removing anodizing

[toryglen-boy]

didnt know where else to put this !!

Has anyone got any experience of removing anodizing? what did you use?

strange question i know.

thanks

;)

[koputai]

I build and sell dive gear as a bit of a passion/hobby/sideline http://www.deepdiving.net and my handsets are anodised. I have used both standard and hardcote anodising, hardcote being the most appropriate for my purpose.
Anyhow, I had one batch of handsets that were badly (hard) anodised by a mob here in Sydney, and they were not good enough to sell. I sent them to a specialist hard anodiser in New Zealand who removed the old hard anodising and then re-did them, and they turned out very nicely. The removal of the first anno was done by chemical etching.
I can highly recommend Anodizers Pty Ltd (http://www.anodizers.com) in Mortdale (Sydney). It's probably worth giving them a call to see if they can do the removal for you.

Cheers,
Jason.

[toryglen-boy]

Hi Jason, thanks for the post, and for the great advice.

:thumbsup:

Although in this instance, its a bit over kill, and would cost a bit. I was looking more for something i could buy from Bunnings etc, to get rid of it.

oven cleaner maybe?

;)

[mental4astro]

Hi,

what is the item you're wanting to remove the anodising coat from.

If it a robust thing, you may be able to remove it using a stainless steel brush, the type of rotary brush you mount into a drill like a buffing wheel.

This thing is aggressive, so do it carefully and WEAR at least safety glasses!!!!

You may be able to mount the drill onto a work bench, and hold the piece firmly in your hands. Do it slowly as the brush can catch the item and turn it into a projectile, :scared:.

Being stainless steel, it is less likely to contaminate to aluminium surface.

Mental

[toryglen-boy]

Yeah, i have a dremel with a fine sander head. i never thought of that !

;)

[mental4astro]

Mate, Dremel even better.

Use the finest grade you have, then you can polish it back up.

[mercedes_sl1970]

You could also try a buffing wheel with a cutting compound - available from most hardware stores. Probably easiest if the buffing wheel is attached to a bench grinder, although one attached to an electric drill might work too.

Andrew

[koputai]

Don't forget, anodising is not merely a coating like paint or powdercoat, it actually modifies the material. Approx 50% of the anno thickness is growth above the pre-treatment surface, and 50% is etched into the old surface. If it's a decent anodising job, there'll be a reasonable amount of material you'll have to remove. If it's hard anodised, you'll not do it satisfactorially at home without ruining the object.

Good luck!

Cheers,
Jason.

[mental4astro]

How does hard anodising differ from 'normal'? How does the process affect the material?

[marki]

If you want to remove anodising without damaging the part you will have to submerge the part in a solution of sodium carbonate and sodium hydroxide and then place into a solution of nitric acid and sodium fluoride. AlO3 is a tough compound to break down. If you want a recipe PM me but only if you have experience in handling chemicals. Conc HNO3 bites back.

Hard/soft anodising refers to the pore size present in the aluminium oxide (AlO3) layer.

Hard anodising is done at cool temps with about 10% sulfuric acid. It leaves small pores which makes a hard surface but is not good at absorbing dyes if you wish to colour it.

A softer anodise layer can be made by using higher temps and about 15% sulfuric acid solution. This has larger pores and is much better at absorbing coloured dyes at the loss of hardness.

Mark

[scopemankit]

Can't you get them re-anodised?

[koputai]

To re-anodise you first have to remove the original anodising to get back to the aluminium surface, as the anodised finish in an electrical insulator, but the surface has to be conductive during the process.
As Mark says, soft anno can be readily coloured, and a good job can be a beautiful thing! Hard anno can pretty much be clear or a greenish-browny colour. There's also a method of hard anodising called 'hardcoat'. Hardcoat can be coloured a very nice even black colour. Unfortunately, not many anodisers can actually do a proper hardcoat job.

Cheers,
Jason.

[marki]

Jason is 100% correct, ALO3 is an ionic solid and will not conduct and cannot be done again until the old layer has been removed. All you would achieve is to cause pits in the item (I know I have tried). The chemicals I have suggested are part of the alkaline and pickeling cleaning process which must be carried out if a decent layer is to be applied to the metal.

Jason there are a lot of different processes out there and many are based on using electrolytes other than H2SO4. I was trying to keep it simple. I do my own anodising at home as I often turn and mill parts out of ali that would cost me a small fortune to get done commercially. I find the final colour if not dyed is dependant on the alloy used.

Mark

[toryglen-boy]

i think maybe some very fine wet and dry, and loads of water is the way to go

:thumbsup:

[OneOfOne]

If it is a regular shaped object you may find it better to machine it off, or some at least. If it was a "tube" shape, it could be turned off on a lathe or if it is mainly flat, a milling cutter will take it off. Of course if you don't have any of the machinery, the point is a bit moot :(

[bloodhound31]

Your standard aluminium window or door trim is an anodised 6060 T5 aluminium, anodised to 10 or 15uM (microns thickness) for indoor, and 25uM for outdoor, (penetrates deeper, lasts longer and a bit more durable)

Have a practice on a bit of that old stuf if you have any around to see how it reacts to abrasion. Remember, most aluminim is pretty darn soft, which is why we anodise the surface to make it harder to scratch.

I regularly send a lot of our profiles in my factory at work, back to the anodisers to be acid dipped to remove the old anodise, then re-anodised with a different colour.

You could try Sapphire anodising in Somersby, north of Sydney, or Australian Aluminium Finishing in Sydney. In Canberra/Queanbeyan we also have a small anodiser called Fink & Co. Robert there should have lots of good advice for you if you like and he specialises in small items.

PM me if you want any of their details.

Baz.

[toryglen-boy]

lots of good advice. thanks fellas

;)