Stainless steel coil/sheet has the ability to resist air oxidation, and also has the ability to resist corrosion in substances such as acid, alkali and salt, that is, corrosion resistance. However, the size of its corrosion resistance capacity is changed with the organic chemical composition of its steel itself, mutual conditions, application standards and the types of natural environment substances. For example, 304 raw materials have certain high-quality corrosion resistance in the dry and clean air, but if it is moved to the Haibin area, it will corrode immediately in the sea fog with a lot of salt. Therefore, stainless steel products are not corrosion-resistant and rust-free at all times.

Stainless steel relies on a thin, firm and smooth chromium-rich air oxide film (protective film) produced on its surface to prevent oxygen molecules from re-penetrating and re-oxidizing in air, so as to obtain corrosion-resistant working ability. If this kind of protective film is continuously damaged, the oxygen molecules in the gas or liquid will continue to penetrate or the iron atoms in the metal material will continue to separate out, resulting in loose compounds, and the surface of the stainless steel coil/ sheet will suffer continuous rusting. .

There are many reasons for the damage of the surface film, such as the smoke and dust of other chemical elements on the surface of the stainless steel coil/sheet or the appendages of the orc metal material particles. In the humid and cold air, the condensation water between the appendages and the stainless steel will cause the two connected into a micro-rechargeable battery, causing electrochemical corrosion and damage to the protective film. There are acid, alkali and acid salt chemicals (such as edible alkali and lime slurry spray test on interior decoration walls) on the surface adhesion, which cause partial erosion.