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Technology: how to deal with the surface of high-frequency welded steel pipe(1)

    With China’s sustained economic development, national energy industry has been developed, and long-distance oil and gas pipelines is an important way to energy security. In the oil (gas) pipeline anti-corrosion construction process, the steel pipe surface treatment is one of the key factor to determine the pipeline anti-corrosion. It is the premise of whether the steel pipe can combine with a solid coating. Verified by research institutions, in addition to the life of the coating depends on coating type, coating quality and construction of environmental factors, the steel tube surface treatment on the coating affect their lives about 50%. Therefore, we should be strictly in accordance with specifications of the coating steel surface, continually explore and summarize the continuous improvement of steel surface treatment.
    1, cleaning
    Using of solvent, emulsion to clean the steel surface, in order to achieve the removal of oil, grease, dust, lubricants and similar organisms, but it can not remove the steel surface rust, oxide, welding flux, etc., and therefore it’s only as a supplementary corrosion means of the production.
    2, tools rust cleaning
    Tools rust cleaning mainly uses a steel wire brush and other tools to polish the steel surface, which can remove loose or tilt of oxidation, rust, welding slag. Hand tools rust can reach Sa2 grade, power tools rust can be up to Sa3 level. If the steel surface attached to a solid oxide scale, the result of tools rust cleaning is not ideal, corrosion construction requirements is not reach the depth of the anchor pattern.
    3, pickling
    Generally two methods used to do chemical and electrolytic pickling process, pipeline corrosion using only chemical etching to remove oxidation, rust, old coatings, sometimes used as a sand-blasting after reprocessing. Although chemical cleaning can achieve a certain surface cleanliness and roughness, but the anchor pattern is light, and easily caused by pollution of the environment .
    4, spray cleaning rust
    Spray cleaning rust is driven by high-power motor spray shooting high-speed rotating blades, so that steel grit, steel shot, steel wire segments, minerals and other abrasive under the centrifugal force on the steel surface spray processing. Not only can it completely remove rust, oxides and dirt, and pipe in severe abrasive impact and the role of friction, but also to achieve the required uniform roughness.
    After spray cleaning rust, the surface of the pipe can expand not only the physical adsorption, and can enhance the surface of the pipe coating and mechanical adhesion. Therefore, the spray cleaning rust is the ideal way to pipe corrosion. In general, shot blasting cleaning rust is mainly used for the inner surface treatment of the steel pipe, ball blasting is mainly used for pipe outer surface treatment. The use of spray cleaning rust should be noted five problems.
    4.1 derusting grade
    For the Common use of steel pipe of epoxy, vinyl, phenolic type anti-corrosion coating, etc. construction technology generally requires the steel pipe surface reached to nearly white level (Sa2.5). Practice has proved that using this level of rust can get rid of almost all of the oxide, rust and other contaminants, anchor pattern depth can reach 40 ~ 100¦Ìm, fully meet the adhesion of coating and steel requirements, and spray cleaning rust technology can use at a lower operating cost and reliable quality to almost white level (Sa2.5) technical conditions.
    The another four points will also be introduced tomorrow by us.

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