Where to buy chemicals

[JimM]

Sorry a bit off topic this but.....

A friend of mine want's to try anodising some aluminium parts and needs to get his hands on some sulphuric acid. I'm sure in 'olden days' you used to be able to buy acids etc from the local chemist but with the new fangled H&S laws I doubt this is the case.

Any ideas of where the general public can get their hands on this sort of thing these days. (Preferably somewhere in Surrey)

Cheers

Jim
ps I know Frost & co do anodising kits but he's looking for a more cost effective method

 

[JayRS4]

There`s actually a chemists not far from you that should help you out, i used to get odd things from them. Can`t remember the name but it`s between M&S and the Tesco`s petrol station on tolworth broadway, on the same side almost dead in the middle.

 

[knoba]

I wouldn't know if it's possible, but as another suggestion to research, couldn't your friend use a an old car battery, de-mineralised water and a battery charger to make his own?



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[rtbcomp]

I wouldn't know if it's possible, but as another suggestion to research, couldn't your friend use a an old car battery, de-mineralised water and a battery charger to make his own?

View attachment 5679

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Better fit a plastic tap though.

Look in Yellow Pages for Laboratory Supplies. They may insist on delivering it (at a price) to cover hazardous goods in transit regs.

 

[Varnish5000]

We use this company at work.

http://www.sigmaaldrich.com/catalog/search/ProductDetail/FLUKA/84736/?langId=-1&storeId=11001

Not sure but you'll probably need an account with them.

 

[fingers99]

Failing that, I get my acid (no not that kind, but it may be there!) from eBay. You may find that a local tannery is willing to sell you analyne dyes in small quantities.

 

[hareng]

Should use fresh sulphuric rather than reclaimed, plus the mix ratio is different.

I am lucky i deal with a largish company with several sales staff etc, but immediately ask for The Lab and the persons name. Once they get to know you and the proverbial stuff, happy to dispense gallons at seemingly bargain price. IE 2.5 Ltr containers cost more than the contents.
Same with hydrochloric at 33%, now that takes your breath away outside! Carefull.

Pricing from memory 25 Ltrs of Hydrochloric @ 33%, 25 Ltrs of Sulphuric @ 40+% and 25 Ltrs of distilled water all in £20. Way too much for a 4ft fish tank that broke
Havent done any anodising for over two years but the colouring was a major problem tried everything i could get my hands on plus in the end bought what the pros use from a place in Leicester.
There are quite a few web sites on anodising, 'All tell porkies' or not the whole truth.

 

[barjac]

Hi there all,
I just fell across this thread and feel that I may be able to help your friend if he is new to anodising. I did a lot of coloured anodising over several years many years back on a semi D.I.Y. basis. It seems simple in principle but there is a bit more to it than meets the eye to get a good result.
He will need wire wool, 10% Nitric acid, Caustic Soda solution, 10% Sulphuric acid (from memory) (which is weaker than car battery acid so you can use that diluted). Aniline dye or cotton dye from Woolworths works well and a vessel large enough to boil the finished item in water to seal the anodise at the end. Preferably this boiling seal should contain nickel acetate. That last chemical was the one that I had most difficulty finding at the time, although clean water does a fair job.
A continuous flow of clean water is needed to wash each item between the baths of individual chemicals. The actual anodising tank needs to be able to hold the largest item to be treated and have a lead cathode over the whole of the base at least.
A variable current D.C. supply with ammeter is needed that will provide a current of around 10 Amps per square foot of job surface area at up to 20volts. (You don't need to count the inside surface of long thin tubes)
In sequence the process is
1. Wire wool the item and connect aluminium wires to it. From now on don't touch with fingers - use the wires.
2. Etch the item in caustic soda.
3. Wash the item in the clean water rinse.
4. Dip the item in the nitric acid dip.
5. Wash again. (by now the wash water should be clean after the first wash).
6. Mount the item in the Sulphuric tank and connect the wires to the positive terminal of the power source. Negative to the lead cathode of course.
7. Apply the power (10A/sq foot) for about one hour.
8. Wash again.
9. Mount in the dye bath for about 20 mins
10. Rinse again.
11 Drop into the boiling seal for 2 minutes
12 Rinse
13 Dry off and wax polish.
Done!
Now a few points to note.
The cooler the acid during the process, the harder the coating.
The softer the coating the better it will absorb the dye. 20 deg C is a good compromise (the start temp should be lower)
There is a lot of power being dissipated in the acid which warms it up during the process. For a long thin tank it is essential to have a means of circulating the acid during the process or the temperature will be higher in the middle and the colour will be deeper.
A good extractor fan behind the acid tank is essential as the fumes are choking.
If he has any questions I will be happy to answer them.
Have fun!

 

[JimM]

Hi all, thanks for the responses.

I've pointed him towards this thread and told him to sign up as a member if he wants more info.

Cheers

Jim

 

[hareng]

Nice one, thats the first time i have heard of nitric being used to clean.
Most items were fresh machined normally classed as clean at this point, then bead blasted or mop polished then hydrochloric job and wash off. Semi pro as well usually twice a week for 6 years.
Hydrochloric to strip anodising as well.

