Multiple GP Plates?

[mti11988]

Is it practicable to use multiple GP plates on EACH Side of a part? I have to anodize a 24" long part and I would like to do it in one immersion. I currently use a pair of 8x8 GP plates (one per side). I am concerned whether the plates are big enough to anodize a 24" long part so I thought I would purchaes a couple more plates and have two per side. I am using a Cooler for a tank. Inside measurements of the cooler are 26" x 12" x 10".

[sswee]

What is the SA of the part? The general rule is equal or more cathode surface area as the part. Multiple GP plates is no problem as long as you have good electrical connections. SS

[mti11988]

Hmm. That is interesting. I called Caswell before I did some plates earlier (yes the ones I had all the trouble with) and asked if my 8 x 8 GP plates would be OK to Anodize a part that was 20 x 12 x 0.5 and they told me the plates would do that part just fine with one 8 x 8 plate on each side. So I had less than 1 sqaure foot of total plate (cathode) area to Anodize about 3.5 square feet of part (anode). I was told by them that I would be fine and that I just need to make sure I had the plates between 3 and 9 inches from the part. I had a LOT of trouble with those plates and according to this it is perfectly understandable.
OK, one more question. Does the rule work both ways or can I keep 4 plates in the tank even for smaller parts?
Thanks

[sswee]

I have seen other places where it was said that you needed a cathode approx. 1/3 the size of the anode. I was taught by Fibergeek that you needed a cathode equal to the anode in SA and more cathode would not cause any problems but would not benefit either. I have a cathode that covers 3 out of 5 sides of my tank and run all size parts with no problems. There are pics of the tanks I have gone through to the one I use now in the members gallery if you're interested. SS

[mti11988]

I ordered 4 more plates from CASWELL. I will have a total of 6 then. I think I will look at those pics. Thanks. Bill

[neilfj]

Originally Posted by sswee

I have seen other places where it was said that you needed a cathode approx. 1/3 the size of the anode. I was taught by Fibergeek that you needed a cathode equal to the anode in SA and more cathode would not cause any problems but would not benefit either. I have a cathode that covers 3 out of 5 sides of my tank and run all size parts with no problems. There are pics of the tanks I have gone through to the one I use now in the members gallery if you're interested. SS

I haven't been around much since Fibergeek died, but Paul and I did testing on this just prior to his death in conjuction with some testing on cathode shadowing effects. We found that we were able to anodize with smaller sized cathodes, but success was spotty. The smaller the cathode got, the less the chance of success. One time it would work, and the next it wouldn't, with no other change in variables.

We never did identify the reason for this, but we did determine that there is a relationship between the cathode size and the success rate. The closer the cathode size came to equaling the anode size, the higher the chances of a successful anodization, and once you got to a 1:1 ratio, it was a good as it was going to get. And as sswee stated, over a 1:1 ratio there would be no benefit, but it didn't hurt anything. So, to keep with the reason behind the development of LCD, we decided to recommend that the cathode at least have the same surface area as the anode.

[sswee]

Glad to see you back around. SS

[neilfj]

I was talking with Mike Caswell earlier today and it reminded me that I hadn't been around in a few months. I had stopped by a few other times, just not much to say...you seem to have everything well-in-hand so there wasn't much of a need for me to add anything constructive.

[sswee]

Don't be a stranger. I still run into things new to me. SS

[neilfj]

I'll try to remember to check in once in a while.