In the whole process of applying carbon steel seamless pipe, if the carbon steel seamless pipe corrode, which will affect all normal applications, what are the reasons for the corrosion of carbon steel seamless pipe?
1. Pitting corrosion. It refers to a form of corrosion damage that occurs in some areas of the metal surface of carbon steel seamless pipe. After the occurrence of crevice corrosion, it can quickly develop to a deep trend through carbon steel seamless pipe. Pitting corrosion is very harmful, especially for all kinds of high-pressure vessels. After corrosion occurs, it should be polished or painted immediately to prevent further corrosion.
2. Symmetric corrosion. This means that all seamless steel pipe pipelines exposed to corrosive natural environments will undergo chemical changes and suffer symmetrical corrosion. This type of corrosion can accurately measure its corrosion rate and predict and analyze its corrosion level. According to the accurate measurement results, the safety performance and service period can be set. Therefore, in many types of corrosion, symmetrical corrosion is not a risk. The corrosion level of symmetrical corrosion is generally measured and predicted and analyzed accurately based on the quality of carbon steel seamless pipe and the reduction of seamless steel pipe thickness. Outside of the unique natural environment, carbon steel seamless pipe have a low symmetrical corrosion rate, a long service life, and low maintenance costs.
3. Intergranular corrosion. It refers to corrosion along dislocations, which destroy the connections between crystals. It will make the seamless steel tube brittle or lose the compressive strength, which is very easy to cause safety accidents. Intergranular corrosion is a key corrosion method of martensitic carbon steel seamless pipe. It is because the dislocation area and the crystal composition or ground stress are different, which causes the regional electrode potential of the dislocation area to be significantly reduced, which in turn causes the difference in electrode potential.
4. Fatigue and corrosion. Refers to the damage of carbon steel seamless pipe under the effects of corrosive substances and alternating ground stress, characterized by corrosion pits and many cracks. Significantly reduce the fatigue limit of carbon steel seamless pipe, causing premature rupture. Corrosion fatigue of seamless steel pipe does not mean fatigue of mechanical equipment, it does not have a certain fatigue strength. As the frequency of the circulatory system increases, the fatigue limit is reduced.
Therefore, the corrosion of carbon steel seamless pipe can be divided into these four types, and the appropriate solution should be selected according to the specific situation.