Aluminium oxidisation

[Ray153]

I am looking at incorporating aluminium tubing into a project that I will have cleaned up with 1000 grit and higher wet and dry to get rid of any ridges, scratches etc. It will also take off the oxidisation which is the look I want (the non oxidised look).

I would much rather keep the satin type look to the aluminium over time and am seeking advice on how best to prevent the oxidising from reappearing.

Are there any thoughts out there?

[joe greiner]

For outdoor use, cast aluminium car wheels are usually covered with clear coat lacquer. Should be available at auto parts stores.

Joe

[BobL]

Can you tell us any more about your project.

Indoor/ outdoor.
Surfaces flat or curved, subject to wear, handling??
Size?

Cheers

[Bob38S]

To clean Aluminium - the best/easiest solution is to take the pieces to you local Aluminium fabrication place - they use industrial [hydrofluoric acid] to clean the stuff.

If none locally - try the paint stores or Supa cheap and get the Septone AliBrite which contains Hydrofluoric and Sulphuric acids - not sure as to the concentrations but it appears to be fairly gentle compared to the fabricator's stuff - but also takes a lot longer to get the stuff clean - it says that it is for cleaning bull bars and ute trays etc.

1000 grit wil still leave scratches - when you are finished - polish the alum with abrasive powder to get it mirror bright.

Regards,
Bob

[Master Splinter]

You can't keep the oxide from reappearing, but you can control how it reappears.

If you are after a smooth frosted effect, I've found the best way is to polish it to a mirror finish (this makes sure there are no scratches hiding in the finish which will only show up when you are inspecting the frosted product), degrease it with solvent, and then etch it in an acid/alkaline solution, wash it well, dry it and cover it in clear lacquer to stop fingerprinting etc. Supa-Cheap sell a handy spray can of clear lacquer specifically for aluminium.

But you can have more fun if you anodise it....(you can skip the dye if you dont want it, just seal the pores with boiling in distilled water)

http://astro.neutral.org/anodise.shtml

[Burnsy]

You can't keep the oxide from reappearing, but you can control how it reappears.

If you are after a smooth frosted effect, I've found the best way is to polish it to a mirror finish (this makes sure there are no scratches hiding in the finish which will only show up when you are inspecting the frosted product), degrease it with solvent, and then etch it in an acid/alkaline solution, wash it well, dry it and cover it in clear lacquer to stop fingerprinting etc. Supa-Cheap sell a handy spray can of clear lacquer specifically for aluminium.

But you can have more fun if you anodise it....(you can skip the dye if you dont want it, just seal the pores with boiling in distilled water)

http://astro.neutral.org/anodise.shtml

That is a great link and the results he is getting is fantastic. I recently bought a old Number 4 that has an alloy tote, might have a go at anodising it black, or maybe bright blue for something different. Pitty I don't have a daughter, I reckon any girl would be hard pressed to put down a plane with a handle that is the colour of his first effort, would be a great way to get them interested. Then again maybe I will do one that colour and give it to my brother just so he thinks of me every day when the fellas on site give him heaps about his pretty pink plane.

[soundman]

Just a word about hydrofluric acid..... this stuff is very very nasty.... as well as being corosive it will kill you in very short time.
It is such a problem QLD workplace health and safety DPT have a brocure on the dangers. and there are specific regulations concerning it.
It sucks the calcium out of your blood stream till you brain fails to work.
In concentrated form it will do this thru the skin very quickly, it will do it by any other form of exposure too.

It is suposed to be very effective for cleaning brass and copper.

there are safer and easier ways to clean aluminium.

Spraying freshly cleaned aluminium with ordinary nitro laquer works well, just dont polish it too far.

cheers

[Burnsy]

Just a word about hydrofluric acid..... this stuff is very very nasty.... as well as being corosive it will kill you in very short time.
It is such a problem QLD workplace health and safety DPT have a brocure on the dangers. and there are specific regulations concerning it.
It sucks the calcium out of your blood stream till you brain fails to work.
In concentrated form it will do this thru the skin very quickly, it will do it by any other form of exposure too.

