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Do you know how important is the passivation film quality on the surface of stainless steel pipe?

Do you know how important is the passivation film quality on the surface of stainless steel pipe?

Time:2022-03-17 Source:China Wuxi JiaNuo Special Steel Co.

Stainless steel is relying on its surface to form a layer of very thin and strong and fine stable chromium-rich oxide protective film to prevent the continued infiltration of oxygen atoms, continued oxidation, and the ability to obtain rust and corrosion resistance. Once there is some reason, this film is constantly destroyed, the oxygen atoms in the air or liquid will continue to infiltrate or metal iron atoms continue to precipitate out, the formation of loose iron oxide, the metal surface is also subject to constant rust.

2520 stainless steel tube This surface film is damaged in many forms, common in daily life, the surface of stainless steel containing other metal elements of dust or foreign metal particles of adhesion, in the humid air, adhesion and stainless steel between the condensation, the two will be connected into a microcell, triggering an electrochemical reaction, the protective film is destroyed, called electrochemical corrosion. 2520 stainless steel tube Surface adhesion of organic matter juice such as squash, noodle soup, spit, etc., in the presence of water oxygen, constitutes organic acid, a long time then organic acid corrosion of the metal surface. 2520 stainless steel pipe surface adhesion containing acid, alkali, salt substances such as decorative walls of alkaline water, lime water spray, causing local corrosion. In polluted air such as the atmosphere containing a large number of sulfides, carbon dioxide, nitrogen oxide, condensate, the formation of sulfuric acid, nitric acid, acetic acid liquid point, causing chemical corrosion.

2520 stainless steel pipe so that it has more irreplaceable advantages of other pipes, engineering applications will be more and more, the use will become more and more popular, the prospects are good. With the implementation of China’s reform and opening-up policy, the national economy has gained rapid growth, urban residential, public buildings and tourism facilities are built in large numbers, the hot water supply and domestic water supply has put forward new requirements. Especially water quality issues, people pay more and more attention to the requirements are also increasing. 2520 stainless steel is austenitic chromium-nickel stainless steel has good oxidation resistance, corrosion resistance, because of the higher percentage of chromium and nickel makes have much better creep strength, at high temperatures can continue to work, with good high temperature resistance. 2520 stainless steel plate because of the high content of nickel Ni, chromium Cr, has good resistance to oxidation, corrosion, corrosion resistance. Acid salty, high temperature resistance, high temperature resistant steel tubes are used for manufacturing electric heating furnace tubes and other occasions, austenitic stainless steel increased carbon content, due to its solid solution strengthening effect to improve the strength, austenitic stainless steel chemical composition characteristics of chromium, nickel based on the addition of elements such as molybdenum, tungsten, niobium and titanium, due to its organization for the face-centered cubic structure, and therefore at high temperatures have high strength and creep strength 2520 Stainless steel is an abbreviation of the Chinese stainless steel standard.

However, in the actual processing, pickling passivation processing has considerable difficulty, mainly focusing on the aspects of stainless steel materials can not be removed by conventional stainless steel descaling methods to remove the surface oxide skin of the parts, stainless steel pickling to remove the oxide skin applicable to the material. Material passivation processing process materials encounter air will not corrode, and destroy the size of the parts and surface finish, but in the processing process and must be used pickling passivation such a strong oxidizing agent to make the surface of the parts to generate a passivation film to achieve corrosion resistance. Removal of oxide after heat treatment: stainless steel mainly Ti, Cr, Ni, Si, V, Mn, Mo and other elements, these elements in the heat treatment process to form a thicker and more dense oxide, and can be composed of iron, chromium, nickel and oxygen with a spinel structure of dense oxide film FeCrO4, and chemically stable. Therefore, it is not easy to remove the oxide film. Low-temperature solidification aging parts oxide is thin, generally lavender, for this type of parts of the oxide processing is relatively easy to some.

Parts according to the stainless steel pickling passivation pickling, the surface of the oxide has been basically clean, and not corrosive parts, parts surface does not leave hanging ash, can be directly followed by passivation treatment process. Passivation process after pickling parts in the air corrosion resistance is poor, such as exposure to the air, the surface of the parts will rust. To enhance the corrosion resistance of the parts, the surface of the parts must generate a dense, good corrosion resistance passivation film to achieve the purpose of corrosion resistance.