The low-acid alternative for titanium and other metals
Using Multi-Etch® on various metals
Multi-Etch® is a low-acid (pH 6.8) alternative to hydrofluoric acid and can be used on the following metals:
Click here for chart of Etch Times and Effects (PDF) for all metals tested with Multi-Etch®.
More information on select metals is below. For metals not included here, ask us or send a sample and we’ll test it for you.
On titanium and niobium, I use Multi-Etch to remove anodizing mistakes and to clean off contamination—iron from rolling mills, minor heat oxides, etc. Multi-Etch will maintain the finish/texture on titanium and niobium as long as the metal is not etched too long. Above is 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.
Copper and brass etch more quickly than titanium. You can use Multi-Etch to remove light firescale from silver but not from gold. 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 have not tested it with rhodium plating but I assume there would be no effect on that either. Although Multi-Etch will etch glass, it does so too slowly to be practical for decorative etching.
I have used Multi-Etch to remove broken steel drill bits trapped in titanium and gold.
Multi-Etch will enhance the patterns in mokume and the crystals in meteorites by etching the different metals at different rates, thus slightly raising one over another.
Here is some meteorite showing before and after treatment with Multi-Etch:
Although my experience is with jewelry, there are many other industries where Muti-Etch is used, such as the dental and medical industries which use a lot of titanium.
Other questions and answers
Make sure to read all the instructions for titanium welding or anodizing.
How long will Multi-Etch last?
For dry powder: at least 11 years.
The shelf life for mixed UNUSED Multi-Etch solution is at least 8 months. (Keep it capped!)
One way you can maximize the usefulness of a Multi-Etch bath is to etch as many parts as possible before anodizing. After the titanium pieces are etched, place them into a holding tank of deionized water or base coat them with 10 volts. Either method seals the surface, inhibiting any oxidation. Later, the pieces can be anodized at the required level. We’ve tested samples that were base-coated (anodized 10 volts) and years later they will anodize vividly with the application of higher voltages.
How much titanium or niobium will one gallon of Multi-Etch etch?
Approximately 1,500 square inches of titanium when dipped for three seconds at 120–150°F. As you etch, the etchant gradually becomes ineffective and trends toward a lower pH.
Can I restore the effectiveness of Multi-Etch after it has been used?
No, that’s why it’s best to use only as much as you need in any one sitting, leaving the rest unadulterated.
How long should I etch to remove anodizing mistakes?
If you simply went past your target color, you can dip the piece briefly in Multi-Etch and it will work backward through the colors. Be sure to rinse as soon as you see the color you want.
If the color is uneven and you want to start over, etch time will be longer than when you etched the raw metal. Just keep etching until the color disappears.
If you discover something not covered here, please let us know! firstname.lastname@example.org
Safety of Multi-Etch®
Just how safe is Multi-Etch compared to hydrofluoric or nitric acid? Well, while I would never recommend this, I have reached my hand into 100°+ F heated Multi-Etch to retrieve a part and I suffered no ill effects (all ten digits and skin intact). You would suffer significant damage if you tried that with hydrofluoric or nitric acids.
- Download the Multi-Etch Material Safety Data Sheet (PDF) (Dry Powder).
- Download the Multi-Etch Material Safety Data Sheet (PDF) (Liquid).
For 24-hour emergency assistance, call (800) 535-5053.
History of Multi-Etch®
Why did I pursue an alternative to hydrofluoric acid?
Although in my youth I had my share of unfortunate experience—exploding kick presses, dense orange clouds of acid gas, and even getting shot in a hold-up of my jewelry store—as a full-time artisan-jeweler-metalsmith since 1971, my goal is not to die in an industrial accident, but rather, of old age. I’m getting closer every day.
Artists and metalsmiths working with hydrofluoric acid need to realize the dire peril involved. I etched titanium for ten years with hydrofluoric acid and used a full face mask with a separate air supply and a powerful fume hood. But I decided I didn’t want to find out years from now that my fume hood had back draft, releasing acid fumes into my studio.
Here is one report on the seriousness of exposure to hydrofluoric acid. I spent several years testing different formulations until I perfected a product that met my exacting quality standards and that I’m proud to use in my own work.
Multi-Etch is available in the United States through:
- Reactive Metals Studio, Clarkdale, AZ
- Email Reactive Metals
- (800) 876-3434 or (928) 634-3434
Available in Canada through The Ring Lord.
- Order online (Canada only)
- Email The Ring Lord
- (855) 746-4567
Anodizing production equipment
When you’re ready to scale up your operation to a custom production anodizing system, contact AnodizeTitanium.com and click on “request a quote” or “hire an expert.”
Other uses of Multi-Etch®
I am always eager to learn more about what Multi-Etch® can and cannot do. Please email me with comments, complaints, or kudos: email@example.com.
—Chris Boothe, developer, Multi-Etch®