How to remove excess sulphate in chromate conversion

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 sulphate that are dragged in from the deoxidizer. However, if you have overloaded with sulphate, 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.