Anodising

Had another go today with the new set up but still using the original acid in the ano tank. This time the tank is placed in a larger one filled with water which is heated with an aquarium heater (24 C). The ano tank has an 'agitator' made from an ali tube drilled with smallholes and fed by a small aquarium air pump and the test piece was suspended on a piece of titanium strip. A milli-ampmeter really needs to be in circuit as the amp meter on the unit is too 'coarse' to get a reading on - back to the test meter then though if the parts get larger or the part count goes up then the current will need to increase relative to the surface area

Not anything to write home about I agree and nowhere near as good as hoped for but you have to agree it is green   At this stage it has not been sealed in a steam bath and is much shinier than the pic suggests but importantly, no, it doesn't rub off  

Edited By Ramon Wilson on 14/05/2010 23:11:07

Electrics are not my strong point I'm afraid - I do know how to wire a plug - that kind but I think I'm learning

Edited By Ramon Wilson on 15/05/2010 13:40:34

I'm just completing the Hemmingway Centering Microscope and would like to anodise the parts once completed.

However I have made the male and female threads to a really good fit, I'm concerned that after anodising the treads will be too tight.

When anodising, is there a process whereby curtain areas of a component can be protected from being anodised ie. close fitting parts?

Martin

Hi Martin,

I have not had to worry about this situation and as such cannot tell you if dimensions grow slightly or indeed reduce some. I would hazard a guess that if it does it will be microscopic but that may be enough if your fits are that close.

You could mask the external threaded area using tape possibly PTFE thread tape so that the tape forms to the thread but what you could use for the internal I'm not sure - possibly silcone grease or a layer of silicone sealant allowed to cure - that would certainly be easy enough to remove. Watercolourists masking fluid may do the trick too but these are suggestions - nothing positive based on past experience.

Perhaps others may be able to help.

Whatever perhaps you would be good enough to report back on the method you use - successful or not as that way we all get some benefit

Regards - Ramon

Martin
My understanding is that the parts shrink when annodised ( the oxide is denser that base metal thats why it is impervious ..like cromium and unlike iron who's oxide is less dense and thus larger) thus threads "loosen"... about 5-10 microns.
Manufactured thousands of anodised parts and never needed to use "preplating" gauges for fit. but home anodising ? sorry can't say..

If components are "hard anodised" then you you will finish with an increase in dimension on outside surfaces.

Eg. If you want .002" hard anodising you will get approx. .001" growth and .001" penetration.

This is not an exact science and the figures can vary usually  between 50-60%

Len. P.

Edited By The Merry Miller on 09/12/2012 14:26:45