The difference between electro-galvanizing and hot-dip galvanizing

1. The zinc layer of hot-dip galvanized sheet is generally thicker, about 10um or more, and the anti-corrosion ability is strong. Therefore, it is a commonly used galvanizing process. The electro-galvanized sheet is very thin, about 3-5um, and the surface of hot-dip galvanizing is rough and bright. , In severe cases, there are zinc flowers, and the electroplating is smooth and dark (stained).

The galvanized steel coil produced by the electroplating method has good processing performance. However, the coating is thin and the corrosion resistance is not as good as that of the hot-dip galvanized sheet. Galvanized --- both inside and outside), only 10-50g/m2, its own corrosion resistance is much different than that of hot-dip galvanized sheet tube.

2. In chemical industry, there are many electro-galvanized sheets, which are suitable for small parts; hot-dip galvanized sheets are generally used for electrical equipment and components, and are suitable for large parts and equipment.

Electrogalvanizing, commonly known as cold galvanized sheet, is an electrochemical method. The zinc ingot is used as the anode. After the zinc atom loses electrons, it becomes an ionic state and dissolves into the electrolyte. The steel strip is used as the cathode, and the zinc ions are reduced by electrons on the steel strip. Zinc atoms are deposited on the surface of the steel strip to form a coating.

The hot-dip galvanized sheet 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 a tank of ammonium chloride or zinc chloride aqueous solution or a mixed aqueous solution of ammonium chloride and zinc chloride, and then sent to the hot-dip galvanized sheet. into the hot dip bath.

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 cannot be too small, generally the minimum is 50-60g/m2 on both sides, and the maximum can reach 600g/m2. The galvanized layer of the electro-galvanized sheet can be very thin, the minimum is 15g/m2, but if the coating is thicker, the production line speed is very slow, which is not suitable for the technological characteristics of modern units, generally the maximum is about 100g/m2. Because of this, the production of electro-galvanized sheet 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. When the pure zinc coating is crystallized, most of the zinc flowers are formed, and the coating is uniform and free of pores. The zinc atoms of the electro-galvanized layer are only deposited and precipitated on the surface of the steel strip, and 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, the hot-dip galvanized sheet is more than electro-galvanized. Plates are more resistant to corrosion.

5. The heat treatment process of hot-dip galvanized sheet and electro-galvanized sheet is also completely different. Hot-dip galvanized sheet is generally made of chilled sheet, which is continuously annealed and hot-dip galvanized on the galvanizing line. After internal heating, it is cooled again, 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 in a professional production line. Electrogalvanized 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 also become the main variety in the galvanized sheet market.

6. The hot-dip galvanized sheet tube 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. In order to ensure the quality, most regular galvanized pipe manufacturers do not use electro-galvanizing (cold plating). Only those small enterprises with outdated equipment use electrogalvanizing, and of course their prices are relatively cheap. The Ministry of Construction has officially issued an order to eliminate cold galvanized steel pipes with outdated technology, and do not allow cold galvanized steel pipes to be used as water and gas pipes.