It is suposed to be very effective for cleaning brass and copper.

there are safer and easier ways to clean aluminium.

Spraying freshly cleaned aluminium with ordinary nitro laquer works well, just dont polish it too far.

cheers

I believe that is a controlled substance so most peole will not be able to get hold of it anyway. We had to do a pretty serious risk assessment before we could keep it on site at the last Gold mine I worked at.

[soundman]

I havn't checkd the alibrite product sold here, but in the US it can be found in a variety of easily available products in low concentrations.... even then it can kill quite rapidly if swallowed.
First aid for skin exposure needs to be swift and appropriate, first aid for injection or inhailation would be very difficult.

As far as I know all industrial users of the concentrated form must have the appropriate first aid chemicals on hand and people who know how to use it.

cheers

[Barry Hicks]

One sure way to stop nastys from forming on aluminium is to have it anodised. A hunt through the yellow pages or the internet should find someone to do it. With anodising, you can still retain a believeable metal finish as well as a range of different colours.
I would be careful applying clear finishes unless you are sure it won't react over time with the bare metal.

Barry Hicks

[soundman]

Nitro is pretty reliable over aluminium, and is easy to get off if the item needs refinishing.

anodising would certainly be the best option.

cheers

[Paul B]

Just a word about hydrofluric acid..... this stuff is very very nasty.... as well as being corosive it will kill you in very short time.
It is such a problem QLD workplace health and safety DPT have a brocure on the dangers. and there are specific regulations concerning it.
It sucks the calcium out of your blood stream till you brain fails to work.
In concentrated form it will do this thru the skin very quickly, it will do it by any other form of exposure too.

It is suposed to be very effective for cleaning brass and copper.

there are safer and easier ways to clean aluminium.

Spraying freshly cleaned aluminium with ordinary nitro laquer works well, just dont polish it too far.

cheers

Agreed. I'd avoid hydrofluric acid (HF) like the plague, and any product containing it. I had to do a risk assesment of it at the last place I worked at. If you get just a little on your skin you can be in big trouble and lots of pain, any more than 3ppm in air and you're in trouble. It has a delayed reaction too, so the immense pain won't start til about 4 - 6 hours after exposure. Immersing your hand in a 70% solution (5% of your body surface) will kill you in around 8 hours, even if you wash it off immeadiatly, pulmonary adema - drowning as the lining of your lungs liquify is a nasty way to go.

I've worked in chemistry labs for about 15 years, and this stuff is the nastiest stuff I've come across, sure it's good at passivating aluminium, but at what risk. We used to get 25% solutions delivered in drums - anyone could buy it.

[Ray153]

Thanks to all for the advice.

I have no desire to suffer a long slow painful death so will be avoiding the anodising method. I think the best option will be to polish the tubes with wet and dry and then micro mesh pads, followed by the spray on lacquer that has been suggested.

The tubes will be used as legs for a turned piece that is a work in progress and will have little or no handling so I think this method is the best option.

[Barry Hicks]

G'day Ray153
You have lost me: Where does the long slow etc death fit in with anodising?

Barry Hicks

[Master Splinter]

You dont need hydrofluric acid for anodising aluminium...I'm not quite sure where that idea has come from!

You need:
Sulphuric acid (battery acid) for cleaning and opening the pores of the aluminium
Distilled water
12 volt power supply (car battery charger or just a car battery)
Dye (if you want a coloured anodised finish) - the Dylon and Rit clothes dyes seem to work ok.

That's the basics...you can then get as fancy as you want....

See here for a more detailed piece on the process:
http://www.focuser.com/atm/anodize/anodize.html

And here's a good link for buffing and polishing metals:
http://www.caswellplating.com/buffs/buffman.htm
(they also sell cerium oxide for polishing glass)

And - for all you wanting to restore plating on old planes...I like these two sites...
http://www.janekits.com.au
http://www.eplate.com.au