Aluminum die-casting parts and some stainless steel products are very resistant to oxidation, but once this film is continuously exposed for some reason, air or liquid oxygen atoms will continue to infiltrate or metal iron atoms will continue to stray, forming loose iron oxide , The metal surface is rusting constantly.
There are many environments in life that can cause damage to the surface of aluminum products and stainless steel. For example, the deposits on the surface of stainless steel and the metal elements other than the adhesion of dust or foreign metal particles, in the humid air, and the adhesion of condensed water, will cause the two Those connected into a micro battery trigger an electrochemical reaction, and the protective film is destroyed, which is called electrochemical corrosion. Encounter some organic matter (such as watermelon juice, soup, sputum), oxygen water, organic acid, long time, organic sulfonic acid corrosion on the metal surface, the adhesion of the stainless steel surface. Containing acid, alkali, salt substances (such as wall decoration water, lime water splashing), adhesion to the surface of stainless steel that causes local corrosion. Condensed water, sulfuric acid, nitric acid, and acetic acid in air pollution (such as containing a large amount of sulfide, carbon dioxide, nitrogen oxide, and air) in liquid form causes chemical corrosion.
A thin layer of chromium oxide (protective film) is formed on the fine and stable surface of stainless steel to prevent the permeation and oxidation of oxygen atoms and obtain corrosion resistance.
When the surface of the stainless steel pipe is brown rust (spot), people are surprised: "Stainless steel does not rust, rusty stainless steel, steel may be a problem." In fact, this is a one-sided view of the lack of understanding of stainless steel. wrong. Stainless steel will also rust under certain conditions. Stainless steel has the ability to resist atmospheric oxidation, does not rust, and is resistant to corrosion in acid, alkali, and salt media. But the steel for its corrosion resistance has its own chemical composition size, improved condition, use and environmental change conditions of the media type. Because 304 steel pipe has good corrosion resistance in a dry and clean atmosphere, it will be moved to coastal areas. It contains a large amount of sea salt spray and will rust soon. Therefore, there is no stainless steel of any kind. It can resist corrosion in any environment. Even if it is aluminum die casting, although aluminum is not easy to rust, it will slowly rust if it is placed in a relatively strong acid and alkali environment for a long time.
