What is the difference between electro-galvanized sheet and hot-dip galvanized sheet?
1. Concept analysis
Hot-dip galvanizing: also called hot-dip galvanizing and hot-dip galvanizing: it is an effective method of metal anti-corrosion. It melts zinc ingots at high temperatures, then puts in some auxiliary materials, and then immerses the metal structural parts in a galvanizing bath. In it, a layer of zinc is attached to the metal components to achieve the purpose of anti-corrosion. The advantage of hot-dip galvanizing is that it has strong anti-corrosion ability and the galvanized layer has good adhesion and hardness, thus achieving the purpose of anti-corrosion.
Electrogalvanizing: It is cold galvanizing. The amount of zinc applied is small, only 10-50g/m2. It is a process that uses electrolysis to attach a metal film to the surface of metal or other material parts. The process of forming a uniform, dense, and well-bonded metal layer can prevent corrosion, improve wear resistance, conductivity, reflectivity, and enhance aesthetics.
2. Differences in reaction methods
Hot-dip galvanizing is a chemical treatment and is an electrochemical reaction. Hot-dip galvanizing makes the molten metal react with the iron matrix to produce an alloy layer, thereby combining the matrix and the coating.
Electro-galvanizing is a physical treatment, just brushing a layer of zinc on the surface, so the zinc layer is easy to fall off.
3. Process differences
Hot-dip galvanizing involves degreasing, pickling, dipping, and drying the workpiece, then immersing it in the molten zinc solution for a certain period of time and then lifting it out.
Electro-galvanizing uses electrolysis equipment to degrease and pickle the workpiece and put it into a solution composed of zinc salts, and connect it to the negative electrode of the electrolysis equipment; place a zinc plate opposite the workpiece and connect it to the positive electrode of the electrolysis equipment, and turn on the power. Using the directional movement of current from the positive electrode to the negative electrode, a layer of zinc is deposited on the workpiece.
4. Differences between galvanized finished products
The surface of hot-dip galvanizing is not as delicate and bright as electro-galvanizing, and the coating is uniform. However, the thickness of the zinc layer is dozens of times that of electro-galvanizing. The anti-corrosion performance is also dozens of times that of electroplated zinc.
Electro-galvanized, the surface of the workpiece is smooth and flat, but because the coating is relatively thin, electro-galvanized is generally within 5-30 microns, so the anti-corrosion time will be relatively short.
In suburban environments, the standard hot-dip galvanized rust-proof thickness can be maintained for more than 50 years without repair; in urban or offshore areas, the standard hot-dip galvanized rust-proof layer can be maintained for 20 years without repair;
5. Differences in uses
Hot-dip galvanizing: suitable for long-term rust prevention of steel parts for outdoor work, such as highway fences, power towers, large-size fasteners and other relatively "rough" workpieces. Earlier iron water pipes were also hot-dip galvanized.
Electro-galvanizing: It is used to prevent rust of indoor parts, such as the bottom of the casing, panels, small-size fasteners, etc.
6. Price difference
Electro-galvanizing can only be plated on one side, while hot-dip galvanizing must be fully plated. And hot-dip galvanizing generally has a thicker galvanized layer than cold-dip galvanizing, so the price of hot-dip galvanizing is higher than that of electro-galvanizing.
7. Environmental issues
Hot-dip galvanized square and rectangular pipes emit less pollutants, mainly waste acid from pickling workpieces.
The pollutants of electroplating zinc mainly include waste acid from pickling workpieces, waste electroplating liquid, waste passivation liquid, etc. The types and quantities of emissions are much greater than those of hot-dip galvanizing.
Main application industries of galvanized sheets:
A large number of galvanized sheets are used in automobile manufacturing, refrigerated containers, the construction industry, ventilation and heating installations and furniture manufacturing. (Galvanizing has become an important anti-corrosion method for steel, not only because zinc can form a dense protective layer on the surface of steel, but also because zinc has a cathodic protection effect. When the galvanized layer is damaged, it can still prevent iron from corrosion through cathodic protection. Corrosion of base metal.)
Construction industry: roofs, roof components, balcony panels, window sills, kiosks, warehouses, rolling shutter doors, heaters, rainwater pipes, etc.
