Chemistry in everyday life – the corrosion spots on stainless steel kitchen knives
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After using the kitchen knife for some time, I noticed small pits on its surface; I suspect it has been corroded by salt. Please explain the underlying principles, as well as ways to prevent this from happening, and also discuss any engineering applications related to this issue. The kitchen knife is made of 304 stainless steel.
It might be caused by salt, electrochemical corrosion. I really can’t say why either. Prevention requires thorough rinsing promptly.
I think there’s something about chloride ions causing corrosion, so it needs to be cleaned thoroughly
The intergranular corrosion of 304 stainless steel by table salt, no
First of all, it should be noted that stainless steel is not a type of steel that does not rust; rather, it is a steel that is less prone to rusting. Stainless steel can also corrode under certain conditions: pitting corrosion, intergranular corrosion, stress corrosion, crevice corrosion, and so on. Additionally, higher-quality stainless steel kitchen appliances will have the indication \"18-8 stainless steel\" or \"18-10 stainless steel\" marked on them.
This post was last edited by cflt111 on 2015-9-10 at 20:18. In simple terms, stainless steel is steel that does not rust easily; in fact, some types of stainless steel possess both rust resistance and acid resistance (corrosion resistance). The rust resistance and corrosion resistance of stainless steel are due to the formation of a chromium-rich oxide film (passivation film) on its surface. This resistance to rust and corrosion is relative. Tests have shown that in weak media such as air and water, as well as in oxidizing media such as *ao acid, the corrosion resistance of steel increases with the increase in chromium content. When the chromium content reaches a certain percentage, there is a dramatic change in the steel’s corrosion resistance – it goes from being prone to rusting to less prone to rusting, and from being non-corrosion-resistant to corrosion-resistant. A severe form of corrosion in stainless steel is local corrosion (i.e., stress corrosion cracking, pitting corrosion, intergranular corrosion, corrosion fatigue, and crevice corrosion). Prevention method: Keep the blade clean.
Stress corrosion is the corrosion that occurs when materials are subjected to both corrosion and stress. It only occurs in certain specific \"material-environment\" systems, such as \"austenitic stainless steel–Cl–\" and \"carbon steel–NO3–\", and stress must also be present (external forces, or residual stresses resulting from welding, cold working, etc.). It must be the Cl ions causing the problem
I just took a look; it says 3Cr13 engraved on the dish. I’m not sure what material it is – it’s corroded, with very small pits
I just took a look; it says 3Cr13 engraved on the dish. As for this material, I think it’s been corroded by table salt as well
3Cr13 belongs to the martensitic type of stainless steel. It has good machinability, and after heat treatment (quenching and tempering), it exhibits excellent corrosion resistance, high polishability, as well as strength and wear resistance. It is suitable for manufacturing plastic molds that are subject to high loads, high wear conditions, and exposure to corrosive environments. 3Cr13 materials with a hardness below HRC30 after quenching and tempering have good machinability and can achieve good surface quality. For parts manufactured with a hardness greater than HRC30, although the surface quality is good, the cutting tools tend to wear out easily. Therefore, after the material arrives at the factory, it is first subjected to quenching and tempering treatment to achieve a hardness of HRC25–30, and then machining is carried out.