When brown rust spots (spots) appeared on the surface of stainless steel countersunk bracket bolts, people were greatly surprised: they thought that "stainless steel is not rusted, rust is not stainless steel, and there may be a problem with steel".  In fact, this is a one-sided wrong view of the lack of understanding of stainless steel.  Stainless steel will rust under normal conditions.  Next, our professional Bolt Factory will make a detailed introduction in this respect.
Stainless steel has the ability to resist atmospheric oxidation-i.e. corrosion resistance, and also has the ability to corrode in medium containing acid, alkali and salt-i.e. corrosion resistance.  However, the corrosion resistance varies with the chemical composition of the steel itself, the state of addition, the conditions of use and the type of environmental medium.  For example, 304 steel pipe has excellent corrosion resistance in a dry and clean atmosphere, but when it is moved to coastal areas, it will soon rust in sea fog containing a large amount of salt.  However, 316 steel tubes performed well.  Therefore, it is not any kind of stainless steel and can resist corrosion and rust in any environment.  The stainless steel countersunk bracket bolt is a thin, firm and fine layer of stable chromium-rich oxide film (protective film) formed on its surface to prevent oxygen atoms from continuing to infiltrate and oxidize, thus obtaining the ability to resist corrosion.  Once there is some reason, this kind of film is continuously destroyed, oxygen atoms in air or liquid will continuously infiltrate or iron atoms in metal will continuously separate out, forming loose iron oxide, and the surface of gold metal will be continuously corroded.
This kind of surface film is damaged in many forms. The following are common in daily life:
1. Dust containing other metal elements or attachments of heterogeneous metal particles are deposited on the surface of stainless steel countersunk bracket bolts. In humid air, the condensate water between the attachments and stainless steel connects the two into a micro battery, triggering electrochemical reaction and damaging the protective film, which is called electrochemical corrosion.
2. Organic juice (such as melon and vegetable, noodle soup, phlegm, etc.) adheres to the surface of stainless steel countersunk bracket bolt, which forms organic acid in the presence of water and oxygen, and corrodes the metal surface for a long time.
3. The surface of stainless steel countersunk bracket bolt is adhered with acid, alkali and salt substances (such as alkaline water and lime water splashing on decoration walls), causing local corrosion.
4. In polluted air (such as air containing a large amount of sulfide, carbon oxide and nitrogen oxide), condensed water will form sulfuric acid, nitric acid and acetic acid liquid spots, causing chemical corrosion.
All of the above conditions can cause corrosion due to the destruction of the protective film on the surface of stainless steel Countersunk Carriage Bolt.  Therefore, in order to ensure that the metal surface is bright and not rusted.  We have to clean the surface.  Passivation, etc.