Corrosion mechanism of oil and gas steel pipe

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Corrosion mechanism of oil and gas steel pipe

At present, most of the current oil pipelines in China are steel pipes. The steel pipes have their inherent defects, that is, under the condition of oxygen and water, steel pipe will react under the chemical or electrochemical action of the environmental medium. For example, due to the different potential of the electrode, when the electrochemical reaction occurs, the parts with low electrode ratio are easy to lose electrons and form anode, and the potential ratio of the electrode is very low. In the higher part, it is easy to get electrons and form cathode. In the case of oxygen and water, the steel pipe will generate rust due to this chemical reaction. This kind of reaction is very harmful to the pipe, especially in the internal part of the steel pipe, where the protective measures such as nozzle and joint are relatively weak, long-term occurrence of this chemical reaction will cause leakage and perforation, which will affect the normal transportation function of the pipeline.

Steel pipe corrosion also has a great relationship with the surrounding media. The acid-base properties of soil and its microorganisms have a great relationship with the speed of pipe corrosion. At the same time, the change of groundwater level and the alternation of soil moisture are closely related to corrosion. The change of temperature is also closely related to the size of corrosion process. The higher the temperature is, the faster the corrosion is. Corrosion occurs not only outside the pipe, but also inside the pipe. Due to the moisture and oxygen contained in the transported materials, the corrosion will occur on the inner wall of the pipeline, resulting in the physical changes such as the rupture of the anti-corrosion coating, the perforation L and the deformation. Some of them can even directly damage the anti-corrosion coating and promote the peeling of the anti-corrosion coating. Soil stress, external force and material aging are the main causes of fracture. At the same time, the pipeline is easy to be corroded if it is not operated according to the standard procedures or the materials are not strictly controlled. For example, the use of hydrochloric acid and other chemicals to treat the inner wall of metal pipes will also cause scaling which will accelerate the corrosion of the inner wall of pipes.

2019-10-30T15:54:18+08:00 October 30th, 2019|