​The surface of stainless steel pipes is divided into AP grade, MP grade, BA grade, and EP grade? Is there any difference?

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

AP (Acid Pickling) Pickling Treatment

The corrosion resistance of 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 role of the pickling process is to allow it to react in advance to improve the corrosion resistance of stainless steel pipes. During the pickling process, the oil stains and dirt attached to the surface of the stainless steel pipe and some substances contaminated during production will be thoroughly removed. The inner and outer surfaces of the pipe are rough and easy to adhere to suspended impurities and residues.

AP grade stainless steel pipe BA (Bright Annealing)

Bright annealing polishing wheel or polishing belt uses abrasives in the polishing agent to grind and polish the surface of 316L stainless steel pipe, so that the surface of 316L stainless steel pipe can achieve a smooth polishing effect. 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 a corrosive environment, it needs to be passivated, and polishing materials often remain on the surface of 316L stainless steel pipe.

MP (Mechanical polishing) Mechanical polishing

During the production process of 316L stainless steel pipe, the grease grains used for lubrication may be deformed due to production and processing. In order to avoid grease residue in 316L stainless steel pipe as much as possible, high temperature is used to use argon as the furnace atmosphere during the annealing process. Argon gas is combined with carbon and oxygen on the surface of 316L stainless steel pipe to burn, and the surface of 316L stainless steel pipe is further cleaned to form a bright surface effect. This method of using pure argon gas for annealing heating and rapid cooling to brighten the surface is called bright annealing. Although this method can keep the surface of 316L stainless steel pipe clean and free of any external pollution. But the brightness of this surface will feel matte compared with other polishing methods such as mechanical, chemical, and electrolytic. Of course, its effect is also related to the content of argon and the number of heating times.

EP (Electro Polishing) Electrolytic Polishing

Electrolytic polishing is a method of using anodizing. 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, but also enhance the corrosion resistance of the surface. Therefore, it is a good method for brightening the surface. Of course, its cost and technology will also increase accordingly.

If you want to know more, you can contact me by email at Julie@gaoshengpipe.com