Stripping of titanium oxide layer

A. When racks do require cleaning, this can be accomplished using either mechanical or chemical methods.

The mechanical cleaning consists of bead blasting to remove any oxide or scale followed by wire brushing or filing, if necessary, of contact points.

The fastest method for chemical cleaning is immersion in a solution of hydrofluoric acid or ammonium bifluoride until gassing occurs, usually within 15 seconds. The rack should be pulled from the solution as soon as gassing begins and rinsed. Hydrochloric acid can also be used, but is much slower. In this case, the racks are immersed for 2 hours or more, with periodic inspections to visually determine when the oxide is removed. The rack is then rinsed.

Another easy and inexpensive cleaning method utilizes the anodizing tank with the current off. This is conducted overnight. The racks are then rinsed and returned to service the following morning.

A. What about treating titanium racks cathodically in spent sulfuric acid anodizing bath using aluminum as anode?

A. The best answer is the chemical cleaning as described by Mr. Terry Ciszewski.

In regards to this question I had, our chemist has found a solution in a book to strip our rack and I thought I would share it with anyone else who may be looking for it:

A. Hello, Masood. The reason for using titanium racks rather than aluminum racks is that they don't need to be stripped. The anodized layer on the titanium is thin and does not interfere with getting current from the racks to the parts.

A. Hello,

While what Ted says is correct, every once in a while something screwy can happen and you do end up having to strip it. Not entirely sure why; but I do know that it occasionally happens. See letter 22422, "Loss of amperage and glowing parts".

Soak your cylinders/racks overnight in a weak sulfuric solution with no electricity and you should be okay. If that isn't sufficient for you, look up recipes for a titanium etch - be forewarned; don't do either process too often, it WILL mess up your titanium over time. See the letter I referenced above for more info -- it is from when I had a similar issue.

Good luck!

A. Like stated in letter 22422, we used a quick dip in a nitric-fluoride tank. the secret is a minimum time in the tank based on the tips, not the main body. The oxide is blue, so it is very easy to tell when it is removed. We probably stripped once a week. This was a total hand operated line. Our philosophy was quality. A rerun of several parts is rather costly. A few arced parts was very costly. So, replacing fingers every couple of years was actually the cheaper option and helped keep turnaround times to a minimum.

A. I agree with everything stated in the previous answers but keep in mind that titanium will not work for electrocolouring, for this process you need to use aluminum racks.

A. I don't think you're going to find a much more effective anion than fluoride. Titanium dioxide is not easy to remove, chemically. If you are seeking an effective alternative, I would think an electropolishing process would be your best bet, but that seems a bit expensive for cleaning your anodizing racks.

What is the desire for removing this jig. Titanium Dioxide is an n-type semiconductor, so your should still conduct electricity while anodizing.

Titanium is a preferred material for anode baskets over steel for this very reason. It conducts electricity and it won't leach into the bath.

A. Kavitha,

Dipping the Titanium Rack in Sulfuric Acid electrolyte for 1 day can remove TiO2.

As Robert says it is conductive even if you don't remove the oxide layer.

Hope this helps

A. It is very true that you do not need to strip Ti racks before each plating run, but periodic stripping reduces anodize problems.
You need some acid with the bifluoride. Make a solution of about 10% nitric acid and 1% bifluoride. It will work much faster and have far less of a problem with the F ion.