Read here, help now, feel like a hero!!

[karmaarma]

Hello all. I have been running my line for about 6 months now with great success but have recently come across some issues.
The pump that came with the kit died after a couple of months, so I bought another but that died too. I haven't run a pump for a couple of months. The SP degreaser is a month old, deox 6 months old, ano tank is a couple days old, and all dyes are 6 months old.
Lately my OD green and black have been blotchy when coming out of the dye. This is especially a problem with the OD green. Both dark dyes have a foamy scum that floats on top, and the deox tank has a slight oil slick on the surface. I also only spray to rinse because I don't have running water where the ano line is.
What could be causing this blotchy effect? I thought it could be the oil slick in the deox tank getting on the parts, but the parts never bead water. I have never tested the PH of my dye, but I have the tester on the way from Caswell, (I hope that it was worth the money).
I suppose that it could also be the lack of water circulation in the ano tank, but all other colors seem to take dye just fine. I know that it is time for a new pump though and I'll probably go for the semi corrosive Little Giant.
So, to be clear my questions are:

Why are the dark dyes coming out blotchy?
Why is there a foamy scum on top of the dyes and is this OK, or how do I get rid of it?
Would the oil slick in the deox tank have much effect on the parts?
Should I be doing some other degrease operation before the SP degrease tank?
And lastly, is not having water circulation having an adverse effect on the process.

Thanks for the help everyone, and check out my website to see some of my work.

Take care,

Blane Nelson
TacticalPyrotechnics.com

[karmaarma]

No one wants to feel like a hero? Please help.

[acidrain]

You definitely need agitation. That could be a source of blotchy-ness.
The scum on your chemicals is a problem... usually just using some paper towels on the surface will soak up any oils, but it sounds like there is more to the dye issue than just oil. Could the dye be moldy? Moldy dye is characterized by stringy blobs of dark material suspended in the tank.
If your parts are greasy, you should degrease with lacquer thinner first, then with the SP degreaser.
Always rinse well... I always spray into he tank, hen dunk in fresh RO water before going to the next step.

[karmaarma]

Acid, you are a hero! Thanks man.

Mold can grow on the dye? It doesn't look "moldy". Maybe I'll just try to strain it through a coffee filter.

I have been looking into the Little Giant HC pumps, but after further reading it seems like people are using air. What are you all using for an air source to feed your air manifolds? Also, what might be a good source for a Little Giant HC pump?

Thanks everyone.

[acidrain]

I use air for ano tank agitation... I have it plumbed off my main compressor & filtered with a spraypaint quality filter/regulator.

I use an HC rated Little Giant for circulating the acid through my heater and chiller.

[karmaarma]

I purchased a LG HC pump today that I plan on using for agitation. Is there a benefit to using air for that purpose?

Thanks again, Acid.

[dmiom]

I purchased a LG HC pump today that I plan on using for agitation. Is there a benefit to using air for that purpose? .....

Blane,

This is our take on circulation / agitation :

With a small tank, air can provide a measure of agitation, and promote limited circulation.

Just the action of circulating the electrolyte (we too use a Little Giant magnetic drive HC pump) means it mixes better (the more homogeneous the bath the better). Having the pump has then also allowed us to circulate via chiller/heater unit.

With the LG pump essentially providing circulation, there is still one aspect where we feel we may be getting benefit from the air we still run as well. When the electric current passes through the tank, as well as building the ano layer, it also electrolyses the dilute H2SO4 and (if my memory serves) Hydrogen comes out on the anodes. Especially if there is any 'texture' on the part you're anodising, small bubbles can build up on the surface of the anode, and those gas bubbles form a small non-conducting patch which consequently doesn't get any further anodising. I have even seen someone advocate (in absence of anything else better) that periodically you lift your work out of the ano tank to allow the micro bubbles of H2 to burst in the fresh air! Our view was that it was worth continuing to run air agitation as the rising air bubbles might 'sweep' some of the other gas bubbles off the surface of the workpiece anode.

So, proper pumped circulation is great, but air agitation may possibly still be a little help as well.

Dave

[acidrain]

As always, good stuff Dmiom...
My take is this:
The most important part of agitation is removing the heated micro layer of electrolyte from the surface of the part.
In other words, even if the ambient temperature of the electrolyte is 70F, it may be much higher at the couple of molocules actually in contact with the part.
In my opinion, the best way to remove that micro layer is with vigorous air agitation. It just seams like mechanical agitation is not a uniform.
It's just my opinion.

[karmaarma]

Very good information fellas. I was considering installing some type of venturi in line with the output so that the water pumping into the tank will have bubbles included. Any thoughts?