Anodizing equipment

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Lone Watie

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I'm looking at DC power supplies. What is a good amperage/12V variable power supply range I would need for general purpose and to have enough current for anodizing? Is there such an animal?

Thanks.
 
I just bought a commercial battery charger off Craig's List. I plan on using a Variac for the voltage adjustment and the charger will provide more than enough amperage for my needs. If you want a commercial power supply, Ron Newman sells them, but they start at around $250.

Tom
 
TLGriff said:
I just bought a commercial battery charger off Craig's List. I plan on using a Variac for the voltage adjustment and the charger will provide more than enough amperage for my needs. If you want a commercial power supply, Ron Newman sells them, but they start at around $250.

Tom
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Was it a car battery charger you bought? I have one of those, but no way to adjust the amperage.
 
I've only started experimenting with anodising, so...

I've a couple of power supplies to use, a 5-15V 5A variable supply and an old 30A "start and charge" battery charger - the charger seems to have worked OK, the current seems to self-limit depending on the size of the workpiece? I suppose that each square inch can only flow so much current (I've heard things like 10A / square foot) before the gases given off start reducing the wetted surface area?

As a cathode I'm using 1/4" x 8" carbon rods as used for arc brazing (which came to me I know not how!) with the copper coating stripped off using ferric chloride PCB etch solution, apart from the last inch or so to give the clips somewhere to grab.

For electrolyte, I'm using battery acid diluted about 2:1 with distilled water, again it seems to work OK :) The bath varies from a Pot Noodle pot to a photographic darkroom tray, both have been fine and are chemical resistant (well, a Pot Noodle's quite corrosive and chemical, gets put in the "non-foods" cupboard at home...) For long pieces I plan on using PVC roof gutter with siliconed-on end caps, they're available in 8 ft lengths, which should be far more than I'll need?

What I'm struggling with is dyes that give the right colours without costing an arm and a leg - an early experiment used black inkjet printer ink, but gave a really nice copper colour! I have a few small items I plan to anodise (scope rails for my lad's air-rifle and some telescope accessories for me being among 'em) and a good black is what I'm after... A Dylon cloth dye was recommended on a site I looked at, but doesn't seem to be available any more, the same manufacturer's "new, improved, all-purpose" cloth dye I tried was completely useless and washed straight off when the work was put to boil and seal the surface :(

I've found a saturated caustic soda (lye) solution is a bit fierce for cleaning / etching the surface before it goes in the anodising bath, and does produce a surface that's a bit more matt than I'd like, although diluting it seems to make it a bit gentler - any tips from Those Who Know?

Dave H. (the other one)
 
It is a commercial battery charger rated for 35 amps at 18 volts. I plan on using Variac to adjust the voltage on the primary side. Less voltage in equals less voltage out.

Tom
 
Thanks for the suggestions. Just thinking ahead if I ever want to do this, but also looking for a variable supply for other projects.
 
I am using a PC power supply rated at 400WATTS. it has circuits for 12vdc, 5vdc, and 3vdc and should support up to ~32Amps. unfortunately I'm still experimenting with different electrolyte solutuions and have not had success yet so take this with a grain of salt - just thought I'd put this option out there.
 
Just so ya knows it was me that move this thread to the finishing forum. Carry on.
 
The power supply needs to be a constant current source or a constant voltage source. A battery charger or a PC supply would be considered a constant voltage source. In most anodizing of aluminum it is suggested a voltage range of 12 to 18 vdc. To high a voltage on a constant voltage source will give the potential for the current to rise high. The higher the potential the higher the current that will flow in the solution. The result will be the anodizing solution becoming to high a temperature causing the process to fail. Another time this happens is when the bath is not big enough for the amount of parts you are putting in. The current will rise and the bath will overheat. In anodizing heat will be your enemy. The crystalline layer will not build correctly or will start to seal itself to the point where it will stop all together. In a hobbyist environment it is best to try to keep that temp no higher than 100F but ambient is best. This is not to say that you should make the temperature real low if you could because it is not needed. In the hobbyist environment once again you are trying to create really good anodizing not a military or industrial spec finish. If you are after this it would probably be best to go to a professional anodizer that has total control over process. There is no doubt though that you can't create really good results at home.

Ed
 
From what I understand in an anodizing tank nothing other than aluminum, titanium or lead should be used for the cathode. Some other materials will contaminate or cause the process to fail.
I am not a chemist or engineer but all the papers I have read on anodizing are very particular about what other materials are introduced to the tank. Precaution must even be taken in what you use for the tank.
Plastic is best but I have even seen where they frown on stainless steel tanks. The one problem with anodizing aluminum that some get confused is it is not like other plating or electro-polishing.
I will re-post a lot of the link under the General Thread on Anodizing Aluminum. They were accidentally lost when the forum crashed the other day.

Ed
 
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