[compfranon]

I have machined some small pieces from aluminium sheet and would like to anodise and dye black.

In general i'm happy with the process but I think I've trawled my way into brain gel trying to establish the anodising time and current.

I have a variable voltage linear power supply 3-15v 25/30A

Surface area of part is 43.53 in sq.

Can someone help establish the correct voltage/amperage and anodising time.

[derek]

Here is a link to a calculator
720 Rule Anodizing Calculator

Be careful with your acid temps as that will cause burning. I float plastic bottles with frozen water in the acid to keep it cool

derek

[compfranon]

Thanks for the reply Derek, spent a fair bit of time again today, and I've looked at the 720 calculator.

I don't have accurate control of the current, so tomorrow I plan to work to the guidelines supplied by the kit supplier and use the rating of 120 milliamps per sq in, which in my case works out at 5.22A

So starting at zero volts, i'll slowly increase the voltage until the draw is around 5.25A, and then monitor and adjust voltage to maintain that current, running for around 60 minutes.

I'm hoping it will work out ok.

Hoping some knowledgeable person will read this before I proceed and advise.

Oh and thanks for the info on temp control, I plan to use similar to keep mine around 20 degrees C.

[derek]

I have an amp meter wired into my power supply. It's a panel mount style. Since its a manual voltage unit I have to adjust it a bit during the process but I can keep a fairly steady amp reading most of the time with little tweaks

[compfranon]

Theres an amp meter built into my psu, so i'll adjust voltage as necessary to achieve the value.

[derek]

Sounds like a plan.
Mind the fumes! When I first got started I would keep the acid bath by the door with a fan on it during the process. I now have an enclosed box that vents to the outside.

[compfranon]

I planned to do the anodising outside rather than in my man cave, but rain has stopped play so far :-(

Good idea on the vented box, I could do that as there is a window right beside the bench in my shed, that's one for the work to list

[compfranon]

Well today was dry, but I put up a canopy outside just in case, so I could work in the open air.

Followed the process and placed the part into the acid, adjusted the voltage, kept going but at max 15v the current was only 2A, not sure why. Anyway, after a very short time, agitated the part a little and must have lost the connection, current draw went to zero.

Re done the process through etch again, and made better connections. This time managed 3A, so decided to run for 2 hours instead of the originally planned 1 hour at 5A. It's now 90 minutes in and the current has risen to 4A !!! I expected the reverse.

Just hope i'm on the right track, dye is ready for the next dip and i'm about to get the water on the go to boil for sealing.

Any comments welcomed.

[compfranon]

Well the first part is finished, looked odd like a velvety finish on it, but when dried and polished with a cloth looks real good. Very little black residue came off on to the cloth.

Next parts are in now, much smaller so able to run them at the necessary 2A for an hour, will see how they turn out.

[BAMCNC.COM]

Only advice I have is watch Grimsmo videos, and check out casewell forums. Oh and CLEAN CLEAN CLEAN

[compfranon]

Parts worked out real well, I had read caswell and many more, some very helpful information, possibly too much ;-) Don't think I saw any of those videos, will check to see if theres anything else helpful - thanks

Only thing i'm curious about now is why the larger plate drew 2A at the start and gradually increased to 5A, the smaller parts drew 2A and stayed there.

[compfranon]

I've done a bit more anodising now, and things are improving, still having diffs with some small pieces though, I try to batch 4 together and only 1 takes the anodising properly.

Still no idea why the current isn't at the value the calculations say it should be, 44 sq in = around 5A, but in the process it draws around 2 - 2.8 max

[BAMCNC.COM]

To much resistance. Bad part connection, to small cathode, solution is to weak, wires to small, power supply can't handle it.. just some things that come to mind. I anodoze Titanium everyday, but not Aluminum, sorry.