Is the 20 amp CC rectifier big enough for this?

[bbqboyee]

I'm a complete newbie at anodizing. All I've done so far is to anodize and dye a couple of small parts using an automotive battery charger. I plan on getting Caswell's LCD kit and a rectifier, but I'm wondering if the 20 amp rectifier is large enough for what I want to do, and if not, what do I need instead?

I am a drummer, and there is a particular type of drum made from an aluminum shell that is very popular. These drums are usually chrome plated (though there is also an anodized version) and the plating tends to pit and flake off over time, making them very ugly. Some people have had some success stripping the chrome and anodizing these drum shells, and I'd like to try my hand at it. Here is an example of what I'm talking about:



These drum shells measure 14" in diameter and 5" tall, with about 1/2" flange at each end of the cylinder. I figure this to be roughly equivalent to a 48" x 6" sheet of aluminum, or about 4 square feet. The specifications for the 20 amp rectifier says it can handle 4.4 square feet in area, so it seems like it will do the job, but I'd like to know if you experts think this is practical and doable? Any other advice would be more than welcome. Thanks!

[sswee]

No problem.
Body
14"dia x 3.14 = 43.96"
43.96" x 5" = 219.8"
219.8" x 2 (ID & OD) = 439.6"

Flanges
R7.5squared = 56.25" x 3.14 = 176.625"
R7.0squared = 49" x 3.14 = 153.86"
176.625" - 153.86 = 22.765"
439.6" + 22.765" = 462.365" SA approx.(3.21ft sq)

By the 720 rule:
For 4.5A CD
4.5 / 144 = .03125A per in. sq.
462.365 x .03125 = 14.5A setting on PS
720 x .5mil = 360
360 / 4.5CD = 80 min anodize time

The math is only the start. It's a do'able project if you take the time to prepare in advance and don't get impatient. There are plenty of good cheap containers that would accomadate that size part. The thing to think about is , how many are you planning to do? Just a guess but I figure you'll need approx. 15 to 20 gal tank. That means 5 gal. of battery acid. You can find smaller containers to DeOx and Dye in, so that you can get away with 8 to 10 gal. for these. This would be a decent size setup if done. I highly recommend getting some smaller parts to learn and practice on if you decide to go for it. If you only plan 1 or 2 pieces, you should price having it done first. Best of luck. SS

[bbqboyee]

Thanks for all the great info!

I'll only be doing one drum at a time, so I don't think I'll need a tank quite so big as 15 or 20 gallons. Actually, when I put the drum in the round tub I plan to use (I think it's about 18" or 20" in diameter), it only takes about 5 or 6 gallons to totally submerge the shell. Is there an advantage to using more liquid?

Another thing I'm curious about is the placement of the anode(s). I'm sure the plating manual probably covers all this stuff, but I haven't order the LCD kit yet so I don't have all this good information handy. Can the entire inside and outside surface of the shell be anodized in one shot, or should I do the inside and the outside in separate steps? Will I need to reposition the shell with respect to the anode(s) throughout the process? If so, will the purchase of additional plates alleviate this need, or will that overtax the capabilities of the power supply?

I apologize if these seem like dumb questions! I just don't want to go off and order a bunch of things I won't need, or have to place additional orders to get the job done.

Thanks!
Steve

[sswee]

The cathodes need 3" clearance to the part if I remember right. The reason for the extra liquid is to help with temp control. A part that size running that many amps will generate a little heat. You will start to have problems after a 5 or 6 degree increase in temp. You may need to have your tank in a bigger tank with an ice water bath to dissapate the heat. The size tank you describe sounds good for DeOx and dye. Boiling to seal may be a hassle.

The cathodes are 8"x 8" if they haven't changed sizes. You will need 4 if they are mostly submerged. You need the same SA of cathode submerged as the part or more won't hurt. A problem will be getting good electrical connections from PS to cathode or cathode to cathode. No problem for the PS. ID and OD are done at the same time. If you leave a part in the tank after it is anodized, it will dissolve the coating back off. Placement of cathodes effects anodizing but not as critical as plating.

[M_D]

swwee mentioned 2 reasons I can see for needing a larger tank. It has been some time since I used a tank about 15 gallons in size, but I think to assure good results you would need to use extra cooling. It may help to also hang a cathode in the center (inside) if you want that to look as nice as possible.

Also, you will need some agitation. If the connections are secure and mechanically strong enough you could stand there and lightly swish the part around every minute or two. Otherwise you will need a pump and spray bars or air lines. One more reason to have some extra room in the tank.