It is well known that the quality of galvanized square and rectangular tubes and the installation method directly affect the stability of steel structures.
At present, the support materials on the market are mainly carbon steel. The raw materials of carbon steel are generally Q235 and Q345, which are treated by hot galvanizing. The support is made of strip steel coil through cold bending, welding, hot galvanizing and other processes. Generally, the thickness should be greater than 2mm, and especially for some coastal, high-rise and other windy areas and areas, it is recommended that the thickness should not be less than 2.5mm, otherwise there is a risk of tearing at the steel connection point.
In large building structures, for carbon steel galvanized square and rectangular pipes, how much thickness of zinc coating should be reached to meet the requirements of environmental corrosion service life?
As we all know, the thickness of hot-dip galvanizing is an important quality and technical index of galvanized square pipe, which is related to the safety and durability of the structure. Although there are national and professional standards, the unqualified zinc coating thickness of the support is still a widespread technical problem of the support.
The hot-dip galvanizing process is a relatively stable and reliable steel surface treatment plan to resist environmental corrosion. There are many factors that affect hot-dip galvanizing, such as the composition of the steel substrate, the external state (such as roughness), the internal stress of the substrate, and several sizes. During this process, the thickness of the substrate has a greater impact on the thickness of the hot-dip galvanizing. Generally, the thicker the plate is, the greater the thickness of the hot-dip galvanizing. The support with thickness of 2.0mm is taken as an example to illustrate how much thickness of zinc coating is required to satisfy the environmental corrosion service life requirements.
Assume that the thickness of the support base material is 2mm, according to the standard GBT13192-2002 hot galvanizing standard.
What is the thickness of galvanized layer of galvanized square pipe required to meet the service life requirements?
Galvanized square pipe
According to the requirements of national standard, the thickness of 2mm base material should not be less than 45 μ m. Uniform thickness should not be less than 55 μ m。 According to the results of atmospheric exposure test conducted by the Japanese Hot Dip Galvanizing Association from 1964 to 1974. What is the thickness of galvanized layer of galvanized square pipe required to meet the service life requirements?
If calculated according to the national standard, the zinc content is 55x7.2=396g/m2,
The service life available in four different environments is about:
Heavy industrial zone: 8.91 years, with annual corrosion degree of 40.1;
Coastal zone: 32.67 years, with annual corrosion degree of 10.8;
Outskirts: 66.33 years, with annual corrosion degree of 5.4;
Urban area: 20.79 years, with annual corrosion degree of 17.5
If calculated according to photovoltaic service life of 25 years
Then the sequence of the four zones is at least:
1002.5270135437.5, i.e. 139 μ m，37.5 μ m，18.75 μ m，60.76 μ m。
Therefore, for the distribution of urban areas, the thickness of zinc coating shall be at least 65 μ M is reasonable and necessary, but for heavy industrial areas, especially those with acid and alkali corrosion, it is recommended that the thickness of galvanized square pipe and zinc coating should be properly added.
Post time: Sep-21-2022
