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Relevant Steel Pipe Rust
Oct 17, 2017

First, in the pipe surface coating coating, is the most effective way to avoid the pipeline corrosion, but if the pipe surface rust of poor quality, reduced the adhesion of coating and surface coating of pipeline, simple cracking and drop, the effect can not be fully reflected.

Two. The influence of rust removing quality on pipeline service life

The anticorrosive coating must be coated evenly and completely, and adhesion to the tube surface is strong, so as to reach the anticorrosion intention. The quality of pipeline anticorrosion depends largely on the degree of adhesion coating and tube surface, adhesvity and depends on the quality of the rust tube surface, that is to say, the derusting quality factors, anticorrosion layer thickness, varieties, effects of derusting quality on the service life of the maximum.

Therefore, it is necessary to attach great importance to the quality of derusting. The quality of derusting includes two aspects: cleanliness and appearance roughness. The outer surface of the rust removing pipe ensures a great adhesion to the anticorrosive coating. Avoid coating during transportation and storage, ditch and backfilling process, due to collision, conflict, and soil pressure drop of cracking and smashing, maintain integrity, anti-corrosion layer sealing, effectively obstruct the flow of corrosive medium and water vapor intrusion in the anticorrosion layer of the coating and real play it shows the antiseptic effect. Production practice has proved that the quality of rust removal is better than that of rust removing, and the service life is 3~5 times longer. There are some data even thought that the failure factor of anticorrosive coating is 90%, because the quality of derusting is poor. Therefore, as long as the progress of rust removal quality, to ensure the quality of anti-corrosion layer, thereby extending the service life of the pipeline.

Three. The influence of derusting method on the appearance and adhesion of steel pipe

The appearance of the steel pipe is closely related to the selected derusting method, and it has a great influence on the adhesion of the anticorrosive layer and the tube surface. The steel wire brush can be used to remove the oxide and dirt caused by floating rust, but the oxide skin adhered to the tube surface can not be brushed off. The throwing pill (spray) rust, not only can completely remove rust, oxide skin and dirt, and the outer strong impact and friction in steel corrosion, a uniform roughness.  It is reported that the shape of the anchor bar formed by throwing (shot) pills can increase the metal surface by polishing many times. In this way, not only the physical adsorption area of the pipe surface is enlarged, but also the mechanical effect of the anticorrosive coating and the pipe surface is greatly strengthened. The application of throwing (spraying) pill rust removal can improve the quality of derusting, change the appearance of steel pipe, expand the appearance of products, and greatly increase the adhesion of the anticorrosive layer and the outer surface of the pipe. With the pipe through the cast (spray) pill after cleaning tube because of the strong impact was shot while strengthening. The data intensity improved by about 80%. The corrosion resistance is nearly doubled. The surface hardness also do not have the same degree of progress, in addition, the shot hit the post, eliminating the internal stress of weld crack can, to shade the wall of the tube surface and excessive corrosion, a comprehensive view of the effect. For the surface roughness of steel pipe after shot blasting, if it is too large, not only consumption of paint, but also in the tooth shape anchor groove "trough" to intercept the air, damage to the anti-corrosion layer. It may appear to cut coating "peaks", destroy the integrity of the anticorrosive coating, leading to corrosion. As for how rough the surface roughness is, some claim to be below 50 m, and the British standard does not exceed 100 m. Some people expect to be below 75 M. The roughness of the steel tube depends on three major factors, namely, the specific gravity, the size and the velocity of the projectile. By adjusting the three factors, different surface roughness can be obtained.

Four, domestic and foreign steel pipe rust skills outlined

China's pipeline derusting technology is relatively backward, in 1965, the use of artificial steel wire brush, sand derusting, low power, poor quality, high labor intensity, severe air pollution.  Later, the mechanical steel wire brush was used to remove the rust, and the asphalt anti-corrosion factory was prefabricated. It has a certain effect on extending the service life and improving the economic benefit of the pipeline. Although it is still improving, but the basic skills of wire brush rust, anticorrosion asphalt, and has been used until now. This situation is in line with the current foreign widely used shot blasting rust and polymer composition data anti-corrosion, backward generation. In recent years, with the oil industry development, excellent anticorrosion coating polymer composition appeared in large numbers, to promote the pipeline anticorrosion technology development, also put forward higher request to the steel tube derusting quality, derusting in various way, as long as the throwing pill (spray) was satisfied with the request, but is unable to reach this brush cleaning a grade.