The use of internal epoxy coatings is an effective measure of corrosion protection of pipelines. However, in case of degradation of the coating properties after a certain time or in case of a construction or manufacturing defect of the coatings the operation of pipelines with an internal anti-corrosion coating can cause a significant problem for the operating organization. The service life of pipes with a violation of the integrity of the internal epoxy coating can be from 1 to 3 years. In this article the possibility of pipes inhibitor protection with defects of the internal polymer coating was investigated. The dependences of the coating size defect on the metal corrosion rate are considered. The dosages of the corrosion inhibitor at which there is a significant decrease in the local corrosion rate of samples with coating defects are estimated. It was found that the corrosion rate depends on the size of the coating defect. It is shown that the smaller the size of the coating defect, the higher the corrosion rate due to the localization of corrosion processes in a small area and an increase in the corrosion current density. As a result of the experiments it was found that the efficiency of inhibition of samples with a violation of the integrity of the internal coating in comparison with samples of base metal is significantly lower. A decrease in the corrosion rate of samples with defects occurs at higher dosages of the corrosion inhibitor. An economic calculation confirmed the possibility of pipe inhibition with a violation of the integrity of the internal coating before reconstruction and replacement. An analogy is made between pipes with a violation of the integrity of the internal coating with steel pipelines that fail due to localized corrosion. It has been suggested that in order to decrease local corrosion processes on the inner surface of pipelines, increased dosages of corrosion inhibitors should be used to achieve a corrosion rate not higher than the standard value.
References
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