Stainless steel is an alloy that has a certain amount of chromium added to iron to resist corrosion. The reason why stainless steel does not rust easily is because the chromium it contains forms an ultra-thin passive film on its surface, making it resistant to corrosion. For the common person (people who are not involved in the manufacturing industry), stainless steel is perceived as not rusting, but stainless steel is only “rust-resistant”. In reality, it can easily rust in the environment. There are also different types of stainless steel, including “austenitic”, “martensitic”, and “ferritic”, which have strong corrosion resistance, high strength, magnetic properties, non-magnetic properties, and do not become brittle even at extremely low temperatures. There are characteristics, and the differences between these types are managed separately in each standard.