Thread: Anodising or alternatives in the shed

I have a couple of projects made with Al that are literally waiting to be finished - they call up anodising as the surface finish.
Having worked in a place with Al treatment baths, I know that anodising can be involved if done properly. Has anyone got a home set up that is not horribly expensive, toxic or complex? Alternately, does anyone have an alternative way of finishing Al parts (a dip or something) that gives a reasonable finish? (I have an optical centre scope kit that I've made that should be black to cut down reflections)
The parts are not big and I'd only use the set up once every 6 months or so, so simple and compact are pluses for me.

Michael

Hi Michael,
From memory, all you need is a pyrex dish of some sort, a lump of lead for your negative charge and the positive charge goes on the ally. The whole lot needs to be immersed in sulfuric acid and powered up with 12v for 1/2 an hour or so. The ally can than be rinsed and dyed with ink or fabric/leather dye, diluted in another container with warm water. then it is put in boiling water to set it.......its been a long time but thats how i remember it.

I think you can buy commercial products too though, not sure on the process with these.

Edit: the piece has to be REALLY clean before you start, no fingerprints or other traces of foreign matter.

Originally Posted by Michael G

I have a couple of projects made with Al that are literally waiting to be finished - they call up anodising as the surface finish.
Having worked in a place with Al treatment baths, I know that anodising can be involved if done properly. Has anyone got a home set up that is not horribly expensive, toxic or complex? Alternately, does anyone have an alternative way of finishing Al parts (a dip or something) that gives a reasonable finish? (I have an optical centre scope kit that I've made that should be black to cut down reflections)
The parts are not big and I'd only use the set up once every 6 months or so, so simple and compact are pluses for me.

Michael

Hey Michael,

Is the kit scope something you bought from Hemmingway in England? Even if it's not , how about a show and tell.

BT

Kits containing all the necessary bits are available from Caswells. Not sure how it meets your expensive/toxic/complex criteria. . The process doesn't seem too complex but disposal of used chemicals would be a concern. What does a commercial outfit charge for anodising small items?

There's a group on Yahoo that's pretty good.

It is one and the same Bob. Once it's in a fit state to be tested I'll do that - I have all but one of the parts machined but as you can see have not worked out how to finish it.

Michael

I did a bit of experimenting with anodizing a few years ago, and with a bit of advice from others it came down to a degrease dip in caustic soda solution to remove any finger prints, oil etc, then a dip in a nitric acid solution to "desmut" the aluminium or remove the grey deposits from the caustic to give a nice bright almost whitish surface and then into the sulphuric acid for the anodize. I used the yellow and blue food dyes from the supermarket to dye it. I still haven't worked out how to seal it properly without washing out the dyes from the surface so I chickened out by melting beeswax into the surface which has lasted 10 years so far.

Surface finish is very important as any scratches or machining marks will show up through the anodize, I found a glass bead blast gave a nice satin finish without rounding off corners or the aluminium.

I'm told that dies can be sealed into the anodising with steam - it makes the oxide pores close up apparently. Haven't tried it myself though or seen it done first hand.

Michael

Originally Posted by Michael G

It is one and the same Bob. Once it's in a fit state to be tested I'll do that - I have all but one of the parts machined but as you can see have not worked out how to finish it.

Michael

You sound like me with my tool holders, I still don't know what fish they are getting to stop rust.

Google anodizing and you will get some good hits. I did this 12 months or so ago and there are some easy set ups around. Never tried it myself though.

Dave