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.
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.
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
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....
Visit the new Model Engineering adverts page at:-
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.