The mystery of stainless steel not rusting

    The "mystery" of stainless steel not rusting Michael L. Free, a metallurgical engineer at the University of Utah, provided an explanation for the "mystery" of stainless steel not rusting: the reason why stainless steel remains stainless or does not rust is due to the alloy elements and The chemical and reaction between the environment. Stainless steel contains iron, chromium, manganese, silicon, carbon, and in many cases, it also contains a large amount of nickel and molybdenum. These elements react with oxygen from water and air to form a very thin and stable film composed of corrosion products such as metal chlorides and hydroxides. Aluminum plays a leading role in the formation of this corrosion product film by reacting with oxygen. In fact, all stainless steel accounts for 10% by definition.

The existence of this stable film as a barrier restricts oxygen and water from proceeding to the underlying metal surface and avoids further corrosion. Because the formation of this kind of film is so easy and fast, so even with only a small amount of atomic film layer, the corrosion degree is reduced to a very low level. The fact that this film is much thinner than the wavelength of light makes it visible to the naked eye only with modern tools. Therefore, although steel is corrosive at the atomic level, stainless steel exhibits non-corrosive properties. On the contrary, cheap steel reacts with oxygen from water to form a relatively unstable iron oxide/hydroxide film. This kind of film continues to grow over time and continues to be exposed to water and air. In this way, this kind of film, also known as rust, will quickly reach a thick enough point after being exposed to water and air, making it easy to see with the naked eye.

In short, stainless steel does not rust because when it comes in contact with air and water, it can fully react with the oxygen in it to form a thin layer of passivation corrosion products to avoid further corrosion attacks. (Other metals such as titanium and aluminum also rely on this passivation film to form their corrosion resistance.) Stainless steel is widely used in various products due to its durability and aesthetic effects. These products range from tableware to banks. Safe storage to the kitchen sink.