The factors that affect the thickness of the zinc steel grating coating are mainly: the metal composition of the steel grating, the surface roughness of the steel grating, the content and distribution of active elements silicon and phosphorus in the steel grating, the internal stress of the steel grating, the geometric dimensions of the steel grating workpiece, and the hot-dip galvanizing process of the steel grating. The current international and Chinese hot-dip galvanizing standards are divided into sections according to the thickness of the plate. The average thickness and local thickness of the zinc coating should reach the corresponding thickness to determine the anti-corrosion performance of the zinc coating. The time required to achieve thermal equilibrium and zinc-iron exchange equilibrium for steel grating workpieces of different thicknesses is different, and the thickness of the coating formed is also different. The average coating thickness in the standard is an industrial production experience value based on the above-mentioned galvanizing mechanism, and the local thickness is an experience value required to take into account the uneven distribution of the zinc coating thickness and the requirements for the corrosion resistance of the coating. Therefore, the ISO standard, the American ASTM standard, the Japanese JS standard and the Chinese standard have slightly different requirements for the thickness of the zinc coating, which are similar. According to the provisions of the hot-dip galvanizing standard GB B 13912-2002 of the People's Republic of China. The zinc coating standards for hot-dip galvanized steel grating products are as follows: For hot-dip galvanized steel gratings with a thickness greater than or equal to 6mm, the average zinc coating thickness on the hot-dip galvanized steel grating should be greater than 85 microns, and the local thickness should be greater than 70 microns. For hot-dip galvanized steel gratings with a thickness less than 6mm and greater than 3mm, the average zinc coating thickness on the hot-dip galvanized steel grating should be greater than 70 microns, and the local thickness should be greater than 55 microns. For hot-dip galvanized steel gratings with a thickness less than 3mm and greater than 1.5mm, the average zinc coating thickness on the hot-dip galvanized steel grating should be greater than 55 microns, and the local thickness should be greater than 45 microns
The role and influence of hot-dip galvanizing coating thickness
The thickness of the hot-dip galvanized coating on the steel grating determines the anti-corrosion performance of the steel grating. Users can choose a zinc coating thickness that is higher or lower than the standard. It is difficult to obtain a thicker coating in the industrial production of thin steel gratings with a smooth surface less than 3mm. In addition, the zinc coating thickness that is not proportional to the thickness of the steel grating plate will affect the bonding strength between the coating and the substrate and the appearance quality of the coating. Too thick plating cloud will cause the coating to appear rough and easy to peel off. The plated steel grating cannot withstand collisions during transportation and installation. If there are more active elements silicon and phosphorus in the raw materials of the steel grating, it is also very difficult to obtain a thinner coating in industrial production. This is because the silicon content in the steel affects the growth mode of the alloy layer between zinc and iron, which will cause the (, phase zinc-iron alloy layer to grow rapidly and (to the surface of the coating, resulting in a rough and dull coating surface, forming a gray coating with poor adhesion. Therefore, as discussed above, there is uncertainty in the growth of the galvanized layer of the steel grating. It is often difficult to obtain a certain range of coating thickness in actual production. The thickness specified in the hot-dip galvanizing standard for steel grating is an empirical value generated after a large number of experiments, taking into account various factors and requirements, and is more reasonable.
Post time: Aug-19-2024