The Main Difference Between Hot Galvanized Sheet And Cold Galvanized Sheet

As a professional galvanized steel composite panel manufacturer and supplier, today we will talk about the main difference between hot-dip galvanized sheet and cold-dip galvanized sheet.

1. Hot-dip galvanized sheets generally have a thicker zinc layer, about 10um or more, and have strong anti-corrosion ability. So it is a commonly used galvanizing process. Electro-galvanizing is very thin, about 3-5um, and the hot-dip galvanized surface is rough and bright In severe cases, there are spangles, while electroplating is smooth and dull (soiled). The galvanized steel sheet manufactured by the electroplating method has good processing performance. However, the coating is thinner and the corrosion resistance is not as good as the hot-dip galvanized sheet. The cold galvanized sheet is electro-galvanized, and the amount of galvanizing is small, and only the outer pipe wall is galvanized (hot Plating---plating both inside and outside), only 10-50g/m2, its own corrosion resistance is much worse than that of hot-dip galvanized steel tube.

2. Generally there are more electro-galvanized in chemical industry, which is suitable for small parts; hot-dip galvanized sheet is generally used for power equipment and components, and is suitable for large parts and equipment. Electro-galvanization is commonly known as cold galvanized sheet. It uses an electrochemical method. The zinc ingot is used as the anode. After the zinc atoms lose electrons, they become ionic and dissolved in the electrolyte. The steel strip is used as the cathode. The zinc ions are reduced by electrons on the steel strip. Zinc-forming atoms are deposited on the surface of the steel strip to form a coating. Hot-dip galvanized steel pipes are first pickled. In order to remove iron oxide on the surface of the steel pipes, after pickling, they are cleaned in an ammonium chloride or zinc chloride aqueous solution or a mixed aqueous solution tank of ammonium chloride and zinc chloride, and then sent Into the hot dip plating tank.

3. There is a big difference in the amount of galvanizing between hot-dip galvanized sheet and electro-galvanized sheet. The galvanizing amount of hot-dip galvanized sheet can not be too small, generally the minimum is 50-60g/m2 on both sides, and the maximum is 600g/m2. The galvanized layer of electro-galvanized sheet can be very thin, the minimum is 15g/m2, but if the coating is required to be thicker, the production line speed is very slow, which does not adapt to the technological characteristics of modern units, generally the maximum is about lO0g/m2. Because of this, the production of electro-galvanized sheets is greatly restricted.

4. Hot-dip galvanized sheet and electro-galvanized sheet are fundamentally different in the structure of the coating. There is a slightly brittle compound layer between the pure zinc coating of the hot-dip galvanized sheet and the steel strip substrate. Spangles are mostly formed when the pure zinc coating is crystallized, and the coating is uniform and non-porous. The zinc atoms in the electro-galvanized layer are only deposited on the surface of the steel strip, and they are attached to the surface of the steel strip by physical action. There are many holes to dry, and it is easy to cause pitting corrosion due to corrosive media. Therefore, hot-dip galvanized sheets are better than electro-galvanized sheets. The board is more resistant to corrosion.

5. The heat treatment process of hot-dip galvanized sheet and electro-galvanized sheet are also completely different. The hot-dip galvanized sheet is generally made of chilled plate as raw material, and continuous annealing and hot-dip galvanized sheet are carried out on the galvanizing line. The steel strip is heard in a short time. It is cooled after internal heating, so the strength and plasticity are affected to a certain extent, and its stamping performance is worse than that of the same chilled plate after degreasing and annealing on a professional production line. Electro-galvanized sheet uses cold-rolled sheet as raw material, which basically guarantees the same processing performance of cold-rolled sheet, but its complicated process also increases production costs. In short, the production cost of hot-dip galvanized sheet is lower and the application range is wider, and it has become the main variety in the galvanized sheet market.

6. Hot-dip galvanized steel 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 galvanized sheet has the advantages of uniform coating, strong adhesion and long service life. Most of the regular galvanized pipe manufacturers do not use electro-galvanized (cold plating) in order to ensure quality. Only those small enterprises with small scale and outdated equipment use electro-galvanization, and of course their prices are relatively cheaper. The Ministry of Construction has officially announced that cold-galvanized steel pipes with backward technology should be eliminated, and cold-galvanized steel pipes are not allowed to be used as water and gas pipes. Generally, the galvanized sheets used today are hot-dip galvanized sheets, while the electrical ducts are cold-dip galvanized sheets, and the colors are different.

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