How to prevent corrosion of steel pipes

　　1. Cleaning

　　Use solvent and emulsion to clean the steel surface to remove oil, grease, dust, lubricant and similar organics, 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-corrosion production.

　　2. Tool derusting

　　It mainly uses tools such as steel wire brush to polish the steel surface, which can remove loose or cocked oxide skin, rust, welding slag, etc. The derusting of manual tools can reach grade SA2, and the derusting of power tools can reach grade SA3. If the steel surface is attached with solid oxide scale, the derusting effect of tools is not ideal, and the depth of anchor lines required for anti-corrosion construction cannot be reached.

　　3. Pickling

　　Generally, chemical and electrolytic methods are used for acid pickling. Only chemical acid pickling is used for pipeline corrosion prevention, which can remove oxide skin, rust and old coatings. Sometimes it can be used as the reprocessing after sand blasting. Although chemical cleaning can make the surface reach a certain degree of cleanliness and roughness, its anchor lines are shallow and easy to pollute the environment.

　　4. Derusting by spraying (throwing)

　　Spray (polishing) derusting is to drive the spray (polishing) blade to rotate at a high speed through a high-power motor, so that steel grit, steel shot, iron wire segment, minerals and other abrasives can be sprayed (polished) on the surface of steel pipes under the action of centrifugal force. It can not only completely remove rust, oxides and dirt, but also achieve the required uniform roughness of steel pipes under the action of violent impact and friction of abrasives.

　　After spraying (throwing) 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, spraying (throwing) is an ideal rust removal method for pipeline corrosion prevention. Generally speaking, shot blasting (sand) rust removal is mainly used for the internal surface treatment of pipes, and shot blasting (sand) rust removal is mainly used for the external surface treatment of pipes. Several problems should be paid attention to when using spray (throwing) to remove rust.

　　4.1 rust removal grade

　　For the construction process of epoxy, ethylene, phenolic and other anti-corrosion coatings commonly used for steel pipes, the steel pipe surface is generally required to reach the near white level (Sa2.5). Practice has proved that almost all oxide scale, rust and other dirt can be removed by using this rust removal grade, and the depth of anchor pattern can reach 40~100 μ m. Fully meet the requirements of the adhesion between the anti-corrosion coating and the steel pipe, and the spray (throwing) derusting process can meet the technical conditions of near white level (Sa2.5) with low operation cost and stable and reliable quality.

　　4.2 abrasive spraying (throwing)

　　In order to achieve the ideal derusting effect, the abrasive should be selected according to the hardness of the steel pipe surface, the original rust degree, the required surface roughness, coating type, etc. for single-layer epoxy, two-layer or three-layer polyethylene coating, it is easier to achieve the desired derusting effect by using the mixed abrasive of steel sand and steel shot. Steel shot can strengthen the steel surface, while steel sand can etch the steel surface.