(1) Weathering steel: The steel with corrosion resistance better than that of general structural steel is called weathering steel, which generally contains phosphorus, copper, nickel, chromium, titanium and other metals, so that the metal surface forms a protective layer to improve corrosion resistance. Its low-temperature impact toughness is also better than that of general structural steel. The standard is “weathering steel for welded structures” (GB4172-84).
(2) Hot-dip galvanizing: hot-dip galvanizing is to immerse the derusted steel components into the molten zinc melted at a high temperature of about 600 °C, so that the surface of the steel components is attached to the zinc layer, and the thickness of the zinc layer shall not be less than 65μm for thin plates below 5mm, and not less than 86μm for thick plates. So as to play the purpose of anti-corrosion. The advantages of this method are long durability, high degree of production industrialization, and stable quality. Therefore, it is widely used in outdoor steel structures that are seriously corroded by the atmosphere and are not easy to maintain. Such as a large number of transmission towers, communication towers, etc. In recent years, a large number of light steel structure systems in the profiled steel plate. It also uses hot-dip galvanizing to prevent corrosion. The first process of hot-dip galvanizing is pickling and rust removal, followed by cleaning. These two processes are not thorough, and both will leave hidden dangers to corrosion prevention. So it must be dealt with thoroughly. For the steel structure designer, it should be avoided to design components with a fitting surface, so as to avoid incomplete pickling or acid washing in the gap of the fitting surface. Cause the phenomenon of yellow water flowing on the galvanized surface. Hot-dip galvanizing is carried out at high temperatures. For tubular members, the ends should be open. If the two ends are closed, the air in the pipe will expand and the head plate will burst, resulting in safety accidents. If one end is closed, the flow of zinc liquid is not smooth, and it is easy to accumulate in the tube.
(3) Thermal spray aluminum (zinc) composite coating: This is a long-term anti-corrosion method comparable to the anti-corrosion effect of hot-dip galvanizing. The specific method is to blast and remove rust on the surface of the steel member, so that the surface of the surface is exposed to metallic luster and haired. Then the aluminum (zinc) wire continuously sent out is melted with acetylene-oxygen flame, and is blown to the surface of the steel component with compressed air to form a honeycomb-shaped aluminum (zinc) spray coating (thickness of about 80μm~100μm). Finally, the pores are filled with coatings such as epoxy resin or neoprene paint to form a composite coating. This method cannot be constructed on the inner wall of the tubular component, so the two ends of the tubular component must be sealed with air tightness so that the inner wall will not corrode. The advantage of this process is that it is highly adaptable to the size of the component, and the shape and size of the component are almost not limited. Locks as large as Gezhouba were also constructed in this way. Another advantage is that the thermal effects of this process are localized and constrained, so there is no thermal distortion. Compared with hot-dip galvanizing, this method is less industrialized, and the labor intensity of sandblasting aluminum (zinc) is high, and the quality is also susceptible to the emotional changes of the operator.
(4) Coating method: The corrosion resistance of the coating method is generally not as good as that of the long-term anti-corrosion method (but the current anti-corrosion life of fluorocarbon coatings can even reach 50 years). Therefore, there are more outdoor steel structures that are used for indoor steel structures or relatively easy to maintain. It has a low cost at a time, but it is expensive to maintain when used outdoors. The first step in the application of the coating method is to remove rust. A good coating relies on thorough rust removal. Therefore, the coating with high requirements is generally used to remove rust with sandblasting shot blasting to expose the luster of the metal and remove all rust and oil stains. The coating applied on site can be removed by hand. The choice of coating takes into account the surrounding environment. Different coatings have different tolerances to different corrosion conditions. Coatings are generally divided into primer (layer) and topcoat (layer). The primer contains more powder and less binder. The film is rough, the adhesion to steel is strong, and the combination with the topcoat is good. The topcoat has many base materials, and the film formation is shiny, which can protect the primer from atmospheric corrosion and resist weathering. There is a problem of compatibility between different coatings, and it is necessary to pay attention to their compatibility when choosing different coatings before and after. The construction of the coating should have an appropriate temperature (between 5~38 °C) and humidity (relative humidity is not more than 85%). The construction environment of the coating should have less dust, and there should be no condensation on the surface of the component. Do not get wet in the rain within 4 hours after painting. The coating is generally done 4~5 times. The total thickness of the dry paint film is 150 μm for outdoor engineering and 125 μm for indoor engineering, and the allowable deviation is 25 μm. In the seaside or sea or in a strongly corrosive atmosphere, the total thickness of the dry paint film can be thickened to 200~220μm.
(5) Cathodic protection method: add more active metal to the surface of the steel structure to replace the corrosion of the steel. It is often used in underwater or underground structures.
Precautions for the design of the steel structure factory house
