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  • Writer's pictureBona House Materials

Why are stainless steel doors rusty?

Updated: May 6, 2023

When there are brown rust spots (spots) on the surface of stainless-steel doors, people will feel very strange: they think that "stainless steel doors do not rust, rust is not stainless-steel doors, 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 doors. Stainless steel doors will rust under certain conditions.

  • Cause of rust

Stainless steel door is a thin, firm and fine stable chromium rich oxide film (protective film) formed on its surface to prevent the continuous infiltration and oxidation of oxygen atoms, so as to obtain the ability of anti-corrosion. Once the film is continuously damaged for some reason, the oxygen atoms in the air or liquid will continuously penetrate or the iron atoms in the metal will continuously separate out, forming loose iron oxide, and the metal surface will be continuously corroded. There are many forms of destruction of the surface film.

1. There are dust containing other metal elements or attachments of dissimilar metal particles on the surface of the stainless-steel door. In the humid air, the condensate between the attachments and the stainless-steel door connects them into a micro battery, which leads to electrochemical reaction and damage to the protective film, which is called electrochemical corrosion.

2. The surface of stainless-steel door is adhered with organic juice (such as melons and vegetables, noodle soup, phlegm, etc.), which constitutes organic acid in the case of water and oxygen. For a long time, the corrosion of organic acid on the metal surface will be reduced.

3. The surface of stainless-steel door contains acid, alkali and salt substances (such as alkali water and lime water splashing on the decoration wall), causing local corrosion.

4. In polluted air (such as atmosphere containing a large amount of sulfide, carbon oxide and nitrogen oxide), sulfuric acid, nitric acid and acetic acid liquid points are formed in the presence of condensate, causing chemical corrosion.

  • Precautions for use

The above conditions can cause the damage of the protective film on the surface of the stainless-steel door and lead to corrosion. Therefore, in order to ensure that the metal surface is permanently bright and not corroded, we suggest:

1. The surface of decorative stainless-steel door must be cleaned and scrubbed frequently to remove attachments and eliminate external factors causing decoration.

2. 316 stainless-steel doors shall be used in coastal areas, which can resist seawater corrosion.

3. The chemical composition of some stainless-steel doors in the market cannot meet the corresponding national standards and cannot meet the 304 material requirements. Therefore, it will also cause rust, which requires users to carefully select the products of reputable steel door manufacturers.

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