Multi-Etch—the Safer Way to etch Titanium

Times and regulations have changed since we first started etching titanium in 1978.  During our first experiments, while preparing the hydrofluoric/nitric acid solution, orange clouds of vapor had us running out the door to escape.

We began as titanium jewelers when you could still drive to the chemical supplier and pick up dangerous chemicals in your car.  A worker who brought out our order said, “We make a lot of bad stuff here, but this is the BADDEST.”

We quickly adopted some safety protocols needed to protect ourselves: fume hood, separate air supply with a full face respirator, and air quality monitoring with Draeger tubes.  Although we took what seemed to be all the necessary precautions, we couldn’t be confident that thirty years down the road we might discover we had not been cautious enough.

The insidious nature of hydrofluoric acid means that if you spill some on your body, the tissue damage may not be apparent until the next day. The CDC says, “Even small splashes of high-concentration hydrogen fluoride products on the skin can be fatal.”  Another specific danger of HF/nitric is that when etching, fluoride gas is released and you better be sure the fume hood is working 100% with no back drafts.

We dealt with the fear for years and produced anodized titanium jewelry for many accounts including the Smithsonian Air & Space Museum.  But, we decided there had to be a safer way because we were not willing to die for our art.

After much research and experimentation with different solutions, we perfected an etchant that is orders of magnitude safer than the HF/nitric combination.  One key advantage of Multi-Etch is that the fluorides are bound up in the solution and are never released as a gas.  Draeger tubes read in parts per billion and the readout was always zero!  (And yes, we checked to make sure they were working.)  Although the spent solutions of Multi-Etch have to be treated/neutralized before sewering, it’s easier than dealing with Hf/nitric waste.

We started by selling Multi-Etch to the titanium jewelry industry and a few bicycle manufacturers.  Then, about ten years ago, different titanium users showed up.  Our largest users now are from medical, dental, optical, and aerospace industries.

The efficacy of Multi-Etch is not only useful in the anodizing field but excels for welding prep too.  It can also be used for chemical milling.  One company needed to take off microns of material which standard mechanical milling just couldn’t do effectively, and they didn’t want the aggressive bite of Hf/nitric. When you check our etch rate table you can see how these “slow” etch rates can be useful.

Multi-Etch is also effective on stainless steel, tool steel, brass, copper, and zirconium.  For platinum, Multi-Etch is faster and, of course, safer than the historical standard using nitric acid.  With niobium and tantalum, as with titanium, Multi-Etch can erase anodizing “mistakes” and be re-anodized.

Just how safe is Multi-Etch compared to hydrofluoric or nitric acid? Well, while we would never recommend this, we have reached a hand into 100°+ F heated Multi-Etch to retrieve a part and  suffered no ill effects (all ten digits and skin intact).  You would suffer significant damage if you tried that with hydrofluoric or nitric acids.

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