Anodising tank

[Julian M]

Does anyone know how othen you need to replace the dilute sulphuric acid
in the anodising tank.How do you know when it needs replacing?

THanks for any help

Julian

[martinw]

[QUOTE=Julian M;287299]Does anyone know how othen you need to replace the dilute sulphuric acid
in the anodising tank.How do you know when it needs replacing?

THanks for any help

Julian[/QUOT

Dear Julian,

This probably will not be much help unless you have access to a better chemist than me, but this document tells you how to analyse the chemical composition of your electrolyte...

http://www.metroplating.co.uk/pdf/DE...AN%2003-25.pdf

Annex A and B describe the tests.

I have no idea of the range that is acceptable for each component in the electrolyte.

Bring on the chemists!

Best wishes

Martin

[Geof]

Martin: your link does not appear to work.

Julian; did your chemical supplier or equipment supplier not tell you anything? I know the acid is consumed during the anodising; in your other thread you mention ugly fumes emanating from the tank, your acid is loosing sulphate to those fumes.

Ask your chemical supplier, they should have some kind of kit so you can titrate a sample of your sulphuric and find its concentration. I doubt whether you can do it just measuring pH because you are so far down the acid end of the scale.

[martinw]

Originally Posted by Geof Martin: your link does not appear to work. Julian; did your chemical supplier or equipment supplier not tell you anything? I know the acid is consumed during the anodising; in your other thread you mention ugly fumes emanating from the tank, your acid is loosing sulphate to those fumes. Ask your chemical supplier, they should have some kind of kit so you can titrate a sample of your sulphuric and find its concentration. I doubt whether you can do it just measuring pH because you are so far down the acid end of the scale.

Dear Geof,

Yes, you are correct, the link is wonky.

Post #6 on this thread might bring up the MOD document. Annex A and B give the titration proceedures ( I think!)

Anodising

Best wishes

Martin

[Geof]

Originally Posted by martinw ...Post #6 on this thread might bring up the MOD document. Annex A and B give the titration proceedures ( I think!)...Martin

Quite correct, they do. Julian break out your burette and hit the chemistry books.

For a small fee you could convince me to pay a visit and train you in the technique of titration. Lets see, airfare, rental car from Heathrow, few nights in a nice hotel...possibly you can get less expensive assistance .

[martinw]

Originally Posted by Geof Quite correct, they do. Julian break out your burette and hit the chemistry books. For a small fee you could convince me to pay a visit and train you in the technique of titration. Lets see, airfare, rental car from Heathrow, few nights in a nice hotel...possibly you can get less expensive assistance .

Dear Geof,

A public offer like that will have you lifted to a certain Navel Base in Cuba by the DEA.

Best wishes

Martin

[Julian M]

Martin, thanks for this i will have a look over the weekend. I wish i had paid more attention in chemistry class now!!

Geof, consider yourself hired!! LOL. Unfortunately our equipment supplier
seems reluctant to share his knowledge, its like getting blood from a stone.
I think he want us to pay him to do it every 3months, not good economics, would prefer to learn myself. Thanks again

JUlian

[Geof]

Originally Posted by Julian M ......I think he want us to pay him to do it every 3months, not good economics, would prefer to learn myself. Thanks again JUlian

Just off the top of my head as a chemist, I think you should do it every 20 hours of tank use or something like that. The completeness of the anodising is a function of acid concentration, tank temperature, current flow (voltage) and time in the tank. If you want good consistent results you need to keep these all closely controlled.

I thinl the best approach would be to monitor very closely for several months until you have determined how the different factors interact. Then you can compensate for one by varying another and know what to expect.

[pinskip]

Julian

The anodising solution when made up new requires about 10 to 20 g/l of aluminium sulphate to work better. As the bath ages the aluminium begins to rise and will reach a point where it will have an adverse affect on the performance of the bath. You could probably look at doing a dilution of the bath every few months depending on how much you use it and add back new acid and water in proportion to the dilution that you did. You should also use Deionised or distilled water for making up an anodising bath, the chloride in tap water is not good for anodising. Oil and shop soil will also play a role in how long you can operate the bath without problems.

If you can analyse the bath that would be good. I can post you some information if you require any more help.

Regards,
Paul

[pinskip]

Julian

Some good web sites for electroplating and anodising are:

finishing.com (look in the forums.)

and

PF Online

They should come up using you search engine.

Regards,
Paul Inskip

[Julian M]

Originally Posted by pinskip Julian The anodising solution when made up new requires about 10 to 20 g/l of aluminium sulphate to work better. As the bath ages the aluminium begins to rise and will reach a point where it will have an adverse affect on the performance of the bath. You could probably look at doing a dilution of the bath every few months depending on how much you use it and add back new acid and water in proportion to the dilution that you did. You should also use Deionised or distilled water for making up an anodising bath, the chloride in tap water is not good for anodising. Oil and shop soil will also play a role in how long you can operate the bath without problems. If you can analyse the bath that would be good. I can post you some information if you require any more help. Regards, Paul

Thanks for this Paul, i would appreciate any more information you have as i woud like to learn how to analyse the tank, or get my hands on a test kit if one exists. We use the anodising tank as and when we need it about 5-10hours a week.

julian

[martinw]

Dear Julian,

The PF site that Paul mentioned has lots of good stuff. Here is a post from that site which seems to indicate when you need to put in fresh chemicals......( I think )..

http://www.pfonline.com/dp/forums/pf...74&pub=PF&cat=

Best wishes

Martin