Steel Pipe surface treatment method

What is the most effective steel surface treatment method? With China's sustained economic development, energy security energy industry to develop the country, long-distance oil and gas pipelines, oil (gas) pipeline anti-corrosion construction process and the surface treatment is the key factor in determining the service life of pipeline corrosion First, it is the premise of the anti-corrosion layer pipe can be firmly bonded. Validation by the research institutions, the life of the coating depends on the type of coating, coating quality and construction environment and other factors, the surface of the steel pipe processing affects about 50% of the life of the coating, therefore, should be in strict accordance with the coating specification the requirements of the steel pipe surface exploration and summary, the continuous improvement of the steel pipe surface treatment methods.

 

    1, the cleaning using a solvent, emulsion cleaning the steel surface, in order to achieve the removal of oil, grease, dust, lubricants and similar organic matter, but it can not be removed the steel surface rust, oxide, solder drugs, therefore only as a preservative production adjunct.

 

2 tools rust using a wire brush tool to polished steel surface, you can remove loose or tilt of the scale, rust, welding slag. Hand tools rust Sa2 the power tools rust Sa3 level, if the steel is attached to the surface of the solid oxide scale, the effect is not ideal tools rust, anchor pattern depth up to less than the requirements of anti-corrosion construction.

 

3, pickling generally use chemical and electrolytic two methods to do the pickling pipeline corrosion using only the chemical pickling, descaling, rust, old paint, can sometimes be used as a sand-blasting after reprocessing. Chemical cleaning surface can reach a certain cleanliness and roughness, but the anchor pattern shallow, and easy to pollute the environment.

 

Spray (throwing) radio rust spray (throwing) radio rust is driven by a high-power motor spray (throwing) shot leaves the high-speed rotating abrasive grit, steel shot, wire segment, minerals and other under the centrifugal force steel surface spray (throwing) shot treatment, not only completely remove rust, oxides and dirt, and the steel pipe under severe abrasive impact and friction force, but also to achieve the required uniform roughness.

 

    After spray (parabolic) radio rust, can not only expand the physical adsorption of the surface of the pipe, but also can enhance the mechanical adhesion of the coating with the surface of the tube. Therefore, the pipeline corrosion rust spray (throwing) radio rust. Generally, shot peening (sand) rust is mainly used for processing the inner surface of the pipe, shot blasting (sand), rust is mainly used for processing the outer surface of the pipe. Using spray (throwing) radio rust should pay attention to several issues.

4.1 rust grades for the construction technology of steel pipe commonly used epoxy, vinyl, phenolic anti-corrosion coatings, general requirements for steel pipe surface to reach nearly white (Sa2.5). Practice has proved that this rust grades almost get rid of all scale, rust and other contaminants, anchor pattern depth of 40 to 100μm, coating and steel adhesion spray (throwing) shot in addition to the the rust process can be used lower operating costs and a stable and reliable quality to nearly white level (Sa2.5) conditions.

 

4.2 spray shot (throwing) abrasive in order to achieve the desired blasting effect, should be based on the hardness of the surface of the pipe, the original extent of corrosion, the required surface roughness, coating type to select abrasive monolayer epoxy, two or three layer polyethylene coating, using the mixed abrasive grit and steel shot rust more likely to achieve the desired effect. Steel shot to enhance the role of the steel surface, etching the surface of the steel Grit role. Grit and steel shot abrasive mixed material (usually steel shot hardness 40 ~ 50HRC, grit hardness of 50 ~ 60HRC can be used for a variety of steel surfaces, even if it is used in the C-and D level of corrosion on the steel surface, in addition to The rust was also very effective.

 

4.3 abrasive particle size and ratio in order to obtain a better uniformity of cleanliness and roughness distribution of abrasive particle size and the ratio of design is very important. The roughness too big could easily lead to thinning of the coating at the peak of the anchor pattern; too deep anchor pattern coating in the corrosion process is easy to form bubbles, seriously affect the performance of the coating. The roughness is too small will cause the adhesion of the coating and impact strength decreased. For serious internal pitting, not only by the high impact of the large particles of abrasive, must also rely on small particles polished off the corrosion products to achieve the cleaning effect, the reasonable mix design can not only slow down the abrasive wear of pipes and nozzles (blades) and the utilization of the abrasive can also be greatly improved. Typically, the particle size of the steel shot as 0.8 ~ 1.3mm, the steel grit particle diameter of 0.4 ~ 1.0mm, as the main component of which 0.5 ~ 1.0mm. Sand pill than the average for the

 

5 ~ 8. Should be noted that in practice, the ideal ratio of abrasive grit and steel shot is difficult to achieve, due to the hard and brittle grit crushing rate than steel shot. To this end, in operation, should continue to sampling and testing of mixed abrasive, based on the distribution of particle size, to the incorporation of new abrasive blasting machine, and the number of new doped abrasive grit predominant.

 

4.4 rust speed steel pipe the descaling speed vary depending on the type of abrasive and abrasive displacement per unit time, the abrasive is applied to the total kinetic energy E of the steel pipe and a single abrasive particle kinetic energy E1.