Corrosion causes of seamless steel pipes

If the seamless steel pipe is corroded, it will affect the application of the steel pipe and increase the economic cost. The corrosion of the seamless steel pipe can be divided into four types, which will be introduced in detail next.

1. Intergranular corrosion. It refers to corrosion along dislocations, which destroys connections between crystals. This type of corrosion is very harmful, it will make the seamless steel pipe brittle or lose its compressive strength, which is very easy to cause safety accidents. Intergranular corrosion is the key corrosion method of martensitic seamless steel pipe. It is because the dislocation area and the crystalline composition or ground stress are different, resulting in a significant reduction in the electrode potential in the dislocation area, which in turn results in a difference in electrode potential.

2. Uniform corrosion. This means that all seamless steel pipe piping exposed to corrosive environments will undergo chemical changes and suffer uniform corrosion. This type of corrosion can accurately measure its corrosion rate and predict its corrosion level. Based on precise measurements, its safety performance and lifetime can be set. Therefore, in many types of corrosion, uniform corrosion is not a risk, and the corrosion level of uniform corrosion is generally accurately measured and predicted according to the reduction of seamless steel pipe quality and seamless steel pipe thickness. Outside the unique natural environment, the uniform corrosion rate of seamless steel pipes is very low, the service life is long, and the maintenance is low.

3. Pitting corrosion. It refers to a form of corrosion damage that occurs in part of the metal surface of the seamless steel pipe. After crevice corrosion occurs, it can rapidly develop into a deep, through seamless steel pipe. Pitting corrosion is very dangerous, especially for various high pressure vessels. After corrosion occurs, it should be polished or painted immediately to prevent further corrosion.

4. Fatigue corrosion. Refers to the damage of seamless steel pipes under the action of corrosive substances and alternating ground stress, characterized by corrosion pits and many cracks. Significantly reduces the fatigue limit of seamless steel pipes, resulting in premature rupture. Corrosion fatigue of seamless steel pipe does not mean fatigue of mechanical equipment, it does not have a certain fatigue strength. With the increase in the frequency of the circulatory system, the fatigue limit is reduced.

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