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High corrosion resistance of aluminum zinc plating
发布时间:2021-04-06 06:20:21浏览次数:319
The corrosion resistance of Al Zn coated steel sheet is better than that of galvanized steel sheet in various environments. The unique dendritic structure of Al Zn coating is the main reason for the improvement of corrosion resistance. When the aluminized zinc coating is exposed to the atmosphere, the zinc rich region in the interdendritic network is corroded first, and the oxidation products will fill in the interstices between the dendrites, thus reducing the corrosion rate. The corrosion of zinc coating is linear, but the corrosion of aluminum zinc coating is not a process of uniform thinning. In general, the aluminum rich area is not corroded in the initial stage of corrosion.
In a sense, when the zinc rich area provides galvanic cell protection, the dendritic crystals in the aluminum rich area act as a fence, thus minimizing corrosion at the cutting edge or other places where iron is exposed. There are two main metallographic structures in the coating, one is the dendritic al rich zone formed in the early solidification stage, and the other is the interdendritic network Zn rich zone formed when the concentration of zinc reaches a high level. This kind of microstructure can obtain the ideal anticorrosion performance. Other metallographic structures include: silicon in the form of discrete tiny grains and iron rich zone formed due to the saturation of iron concentration in the production process. Due to the wide existence of network structure zinc rich zone in the microstructure of Al Zn coating, the cooling rate must be strictly controlled in the solidification process, which is higher than that of hot dip galvanizing.
According to the test and feedback from the enterprise, the salt spray test effect of environmental protection metal surface pretreatment for hot-dip galvanized sheet is not ideal. Cold rolled sheet metal products are mainly used in building materials, light industry, home appliances, automobile and other industries, while cold rolled sheet metal is mainly used in the field of steel structure construction in the building materials industry, Organic anti fingerprint treatment solution (anti fingerprint film) was coated on the passivation film by roller coating. Stainless steel liner was completely eliminated in the field of electric water heater, and enamel liner was used.
Aluminum zinc plating steel plate has not only outstanding coloring, corrosion resistance, decoration, but also high strength and easy processing, so it is very popular with users. But in the process of application, sometimes there will be paint explosion. The paint explosion of aluminum zinc plated steel plate not only affects the beautiful decoration of the plate, but also directly corrodes and oxidizes the zinc layer of the substrate without oil passivation after the paint film is exposed, which will seriously affect the anti-corrosion ability of the color plate and reduce the service life of the color plate. Protect and update the curing furnace plate thermometer regularly, calibrate the temperature coefficient of the tracking plate thermometer with the temperature measuring paper, and finally confirm the temperature coefficient of different color plates, so as to ensure that the error between the display temperature of the plate thermometer and the calibrated plate temperature of the temperature measuring paper is ± 4 ℃, so as to control the production. In strict accordance with the requirements of passivation solution curing temperature 50 ~ 80 ℃ supplied by the treatment manufacturer, measure by low-temperature temperature temperature measuring paper roll by roll, and check the boiling aging of color roll samples with quality problems.
At present, the surface of aluminized zinc plate used in the market is treated with anti fingerprint treatment, which is equivalent to making a layer of varnish on the surface of aluminized zinc plate. The anti-corrosion performance of the product is increased without affecting the appearance. The corrosion resistance of aluminized zinc steel coil is mainly due to the protection function of aluminum. When zinc is worn, aluminum forms a layer of dense alumina to prevent corrosion-resistant substances from further corroding the interior. Therefore, the performance of aluminized zinc plate is similar to that of color steel plate, and it is also widely used in various industries. The thin plate is mainly used in household electrical plate, steel structure roof panel, mechanical equipment plate, and thick plate is used in switch cabinet, electrical cabinet, insulation pipe and ventilation pipe It is widely used on the road.