I used to work at a company that made (among other things) fertilizer handling equipment. The fetiliizer could be corrosive so there was the option to have the equipment made out of stainless steel. We had 2 grades of stainless. I think we referred to them as 304 & 409. As I recall, a magnet would stick to one of them, although not nearly as well as normal steel alloys. I think it was the 409 but that was about 25 years ago & my memory ain't what it used to be.