The damage caused by oil contamination to the quality of anti-corrosion pipes
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Dear experts: As the title suggests, I have encountered the aforementioned issue at work, and I hope to discuss it with everyone! Currently, prior to anti-corrosion treatment for long-distance pipelines, pre-treatment of the steel pipe surface is required. If there is oil on the surface of the steel pipe, in my opinion: first, in the case of pipes with oil on their surfaces, sandblasting for rust removal cannot completely remove the oil film from the surface; the anti-corrosion coating is applied directly to this oil film rather than directly to the steel pipe itself. As a result, the adhesion between the coating and the steel pipe substrate cannot be ensured. Secondly, after shot blasting of oil-stained pipes, the abrasives themselves become contaminated; subsequently, when pipes that are free of oil are subjected to shot blasting using these contaminated abrasives, it leads to secondary contamination of the pipes during the sandblasting process. Therefore, this issue is brought up for discussion, with the hope of gaining more knowledge on this subject.
Why is there no reply, no participation in the discussion?
Yes, in addition to rust removal, oil removal is also necessary; unfortunately, too few people understand this these days.
According to the standards, oil should be removed first, followed by rust removal； These days, oil removal treatment is rarely carried out during the construction of engineering projects. Firstly, the steel structures used in such projects are usually new, and they are hardly contaminated by oil, so there is little practical need for oil removal ； Secondly, the oil removal process is relatively complex; ordinary construction firms (with a qualification level of two or lower) usually do not have technicians who truly understand this process, let alone the workers on site ； In my opinion, oil removal prior to anti-corrosion treatment should be made mandatory as part of the **standards for structures that are under stress, exposed to certain temperatures, have highly strong steel components, or are recycled steel structures**
I’ve encountered a similar problem recently as well; the steel pipes are covered in oil, and I’m afraid sandblasting alone won’t be sufficient
Indeed, removing oil stains is an important step in preventing corrosion; with a lot of oil stains present, even the best coatings can develop problems. Furthermore, optimal surface treatment is achieved if the levels of nitrates, sulfates, and chlorides are also properly controlled.
I agree with the view from floor 4; although it is said that oil should be removed first and then rust, in practice very few people do this – some even don’t know how to remove oil at all. There are many reasons: it’s troublesome, as after degreasing one has to clean the surface, wait for it to dry, and then remove rust – which means several workdays of waiting. So, increased costs are of course the main reason. Also, what kind of oil it is, what type of oil phase it belongs to, and what materials can be used to remove the oil – these are not things that everyone understands.
The simplest solution is to use non-metallic pipes, which eliminates a lot of hassle.
The rust removal process on the surface of steel pipes requires first removing any oil and other impurities from the surface, such as dust. However, since most long-distance pipeline pipes are made by rolling sheet metal, it is inevitable that some oil from the manufacturing process ends up adhering to the surface of the steel pipes. It is generally required to inspect the surface of the steel pipe before sandblasting; sandblasting can only be carried out if there is no significant oil contamination. If there is a small amount of oil, it is necessary to use an alkaline detergent solution to remove the oil, while in cases of very little oil, the surface can be wiped clean with a cloth directly. In actual on-site operations, oil removal is generally not done; instead, sandblasting is used to remove it directly, with the sandblasting time needing to be extended.