Q. I thought stainless steel wouldn't rust, but it did.

The cause of rust is due to the destruction of the surface film.Continued contact between different materials such as iron and aluminum.Continued exposure to salt or acid. These conditions lead to the formation of rust.

Q. The inside of my stainless steel cookware has discolored to a rainbow color.

This phenomenon occurs when ions, iron, and copper in the water adhere to the surface due to evaporation, causing a rainbow-like appearance. It is more likely to occur in relatively new conditions, and the product itself has not discolored (deteriorated), so please use it with confidence.