I originally perfected Multi-Etch® for titanium production. It’s a nonacid (pH 6.8) alternative to hydrofluoric acid. I’ve also tested it on other metals with great results.
You can clean iron contamination from platinum without removing any platinum ions. I’ve done limited testing with Multi-Etch® on platinum for etch effects—that is, removal of platinum ions—and there doesn’t seem to be any effect.
I manufacture a line of titanium wedding rings with platinum inlays. As all platinum fabricators are aware, the accepted method to remove cross-contamination prior to welding or soldering is a 15 minute soak in nitric acid or bisodium sulfate. With Multi-Etch®, a 15-second dip is sufficient to eliminate all impurities that could interfere with a perfect weld or solder joint. I dangle the platinum from a niobium wire into the Multi-Etch® for 15 seconds and then rinse in distilled water. It’s now ready for a perfect weld.