In recent years, with the rapid development of the highway, along the more perfect facilities, a variety of safety products continue to emerge and its increasingly demanding high quality. Among them, the steel components are hot dip galvanized products widely used. Adhesiveness of zinc coating and a variety of factors. For example: the temperature of molten zinc, the chemical composition of the steel substrate, the chemical composition of liquid zinc and pre-treatment, and other factors can affect the zinc coating adhesion properties.
Fluid temperature on hot-dip galvanized zinc adhesion significantly affected. Iron temperature can accelerate the diffusion rate of the zinc. At less than 480 ℃ galvanized iron loss system according to the parabolic law varies with galvanizing time. When the temperature approaches 480 ℃, iron, and zinc alloy layer will be thicker, resulting in deterioration of the plastic coating. When the zinc liquid temperature exceeds 480 ℃, especially reach 500 ℃, the iron loss can be represented by a linear law. Because when the temperature exceeds 480 ℃, the metal phase of the crystal formation rate becomes small, the formation of only a small number of nuclei with a large gap, which will be immersed in the liquid zinc in these gaps, and has been deep into the metal phase, thus accelerating the diffusion between Fe and Zn, leading to severe thickening of the alloy layer. And when it reaches 480 ℃, the metallic phase of the crystal phase depends mainly on sacrificial metal crystals and grow, leading to brittle zinc coating, adhesion performance.
The content of carbon steel not only affects the performance, but also on galvanized steel has a greater impact. Simply put, the higher the carbon content of steel in the hot dip galvanizing process of iron and zinc will be more intense reflection, this will increase the iron loss, and the resulting Fe -Zn alloy layer thickness increases, the zinc layer is attached performance. Therefore, in the production process, it requires strict control of the steel grades. In the zinc solution may also add some other elements, which add an element to the coating properties have varying degrees of impact, should be properly controlled element content, do not blindly pursue the role of an element, thus ignoring the impact of the elements to each other. For example: Zinc solution containing element Sn, the beautiful spangle can be obtained, but the excess amount of tin element will decrease adhesion of the coating, and different element content of tin not only directly affect iron and zinc alloy layer thickness, but also aluminum in reducing the effective role. In the rolling process, due to different surface finish roll, the surface roughness of the strip thus obtained will be different. If the steel surface rougher, the actual area of ??the steel surface becomes large, so that when the hot-dip galvanizing, zinc coating adhesion performance will improve. It can be said cold-rolled steel sheet surface roughness of the hot -dip galvanizing and then to some extent, affect the adhesion properties of the zinc coating. Pre-treatment is pre-plated surface of the oil, iron oxide, etc. cleaned, wherein the acid is to remove the plate surface of iron oxide, if the pickling time is too long, it will increase the surface roughness of the steel, after hot-dip galvanizing on will get more amount of zinc. Sometimes when the production of zinc coating adhesion found poor performance should be taken to improve the pre- plating method into the zinc pot temperature, so that the product will be improved adhesion properties.
