Austenitic stainless steel has good corrosion resistance, high temperature oxidation resistance, better low temperature performance, and excellent mechanical properties and energy. Therefore, it is widely used in chemical, petroleum, electric power, nuclear engineering, aerospace, shipbuilding, pharmaceutical, light industry, textile and other sectors. Its main purpose is to prevent corrosion and rust. The corrosion resistance of stainless steel mainly depends on the surface passivation film. If the film is incomplete or defective, the stainless steel will still be corroded. In engineering, pickling and passivation are usually carried out to make the corrosion resistance potential of stainless steel play a greater role. In the process of forming, assembling, welding, welding seam inspection (such as flaw detection, pressure test) and construction marking of stainless steel equipment and parts, surface oil stains, rust, non-metallic dirt, low melting point metal contaminants, paint, welding slag and spatter These substances affect the surface quality of stainless steel equipment and components, destroy the oxide film on the surface, reduce the overall corrosion resistance and local corrosion resistance of steel (including pitting corrosion, crevice corrosion), and even cause stress corrosion cracking.
The cleaning, pickling and passivation of the stainless steel surface can not only maximize the corrosion resistance, but also prevent product contamination and obtain a beautiful appearance. According to the provisions of GB150-1998 "Steel Pressure Vessels", "Pickling and passivating the surface of vessels made of stainless steel and composite steel plates with anti-corrosion requirements". This regulation applies to pressure vessels used in the petrochemical industry because these equipment are used in direct contact with corrosive media. From the perspective of ensuring corrosion resistance, pickling passivation is necessary. For other industrial fields, if it is not for anti-corrosion purposes, it is only based on the requirements of cleanliness and beauty, and there is no need to pickling and passivating stainless steel materials. However, the welds of stainless steel equipment need to be pickled and passivated. For nuclear engineering, certain chemical equipment and other applications with strict requirements, in addition to pickling passivation, high-purity media must be used for final fine cleaning or mechanical, chemical and electrolytic polishing and other finishing.
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