Weathering steel

The steel with better corrosion resistance than general structural steel is called weathering steel, which generally contains phosphorus, copper, nickel, chromium, titanium and other metals, so as to form a protective layer on the metal surface to improve the corrosion resistance.Its low temperature impact toughness is also better than the general structure.

Thermal spraying aluminum (zinc) composite coating

This method is equivalent to that of hot dip galvanizing.The specific method is to remove rust on the surface of steel members by sand blasting, so as to expose metal luster and roughen the surface.Then the heat source (acetylene oxygen combustion flame, arc, plasma arc, etc.) of thermal spraying equipment will melt the aluminum (zinc) wire continuously sent out, and blow it to the surface of steel members with compressed air to form a honeycomb aluminum (zinc) spraying layer (thickness of about 80 ~ 100 μ M).Finally, the pores were filled with epoxy resin or neoprene paint to form composite coating.

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.Compared with hot-dip galvanizing, the industrialization degree of this method is lower, and the labor intensity of sand blasting aluminum (zinc) is higher.

Hot dip galvanizing

Hot dip galvanizing is to immerse the derusted steel member into the molten zinc at 600 ℃ to make the surface of the steel member adhere to the zinc layer. The thickness of the zinc layer of the thin plate below 5mm shall be less than 65 μ m, and that of the thicker sheet shall not be less than 86 μ M.In order to achieve the purpose of corrosion prevention.

The advantages of this method are long service life, high degree of industrialization and stable quality.Therefore, it is widely used in outdoor steel structure which is seriously corroded by atmosphere and is not easy to maintain.Such as a large number of transmission towers, communication towers, etc.And in recent years, a large number of profiled steel sheet in light steel structure system have appeared.

Coating method

Coating method is usually used for indoor steel structure or outdoor steel structure which is relatively easy to maintain.One time cost is low.

The first step of coating method is to remove rust.A good coating depends on thorough rust removal.Therefore, the coating with high requirements generally uses sand blasting and shot blasting to remove all rust and oil stains.The selection of coating should consider the surrounding environment.Different coatings have different resistance to different corrosion conditions.

Cathodic protection

The corrosion of steel is replaced by active metal on the surface of steel structure.It is often used in underwater or underground structures.

Matters needing attention in coating construction

Coating method is a commonly used method in waterproof and anti-corrosion construction of steel structure, and the following matters should be paid attention to in the construction process:

　　(1) After coating, steel members shall be isolated to prevent stepping on.

　　(2) After coating, if there is strong wind or rain within 4 hours, it should be covered to prevent dust and moisture from affecting the adhesion of the coating.

　　(3) When transporting coated components, attention should be paid to avoid bumping and dragging on the ground to prevent coating damage.

　　(4) When the air temperature is lower than 5 ℃, the corresponding low-temperature coating material should be used; when the temperature is higher than 40 ℃, the coating operation should be stopped

　　(5) When the air humidity is more than 85%, or there is condensation on the surface of components, coating operation is not suitable.