acid bath acting weird

[mkriegs]

alright, I've been trying to anodize this one part for a while now and I thought before that the lye bath was my problem but I'm not so sure anymore. The surface area calculates out to about 0.6 sq. feet and I'm anodizing at 4.5 amps per square foot which comes out to 2.7 A. So, when I dial in the amperage the voltage goes way up to about 30 but then the acid bath starts to make a hissing noise (I can't find what specifically is making it though) and the voltage levels off at around 21V and the tank continues to hiss.

should the voltage be that high? and should it be hissing like that? I'm using lead cathodes with a larger submerged SA than my part, aluminum racks, 1:3 acid to water, the lead out of the tank looks a little corroded but I'm not sure if that has anything to do with it.

[acidrain]

Corroded leads could be it. Something is making the resistance high. Are you sure of the alloy? When you stripped the part, did it smut terribly?
Maybe your surface calcs are off?

[sswee]

I'm with acidrain. Poor connection in the circuit. Arcing causing the hissing or buzzing noise. I've seen bad connections on parts arc out like a welder in the tank and buzz fairly loud with a light show.
SS

[mkriegs]

One thing I forgot to mention is that to connect the wires to my cathodes I actually soldered the copper wire onto the lead, as in with a soldering iron . It seemed like a good idea at first, but I'm not so sure now.

I think I'll desolder those wires and replace them with something else, what do you recommend? I was thinking some heavy duty alligator clips.

[acidrain]

I have regular crimp lugs on the ends of my wires, then SS screws attaching the wire to the cathode. I only had problems with connector corrosion when I used aluminum cathodes.
These are connected away from the acid of course... the cathode runs up and out of the tank.
You should be able to use your ohm meter to find any bad connections. Have you tried running a scrap piece?