Annodising Aluminium

[Kram]

I tried this years ago, I didnt have bad results for the fact I wasnt using proper dye. I might have another go as Ive got some parts to finish.

Sulphuric/battery acid. This is the difficult one to get now, as some **** like throwing it at women to disfigure So now requires an EPP licence. Its also used as drain cleaner so might be a few options to get it. Anyone want to post me a bottle?

The proper dye looks expensive but should go a long way. I want red and blue.

Sodium hydroxide, easy enough to buy as drain cleaner, purity is a bit questionable but probably adequate for stripping coating.

Anyone had good results?

 

[The_Yellow_Ardvark]

Years ago.
I had a Frost kit, was pricy, bit did a above average job.

The trick is the prep work.

 

[Slowcoach]

Is one shot any good. Available from plumbers merchants. 91%?

 

[Seadog]

Drain cleaner is Hydrochloric acid. Equally disfiguring.

 

[8ob]

I tried this years ago, I didnt have bad results for the fact I wasnt using proper dye. I might have another go as Ive got some parts to finish.

Sulphuric/battery acid. This is the difficult one to get now, as some **** like throwing it at women to disfigure So now requires an EPP licence. Its also used as drain cleaner so might be a few options to get it. Anyone want to post me a bottle?

The proper dye looks expensive but should go a long way. I want red and blue.

Sodium hydroxide, easy enough to buy as drain cleaner, purity is a bit questionable but probably adequate for stripping coating.

Anyone had good results?

Not if you need it for work, it's available from just about everywhere.

Bob

 

[Kram]

Is one shot any good. Available from plumbers merchants. 91%?

View attachment 314553View attachment 314554

That would do it. Needs to be diluted to 30-50 % for this.

Drain cleaner is Hydrochloric acid. Equally disfiguring.

Not when I was a chef we had litre bottles of sulphuric.

 

[Ross365]

This brief article appeared in "Practical Wireless" many years ago.

 

[hotponyshoes]

You can get upto 15% sulphuric without an epp which is fine for soft anno.
For a diy setup i found a weaker mix actually took colours better as well.

It's easy enough to get a licence although it's a load of paperwork and £40 for 2 years I think. It does make the sulphuric a lot cheaper and easier to obtain but you never really use the acid up anyway so it's a one-off purchase.
If you have a friendly scrap yard it's pretty much free though.

The proper dye is expensive, especially if you have big parts and need to fill a big tank with it but it certainly works better than anything else I tried. Again, once you have made the initial purchase the cost to colour each part is pennies if that.

The biggest problem with DIY is, if you want consistent parts, you need a decent amount of space to setup and store multiple tanks.
Temperature has a big effect on how the parts colour (as does how thick the anno coat is) so ideally you need to set up for a run, have the anno tank either fitted with a chiller or so massive the heat change doesn't affect things too much, then ideally you need a warmup tank and a heated dye tank.
I used beer fermenting mats under the tanks as it was easy but 40degC seemed to be about the best for the red sort of colours.
Back, dark green, dark blue all just as well at lower temps
For consistent parts I found it was just not practical to do one or two each weekend, you ideally needed to run thorough them all in one go.
Obviously it's not an issue if the parts are used separately but if you are making 12 red bits to fit to a car it's pretty obvious if they are not all the same shade of red!

 

[hotponyshoes]

Caustic soda works fine for stripping.
You want it warm and you want it outside!

 

[lchris21]

Caustic soda works fine for stripping.
You want it warm and you want it outside!

Yes indeed. Stripped some anodised wheel rims in a bucket of caustic last year prior to polishing.......

They were badly scratched silver, but stripped them back. They turned black then repolished.

 

[Misterg]

Anyone had good results?

Yes! (Well I thought so, anyway! )

You don’t need sulphuric acid - sodium bisulphate solution works and is easily obtainable (as swimming pool pH reducer) and less hazardous than sulphuric acid.

The process is well explained in a youtube video by Mark Preisling.

My small home setup is described here:

Anodising Process - MisterG

Traditional anodising uses sulphuric acid as the electrolyte which has become more difficult to obtain, and is generally not nice stuff to have around. I watched a Youtube video by Mark Presling that showed the use of sodiumbisulphate as an electrolyte instead. (Sodiumbisulphate is readily...

www.misterg.org.uk

- basically just tupperware!

The cathode is two sheets lead flashing (one each side of the main container). Sodium hydroxide bought from the ironmongers, DIW from Halfords.

