I tried the radio Shack etchant & tho it did darken or burned holes in it, it didn’t provide that rust color. I ran across an old MRR article that suggested putting a light coat of olive oil on the surface & heating it over a flame…I heated it over a burner on an electric stove. I was pleased with the results. Depending on the intensity of the heat I got colors from a light rust to a very dark brown. It will not rub off, but should be coated with a flat finish because it retains it’s original gloss. The article states that only olive oil works & not any kind of cooking oil.
Best to do this before you cut it to size & try to vary the amount of heat on the strip to get various degrees of rust. Also, use tweezers to hold the strips. Happy Rusting. jerry