1. Cleaning: use solvent and emulsion to clean the steel surface to remove oil, grease, dust, lubricant and similar organic matters, but it can not remove rust, oxide skin, welding flux, etc. on the steel surface, so it is only used as an auxiliary means in anti-government operations.
2. Acid cleaning: generally, chemical and electrolytic methods are used for acid cleaning. Only chemical acid cleaning is used for pipeline corrosion prevention, which can remove oxide scale, rust and old coating. Sometimes it can be used as the re-treatment after sand blasting and rust removal.
Although chemical cleaning of spiral welded steel pipe can make the surface reach a certain degree of cleanliness and roughness, its anchor pattern is shallow and it is easy to pollute the surrounding environment.
3. Tool derusting: mainly use tools such as wire brush to polish the steel surface to remove loose oxide scale, rust, welding slag, etc.
The derusting of hand tools can reach Sa2 level, and the derusting of power tools can reach Sa3 level. If the steel surface of spiral welded steel pipe is attached with solid oxide scale, the derusting effect of tools is not ideal, and the depth of anchor pattern required by anti-corrosion construction cannot be reached.
4. Spray derusting: spray derusting is to drive the spray blade to rotate at a high speed through a high-power motor, so that abrasive such as steel shot, steel sand, iron wire segment, minerals and other abrasives can spray the surface of the spiral welded steel pipe under the strong centrifugal force of the motor. It can not only completely remove oxides, rust and dirt, but also achieve the required uniform roughness of the spiral welded steel pipe under the strong impact and friction force of the abrasive.
After spray derusting, it can not only expand the physical adsorption of the pipe surface, but also enhance the mechanical adhesion between the anti-corrosion coating and the pipe surface. Therefore, spray derusting is an ideal derusting method for pipeline corrosion prevention.
Generally speaking, shot blasting is mainly used for inner surface treatment of pipes, and shot blasting is mainly used for outer surface treatment of spiral welded steel pipes.
During the production process, the relevant technical indicators of rust removal shall be strictly required to prevent the secondary damage to the spiral welded steel pipe caused by operation errors. After the removal of rust, the appearance of the spiral welded steel pipe will be smoother than that before the removal of rust. The removal of rust from the spiral welded steel pipe is a frequently used technology in the steel pipe industry.