Iron in a Zinc Phosphating System

How to get rid of the iron in a zinc phosphate tank


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Q. We have a small zinc phosphate tank and we were told that it has iron in it (results of 72 hour salt spray test). How do I get rid of the iron?—M.S.

A. I am not sure what the results of your salt spray test were, but the all zinc phosphate tanks have dissolved iron in them. Contact your supplier to provide a recommended range of operation and control procedures. If you have excessively high levels of iron in the tank, it can be oxidized with the use of hydrogen peroxide that will then form a ferric phosphate precipitate. Zinc phosphate alone may not be capable of 72 hours of salt spray resistance. It will depend on the coating weight and final seal rinse, but could still be marginal.