Titanium and Aluminum in same batch

[jlcollins]

Has anyone tried titanium and aluminum hanging wires in the same batch of parts? If so will the parts look different from each other when dyed?

[Fibergeek]

The difference in electrical conductivity between aluminum and titanium is substantial. For this reason use one or the other, but don't mix them in the same batch.

[SX Paintball]

What do you mean by don't use them in the same batch. I have used titanium and aluminum in the same batch many times and never had any problems.

[Fibergeek]

If you anodized two identical parts together, except that one was suspended from aluminum, and the other titanium, the titanium one would receive less current. Why? because aluminum is a better conductor than titanium. Mixing titanium and aluminum adds another variable and provides no benefit.

[jtsuttle]

Would it be necessary to adjust my current density if I started using titanium wire?

Edit: Sorry, I just read another post regarding this. I'll wait around for Fibergeek to post his findings.

Thanks.

[Fibergeek]

I can provide a simple answer to your case.

If you are suspending the work from wires; what's important here is that the surface area of the wires is much less than the surface area of the work, there won't be much of a difference between aluminum wire and titanium wire. The titanium wire will drop a bit more voltage than aluminum wire, but a CC power supply will compensate for this automatically. Nothing to worry about. If you had two pieces of work in the tank together; one with Al wire, and the other with Ti wire, the CC power supply won't know which to believe, so it will strike a compromise.

This situation gets much different with racking, since the surface area of the rack is often larger than the total surface area of the work, so the rack is setting the current density, not the work.

[jtsuttle]

If you are suspending the work from wires; what's important here is that the surface area of the wires is much less than the surface area of the work,...

In my situation the wire would have, as much, if not more surface area than the parts being anodized. Any suggestions?

[Fibergeek]

Use a smaller gauge wire. As an example; 14 AWG is 0.062" dia., assuming a piece 6" long in the electrolyte:

Surface Area (SA) of a cylinder is Pi x D x L (ignoring the area of the end of the wire)

SA = 3.14 x .062 x 6 = 1.17 sq. in. That's about .008 sq.ft. your part is that small?

If you used 18 AWG (.038" dia.) The SA would reduce to 0.71 sq.in. (.005 sq.ft.).

[jtsuttle]

The violet colored part in the pic above had about .0002 sq.ft. If I used .062" wire and only had 1.5" length in the electrolyte then the wire and part would be close to equal. I have been using alum wire and a CV setup to do these so far but would really like to make some reusable Ti fixtures to hold them. The small alum wire breaks after the first use.

[Fibergeek]

Your picture didn't work.

[jtsuttle]

Its working for me. Maybe right click and go to show picture.

[Fibergeek]

Still doesn't work, I'll have to ask you to describe it, sorry.

[jtsuttle]

Hmm, I don't know what the deal is, try this link instead:

http://www.geocities.com/jtsuttle/x_tra_small.jpg

[Fibergeek]

That link says "page unavailable". Don't worry about it.

3.14 x .062 x 1.5 = .093 sq.in. , let's call it 1 sq.in. (.007sq.ft.)

Find some spring temper Ti wire, Servisure sells it among others. You'll want a small gauge, smaller than 18 AWG, let's guess and say 20 or 22 AWG. The stuff should be tough to put in the bends you need to form the appropriate spring, you'll have to experiment to determine what a suitable spring for this should look like. It's clear you want the smallest spring that you can get away with, you'll do this anyway when you see the price of titanium wire.

Since I haven't started my titanium experiments yet, you'll be using "Kentucky Windage" anodizing (you guess the current to apply) start with say 1/3 more current then you would use if the wire wasn't there. See what happens.

[M_D]

Those are small parts for sure. I guess you don't need a big power supply, but you sure would need something that you could control the current with down to a fine level.