When brown rust spots appear on the surface of stainless steel, people are amazed: "stainless steel will not rust, rust is not stainless steel." In fact, this is a kind of one-sided wrong view of the lack of understanding of stainless steel. Stainless steel also rusts under certain conditions.
Stainless steel has the ability to resist atmospheric oxidation, which is not corrosive, but also has the capability of corrosion resistance in the medium containing acid, alkali and salt. But its corrosion resistance is changed by its chemical composition, mutual state, use condition and environmental media type. The 304 material, in a dry, clean atmosphere, has an excellent anti-corrosion capability, but moves it to the coastal area, where it will soon rust in the sea fog that contains a lot of salt. Therefore, not any kind of stainless steel, at any time can resist corrosion, not rust.
Stainless steel is a thin, solid, stable, rich chromium oxide film (protective film) formed on its surface to prevent oxygen atoms from infiltrating, continuing to oxidize, and gaining the ability to resist corrosion. But there is some reason, this kind of film is continuously damaged, air or liquid and oxygen atoms will constantly infiltration or metallic iron atom separation out unceasingly, forming loose iron oxide, metal surface rust by constantly. This kind of surface film is destroyed in many forms, many of which are seen in daily life:
stainless steel surface dust containing other metal elements deposit savings or heterogeneous metal makings of attachments, in the humid air, attachments and stainless steel, the condensed water between the both together as a micro battery, triggers the electrochemical reaction, protective film is damaged, to call the electrochemical corrosion.
The surface of stainless steel adheres to organic juices (such as melon and noodle soup, etc.). In the case of water and oxygen, organic acids are formed, and the corrosion of organic acids to the metal surface is formed in the long time.
The surface adhesion of stainless steel contains acid, alkali and salt substances (such as alkaline water and lime-water spray test) causing local corrosion.
In the polluted air (containing a large amount of sulphide, oxide, hydrogen oxide atmosphere), the condensation water will form sulfuric acid, nitric acid and acetic acid, causing chemical corrosion.
All above can cause damage to stainless steel surface and cause corrosion.Therefore, to ensure that the metal surface is permanently bright and not rusted, we recommend:
It is necessary to clean and scrub the stainless steel surface frequently, remove the attachment, and eliminate the external factors causing the rust.
There is a kind of stainless steel with 201 and 202 materials on the market, which is easy to rust in the coastal area, suitable for use in the absence of industrial pollution and air corrosion.
In the beach area use 304 stainless steel, because 304 can resist seawater corrosion.
(a) chemical methods:
Cream or spray assisted with pickling corrosion parts form a chrome oxide film to passivation to restore it to corrosion resistant ability, pickling, in order to remove contaminants and acid residue, proper wash with water is very important.After all processing, the polishing equipment will be re-polished and sealed with polishing wax.For local slight rust spots can also be used for 1-1 gasoline, oil mixture to wipe away rust stains with a clean cloth.
(b) mechanical methods:
Sandblast cleaning, blasting with glass or ceramic particles, annihilation, brushing and polishing.It is possible to wipe out the pollution caused by materials, polishing materials or annihilation materials that were previously removed by mechanical means.All kinds of pollution, especially foreign iron particles, can be a source of corrosion, especially in humid environments.Therefore, it is better to clean the surface of the machine under dry conditions.Using mechanical method can only clean the surface of the material, and can not change the corrosion resistance of the material itself.Therefore, it is suggested that polishing equipment should be re-polished after mechanical cleaning and sealed with polishing wax.
Edit by Ms. Julia Zhu of KRM/BSW (Sales Dept.)
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