I find it needs about 23V to maintain 6A / square inch through the process. If you haven't got a constant current power supply, you would need to adjust the voltage as the process progresses. )I anodise for 2 hours at those conditions, and this produces a tough surface that takes dye well. I've only used commercial dyes (mostly black). Small packets are quite cheap on ebay and last for a long time if you keep your baths clean.

Before

After:

Black dyed at 60°C

 

[hotponyshoes]

Yes! (Well I thought so, anyway! )

You don’t need sulphuric acid - sodium bisulphate solution works and is easily obtainable (as swimming pool pH and less hazardous than sulphuric acid.

The process is well explained in a youtube video by Mark Preisling.

My small home setup is described here:

Anodising Process - MisterG

Traditional anodising uses sulphuric acid as the electrolyte which has become more difficult to obtain, and is generally not nice stuff to have around. I watched a Youtube video by Mark Presling that showed the use of sodiumbisulphate as an electrolyte instead. (Sodiumbisulphate is readily...

www.misterg.org.uk

Did you try any colours than black?
I found the orange/red/yellows/etc would not work very well if I was not using sulphuric.
Although it might well have been something else in the process that needed adjustment rather than the anno bath itself?

Did you ever measure the thickness of the coating using the sodium solution?

 

[Misterg]

Did you try any colours than black?
I found the orange/red/yellows/etc would not work very well if I was not using sulphuric.
Although it might well have been something else in the process that needed adjustment rather than the anno bath itself?

Did you ever measure the thickness of the coating using the sodium solution?

I've done some olive green - took the colour well, but it's not (IMHO) an attractive colour, so I've not used it much. I want to get some yellow dye so I can try that followed by the green to get a brighter 'apple' green, but not got around to it yet.

I *should* be getting a 0.001" / 25µm layer according to theory. I've not made a proper attempt to measure it.

 

[Kram]

Looks like sulphuric is actually quite easy to make. Simple electrolysis of copper sulphate will give copper metal and sulphuric acid upto 50%. It needs a graphite annode which will break up into powder and need to be filtered off..
Other way is roast pure sulphur, or copper sulphate in a pyrex flask, bubble it into peroxide. That seems much higher risk, smellier and would requite some proper lab glassware, so Im going with the first method, should be here tomorrow.

 

[hotponyshoes]

I would have though the acid would be cheaper than copper sulphate?
Even if you bought weak stuff and boiled it down..

 

[julianf]

Caustic soda (naoh) is about £35 for a 25kg sack off eBay. I buy it frequently.

Or just get 1kg tubs from Wilkinson's etc.

Keep it dry / airtight. I forget the chemistry but it does "stuff" if you leave it open to the air and then looses it's fight.

 

[julianf]

Drain cleaner is Hydrochloric acid. Equally disfiguring.

Are you thinking of concrete cleaner?

Drain cleaner is normally naoh, as it saponnifies fats in common blockages, turning them to soap.

Same as it does to your fat if you get it on your hands...

 

[Kram]

Caustic soda (naoh) is about £35 for a 25kg sack off eBay. I buy it frequently.

Or just get 1kg tubs from Wilkinson's etc.

I looked in wilkos, they only have the 15% oven cleaner solution but Im sure they used to sell it.. unless Im looking in the wrong isles.

I would have though the acid would be cheaper than copper sulphate?
Even if you bought weak stuff and boiled it down..

Not too keen on boiling or distilling acid in my garden (although bubling any vapour through another tub of water should catch any acid fume and avoid wasting it).
I have not seen anywhere to buy dilute sulphuric.

 

[hotponyshoes]

Battery Acid | JENNYCHEM

www.jennychem.com

10litres of 37% for £30
Most auto electrical places sell it as well

 

[julianf]

I looked in wilkos, they only have the 15% oven cleaner solution but Im sure they used to sell it.. unless Im looking in the wrong isles.

Not too keen on boiling or distilling acid in my garden (although bubling any vapour through another tub of water should catch any acid fume and avoid wasting it).
I have not seen anywhere to buy dilute sulphuric.

I'd say I'd send you some but I really don't feel it would be responsible of me to sling flesh melting chemicals into the post. And it's really not big money to buy by the sack full either.

It couldn't be obtained for love nor money about 6 months back, some sort of shortage, but the usual sellers are back now.

Shops that do commercial cleaning kit somtimes sell it in sacks also.