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.
On titanium and niobium, I use Multi-Etch® to remove anodizing mistakes and to clean off contamination—iron from rolling mills, heat oxides, etc. Multi-Etch® will maintain the finish on titanium and niobium as long as the metal is not etched too long. Here’s a single piece of titanium that I left “as is” on the top, cleaned with Multi-Etch® on the bottom, and then anodized. It looks like I anodized them separately but I did it all at once.
For a production run of two dozen pairs of titanium earrings, I use one cup of Multi-Etch® in a two-cup Pyrex container, heated to about 150° F. You can use a thermometer or look for the built in Multi-Etch bubbles which tell you when it’s ready to use (visual check.) These tiny bubbles appear when the Multi-Etch is brought up to the correct temperature. I dangle a pair of earrings from a niobium wire into the Multi-Etch for 10 seconds and then rinse in distilled water. If I did three production runs a week, I would change the Pyrex cup about every three months. If you wait too long, the cup can shatter and make a mess.