The world’s galvanized sheet market is booming, and production is developing rapidly. According to the production method, the galvanized sheet can be divided into hot-dip galvanized sheet and electro-galvanized sheet.
Hot-dip galvanizing and electro-galvanizing not only have different coating formation mechanisms and different production processes, but also have different product properties and uses. The following article will specifically introduce the difference between galvanized sheet and hot-dip galvanized sheet.
Hot-dip galvanizing is a method of metal corrosion protection. After pretreatment, the electroplated metal or non-metal material is immersed in the liquid metal zinc to make the surface of the steel product adhere to the zinc layer, thereby improving the corrosion resistance of the material and improving the performance of the material.
Cold galvanizing is to form a smooth and dense metal coating through electrolysis to meet the requirements of the surface of metal and non-metal products.
The production process of hot-dip galvanizing is as follows: pre-plated parts → degreasing → water washing → pickling → water washing → squeezing → water solvent → drying → galvanizing → cooling → straightening → oiling → packing.
The basic process of electro-galvanization is as follows: pre-plated parts → degreasing → erosion → polishing → galvanizing → hydrogen removal → passivation/dyeing.
Compared with electro-galvanized galvanized steel, hot-dip galvanized steel has the same corrosion resistance, but the production cost of electro-galvanized steel sheet is higher than that of hot-dip galvanized steel.
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 the process of electroplating zinc, the zinc ions in the electroplating solution are sent to the steel plate through electric current. The thicker the coating, the more electric energy is consumed.
Hot-dip galvanized products have the advantages of thick zinc layer, good corrosion resistance, beautiful appearance, conducive to subsequent processing, low production costs, and reduced environmental pollution.
Electro-galvanizing has the advantages of processing formability, better weldability and paintability, better surface quality, and does not change the mechanical properties of the original plate during production.
The zinc layer of hot-dip galvanizing is thicker than that of electro-galvanizing, so it has better corrosion resistance.
The surface of hot-dip galvanizing is darker and slightly rough, and will produce process water lines, dripping tumors, etc., especially at one end of the workpiece, and the appearance is silvery white.
Electro-galvanizing can form a uniform and dense galvanized layer, with a smooth and bright surface, and the quality of the coating is better than hot-dip galvanizing. The surface of electro-galvanized is relatively smooth, mainly yellow-green, of course, there are also colorful, blue-white, white and green light.
The thickness range of hot-dip galvanized products is large, which can reach 60～700g/m2 (double-sided). The surface of the hot-dip galvanized coating is uneven and the surface roughness is large.
Because the zinc liquid often contains impurities such as Pb and Sb, When the zinc liquid solidifies, blossoms of zinc flowers are formed. The presence of spangles will affect the gloss of the paint film. To achieve mirror-grade quality, the thickness of the paint film must be increased. Therefore, it is difficult to produce thin-coated products by hot-dip galvanizing.
In the electroplating process, the thickness of the coating should strictly abide by Faraday’s law, and the thickness of the coating can be accurately controlled by controlling the cathode current density and power-on time.
The electro-galvanized coating is uniform, the surface of the electro-galvanized sheet is free of spangles, and the surface roughness can meet the painting requirements, so it is very suitable for automotive exterior panels. The production of thin-coated products is the advantage of electro-galvanizing.
Hot-dip galvanized sheet has the characteristics of good corrosion resistance, low production cost and environmental protection, so it is widely used in many industries such as automobiles, home appliances, building materials, aerospace and electronics.
Electro-galvanized sheet has good corrosion resistance, processability, weldability and paintability. Electro-galvanized sheet is generally used after painting, and is mostly used for automotive exterior panels, high-end home appliances, office supplies, and products in industries such as light industry.
Moreover, the application of electro-galvanized fingerprint-resistant products in the field of home appliances is becoming more and more extensive. Electro-galvanizing is widely used, especially for electro-galvanizing anti-corrosion of conventional parts.
Hot-dip galvanizing is suitable for all sizes, while electro-galvanizing is only suitable for smaller parts.
The life of electroplated products is very short due to the thin zinc layer. In the short term, if the pickling is insufficient and the air is humid, dezincification and oxidation will occur within a few weeks in severe cases.
Depending on the thickness of the zinc layer, hot-dip products may be severely oxidized in the next few years or decades.
Why use hot-dip galvanized steel coil instead of electro-galvanized steel coil?
Advantages of galvanized steel
(1) Compared with electro-galvanized steel coil, hot-dip galvanized steel coil has the characteristics of thick zinc layer, good corrosion resistance and low production cost.
In recent years, in order to reduce production costs and meet environmental protection requirements, Chinese automobile and home appliance companies have gradually replaced electro-galvanized steel with hot-dip galvanizing.
(2) The production cost of hot-dip galvanized steel is lower than that of electro-galvanized steel. During the hot-dip galvanizing process, the zinc liquid is attached to the surface of the steel plate when the steel plate passes through the zinc pot.
The air knife blows off the excess zinc liquid, so it is easy to produce thick-coated steel plates. In the process of electroplating zinc, the zinc ions in the electroplating solution are sent to the steel plate through electric current. The thicker the coating, the more electric energy is consumed.
Limitations of electro-galvanized steel:
(1) The corrosion resistance of electro-galvanized sheet is not as good as that of hot-dip galvanized sheet.
The cost of investing in the construction of an electro-galvanized production line is about 20% higher than that of building a hot-dip galvanized production line.
(2) Electro-galvanized steel is far inferior to hot-dip galvanized steel in terms of radiation protection, oxidation resistance and heat dissipation.
In recent years, computer case manufacturers, like air conditioners and other home appliance manufacturers, have gradually shown a new trend of replacing electro-galvanized steel with hot-dip galvanized steel.
From the analysis of the above article, the performance of hot-dip galvanizing is much better than that of electro-galvanizing. Although electro-galvanizing has unique advantages, it also has disadvantages that cannot be ignored.
For example, compared with hot-dip galvanizing, the corrosion resistance is poor. The cost of the production line is relatively high, and its anti-radiation, oxidation resistance and heat dissipation are far inferior to the hot-dip galvanized steel sheet, so there is a new trend of replacing the electro-galvanized steel sheet with the hot-dip galvanized steel sheet.
The above is the difference between hot-dip galvanizing and electro-galvanizing, I hope it can help you.