How to remove excess sulphate in chromate conversion
January 14, 2008
I having a contamination of sulphate in the Alodine solution which unable to work with the solution. The thing is I've mis read the instruction of adding the sulphuric acid instead on Nitric acid. How can I remove the extra sulphate in the solution.
Riexal Ars plating chemist - Shah alam, Selangor, Malaysia ^
January 16, 2008
Some other brand names of chromate conversion process include a barium compound that lays on the bottom of the tank and takes out small amounts of sulfate that are dragged in from the deoxidizer. However, if you have overloaded with sulfate, you might just as well dump, waste treat, and start over.
Quite honestly your best bet is to throw out that solution and start over again. Depending on the size of your tanks you may have to remove a huge amount of sulphate.
If you want, you may try precipitation with something like barium carbonate, precipitating out insoluble barium sulphate, filtering the solution to remove the sulphate and then replenishing the nitric acid. You will need to check with the manufacturers whether this is possible or if you are on to a total loser. You may find that whatever you use for the precipitation will detrimentally affect the solution.
Brian Terry Aerospace - Yeovil, Somerset, UK ^
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