Is there any difference between the surface of 316L stainless steel pipes divided into AP grade, MP grade, BA grade, and EP grade

In addition to the brand, material origin, and production and processing technology, a key factor that directly affects the price of 316L stainless steel pipe is the surface treatment method. To further improve the characteristics of 316L stainless steel pipes, there are several specific methods for processing the inner and outer surfaces of the pipes: pickling and passivation (AP), mechanical polishing (MP), bright annealing (BA), and electrolytic polishing (EP). According to test data and actual results, the roughness of 316L stainless steel pipe is reduced and the surface adsorption is weakened. In this case, what are the differences between AP grade, MP grade, BA grade, and EP grade stainless steel pipes?

The corrosion resistance of AP (Acid Pickling) pickled stainless steel mainly comes from the chemical reaction between the chromium element contained in it and oxygen to form a dense oxide film on its surface. The function of the pickling process is to allow this reaction to occur in advance to improve the corrosion resistance of 316L stainless steel pipes. During the pickling process, the oil stains and dirt attached to the surface of the 316L stainless steel pipe and some substances contaminated during production will be completely removed. The inner and outer surfaces of the pipeline are rough, and suspended impurities and residues are easy to adhere to.

The BA (Bright Annealing) bright annealing polishing wheel or polishing belt uses the abrasives in the polishing agent to grind and polish the surface of the 316L stainless steel pipe, thereby achieving a smooth and smooth polishing effect on the surface of the 316L stainless steel pipe. Its brightness depends on the type of processing technology. In addition, although mechanical polishing is more beautiful, it will also reduce corrosion resistance. Therefore, when used in corrosive environments, it needs to be passivated, and there are often polishing material residues on the surface of 316L stainless steel pipes.

During the production process of MP (Mechanical polishing) mechanically polished 316L stainless steel pipes, the grease grains used for lubrication may be deformed due to production and processing. To avoid grease residues in the 316L stainless steel pipes, high temperatures should be reasonably utilized during the annealing process. Argon gas acts as the atmosphere in the furnace, and the argon gas combines with the carbon and oxygen on the surface of the 316L stainless steel pipe to burn, further cleaning the surface of the 316L stainless steel pipe to form a bright effect. This method uses pure argon gas to anneal, heat, and rapidly cool to brighten the surface. The method of polishing the surface is called bright annealing. Although brightening the surface in this way can keep the 316L stainless steel pipe clean without any external contamination. However, if this surface brightness is compared with other polishing methods such as mechanical, chemical, and electrolysis, it will feel matte. Of course, the effect is also related to the argon content and the number of heating times.

EP (Electro Polishing) electrolytic polishing is a method of anodic treatment. According to the principle of electrochemistry, the voltage, current, acid composition, and polishing time are appropriately adjusted to not only make the surface bright, smooth, and clean. , it can also enhance the corrosion resistance of the surface, so it is a good method of brightening the surface. Of course, its cost and technology will also increase a lot.