I have some chrome or shinny silver metal door knobs I want to use on shabby projects. shinny silver won't do! How can I rust them or will I have to resort to painting them??
"Rusting" chrome involves removing the chrome, which releases some toxic waste.
I think if you hand sanded it with a rough grit, say 80 or 100, it will soon rust by itself. Spraying with water once a day would certainly speed up the process.
it partly depends on what they actually are- chrome, chromed plastic, or stainless steel... stainless will indeed rust if you encourage it (220 grit is fine, anything rougher will leave visible gouges. I'm a BIG fan of the scrubby sanding pads, by the way!)
there are spray paints out there that mimic other finishes- bronze, copper, i'll bet Rustoleum even makes a rust-colored textured paint.
again, give is a 'scuff' sanding to assure adhesion (never, ever 'expect' that something will get only minimal handling. it never works that way)
I'd try some fine sand paper and then spray with a strong salt water solution.