Why is Xi'an stainless steel pipe corrosion resistant?

Edit:Shaanxi Tonghui Steel Co., Ltd.UpDate:2020-01-09

Generally speaking, Xi'an stainless steel pipes are steels that are not easy to rust. In fact, some stainless steels have both rust and acid resistance (corrosion resistance). The rust and corrosion resistance of stainless steel is due to the formation of a chromium-rich oxide film (passivation film) on its surface. This stainless and corrosion resistance are relative.

Tests have shown that the corrosion resistance of steel in weak media such as atmosphere and water and oxidizing media such as nitric acid increases with the increase of chromium water content in steel. When the chromium content reaches a certain percentage, the corrosion resistance of steel occurs Sudden change, from easy to rust to not easy to rust, from not resistant to corrosion. There are many ways to classify stainless steel. According to the organization structure at room temperature, there are martensite type, austenite type, ferrite and duplex stainless steel; according to the main chemical composition classification, it can basically be divided into two major systems: chromium stainless steel and chromium nickel stainless steel;

Xi'an stainless steel plate and tube are divided into nitric acid-resistant stainless steel, sulfuric acid-resistant stainless steel, seawater-resistant stainless steel, etc. according to their use; according to the type of corrosion resistance, they can be divided into pitting-resistant stainless steel, stress-resistant stainless steel, and intergranular stainless steel. Feature classification can be divided into non-magnetic stainless steel, free-cutting stainless steel, low temperature stainless steel, high strength stainless steel and so on. Because stainless steel has a series of characteristics such as excellent corrosion resistance, formability, compatibility, and toughness over a wide temperature range, it has been widely used in heavy industry, light industry, daily necessities, and building decoration industries. . All metals react with atmospheric oxygen to form an oxide film on the surface.

Unfortunately, the iron oxide formed on ordinary carbon steel continues to oxidize, causing the rust to expand and form holes. Carbon steel surfaces can be electroplated with paint or oxidation-resistant metals such as zinc, nickel, and chromium, but, as is known, this protection is only a thin film. If the protective layer is broken, the underlying steel begins to rust.

The corrosion resistance of stainless steel depends on chromium, but because chromium is one of the components of steel, the protection methods are different. When the added amount of chromium reaches 10.5%, the atmospheric corrosion resistance of steel is significantly increased, but when the chromium content is higher, although the corrosion resistance can still be improved, it is not obvious. The reason is that when steel is alloyed with chromium, the type of surface oxide is changed to a surface oxide similar to that formed on pure chromium metal. This tightly adhered chromium-rich oxide protects the surface from further oxidation. This oxide layer is extremely thin. Through it, you can see the natural luster of the surface of Xi'an stainless steel pipe, which makes stainless steel have a unique surface. Moreover, if the surface layer is damaged, the exposed steel surface will react with the atmosphere to repair itself, re-form this oxide "passivation film", and continue to play a protective role. Therefore, all stainless steel elements have a common characteristic, that is, the chromium content is above 10.5%.