The metal reacts with oxygen in the atmosphere to form an oxide film on the surface. The iron oxide formed on ordinary carbon steel continues to oxidize, causing the rust to expand and eventually form holes. Carbon steel surfaces can be secured by electroplating 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 damaged, the underlying steel begins to corrode.

The corrosion resistance of stainless steel hose depends on the content of chromium. When the amount of chromium added reaches 10.5%, the atmospheric corrosion resistance of steel increases significantly, but when the content of chromium is higher, although the corrosion resistance can still be improved, it is not obvious. . The reason is that alloying steel with chromium changes the type of surface oxide 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 which the natural luster of the stainless steel surface can be seen, giving stainless steel 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 "passivation film", and continue to play a protective role.