Exactly what i found no one uses or does it the same, some even pump out the sulphuric and cool it.
Found 13.3 to 14.7 volts worked the best the job drawn as much as it required and really fizzes for a few mins 17% to 19% sulphuric diluted with distilled water.
I had the current draw as much as 7 amps for a 5" diameter 1/2" thick wheel for the first few mins gradually depreciating usually to around 3 amps after 5 mins. Break down on contact with the job. Will try titanium next.
Never ever had any success with aluminium wire, used various shaped aluminium wedges attached to anode. Pros use spring clips on a rack, like to know what metal they are from definately not titanium and used many times over.

Tank was lead lined rather than one rod as cathode. Aluminium foil or strip (flat) dont last long.
Dont know how but did hard anodising twice a right bitch to remove though sulphuric is quite hard any way.

Midland Dykem in Leicester for the dye powder, they supply nearly all the pro companies.

 

[barjac]

Most of what I know (including the nitric acid bit) was gleaned from a book by W. Canning & Co (1934) it was loaned to me by the local electro-plating firm who used it as their "bible" - somewhere I still have photocopies of the section on anodising.
I used a heavy transformer with a secondary rated at about 20 volts 12 amps which I fed from a Variac - a variable voltage transformer so that the final rectified output could be swung from zero to around 16v DC. I put about 1 ohm in series with the output to stop the change in temperature of the "cell" formed by the acid and plates causing much change in current over the whole process. (The cell voltage changes with temperature). That's just the opposite of your method hareng - I tried to avoid the gassing!
I was anodising mainly half inch diameter tubes up to six feet long so you can imagine the problems. The tanks were made from diffusers for flourescent light fittings and the boiling seal tank was lead lined steel with a straightened oven element in the base.
Happy days!

 

[hareng]

As said before never ever seen any book or how to with the same requirements.

Yes have had similar with 1 1/2" o/d round just short of 3 foot long, recirculate the sulphuric also agitates.

I use aluminium extrusions and spend a lot of time sanding 180 to 600Grit spun, especially with the tube, wire wool would scratch in which case nitric not needed. The Caustic (drain cleaner though weak.) Rougher the finish usually the better it looks or hides.
Not getting in to a slanging match i havent done any for near on 2 1/2 years but still have the two PSU (rectifiers) numerous thermostatic heaters and so on.

Wish this site was around when trying to figure out voltages and so on but basically confirms what i have found though on a diy scale. Name it Sulphuric near on the same, heat requirements only the caustic and final seal differs.
The only things in the tank should be titanium, aluminium or lead, not steel it contaminates.
http://www.focuser.com/atm/anodize/anodize.html

Some links
http://www.coatfab.com/anodising.htm
http://astro.neutral.org/anodise5.shtml
One site i referred to cant find the other three and all told a totally different story http://homepages.pavilion.co.uk/nickfull/anodise.htm

Unfortunately these couldnt have worked then red and gold was mop polished then etched to tone it down satin!
http://pic20.picturetrail.com/VOL15/728921/1243489/23298707.jpg
http://pic20.picturetrail.com/VOL15/728921/1243588/27381480.jpg
http://pic20.picturetrail.com/VOL15/728921/1243489/16474670.jpg
http://pic20.picturetrail.com/VOL15/728921/1243489/14484289.jpg
http://pic20.picturetrail.com/VOL15/728921/1243489/14626917.jpg
http://pic20.picturetrail.com/VOL15/728921/1243581/27203664.jpg

 

[barjac]

Wish this site was around when trying to figure out voltages and so on

Yes ! It was 30 years ago when I did all this and all I had was a few pages from a book and my own experience to build on. I guess this chap should have more than enough information now!
Isn't the internet wonderful.
Just a point about the wire wool - it was very fine grade and only used on the tube that had been around a while. The nitric dip was mainly for the free cutting high silicon alloy machined parts which tended to go a dull grey in the caustic. The nitric dip turned these bright silver and removed the crud.
The seal tank was fully lead lined with a steel outer. The heater element was between the steel and the lead which was formed around it.
I used a cheap electric motor with a model boat propeller run very slowly to keep the acid moving - all plastic parts in the acid of course.
All those links are really interesting, but best not to get carried away if you are only doing a few parts!

 

[hareng]

With you now, great stuff. Tried everything for the electrical connection except titanium, might have some off cuts when i do the next job, may have a play to see if i can anodise it.
00000 wire wool use it on wood its meant as glass cleaner and good for plumbing connections.

Was going to try some dye used in micro surgery forget what it was called but shows up in blood stream. Need to get some more it crystalised and evaporated plus the heater glass broke in the tanks. Havent tried the Woollies brand if cheap considering the quantities i will try it.
Some places mention printer ink also Quink as an ink, no joy for me its too thick.
Will have to start again voltages, amps mix, temps and so on, see if i can get the oxide layer more porous or something, all trial and error.

Wondered what the pros use when you ask for bright. Had many a scrapper or lost one off parts, especially threaded hydraulic tubes nothing lines up after.

The only reason i started to do my own was nearest decent anodiser doing colours was 15 mile away in an area you just dont want to drive in (50 mins 1 mile) on a Friday afternoon, get there aint done it so minimum of 6 trips when i could be doing something productive. Change of ownership and minimum costs came in as well £50. Aanother great anodisers 200 yardsfrom that one now with web site back in 1994 minimum charge for clear £30, each and every colour £75, so three parts and three colours = £180 + vat. Used to take in bulk though weekly.