How to distinguish stainless steel and stainless iron

Stainless iron is a kind of stainless steel, its material is mainly 409, 410, 430, 444, belong to martensitic and ferritic stainless steel, they will be attracted by the magnet. And stainless steel unified refers to the corrosion of atmospheric or acid and other chemical media steel. But stainless steel is not rust, it is just different corrosion behavior in different media.