, rolling and bending can be carried out without damaging the coating.
Third, scope of application:
With the development of scientific and technological production, the fields involved in the electroplating industry are more and more extensive. At present, the application of electrogalvanizing has spread to various production and research departments of the national economy. For example, machine manufacturing, electronics, precision instruments, chemical industry, light industry, transportation, weapons, aerospace, atomic energy, etc., have great significance in the national economy.
Frist, overview:
Among various coating methods for protecting steel substrates, hot-dip galvanizing is a very good one. It is in the liquid state of zinc, after quite complex physical and chemical action, not only a thick pure zinc layer is plated on the steel, but also a zinc-iron alloy layer is formed. This kind of plating method not only has the corrosion resistance characteristics of electro-galvanizing, but also has a zinc-iron alloy layer. It also has strong corrosion resistance unmatched by electro-galvanizing. Therefore, this plating method is especially suitable for strong corrosive environments such as various strong acids and alkali mists.
Second, principle:
The hot-dip galvanizing 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 to the matrix to form a zinc-iron mutual soluble layer;
3. The surface of the alloy layer is surrounded by a zinc layer.
Third, performance characteristics:
(1) It has a thick and dense pure zinc layer covering the steel surface, which can avoid the contact between the steel matrix and any corrosive solution and protect the steel matrix from corrosion. In the general atmosphere, the surface of the zinc layer forms a very thin and dense zinc oxide layer surface, 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.
(2) It has an iron-zinc alloy layer, which is densely combined and exhibits unique corrosion resistance in marine salt spray atmosphere and industrial atmosphere;
(3) Due to the firm bonding, zinc-iron is mutually soluble and has strong wear resistance;
(4) Due to the good ductility of zinc, its alloy layer is firmly attached to the steel base, so the hot-dip galvanized parts can be formed by cold punching, rolling, wire drawing, bending, etc. without damaging the coating;
(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 forming and welding of the steel parts, and facilitate the turning of 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 is ductile, so it is full of flexibility.
Fourth, the scope of application:
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.