Anodizing titanium with trisodium phosphate (TSP)
I'm curious about the safety of anodizing titanium in a weak trisodium phosphate [linked by editor to product info at Amazon] solution, using a home-built 0-180 vdc variable power supply I made for artwork & jewelry purposes.
The power supply is safe and short-protected, and I use it in a safe way, but after skimming through the plating FAQ's I'm concerned about chemistry/fumes issues, of which I'm ignorant.
1. Does the cathode metal matter safety-wise? I can get good results from any--usually I use a strip of copper. Have used fine silver, aluminum, and titanium also.
2. If I quickly insert a part with the voltage up high, I can see a tiny stream of either gas or steam. Which is it, and is it safe?
3. Is it safe to leave a jar of weak trisodium phosphate out in the open?
4. I took a tiny (1 sq cm) piece of brass and used it for the anode instead of titanium. The result was some gleaming bright green stuff in the water, and a very nice orange patina to the brass. The cathode was copper. I would like the orange patina for certain jewelry but will only use it if it's safe. Was I plating copper onto the brass somehow? I had done a lot of titanium anodizing in the same solution using a copper cathode beforehand. I'm using copper clips which end up in the solution a lot, also.
Interesting web site, lots of fun reading...
St. Louis, Missouri
If I were you, I'd be most concerned about your home-built 180 VDC power supply, as that is more than adequate to kill you if you didn't design and construct it properly.
1. Trisodium phosphate is a pretty mild chemical; I can't foresee any violent reaction with copper, silver, aluminum, or titanium.
2. What is the gas? Probably hydrogen. Depending on pH and other conditions, water separates into 2 parts hydrogen and 1 part oxygen, or 1 part hydrogen and one part OH-
3. Again, trisodium phosphate is a pretty mild chemical, not much different than cola. But there is probably metal dissolved in the solution, so it's somewhat poisonous. Is it safe to leave an open container out? Well, is it safe to leave an open bottle of aspirin out in the open? Yes if you're the only one around; no if there's a toddler about.
4. Ionized copper is normally blue rather than green, still the color is probably coming from the copper. No, you certainly weren't plating copper onto an anode! You were probably oxidizing the brass, and perhaps surface enriching it by leaching out some of the zinc.
As you probably know from spending time on our site, we are not real enthusiastic about hobbyist experimentation in plating and anodizing for a host of reasons, and safety is one of them. Your letter represents a good example. You ask for reassurance that what you are doing is safe, and pose questions where we can't foresee a direct danger. Which leaves us sort of implying: "yeah, that's safe . . . yep, that's safe too . . . uh-huh, no problem with #3 either . . . you're okay with #4, too.
So now you've heard this 4-part mantra of how we see nothing dangerous in what you are doing, and you are probably reassured that you can experiment to your heart's content, although you've acquired no appreciation of the chemistry. So you are right on track to tossing a cup of table salt into your bucket and killing yourself with chlorine gas, or knocking a beaker of solution onto your power supply and lunging for it just as the highly conductive solution runs down into the AC side, or who knows what :-)
Ted Mooney, P.E. RET
Pine Beach, New Jersey
If you used an isolation transformer in the unit , you are fairly safe. Not everyone can stand the same amount of electricity. 180 V is obviously a lot more dangerous than 6 volts and deserves due caution. Amperage is the other part of electricity killing people. Fuse it or circuit breaker the output side with "quick blow" units and fuse to the minimum amount that you can get by with. TSP is still sold for cleaning before wall papering and was the main ingredient of some detergents until it was found to grow great amounts of algae. I would keep the other metals out of the tank. They are dissolving and you are really into some nasty waste disposal problems. Titanium is non regulated and very very little dissolves when used as a cathode. (or anode) Normally a very well organized and neat line with normal lab practices is safe. Rubber protective gloves [linked by editor to product info at Amazon] and safety glasses. Nothing can save you from stupid mistakes, so follow good practices and enjoy the product.James Watts
- Navarre, Florida
Yeah, I only anodize titanium using the 'normal' process I learned under supervision years ago. I've seen it repeated over and over again from different sources also, so figured it was safe enough. But I wouldn't recommend that anyone build any power supply unless they have enough experience with them. It's like a hair dryer in the bathtub the whole time when you anodize, and you must treat it as such. Dry, heavy rubber gloves are absolutely mandatory at all times! I also would never have the power supply on while manipulating items. Makes *nice* colors though, I've made chains from one type of titanium and simple rings from another. Beautiful metal with lots of possibilities! Makes it worth the trouble.
St. Louis, Missouri
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