SUS304L EP Pipe / EP Grade Stainless Steel Pipe for Medical Devices (Electropolished)

SUS304L EP tubes / EP Grade Stainless Steel Pipe for Medical Devices (Electropolished)

Stainless Steel Pipe Grade Classification: AP, MP, BA, EP

AP: Acid Pickling. Uses acidic solutions such as nitric acid and fluorine to remove the oxide layer from the steel pipe. Inexpensive and fast, but prone to causing intergranular corrosion and resulting in a rougher inner and outer surface with a higher likelihood of suspended impurities adhering.

MP: Mechanical Polishing. Commonly used for removing oxide layers, pores, and scratches from the surface of steel pipes. Its brightness and effect depend on the type of processing method. While mechanical polishing results in a more aesthetically pleasing appearance, it also reduces corrosion resistance; therefore, passivation treatment is necessary when used in corrosive environments. Furthermore, polishing material residue often remains on the steel pipe surface.

BA: Bright Annealing. During the drawing process, steel pipes require grease lubrication, and the grains are deformed due to processing. To avoid grease residue in the steel pipe, besides cleaning, high-temperature annealing can be used to eliminate deformation. Argon gas is used as the furnace atmosphere, and the combustion of argon with the carbon and oxygen on the steel pipe surface further cleans the surface, producing a bright finish. This method of using pure argon gas for annealing, followed by rapid cooling to brighten the surface, is called gloss annealing. While this method ensures the steel pipe is completely clean and free of external contaminants, the brightness of this surface, compared to other polishing methods such as mechanical, chemical, and electrolytic polishing, may appear somewhat matte. Of course, its effect is also related to the argon content and the number of heating cycles.

EP (Electro Polishing) utilizes anodizing. By appropriately adjusting the voltage, current, acid composition, and polishing time using electrochemical principles, it can achieve a bright, smooth, and clean surface, and also improve the surface’s corrosion resistance. Therefore, it is a method for brightening surfaces, although its cost and technology are also higher. However, because electropolishing highlights the original state of the steel pipe surface, it is not recommended for surfaces with severe scratches or holes.