Introduction to steel pipe rust removal methods and benefits

(1) spraying (throwing) rust removal uses a high-power motor to drive the spraying (throwing) blades to rotate at high speed so that steel sand, steel shots, wire segments, minerals, and other abrasives spray (throw) the surface of the steel pipe under the action of centrifugal force. ) shot treatment, not only can all rust, oxides, and dirt be removed, but the steel pipe can also achieve the required uniform roughness under the action of the violent impact and friction of the abrasive.
(2) too small roughness will cause the adhesion and impact strength of the anti-corrosion layer to decrease. for severe internal pitting corrosion, we cannot rely solely on high-intensity impact with large-grain abrasives. we also need to rely on small particles to grind away the corrosion products to achieve the cleaning effect. at the same time, a reasonable proportion design can not only slow down the wear of the abrasives on the pipes and nozzles (blade) but 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 sand is 0.4~1.0mm, of which 0.5~1.0mm is the main component. the sand shot ratio is generally 5~8.
(3) after rust removal, it can not only expand the physical adsorption effect on the pipe surface but also enhance the mechanical adhesion between the anti-corrosion layer and the pipe surface. therefore, spraying (throwing) rust removal is an ideal rust removal method for pipeline anti-corrosion. generally speaking, shot blasting (sand) rust removal is mainly used for the inner surface treatment of pipes, and shot blasting (sand) rust removal is mainly used for the outer surface treatment of pipes.
(4) to obtain better uniform cleanliness and roughness distribution, the particle size and proportion design of the abrasive are very important. too much roughness will easily cause the anti-corrosion layer to become thinner at the peaks of the anchor lines; at the same time, because the anchor lines are too deep, bubbles will easily form in the anti-corrosion layer during the anti-corrosion process, seriously affecting the performance of the anti-corrosion layer.

it should be noted that in actual operation, the ideal ratio of steel grit and steel shot in the abrasive is difficult to achieve because the hard and brittle steel grit has a higher breakage rate than the steel shot. for this reason, the mixed abrasives should be continuously sampled and tested during operation, and new abrasives should be added to the rust remover according to the particle size distribution. moreover, among the new abrasives added, steel grit should account for the majority. 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 applied by the abrasive to the straight seam steel pipe per unit time and the kinetic energy e1 of the single-grain abrasive. when the equipment is fixed, m is a constant and y is a constant, so e is also a constant. however, due to the crushing of the abrasive, m1 changes. therefore, abrasives with lower loss rates should generally be selected, which will help improve the cleaning speed and long-term maintenance. leaf life.

for the construction technology of epoxy, vinyl, phenolic, and other anti-corrosion coatings commonly used for steel pipes, the surface of the steel pipe is generally required to reach near white level (sa2.5). the practice has proven that using this level of rust removal can remove almost all oxide scale, rust, and other dirt. the depth of the anchor pattern can reach 40~100μm, which fully meets the adhesion requirements between the anti-corrosion layer and the steel pipe. the rusting process can reach near-white level (sa2.5) technical conditions with lower operating costs 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 original rust degree, the required surface roughness, the coating type, etc. for single-layer epoxy, two-layer, or three-layer polyethylene coatings, the mixed abrasive of steel sand and steel shot makes it easier to achieve the ideal rust removal effect. steel shot has the function of strengthening the steel surface, while steel grit has the function of etching the steel surface. mixed abrasives of steel grit and steel shot (usually the hardness of steel shot is 40~50hrc, the hardness of steel grit is 50~60hrc) can be used on various steel surfaces, even on c- and d-class rusted steel surfaces, except the rust effect is also very good.