Cold galvanized steel pipe which is galvanized. This method is used to protect the galvanized metal to prevent corrosion. To this end the use of the zinc coating filler. In using any coating method to coat the surface to be protected. Forming a zinc coating after drying filler. Having a content of zinc in the dried coating (95%). Suitable for repair work (ie only as long as the repaired surface can be re-applied in place of the protected steel surface damage repair work in process). Cold galvanizing process for a variety of steel products and structures corrosion.Cold Galvanized Steel Pipe Processing
1. The New Steel Surface Treatment
In doing cold galvanizing should be selected before mechanical blasting (sand blasting, shot blasting, etc.). The steel surface cleanliness achieve ISO 85O1-1 Sa 2.5 magnitude. Equivalent to GB 8923 Sa 2.5 magnitude. Its character is defined as: “After the steel after mechanical descaling, surface free of oil, rust and mill scale or other dirt leaving only slight traces of .95% of the steel surface by steel shot (sand) impact is exposed… shiny metal. ”
While our cold galvanized pipe for the quality of the surface treatment of another indicator – – roughness. Different cold galvanized materials require different roughness. In Zinga (Zinga) construction description. It requires average roughness Ra = 12.5. I.e. roughness Rz = 55 ~ 75 microns. In the “strong zinc” and “Luo Balu” construction specification. Roughness requirements slightly lower. Rz = 40 ~ 60 m.
If the cold galvanizing alone film. As the anti-corrosion coating. The surface roughness can be controlled a little smaller. To ensure that the cold galvanized coating thickness. When cold galvanizing as a heavy duty coating bottom. The total package coating thickness greater than 180 microns. To ensure that the entire coating adhesion. Steel surface roughness Rz should be greater than 60 microns.
2. Old Steel Surface Treatment
The best way to use is also blasting to remove old paint, rust after. There is a certain steel surface roughness. If the conditions. It may also be hand-polished and wind (power) dynamic tools grinding rust approach. Rust grade level standards to ISO 8501-1 St 3. That is very thorough hand and power tools rust. Its character is defined as:. “The surface should be no visible grease and dirt and almost no adhesion is not strong oxidation, rust, old coatings and surface debris should have different metallic substrates luster.” Different brands of cold galvanized material surface treatment level requirements vary. Such as Belgium Zinga prior to coating. Allow about 5% of the steel surface has a slight rust area. ROVAL in polished steel surface to Level 3 when st. China Shipbuilding Technology Research Institute tests. 60 to 80 microns (dry film thickness) of ROVAL coating. Excellent adhesion to steel. France opened up to 6.1MPa.
3. Electric Weld Surface Treatment
Weld power is most easily corroded steel component parts. Practice has proved that: in an arc spray zinc (aluminum) and steel members welded hot-dip zinc coating installation. Cold galvanized weld repair. It is economical and effective way. But before repair. Weld surface must carefully remove the “splash”, “slag” and “welding smoke.” Remove grease, weld inspection agents and other contaminants. Polished to ISO 8501-1 grade St 2. Surface treatment has been completed. Now a cold galvanizing paint first.