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Stripping solution titration

2003

We do Type II anodizing and some paint applications of organic finishes. We have an in house stripping solution that is made up of Chromic Acid and Nitric acid and water. We maintain the solution by time it takes to strip the material. If the material takes more than 15-20 min to remove or loosen the material then we dump the tank and recharge. I would like to implement more control over that process. I am looking for a simple titration that we could test the tank and maintain the concentration of chromic acid 48 to 68 oz/gal. Can anyone help me locate such a titration?

Thanks for your help.

Chris Culp
manufacturing and anodizing - Vancouver , Washington, USA

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2003

Chris,

The procedure that I use is as follows: pipette [pipettes on eBay or Amazon] 10 mls into 250 ml volumetric and dilute to volume. Mix well. Pipette 5 mls of above solution into a 250 ml erlenmeyer flask. Add approx. 100 mls DI water. Add 20 mls 50% HCl Add 1 mls Ammonium Bifluoride. Mix well. Add 10 mls 0.1N iodine solution and titrate with 0.1N sodium thiosulphate [on eBay or Amazon] . Record mls as A.

To another flask add 100 mls DI water and 20 mls 50% HCl and 1 ml Ammonium Bifluoride and 10 mls 0.1N iodine solution and titrate with 0.1 N Sodium Thiosulphate. Record mls as B Calculation: (A-B)* 2.23= oz/gal chrome.

Jenn Wright
- Dayton, Ohio, USA