Process for phosphate conversion coating with treatment of rinse water by reverse osmosis and ion exchange

摘要

A process for phosphate conversion coating iron and steel which includes a multi-step water rinsing stage after the conversion coating stage, which comprises subjecting a part of the rinsing water used therein to a reverse osmosis treatment, returning the concentrated liquid thereof to the conversion coating stage, and using the filtrate as replenishing water for the conversion coating and/or the degreasing and water rinsing stages after subjecting it to an ion exchange treatment.