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What is stainless steel? Why do we need stainless steel?

2021-11-30 Page view : 31 views

All metals react with oxygen in the atmosphere to form an oxide film on the surface. Unfortunately, the iron oxide formed on ordinary carbon steel continues to oxidize, causing the corrosion to continue to expand and eventually forming holes. You can use paint or oxidation-resistant metals (such as zinc, nickel, and chromium) for electroplating to ensure the surface of carbon steel, but, as people know, this protection is only a thin film. If the protective layer is damaged, the steel underneath will begin to rust.

Steel that is resistant to weak corrosive media such as air, steam, and water, and chemically corrosive media such as acids, alkalis, and salts. Also known as stainless acid-resistant steel. In practical applications, steel that is resistant to corrosion by weak corrosive media is often called stainless steel, and steel that is resistant to chemical media is called acid-resistant steel. Due to the difference in chemical composition between the two, the former is not necessarily resistant to corrosion by chemical media, while the latter is generally non-corrosive. The corrosion resistance of stainless steel depends on the alloying elements contained in the steel. Chromium is the basic element for the corrosion resistance of stainless steel. When the chromium content in the steel reaches about 12%, the chromium interacts with the oxygen in the corrosive medium to form a very thin oxide film (self-passivation film) on the surface of the steel. , Which can prevent further corrosion of the steel matrix. In addition to chromium, commonly used alloying elements include nickel, molybdenum, titanium, niobium, copper, nitrogen, etc., to meet the requirements of various uses for the structure and performance of stainless steel.