DIY Anodizing

[Andrew Steele]

For those that build their own amplifiers or want to anodize their own heatsinks, I came across this site, as I'm guessing, most places that do anodizing would charge depending on the surface area, and with heatsinks that is quite alot of surface area.

And guess what?... IT'S DEAD EASY!

http://sites.gulf.net/riders/anodize.htm

[PassFan]

That was an excellent link to post here Andrew, Thanks

[cp642]

seems that further search in to the topic of anodizing reveals....

"Current requirements calculations are based on the size of the piece to be anodized. A general guideline is about 900A per minute per sq. ft.Time
in the bath is computed from the guideline, for instance, if you have 5A available and a 1 sq. ft. part it needs to anodize for 180 min.
(900/amps avail. for each sq. ft. )"

..unless it's a small part...it might take you a day or two to get a satisfactory layer of oxide coating. But then again...it's fun trying!

[PassFan]

A word of caution about sulfuric acid. Wear fully enclosed goggles to avoid any splash. You will lose an eye if you get it in there. Keep a 5 gal bucket of water and a hose with sprayer nearby to get it off. Since pure sulfuric reacts with water make sure your skin is dry and not sweaty as the sulfuric will react with the sweat just like water. Pure sulfuric will not burn dry skin but you still have to wash it off with water. If the proper care is taken it is safe to work with. If you have small children around secure it every time you walk away even if for a couple of minutes.

[dice45]

it sure is big fun!







But be prepared that 10 parts meant to be anodized in black have atleast 11 different shades of of black. NO downtalk, even the anodizing pros will find it difficult to keep the intended colour.







So if colours do not come out exactly as intended, don't be disappointed. It is part of the anodizing process, not your mistake.



Just be prepared.







Been there, done that (mechanical engineer). Practical hint: for coloured anodizing AVOID any alu with even the tiniest percentage of lead (Pb) in its alloy. Copper in the alloy also is disadvantageous for anodizing. Colour predictabilty is lousy and (worse) the colour ages, e.g. black turns into dark violet.


With alloys AlMg3 and AlMgSi1 (F22) anodizing should come out ok.


Don't forget to have the surfaces as you want them BEFORE anodizing; surfaces get slighly smoother with anodizing, but a brushed frontplate stays brushed. For precision parts consider that amodizing is specified by the oxide thickness; the oxide of a 20µm thick coating grows like fungus about 13µm deep into the material and 6µm of this fungus stands out, contributes to total dimension. Just for the case you want e.g. a precise seating for a ball bearing or two halves fitting together without play...









Wanna know how to make your anodizing pro crazy? Simply walk into his shop and ask him to anodize a new frontplate and you insist on having exactly the same shade of black as the front plat has he did last week for you.



The anodizing bath changes/ages, the raw alu will have slight alloy changes etc. etc., it is even worse if you insist on a special magenta or purple. Or simple red.

[Lisandro_P]

I saw that one a good while ago... if you have a battery charger, it sounds like a great idea! Acid is not quite cheap, but overall i'd be much cheaper than buying a black anodized sink.

[Andrew Steele]

thanks for the response, I just found another site with pictures and it gives a good Idea of a setup for anodizing.

http://www.focuser.com/atm/anodize/anodize.html

this is another one;

http://wuarchive.wustl.edu/edu/arts/...s/anodize.html


a word of warning, acid is REALLY nasty stuff and most homes are not equipped for a spill e.g; just think what would happen if you spilled it in your garage... but other than that, I cant wait until I can anodize my amps (when i build them)

[AudioFreak]

Just a quick note to anyone considering anodising a multi part case ...... after anodising, you will have to remove the oxide layer @ anypoint when 2 or more panels/walls of the enclosure meet..... if this is not done then chassis earthing may be ineffective thus adversly effecting shielding and possibly causing a safety issue.

[wuffwaff]

seems to be quite easy......except for the little problem with the acid and how to get rid of it.
I would leave it to the pros.

william

[Helix]

VERY tempted to have a go, looks straight forward, if your careful!. I already haave some sulfuric acid, but i wonder hoe strong it is? have to go and get some PH stuff.

i will report back when done