Austenitic stainless steel has excellent corrosion resistance, high temperature oxidation resistance, good low temperature property and good mechanical property. Due to these properties, it is widely used in chemical industry, petroleum industry, power, nuclear engineering, aerospace, marine, pharmacy, light industry, textile industry and other department. Stainless steel mainly depends on the passivation film for the excellent corrosion resistance. If the film is incomplete or defective, the stainless steel will be still corrosive. In order to fully perform the potential ability of corrosion resistance, we usually carry out the pickling and passivation for the stainless steel. During the forming, assembling, welding, checking the welding seam(for example, MT, pressure test) and marking, the surface of the stainless steel equipment and components will be contaminated by oil, rust, non-metal dirt, low melting point metal contaminant, paint, welding slag and spatter. These substances will affect the surface quality of the stainless steel equipment and components; damage the oxidation film; decline the general corrosion resistance property and partial corrosion resistance property (including pitting corrosion and crevice corrosion); even lead to stress corrosion crack.

The surface cleaning, pickling and passivation for the stainless steel can maximumly improve the ability of corrosion resistance, also can protect the products from the pollution and make the products beautiful. In GBI50-1998 ‘Steel Pressure Vessel’ and international standard ‘Inspection of the Passivation Film Which is Formed on the Surface of the Stainless Steel after Electrolytic Polishing, Burnishing and Pickling/Passivation’ ISO15730, it said that pickling and passivation should be done for the stainless steel and containers with the requirement of corrosion resistance which are made of clad sheet steel. This regulation is aimed at the pressure containers which are used in petrochemical industry. Because these pressure containers are in the place where the pressure containers will touch the corrosion medium directly, pickling and passivation is necessary so as to ensure the ability of the corrosion resistance. For other industrial sectors, if they use the stainless steel only for the purpose of cleaning and beauty, not for the purpose of corrosion resistance, it is unnecessary to do pickling and passivation. For the welding seam, it is necessary to do pickling and passivation. If it has strict requirements for the corrosion resistance, such as Nuclear engineering, chemical equipment, storage tanks, stainless steel chemical tankers and so on, besides the pickling and passivation, final precision cleaning or mechanical polishing, or chemical and electrolytic polishing will be done by highly purified medium.