In the whole process of application of
seamless tubes (SMLS), if there is corrosion, it will affect all normal applications. So what are the reasons for the corrosion of seamless tubes?
1. Pitting corrosion. It refers to a corrosion damage method that occurs in part of the metal surface of the 16mn seamless pipe. After the pitting corrosion occurs, it can quickly develop to the depths through the seamless steel pipe. The damage of pitting corrosion is very large, especially it is extremely bad for various high pressure vessels. Pitting corrosion should be polished or painted immediately to prevent further corrosion.
2. Uniform corrosion. It refers to all chemical changes on the surface of stainless steel pipes exposed to the corrosive natural environment and uniform corrosion. This type of corrosion can accurately measure its corrosion rate, and can also predict and analyze its corrosion level, and based on the accurate measurement results, set its safety performance and service life. Therefore, uniform corrosion is a non-risk corrosion among many types of corrosion. Generally, the corrosion level of uniform corrosion is considered and predicted according to the quality of the seamless steel pipe and the reduction of the thickness of the stainless steel pipe. In addition to the natural environment, stainless steel has a very low rate of uniform corrosion, long service life and low maintenance costs.
3. Intergranular corrosion. It refers to the corrosion that develops along the dislocation, which destroys the connection of the crystal. This kind of corrosion is more harmful, it can make the 16mn seamless pipe brittle or lack the compressive strength, which can easily lead to sudden safety accidents. Intergranular corrosion is the key corrosion method of martensitic 16mn seamless pipe. It is caused by the difference between the dislocation region and the intragranular composition or ground stress, resulting in a significant reduction in the electrode potential in the dislocation region and the difference in electrode potential.
4. Fatigue corrosion. It refers to the damage of seamless pipes under the action of corrosive substances and alternating ground stress, which is characterized by corrosion pits and many cracks. Significantly reduces the fatigue limit of stainless steel sheets, resulting in premature rupture. Corrosion fatigue 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 has been reduced.
