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What does iron phosphate do to hot dip galvanized steel

I have some steel that was HDG then powder coated. The powder coater said that he "sealed" the material with an iron phosphate spray, rinsed, then powder coated. Five years later, the powder coating is flaking off and the material is all rusted with only traces of the zinc left on it. Something has eaten the galvanized coating. Any suggestions? Thanks

Tim Lockhart
Sales manager, hot dip galvanizer - Orlando, Florida, USA
October 30, 2008

November 4, 2008

Hi Tim,

I'm not sure for what you want suggestions. Why the HDG corroded? Why the paint fell off? What would be a better pretreatment system?

Five years of protection may be all that is expected for this combination of pretreatment, paint and exposure conditions. Without more details, it's hard to provide a specific answer.

George Gorecki
- Naperville, Illinois

The attached is a picture showing the galvanized coating and the rusting of the steel.

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