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White rust on bonderized steel
Q. A residence in Montana has vertically applied gray bonderized steel. Although there was no "white rust" when the sheets were installed, one year post installation, there is now considerable white crusting from what I assume are zinc oxides. What causes this, how can it be removed, and what can now be applied to stop this from occurring?
John Lindstromconsumer - Gallatin Gateway, Montana
April 7, 2009
A. Hi, John. A bonderized finish is a galvanizing that has received a phosphate conversion coating in preparation for painting. It is supposed to be painted immediately so that it doesn't produce these white corrosion products. At this point, I'd probably power-wash off the discoloration as well as possible and apply a Self-etching primer [on eBay or Amazon] .
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
April 20, 2009
Q. Ted, is there a clear finish that can be brush applied that will protect the surface for a decade? Can a PVDF finish like Kynar be brush applied?
John Lindstrom- Bozeman, Montana, USA
April 27, 2009
A. Hi John. My experience is in general metal finishing, which is a very wide-ranging area, and my specific experience in clearcoating of bonderized siding is non-existent. On fresh bonderize, I would think that a top quality clearcoat like
[adv: Por-15 2k Clearcoat on
eBay or
Amazon]
.
would hold for a decade. But on bonderize that's already corroded, will it look any good?
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
April 27, 2009
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