The technique you need is anodising. Basically the part is treated electrolitically as the anode in a bath of weak sulphuric acid. The part is then soaked in a dye solution (cloth dyes or writing ink) and then boiled in water to seal the colour in. There is quite a lot about home anodising on the web for example.

HTH

Rod

rods correct im wrong not passivate I ment anodise sorry to miss inform you ian

I've been successfully anodising aluminium in my shed for 5+yrs, if/when you find you need a helping hand then give us a shout.

P.S. Black is one of the easiest colours to achieve an impressive result with. It is also the least forgiving, if you find that you can only turn out various shades of blue, I can help.

Mick,

I have been asked to machine a component for a Porsche (I haven't seen the sample yet) which needs to have a black finish. I have never tried to coat anything but I am due to get the opportunity (via redundancy) to spend a great deal of time trying. Any starter pointers would be greatly appreciated.

Phil H

Working with a battery charger can work well but good results will take a lot of trial & error.

Using Caswell's LCD method it is extremely easy to achieve good finishes with very repeatable results. The only thing I feel you need to splash money on is a constant current power supply to replace the battery charger.

My acid bath runs at a temp of 20-22 deg C which I maintain using an aquarium heater & the ambient temp of my shed.

There are lots of ways to anodise a part cheaply but if you wish to dye the part, especially black, then you need to 'grow' the anodise in a controlled manner.

Mick,

Thanks for the response.

I haven't seen the part yet but from its description – it is an 'L' shape bracket with milled slots on its underside and smooth curved surfaces on its top. Dimensions? I'm guessing 70mm long x 50mm wide with the legs of the 'L' being say 20mm x 10mm section i.e., the part would easily fit in your hand. I would try something like HE30 to machine the part from solid.

I'm doing 1 as a favour for a chap who has a Porsche but he says it is a very common fault on these particular models so who knows?

I'm definitely not in this for profit. It is just because he sits next to me at work (at the moment) and he knows I have a miller. However, I have often thought it might be nice to utilise aluminium for say stationary steam engine bases that would look nice with a camera type satin black finish.

The answer might be to get the Porsche part professionally coated but Im still interested for future parts.

Phil H