Introduction of rust removal methods and benefits of steel pipes

(1) Spray (throwing) rust removal is to drive the spray (throwing) blade to rotate at a high speed through a high-power motor so that abrasives such as steel sand, steel shot, iron wire segment, and minerals are sprayed (throwing) on the surface of the steel pipe under the action of centrifugal force. ) shot treatment, not only can altogether remove rust, oxides, and dirt, but also the steel pipe can achieve the required uniform roughness under the action of the violent impact and friction of the abrasive.
(2) If the roughness is too small, the adhesion and impact strength of the anti-corrosion layer will decrease. For serious internal pitting corrosion, it is not only necessary to rely on the high-strength impact of large-particle abrasives, but also requires small particles to grind off corrosion products to achieve the cleaning effect. At the same time, a reasonable ratio design can slow down the abrasive wear on pipes and nozzles (blade), and the utilization rate of abrasives can also be greatly improved. Usually, the particle size of steel shot is 0.8~1.3mm, and the particle size of steel grit is 0.4~1.0mm, of which 0.5~1.0mm is the main component. The ratio of sand to the pill is generally 5~8.
(3) After rust removal, it can not only expand the physical adsorption on the surface of the pipe but also enhance the mechanical adhesion between the anti-corrosion layer and the surface of the pipe. Therefore, spraying (throwing) rust removal is an ideal rust removal method for pipeline anticorrosion. Generally speaking, shot blasting (sand) derusting is mainly used for inner surface treatment of pipes and shot blasting (sand) derusting is mainly used for outer surface treatment of pipes.
(4) To obtain better uniform cleanliness and roughness distribution, the particle size and ratio design of the abrasive are essential. If the roughness is too large, the anti-corrosion layer will become thinner at the peak of the anchor pattern; at the same time, because the anchor pattern is too deep, the anti-corrosion layer will easily form bubbles during the anti-corrosion process, which will seriously affect the performance of the anti-corrosion layer.


It should be noted that in practice, the ideal ratio of steel grit to steel shot in the abrasive is difficult to achieve because the hard and brittle steel grit has a higher breakage rate than steel shot. For this reason, the mixed abrasive should be continuously sampled and tested in operation. According to the particle size distribution, new abrasives should be added to the rust remover, and the amount of steel grit should be the main part of the new abrasives added. The rust removal speed of the steel pipe depends on the type of abrasive and the displacement of the abrasive, that is, the total kinetic energy E of the abrasive applied to the straight seam steel pipe per unit time and the kinetic energy E1 of the single particle abrasive. When the equipment is fixed, m is a constant, y is a constant, so E is also a constant, but due to the crushing of the abrasive, m1 changes, so generally, the abrasive with a lower loss rate should be selected, which is conducive to improving the cleaning speed and longevity. life of leaves.


For the construction process of epoxy, ethylene, phenolic, and other anti-corrosion coatings commonly used in steel pipes, it is generally required that the surface of steel pipes reach the nearly white level (Sa2.5). The practice has proved that this rust removal grade can remove almost all oxide scale, rust, and other dirt, and the depth of the anchor pattern reaches 40~100μm, which fully meets the adhesion requirements of the anti-corrosion layer and the steel pipe. The rusting process can reach the technical conditions of near white level (Sa2.5) with low operating cost and stability and reliability. 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 coating, using The mixed abrasive of steel grit and steel shot is easier to achieve the ideal rust removal effect. Steel shot has the effect of strengthening the steel surface, while steel grit has the effect of etching the steel surface. The mixed abrasive of steel grit and steel shot (usually the hardness of steel shot is 40~50HRC, and the hardness of steel grit is 50~60HRC can be used on various steel surfaces, even on steel surfaces with C and D rust, in addition to Rust works well too.