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Originally Posted by Chunkstyle
hi guys
i'm going to be trying my first shot at home anodizing soon. i've done a lot of research, but haven't found answers to a few specific questions. if any of you could offer any insight, i'd appreciate it.
1. the part i'm doing is a bmx bike brake, disassembled in 2 pieces. any idea what alloy these typically are, and if it's easily anodizable?
You can tell by the smut after stripping/etching... 5xxx and 6xxx won't smut much if any, and require a full .75mil for lighter colors, and 1mil for black.
2xxx and 7xxx will smut a lot, and only require .5mil for lighter colors, and .75 for black.
2. the parts are pretty small -- "L shaped pieces about 3"x4" and 3/4" thick.
can i anodize the 2 pieces together (for color matching purposes), or should i run each separate?
Always ano all the parts at once for best color matching.
3. does aluminum flashing work well as a cathode? do cathodes need to be stripped before use for maximum conductivity in the bath?
Any aluminum will work as a cathode, just make sure there is no clear-coat on the surface. Check with a ohm meter to see if the surface has any non-conductive coating.
6061 will stay bright longest as a cathode.
4. for hanging wire, i got a 3/32" alum welding rod, per a post i saw here -- planning to bend a j & wedge it into a hole in the part (there's nowhere to bolt to on these parts that won't interfere with the finish). do i need to strip the end of the wire where the hook will be (again, for conductivity)?
Welding wire requires no extra effort. Radio Shack sells 8ga wire in a roll too.
5. i'd like to work outdoors, for ventilation, but it's in the 40's-50's here now.
is too low a temp ok for automatic battery charger-type anodizing? as a newbie, i really don't know how much the electricity will raise the bath temp.
Tank temp is a huge factor... it must be between 68F and 70F for best results. Never more than 70F, or pitting/chalky ano layer may result.This is one of the major factors in consistency between batches. Temp variations = resistance variations = amperage variations. Get it?
6. can you hand-agitate the bath, with a dowel or something? how often does it need to be stirred?
Yes, hand agitate is better that nothing, but keep in mind, the tiny bubbles forming on the surface will start a pit. Constant agitation is recommended. I suggest a fish pump for small projects. I use air from filtered air straight from my shop compressor. Creative use of PVC pipe with 1/16in holes works good.
7. when dyeing, can the parts lay on the bottom of the pot (i'd probably heat the dye bath to 140 deg. on my gas stove, so there'd be a flame under the pot where the unsealed parts'd be resting) (too hot on the bottom of the pot -- premature sealing?)? if so, is a stainless steel pot ok for the aluminum to contact when in the dye?
The parts must be suspended, or dark/light areas will occur.
8. for desmutting, i was hoping to use the "scrub with dish soap" method, since this one item may be the only thing i anodize, and it's probably not worth it to buy the official desmutter stuff (plus, i couldn't find it listed by itself on caswell's site -- only as part of a kit). how hard do you have to scrub the part? is it simple to tell when you've got the smut off?
You won't need the de-smut if it's 5xxx or 6xxx, especially if you buff the parts. Dish soap does nothing for smut. The individual de-smut product is there... keep looking. If the parts smut up, you'll need it.
and a really dumb question -- does the smut come out during the anodizing process and needs to be removed before dyeing, or is the smut to be removed before anodizing (like just as part of prep cleaning)?
Smut only happens after the stripping/etching step. It is a black, sooty material that can be wiped off... kind of. You don't want it on your parts before going in the tank, and when dipped in de-smut, the black disappears instantly (almost).
9. when you want a pretty glossy finish and polish the part after stripping & before anodizing, do you have to re-strip the part immediately before final degreasing & rinsing before anodizing it. i know aluminum oxidizes on its own pretty fast in the air, but is is not a problem in this situation?
No, after you polish, clean all the compound off with lacquer thinner or dish soap and elbow grease.
Then, final prep is a few minutes in the SP degreaser (also hard to find by itself, but it's there). This is really important, as the parts need to pass the water break test, and no soaps that I know of will do that like SP degreaser.
sorry for all the questions. thanks for any help you can offer. i downloaded caswell's lcd manual, and am going to print & read it soon.
thank you!
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