Stainless steel is a kind of alloy with iron as the main raw material, its corrosion resistance is mainly from chromium element in alloy. Chromium elements on the stainless steel surface form a thin and solid-rich chromium oxide film (protective film), the film successfully blocked the infiltration of oxygen molecules, so that stainless steel to obtain corrosion resistance. However, if the film is continually destroyed, the oxygen in the air or liquid will continually penetrate or the iron atoms in the metal exposed to the formation of loose iron oxide, the metal surface will continue to be eroded. The surface film of stainless steel products has been destroyed in many forms, common in daily life are:
1. Stainless steel surface stocks with other metallic elements of dust or other metal particles of attachment, in the humid air, the attachment and stainless steel condensation water, the two into a micro-cell, triggering an electrochemical reaction, the protection of the film is destroyed, called the electrochemical corrosion.
2. Stainless steel surface adhesion organic juice (such as melon dishes, noodle soup, phlegm, etc.), in the case of oxygen, constitute organic acids, long-time organic acid on the metal surface corrosion.
3. Stainless steel surface adhesion containing acid, alkali, salt substances (such as decoration walls of alkali water, lime water spray), causing local corrosion.
4. In the polluted air (such as a large amount of sulfide, carbon dioxide, nitric oxide atmosphere), the case of condensation water, forming sulfuric acid, nitric acid, acetic acid liquid point, causing chemical corrosion.