Ask the Expert Question-and-Answer Archive (Wastewater Treatment)
by Mike McGinness, EcoShield Environmental Systems, Inc.
Alternatives to Chrome Passivates
We pretreat (phosphating process) our steel sheets in preparation for powder coating. Is it really necessary to passivate/seal after zinc phosphating? Can I do away with this step and simply rinse the sheets with water after phosphating? I'd like eliminate the use of chrome passivate. If passivation is necessary, can you suggest alternatives to chrome passivates?
I would not suggest eliminating the final sealer / rinse. It acts to improve corrosion resistance and acts to improve paint adhesion. Eliminating the sealer/rinse would substantially reduce paint adhesion and reduce corrosion resistance.
Most, if not all of the metal finishing specialty chemical manufacturers and suppliers have non-chromate sealers readily available. Give them a call.