What makes stainless steel rust?

What makes stainless steel rust?

The stainless steel surface has a layer of extremely thin, tough, dense and stable chromium-rich oxide film (protective film) to prevent the ongoing infiltration of oxygen atoms to continue to oxidize and achieve the corrosion resistance capability. If this film is constantly been damaged under certain circumstances, the oxygen atoms in the air or liquid will continue to infiltrate or the iron atoms in the metal will seep out to form loose iron oxide, thus allowing the metal surface to rust continuously. There are many forms in which the surface film can be damaged; the common types seen in everyday life are as follows:


  1. 1.Scratches caused by using steel brushes, which can even damage the surface to result in oxidation corrosion
  2. 2.When the stainless steel surface is deposited with powder and dust of other metal elements or adhered with heterogeneous metal particles, these attachments will form a micro-cell when combined with stainless steel condensate in the presence of humid air to trigger an electrochemical reaction and damage the protective film. This is known as electrochemical corrosion (water rusting).
  3. 3.When the stainless steel surface is adhered with organic juice (such as vegetable, noodle soup, sputum, etc.) in the presence of water and oxygen, it will form an organic acid to corrode the metal surface over time.
  4. 4.Local corrosion caused by the adhesion of acid, alkali or salty element (such as being splashed with alkali water or lime water during wall renovation) on the stainless steel surface. To clean it, you may wipe the surface with acidic detergent or an acidic object.
  5. 5.When the contaminated air (such as a large amount of sulfide, carbon dioxide, nitrogen oxides in the atmosphere) is encountered with condensate, it will form sulfuric acid, nitric acid and acetic acid droplets to cause chemical corrosion.


The above conditions can damage to the protective film of stainless steel surface to cause corrosion.
Therefore, to ensure a permanent bright metal surface and to prevent rust corrosion, we recommend you to perform the following measures

How to remove rust

  1. 1.You must always wipe the surface of stainless steel ornaments with a neutral detergent or designated stainless steel cleaning agent to remove the attachment and eliminate the external corrosion factor on the stainless steel surface.
  2. 2.Stainless steel #316 is recommended to use around the coastal area as the material is able to resist seawater corrosion.
  3. 3.As the chemical constitution of some stainless steel pipes sold on the market are not consistent with the corresponding national standards, such as unconformity to #304 material requirements, so they will tend to rust. To avoid this, customers are advised to carefully products produced by reputable manufacturers.