1、Concept Analysis
Hot-dip galvanizing: also known as hot-dip zinc and hot-dip galvanising: is an effective way of metal corrosion protection, he is in the high temperature of the zinc ingot melting, in some auxiliary materials, and then the metal structural components immersed in the galvanizing tank, The metal components on the attachment of a layer of zinc layer, so as to play the purpose of anti-corrosion. The advantage of hot-dip galvanizing is that it has a strong anti-corrosion capability and the adhesion and hardness of the galvanized layer are good, thus serving the purpose of anti-corrosion.
Cold galvanizing: electro galvanizing, on the amount of zinc, is small, only 10-50g/m2, and is the use of electrolysis to make the surface of metal or other material parts attached to a layer of the metal film process. The process of forming a uniform, dense, well-bonded metal layer can play a role in preventing corrosion, improving wear resistance, electrical conductivity, and reflectivity, and enhancing the role of aesthetics.
2, reaction mode difference
Hot-dip galvanising is a chemical treatment, belonging to the electrochemical reaction. A hot galvanized pipe makes the molten metal and iron substrate reaction and produces an alloy layer so that the substrate and the plating of the combination of the two
Cold galvanizing is a physical treatment, only a layer of zinc is brushed on the surface, so the zinc layer is easy to come off. Hot-dip galvanizing is mostly used in building construction.
3, process difference
Hot-dip galvanizing is removing oil from the workpiece, pickling, dipping, drying, and then immersing in dissolved zinc solution for a certain period of time, put forward.
Cold galvanizing is the use of electrolytic equipment that will work after oil removal, pickling into the composition of the zinc salt solution, and connecting the negative electrolytic equipment; in the workpiece on the opposite side of the zinc plate connected to the positive electrolytic equipment, connect the power supply, the use of electric current from the positive electrode to the negative electrode of the direction of the movement, will be in the workpiece deposited a layer of zinc!
4、Difference between galvanized products
The difference between galvanized products is: that hot-dip galvanized appearance is not as fine and bright as cold galvanized, and the coating is uniform. However, the thickness of the zinc layer of hot-dip galvanizing is dozens of times that of cold galvanizing. Corrosion resistance is also dozens of times that of electro-galvanising.
Hot-dip galvanizing, also known as hot-dip galvanizing, is the method of removing oil and rust from steel workpieces, presenting a dirt-free, wetted surface, and immediately immersing them in a pre-heated zinc-melted bath to form a layer of zinc coating on the surface of the workpieces.
Cold zinc plating is the same after the degreasing, descaling, presenting no dirt, and wet workpiece into the special electroplating tank on the cathode, the anode with zinc. Connected to a DC power supply, the zinc ions on the anode migrate to the cathode and discharge on the cathode, so that the workpiece is coated with a layer of zinc. Hot-dip galvanizing has a thicker coating, generally 30-60 microns, and the coating has a higher corrosion resistance.
Electro-galvanized, the surface of the workpiece is smooth and even, but because the coating is thinner, electro-galvanized zinc is generally within 5-30 microns, so the anti-corrosion time will be shorter. It is used for rust prevention of indoor-use parts, such as chassis bottoms, panels, and small-size fasteners.
In the suburban environment, the standard hot-dip galvanized rust thickness can be maintained for more than 50 years without repair; in urban or offshore areas, the standard hot-dip galvanized rust layer can be maintained for 20 years without repair.
5、Use difference
Hot-dip galvanizing: suitable for outdoor work on steel components, such as motorway fences, electricity pylons, large-size fasteners, and other more “rough” workpieces for long-term rust prevention. Earlier iron water pipes were also hot-dip galvanized.
Electro-galvanizing: It is used for rust prevention of indoor parts, such as the bottom of the chassis, panels, small-sized fasteners, etc.
- Price difference
The galvanizing process is quicker than other coating methods and avoids the time required to paint on-site after installation.
Low treatment cost: The cost of hot dip galvanizing for rust prevention is lower than that of other paint coatings;
Generally, hot dip galvanizing is less expensive than applying other protective coatings for the simple reason that other protective coatings such as sanding and painting are labor intensive, whereas hot dip galvanizing is a highly mechanized, tightly controlled, in-plant process.
Cold galvanizing can be done on one side only, hot dip galvanizing has to be done all over. Also hot-dip galvanizing is generally thicker than cold-dip galvanizing, so the price of hot-dip galvanizing is higher than cold-dip galvanizing.
7, environmental issues
Hot-dip galvanized square tube pollutant emissions are less, mainly acid pickling workpiece waste acid.
The pollutants of cold galvanizing mainly include the waste acid of pickling workpieces, electroplating waste liquid, waste passivation solution and so on. The types and quantities of emissions are greatly exceeded by hot-dip galvanizing.