Remove rust stains
Throw away the scouring powder and pick up a bottle of resin bed cleaner used for water softeners (about $11 at home centers). Just douse the rust with a foam brush. It’s amazing. Usually the rust will disappear in a few minutes. But long-term stubborn rust buildup may take a few treatments. We’ve even used it successfully on acrylic spas. You really don’t want to scour those! Just try it first on a small area to make sure it doesn’t damage the surface.