Letter 25040

Acid bright dip problems  

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Hai, I have some problems about acid bright dip.

1. why the aluminium in acid bright dip go up very quickly to 50 g/L in about 2 weeks from 39 g/L? What are the factors that determine the rate of dissolution of aluminium?
2. why some aluminium metals especially from china has to be caustic dip for a while before going to the bright dip? or else it will cause excessive pitting?
3. except adding more ammonium sulphate as a fume suppresant, is there anything else that we can use to actually the fume quite significantly? as adding more ammonium sulphate does not actually help properly.
4. what is the average rate of dissolution of aluminium per sq meter against the rate of drag out?
5. what is the recommended usage of acid bright dip per sq meter in a 10,000 litres tank?
6. is it possible to let the aluminium that has been dissolved in acid bright dip to sttle out for some time and reuse the top part of the acid mix with fresh acid bright dip?

Any answer would be very much appreciated. Thank you very much?

Joe Yefrey
chemical company - Melbourne, Victoria, Australia

Hi,

I recomend u to look for book : Technology of Anodizing (SHESBY).

Hadi Khosravi
- Tehran, Iran

Hi Joe,

I'm using an Alupol IV from 23 years without any problem about the quantity of dissolved aluminium But what is your work temperature and what is the density of your bath ? Those 2 parameters are very important for the stabilisation of the dissolved aluminium.

Paul Moreau
aluminum reflectors for lighting - Liège, Belgium

Hi Joe,

Is there a possibility that your Ammonium Sulphate suppressant is causing pitting? Apparently the suppressant for Chrome (probably an entirely different chemical) does lead to pitting, so I'm told.

Re fuming ... ah, I've seen mega fuming during Bright Dip operations, par for the course, I thought.

There is a solution (ie. an answer NOT a chemical!) and that lies in the critical design of the fumehood system to prevent but capture the billowing emission clouds ... I believe that in Melbourne you have people who can solve that.

Freeman Newton - White Rock, B.C. Canada

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