When you scroll through shiny floor drain photos online, they all look identical—until the first brown spot appears.
Behind every mirror finish hides a three-digit code: 201, 304 or 316.
Know the numbers, or pay for rust.
Independent salt-spray data (ASTM B117, public archive) show first red rust at:
201 is strongly magnetic because of its Mn-rich structure.
Carry a pocket magnet on site; if the top plate clings like a fridge sticker, you know the supplier sneaked in 201 even when you paid for 304.
Indoor, low-humidity, zero-chloride, rent-to-sell projects where the warranty ends at hand-over. For every wet room that sees deodorant, sweat or beach sand, insist on 304 minimum.
So, are you ready to pick your stainless steel without looking back?