High strength galvanized bolts are galvanized, so what are the advantages?
Hot dip galvanizing is also used for the surface anti-corrosion of screws, bolts and nuts. The hot-dip galvanized screws have better corrosion resistance than the galvanized screws, but the cost is higher. The structural bolts with high strength are not suitable for hot-dip galvanizing. Because the coating surface is easy to form hard and brittle, it may fracture under high temperature or high load.
There is a linear relationship between the durability of zinc coating of high strength galvanized bolt in corrosive environment and its thickness, that is, the thicker the coating is, the longer its life is. However, in industrial areas containing sulfide, its corrosion resistance is poor. At the same time, a large number of self colored corrosive products will be produced in marine and tropical climate, so chromate treatment must be applied to prevent it. The results show that the average life of zinc coating in rural areas, coastal areas and industrial areas is about 3:2:1, which means that the zinc coating is most prone to corrosion in polluted air, because there are many sulfur oxides (SOx) and nitrogen oxides (NOx) in the waste gas discharged from factories in industrial areas, which will damage the zinc coating. In coastal areas, there are a large number of salt crystals and liquid particles (chlorides) in the atmosphere, which can cause metal corrosion, and the relative humidity of the atmosphere also significantly affects the corrosion rate. The material Protection Institute of Beijing University of science and technology has also carried out the atmospheric exposure corrosion test of zinc coating in different areas of the mainland. The test period is one year. The results show that the areas with the highest content of SO2 and chloride (sea salt particles) and the highest relative humidity are the areas with the highest corrosion rate. Among them, the relative humidity is considered to be the main factor causing the corrosion, and the pollutants in the atmosphere, especially SO2 and chloride, are the main factors to promote the corrosion.
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