It is well-known that stainless steel, as a material for weights, boasts corrosion resistance, which reduces the errors caused by the weights during use. But why does stainless steel have this corrosion-resistant property?
All metals react with oxygen in the atmosphere according to chemical principles, forming an oxide layer on the surface. Unfortunately, the iron oxide formed on ordinary carbon steel continues to oxidize, leading to corrosion expansion and the formation of holes. How to solve this? The common method is to use paint or anti-oxidation metal electroplating to ensure the surface of carbon steel. However, as is well known, this protection is just a thin film. If the protective layer is damaged, the underlying steel will begin to rust. The corrosion resistance of stainless steel depends on chromium, which is one of the components of steel. When the chromium content reaches above 11.7%, the steel's resistance to atmospheric corrosion significantly improves, but when the chromium content is higher, the corrosion resistance does not improve significantly. The reason is that when chromium is alloyed with steel, the type of surface oxide changes, similar to the oxides formed on pure chromium metal. This tightly adhered, chromium-rich oxide layer protects the surface from further oxidation. This oxide layer is extremely thin, allowing the natural luster of the steel surface to be seen through it, giving stainless steel a unique surface. Moreover, if the surface is damaged, the exposed steel surface will react with the atmosphere for self-repair. This oxide "passivation film" will form again, continuing to provide protection.
Therefore, all stainless steel elements share a common characteristic: a chrome content of 10.5% or above.
