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Anodizing Titanium -- Quick Guide
Article © MAIL User: Drax
Anodizing Titanium -- Quick Guide
This guide will give a very quick look at how I anodize titanium. It does not explain how the setup works nor does it tell how to construct your own.
Please note, there's a serious risk for shock hazard. If you do not know how to handle electricity-generating equipment, you must look it up elsewhere.
Although the method to anodize aluminum is similar, it requires a lot more steps that are not listed here. That will require a separate article. Do not use this method to anodize aluminum.
First, here is a picture of the device that generates the voltages needed to change the color of the titanium:
This device is called a "variac" (because you can vary the voltage output, I suppose). We use them in the chemistry lab that I work in, and this one is mounted to my hood. It has a dial that runs from 0 to 140; this is the voltage setting (a setting of 20 is 20V).
Next, a look at the place where the action happens:
The glass dish (you can also use plastic) contains a roughly 5% aqueous solution of trisodium phosphate (TSP). You don't have to use TSP; supposedly any electrolytic solution will work (even Coca-Cola or Pepsi). I haven't tried using anything else. Next to the dish are resting two clips: one black and one red. The black one is clamped onto a generous coil of 12g stainless steel and the red one grasps a small titanium wire, bent into a hook shape. According to what I've read, the surface area of the stainless steel should be equal or greater to the surface area of the titanium that you are anodizing.
That's all of the equipment! The wires on the clips get plugged into the variac device (which is off), and everything is ready to go.
Now, you can place a bunch of titanium rings on the titanium hook, as seen here:
Always hold the rubber part, never touch the metal, even when the electricity is off. In fact, to be safer, you should be wearing rubber gloves.
Now, place both the stainless coil and the titanium hook with the rings in the solution. Do not let the clamps touch the solution (although this is not the end of the world, it makes handling the setup more dangerous). Do not let the stainless touch the titanium, or vice versa.
Then, turn on the electricity to the variac, and turn the dial to the voltage you want:
The titanium will begin to bubble vigorously, usually with very tiny bubbles. Bubbles may also form on the stainless. The color should begin to turn very quickly on the titanium. As you can see here, the rings are blue (voltage setting of 20V). The gauge, solution concentration, and a number of other factors will influence what voltage produces what color. You will have to experiment to find the right conditions.
Here is another look at the rings in the anodizer (the weird beige-white smear is a spill stain on my hood counter, it's not part of this setup at all):
The color change occurs quite quickly. The blue rings only take about 5 seconds to reach their final color. I let them go about 20 seconds total and agitate the hook carefully to make sure all the rings "catch". Sometimes if a ring is hanging oddly on the hook, it may not anodize and so agitation can help it turn properly.
When you are satisfied with the result, turn off the power and then lift the rings out (safest by grasping the wire or the rubber grip).
That's all there is to the process. Repeat over and over until you are done with the rings that you have.
Over the course of anodizing, an orangish-yellow layer will begin to build up on the stainless anode. It will wipe off with a cloth, so you can reuse the anode. I ran the anodizing once in salt water, and this same color (and crud) built up fast on the stainless steel.
When running at higher voltages, the solution will get hot (and may smoke -- that is, water vapor). I've found that adding ice can help reduce this problem. Keep in mind that the ice will dilute the concentration of the solution.
I also suggest washing the rings thoroughly with clean water. This rinsing helps remove any excess TSP and will liven up the color.
After about 40 minutes (including set-up time), here's a pile of rinsed rings that I accumulated (I varied the voltages between 18 and 30 on purpose and mixed the lot):
And that's a quick run-through on how to anodize titanium. Pretty easy!
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