Causes of corrosion of stainless steel plates

In the current market, "stainless iron" products have a 65% share because their prices play an important role. The current price per ton of national standard 304 stainless steel plate products is about 20,000 yuan, and the price per ton of national standard 7075 aluminum alloy is about 1.6 About 10,000 yuan, while the price of "stainless iron" is only 5,000-7,000 yuan per ton; and then look at the tensile strengths of these three materials: national standard 304 stainless steel plate, stainless steel 530-620MPa, national standard 7075 aluminum alloy 540- 560MPa, "stainless iron" 160-180MPa.

Obviously, the tensile strength of "stainless iron" is less than 1/3 of the strength of stainless steel, which can easily lead to accidents. Dust containing other metal elements or attachments of heterogeneous metal particles accumulate on the surface of "stainless iron". In humid air, the condensed water between the attachments and stainless steel connects the two into a micro-battery, triggering an electric shock. Chemical reaction, the protective film is damaged, which is called electrochemical corrosion.

The chemical reasons that cause the destruction of the protective film on the surface of the 304 stainless steel plate and cause corrosion are also as follows:

1. Organic juice (such as vegetables, noodle soup, phlegm, etc.) adheres to the surface of the 304 stainless steel plate. In the presence of water and oxygen, it forms organic acid. For a long time, the organic acid corrodes the metal surface.

2. The surface of the 304 stainless steel plate contains acid, alkali, and salt substances (such as alkaline water and lime water splash on the wall decoration), causing local corrosion.

3. In polluted air (such as an atmosphere containing a large amount of sulfides, carbon oxides, and nitrogen oxides), when encountering condensed water, sulfuric acid, acetic acid liquid points are formed, which can cause chemical corrosion of 304 stainless steel plates.