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How to prevent welded steel pipe from corrosion

2020-04-30 10:15:18   COMMENT:0 HITS:
  The straight welded steel pipe has the advantages of simple production process, high production efficiency, low cost and rapid development. The strength of spiral welded steel pipe is generally higher than that of straight welded steel pipe. It can produce welded steel pipe with larger diameter with narrow blank and different diameter with the same width blank. However, compared with the same length of straight seam pipe, the weld length increases by 30-100%, and the production speed is low.

  Therefore, the small caliber API 5L Seamless Welded Steel Pipe mostly adopts straight seam welding, while the large caliber welded steel pipe mostly adopts spiral welding

  1. Cleaning

  Cleaning steel surface with solvent and emulsion

  2. Tool derusting

  It mainly uses steel wire brush and other tools to polish the steel surface, which can remove loose or raised oxide skin, rust, welding slag, etc

  3. Pickling

  Generally, chemical and electrolytic methods are used for pickling. Chemical pickling is only used for pipeline corrosion protection, which can remove oxide skin, rust and old coating. Sometimes, it can be used as the reprocessing after sand blasting.

  4. Rust removal by spraying (throwing)

  Spray (throwing) rust removal is a high-speed rotation of spray (throwing) blade driven by a high-power motor, so that steel grit, steel shot, wire section, minerals and other abrasives can spray (throwing) the welded steel pipe surface under the centrifugal force, which can not only completely remove rust, oxide and dirt, but also achieve the required uniform roughness under the action of abrasive strong impact and friction force.

  4. Derusting grade

  For the construction process of epoxy, vinyl, phenolic and other anticorrosive coatings commonly used for steel pipes, the steel pipe surface is generally required to reach near white level (Sa2.5).

  4.2 abrasive spraying (throwing)

  In order to achieve the ideal derusting effect, the abrasives should be selected according to the hardness of the welded steel pipe surface, the original degree of corrosion, the required surface roughness, coating type, etc. for single-layer epoxy, two-layer or three-layer polyethylene coating, the combination of steel grit and steel shot is easier to achieve the desired derusting effect.

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