Aluminum Anodising - Actually very simple.

[GlidingDutchman]

Today I experimented a little bit with anodising aluminum.

Actually very easy but be WARNED! A BIT DANGEROUS aswell.

• Battery acid diluted 15 - 30% to distilled water - 70 - 85%
  12 VDC supply - high current
  Pyrex glass container or a ceramic container - capable of withstanding some heat and acid.
  Aluminum clamps or supports for aluminum objects to be anodised.
  Lead sacrificial metal - big old fishing sinkers works fine.

Carefully add acid to distilled water! REMEMBER - ALWAYS ADD ACID TO WATER - not the other way round.

Make an electrical connection to part to be anodised using an aluminum clamp of some kind - very important that it is also aluminum.

Connect lead sacrificial metal to negative terminal of PSU.
Connect part terminal to positive of PSU.

Immerse the two eletrodes in acid solution - be careful

Turn on PSU and let current flow for 45 minutes. Lead sacrificial metal will fizz.

Remove alu part after 45 minutes and rinse using cold water.

Optional: Dip in undiluted food colouring and let sit for 5 minutes. The colouring is absorbed into the pores of the oxide layer.

To seal surface: Boil in water for 30 minutes - rapid boiling works best. This seals the oxide surface to finalise the anolidising.

BE VERY CAREFUL WITH THE ACID! WORK IN A WELL VENTILATED AREA - PREF OUTSIDE.

Maybe a few experts can add to this...

See my result attached. I used blue dye and it came out almost violet.

D

Disclaimer: I will take no responsibility for your stupid actions if an acident happens!

[tade]

You might have known, but the acid is sulfuric. Nice write up. I will probably give this a try if I can find a use. Then again, maybe being able to anodize will be like owning a hammer. Everything is going to start looking like a nail...
Thanks

[despotic931]

Thanks for the info, I think being able to add colors will lead to possibilities for added WAF!

[Nordic]

I have seen some anodising kits, but your description nailed the process for me now... will definately give it a try... what to use as current source?

[john blackburn]

It would be worth mentioning what happens if the acid and water are mixed the wrong way round. When I started my apprenticeship in the 1970s, Health and Safety were just 2 words in the dictionary so dangerous demonstrations were the order of the day.

The college got hold of a large acid bottle (carbuoy) with some acid left in the bottom from a local car battery supplier. A small test tube of water was suspended in the acid bottle by a very nervous workshop technician and we were advised to find something large to hide behind, or eachother.

The string was pulled releasing the water and the 15mm thick glass bottle violently and instantly exploded. The heat and steam generated by the water being boiled by the acid was just too much for it.

There was still a large chunk of glass embedded in the workshop ceiling 5 years later when I finished my time.

Not something you want happening when you are stood over it, no safety goggles on Earth would protect you from that.

[MJL21193]

[Nordic]

Adding acid to water prevents a slaughter.

[GlidingDutchman]

Originally posted by Nordic
I have seen some anodising kits, but your description nailed the process for me now... will definately give it a try... what to use as current source?

Nordic - the whole process was a mistery to me unit today when I decided - what the hell, lets see what happens!

Current source: 12v "alarm" battery.

D

[GlidingDutchman]

Originally posted by tade
You might have known, but the acid is sulfuric. Nice write up. I will probably give this a try if I can find a use. Then again, maybe being able to anodize will be like owning a hammer. Everything is going to start looking like a nail...
Thanks

I think it can be quite handy when working with heatsinks etc... you can have a very snazzy custom enclosure for your next audio project when making it from aluminum.

Volume knobs?

REMEBER: You dont have to colour it - you can simply seal the surface after the electrolesis process by boiling it without coloring.

NOTE: I boiled the part with the bit of colouring which it was dipped in.

D

[GlidingDutchman]

I think the one place where many people goes wrong is that they electrify the part to be anodised with copper wire - I know I have once before and it didnt work. I stood there baffled and wondered what the hack is going on... today I thought ... hey! electrify the alu part with some aluminum. I bent a clamp from some 4mm alu rod to hold the part firm. Ta-dah!