Anti-corrosion measures for I-beam and angle steel

      With the wide range of application of I-beam and angle steel, it involves industrial plants, door awnings, car sheds and other industries, and even steel structure adding floors, platforms, mobile houses and other projects. The use of I-beams and angle steels is too many, which also makes steel structure engineering more popular. Since there are shortcomings, there must be preventive measures. There are many anti-corrosion measures. Today we will introduce three methods.

　　Method 1: thermal spraying aluminum (zinc) composite coating

　　This is a long-term anti-corrosion method with the same effect as hot-dip galvanizing. The specific method is to sandblast and remove rust on the surface of the steel member first to expose the metal luster and roughen the surface. Then, the continuously sent aluminum (zinc) wire is melted with an acetylene - oxygen flame and blown to the surface of the steel member with compressed air to form a honeycomb aluminum (zinc) spray layer (about 80 thick μ m~100 μ m）。

　　The pores shall be filled with epoxy resin or neoprene paint to form a composite coating. This method cannot be used for construction on the inner wall of the tubular component, so the two ends of the tubular component shall be airtight sealed so that the inner wall will not corrode. The advantage of this process is that it has strong adaptability to the size of components, and the shape and size of components are almost unlimited. Shiplocks as large as Gezhouba are also constructed in this way. Another advantage is that the heat effect of this process is local and constrained, so no thermal deformation will occur. Compared with hot-dip galvanizing, this method has a lower degree of industrialization, high labor intensity of sandblasting and aluminum (zinc) spraying, and its quality is also easily affected by the operator's emotional changes.

　　Method 2: coating method

　　The corrosion resistance of coating method is generally not as good as that of long-term corrosion protection method (but at present, the corrosion protection period of fluorocarbon coating can even reach 50 years). Therefore, there are many indoor steel structures or outdoor steel structures that are relatively easy to maintain. It has low primary cost, but high maintenance cost when used outdoors. The key of coating method is rust removal. Generally, the coating with high requirements shall be derusted by sand blasting and shot blasting to expose the luster of metal and remove all rust and oil stains. The coating applied on site can be derusted manually. The selection of coating shall consider the surrounding environment. Different coatings have different resistance to different corrosion conditions. The coating is generally divided into primer (layer) and finish (layer). The primer contains more powder and less base material. The film is rough, with strong adhesion to steel and good adhesion to finish paint. The finishing coat has more base materials and glossy film, which can protect the primer from atmospheric corrosion and can resist weathering.

　　There is a problem of compatibility between different paints. Pay attention to their compatibility when selecting different paints before and after. The coating shall be applied with appropriate temperature (between 5 and 38 ℃) and humidity (relative humidity not greater than 85%). The construction environment of the coating shall be less dust, and the component surface shall be free of condensation. No rain is allowed within 4 hours after painting. The coating is generally done for 4-5 times. The total thickness of dry paint film is 150 for outdoor works μ m. 125 for indoor works μ m. The allowable deviation is 25 μ m。 The total thickness of dry paint film can be thickened to 200~220 at sea or in the strongly corrosive atmosphere μ m。