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How to remove Jasco Prep and Prime (iron phosphate) spots from galvanized roof

March 31, 2009

I have a two year old galvanized roof. I recently noticed two rust spots on the second story (it appears the metal was damaged during installation of a solar collector).

On a windy day, while treating the rust spots with Jasco Prep and Prime, my container blew off and spread the Prep and Prime in a broad streak across the entire first story. Doh. I immediately wiped it up with water, but that just seemed to spread it around.

Is there any way to remove these white splotches, which I understand to be iron phosphate? I imagine that I have plenty of zinc under them, I just need some way to remove the coating and re-expose it.

Thanks for any suggestions.

Sandi Metz
Home owner - Durham, NC, US

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Hi, Sandi. I wouldn't try more chemicals, it will only make a bad situation worse. I'd wait until a good dry day, and then try a stiff brush maybe even a wire brush, to see how much of it you can get off.

Alternately, or after that, try a cold galvanizing spray. It may stick out or it may not.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
April 3, 2009