Hot-dip galvanized sheet is also called hot-dip galvanized. Hot-dip galvanized sheet is a thin steel sheet with a layer of zinc adhered to the surface by immersing a thin steel plate in a molten zinc tank. At present, it is mainly produced by continuous galvanizing process. The coiled steel sheet is continuously immersed in a galvanized bath with molten zinc to make a galvanized steel sheet.
Electro-galvanized sheet, commonly known as cold galvanizing, is an electrochemical method. The zinc ingot is used as the anode. After the zinc atoms lose electrons, they become ions and dissolve into the electrolyte. The steel strip acts as the cathode. Zinc atoms are deposited on the surface of the steel strip to form a coating.
1. The thickness of the galvanized layer is different
The amount of hot-dip galvanizing 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 the electro-galvanized sheet can be very thin, with a minimum of 15g/m2 and a maximum of about 100g/m2. In addition, electro-galvanizing can be galvanized on one side or on both sides, and hot-dip galvanizing must be galvanized on both sides.
2. Different plating organization structure
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 of 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, so the hot-dip galvanized sheet is more resistant than the electro-galvanized sheet corrosion.
Three, the heat treatment process is different
Hot-dip galvanized sheets generally use chilled sheets as raw materials. Continuous annealing and hot-dip galvanizing are carried out on the galvanizing line. The steel strip is heated in a short period of time and then cooled again, and the strength and plasticity are affected to a certain extent. 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.
4. Compared with electro-galvanized steel, hot-dip galvanized steel has the characteristics of thick zinc layer, good corrosion resistance and low production cost.
During the hot-dip galvanizing process, when the steel plate passes through the zinc pot, the zinc liquid is attached to the surface of the steel plate, and the air knife blows off the excess zinc liquid, so it is easy to produce thick-coated steel plates. In recent years, in order to reduce production costs and meet environmental protection requirements, domestic automobile and home appliance companies have gradually replaced electro-galvanized steel sheets with hot-dip galvanized sheets.
The surface quality of the electro-galvanized sheet is better, the coating is evenly distributed, and its weldability, paintability and stamping formability are better than that of the hot-dip galvanized sheet; single-sided, double-sided or poorly thick coating can be easily switched during production. However, in the process of electroplating zinc, the zinc ions in the electroplating solution are sent to the steel plate by electric current. The thicker the coating, the more electric energy is consumed and the cost is higher.
The production cost of hot-dip galvanized sheet is lower and the application range is wider. It is the main variety of galvanized sheet market.
