Anodising at home?

How practical is it to "anodise and dye black" aluminium at home?
( "Anodise and dye black" was the standard finish I recall seeing specified
to give a matt black finish.)
Alternately, tips for preparing and painting aluminium to give a matt black,
protective finish in the home workshop. Small parts only.
Thanks
Brian

Reply to
Brian Reay
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Take a look at
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I'm told that its difficult to make paint adhere long term to aluminium, but I'm not 100% sure.
Reply to
Gary Wooding
You need a special acid etch primer...you might be able to get it from a Land Rover dealer.
Regards,
Reply to
Stephen Howard
home?
aluminium,
Yellow zinc chromate is the traditional etch primer for aluminium iirc if the EU nannies still let us use it
AWEM
Reply to
Andrew Mawson
Anodising is very cheap...........got 4 motorcycle rims, stripped and re-anodised for =A320 a few weeks ago!
If you want to paint, U-Pol do an aerosol can acid etch primer which is easily available from any good car paint supplier.
Finally Caswell do home anodising kits, but this probably isnt really worthwhile unless you need to anodise parts on a regular basis.
k
Reply to
Ken
It can be done - but it will involve quite a bit of time, equipment and chemicals. It's more a garage/workshop than a kitchen process, in fact for safety and marital harmony it should not be done in a kitchen.
You can also buy kits, but I know very little about them.
The modern standard dye process might involve: polish, clean, rinse, dry, wire-up, clean (again, to get the fingerprints off - no touching from now on, even with gloves), rinse, etch, rinse, form a layer of "plates" of Al oxide using electricity in sulphuric acid solution, rinse, dye, rinse, then convert the oxide into the hydroxide by boiling in deionised water, dry.
The hydroxide is bigger than the oxide, and the plates expand to fill in any gaps and to seal in the dye (chemistry is a bit simplified).
Not all these steps are necessary, and some can be combined. You'll need a tried recipe, or time and practice. Recipes are available on the 'net, and there is a quite good beginner's book in the Home Workshop series.

The chromate/chromic acid in some older recipes is too nasty for casual domestic use, but some people do use it at home - be very careful if you do. I recommend against using it for home anodising, it is not necessary and the results aren't worth it.
Professionals also sometimes use hydrofluoric acid for or in an etchant - but IMO it should not be used in the home at all. Gentler etches may take a little longer, but they work just fine.
The other chemicals typically used are no worse than the necessary sulphuric acid, and a good result can be achieved without using any nastier chemicals.
There is a chap on ebay UK who sells the correct type of black dye, which is otherwise a bit hard to obtain - everything else is standard.
That's the new one - in the old days (the 1960's) "black anodising" was a copper / chromate process which significantly increased the hardness and strength of the surface. No black dye was used, and the result was very black. It was very expensive compared to normal anodising - I can't remember the price, but we costed jobs per square inch instead of per 100 sq ft.
A (chromate-free) version of this process is now called "hard anodising", and is sometimes used with black dye nowadays for upmarket saucepans. Still quite expensive, as the high current low temperature bath needs constant cooling.
Reply to
Peter Fairbrother
If anyone manages to get hold of Hydrofluoric acid then they should read
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Probably the nastiest chemical ever mentioned on this NG.
Mike.
Reply to
NewsGroup
You have not seen the coolant in my big TOS lathe. That is evil. Last month it grabbed the H&S inspector playfully by the throat, removed both his socks and shoes, stole his watch and wallet and threw him out on his ear.
It could have been worse, the coolant was in a good mood that day.... -- Regards,
John Stevenson Nottingham, England.
Visit the new Model Engineering adverts page at:-
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Reply to
John Stevenson
In article , NewsGroup writes
"A case report of attempted suicide using an enema of hydrogen fluoride solution resulted in severe hypocalcaemia."
Stone the crows...
Reply to
Nigel Eaton
Sounds like a severe pain in the ass to me
Regards, Tony
Reply to
Tony Jeffree
I use to work in the labs for the oil industry where we had to boil Hydrofluoric acid. We had special plastic everythingand still the labs fell apart. I remember the day when the bloke cutting the grass outside our lab had the lawmower fall into a hole, the clay pipes and grould had disapeared and this was ment to be our clean water discharge. I soon changed jobs for heath reasons.
Mike Cole
Reply to
Mike
Nitrogen dioxide.
Reply to
Steve

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