1. Chloride ion environment.
Chloride ions mainly exist in purified liquids and gases. Chloride ions will react with chromium ions in stainless steel, destroy the dense oxide film of stainless steel, and cause stainless steel to rust, thereby accelerating the corrosion of stainless steel, and even exceeding that of ordinary low-carbon steel.
2. Electrochemical corrosion.
When the surface of stainless steel is in contact with other metals for a long time, a primary battery will be formed in a humid environment, destroying the chromium oxide film and aggravating the rust of stainless steel.
3. Chromium does not meet the standard.
Chromium has a huge impact on the rust resistance of stainless steel. As the proportion of chromium increases, the steel is less likely to rust. Taking 304 stainless steel as an example, when the chromium content reaches 18%, its corrosion resistance suddenly changes, and the best corrosion resistance effect is obtained.
4. Surface scratches.
From a chemical point of view, the most unstable place is most likely to undergo chemical reactions. Surface scratches may also cause damage to the surface dynamic membrane. The scratched place becomes the most unstable place for stainless steel. Oxygen and water will enter the interior of the stainless steel and rust.
5. Mechanical stress.
When stainless steel is made into products, we need to go through processes such as stamping, shearing, punching, stretching, grinding, hot cutting, or welding. At this time, other metal elements, dust, or metal particles will be attached to the surface of the stainless steel, and they will produce chemical reactions when encountering chloride ions and sulfur ions in the air, thereby destroying the corrosion resistance of the stainless steel itself and accelerating the rusting process of the stainless steel.
6. Others.
The influence of organic acids, the influence of sulfides, etc., will destroy the passivation film of stainless steel.

The standard tensile strength of 304 stainless steel in China, Japan, and the United States is:

National Standard: 06cr19ni10, tensile strength ≥515Mpa
Japanese Standard: SUS304, tensile strength＞520N/mm²
American Standard: 304, tensile strength＞515N/mm²

Tensile strength is the critical value of the transition of stainless steel from uniform plastic deformation to local concentrated plastic deformation, and it is also the maximum load-bearing capacity under static tensile conditions. In short, it is essentially the resistance to the maximum uniform plastic deformation of stainless steel, the symbol is Rm, and the unit is MPa.

The standard tensile strength of 304 stainless steel in China, Japan, and the United States are:

National Standard: 06Cr19Ni10 (new grade), tensile strength greater than or equal to 515MPa;

Japanese Standard: SUS304, tensile strength greater than 520N/mm²;

American Standard: 304, tensile strength greater than 515N/mm².

Yes. Stainless steel flanges are an important component for connecting pipes. They are composed of two flanges and several bolts. Stainless steel flanges have the advantages of high-pressure bearing, good sealing performance, and long service life, so they are widely used in petrochemical, chemical, pharmaceutical, and other industries.

There are many kinds of materials for stainless steel flanges, including common 304 and 316 stainless sheets of steel, duplex stainless steel, acid and alkali-resistant stainless steel, etc. Different materials have different characteristics, and choosing the right material is an important factor in ensuring flange performance.
Stainless steel flanges have good corrosion resistance, high-temperature oxidation resistance, and wear resistance, and they are not easy to rust, but they are easy to clean and maintain.

However, it should be noted that not all flanges are made of stainless steel. For example, carbon steel flanges are made of carbon steel, while cast iron flanges are made of cast iron. Different materials have different applicable scenarios and need to be selected according to actual conditions.