What are the grades of rust removal for anti-corrosion steel pipes?

Anti-corrosion steel pipes refer to steel pipes treated with anti-corrosion technology, which can effectively prevent or slow down corrosion caused by chemical or electrochemical reactions during transportation and use. Anti-corrosion steel pipe base materials include spiral pipes, straight seam pipes (such as LSAW pipes, ERW pipes), seamless pipes, etc. It is widely used in pipeline engineering fields such as long-distance water transportation, petroleum, chemical industry, and natural gas, thermal power, sewage treatment, water sources, bridges, steel structures, marine water transportation piling, etc.

The rust removal levels of anti-corrosion pipeline surface treatment are summarized as follows:

For the construction techniques of epoxy, vinyl, phenolic and other coatings commonly used for steel pipes, the surface of the steel pipe is generally required to reach near white level (Sa2.5). Practice has proven that using this level of rust remover can remove almost all skin, rust and other dirt, and the anchor pattern can reach 40~100μm, fully meeting the adhesion requirements between the layer and the steel pipe. The spray (throwing) jet rust removal process can reach the technical conditions of near white level (Sa2.5), with low operating cost and stable quality.

In order to achieve the ideal rust removal effect, the abrasive should be selected according to the hardness of the steel pipe surface, the degree of original rust, the required surface roughness, the type of coating, etc. For single-layer epoxy, two-layer or three-layer polyethylene coatings, ideal rust removal is easily achieved using a mixture of steel sand and steel shot. Steel shot has the function of steel surface, while steel grit has the function of etching the steel surface.

In order to obtain better and even cleanliness and roughness distribution, the particle size and proportion design of the abrasive are very important. If the roughness is too large, the layer at the peak of the anchor pattern will become thinner; at the same time, because the anchor pattern is too deep, the layer will easily form bubbles during processing, seriously affecting the performance of the layer.

If the roughness is too small, the interlayer adhesion and impact strength will be reduced. For severe internal pitting corrosion, the cleaning effect cannot be achieved only by the impact of large-grained abrasives. Small-grained corrosion products also need to be worn away. At the same time, reasonable proportion design can not only slow down the wear of the abrasive on the pipes and nozzles (blade), but also improve the utilization rate of the abrasive. Usually the particle size of steel shot is 0.8~1.3mm, and the particle size of steel sand is 0.4~1.0mm, of which 0.5~1.0mm is the main component. The sand to grain ratio is generally 5 to 8.

ERW pipe：https://www.eastern-steels.com/products/erw-steel-pipe.html