Painting galavanized metal

How can I paint successfully galavanized metal. I tried regular paint but I can scrape it off with my fingernail. The metal was used in
cocnstruction, to replace wooden joists. Thanks
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Jameko wrote:

I went to an auto paint store and bought a can of primer just for galvanized. Worked for me ..
GWE
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The surface needs to be very clean, and not oxidized. The reliable method of prepping the galvanizing is to etch it before applying primer, and applying paint to the primer coat (not to the galvanizing).
Etching is accomplished by wetting the surface with a diluted phosphoric acid solution. The etching agent is available at paint and refinishing product suppliers, and is commonly referred to as metal prep or etchant. It's other uses are for etching new metal parts, including mild steel, aluminum or stainless steel, to prepare the surfaces for primer.
Alternative methods would be to use other products such as etching primer, or zinc chromate primer. These products also require very clean surfaces.
WB metalworking projects http://www.kwagmire.com/metal_proj.html ...........
Jameko wrote:

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http://www.galvtech.com/product_info/coating_repair/cold_galv.htm

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Get the right primer and paint. Suggest talking to an industrial paint supplier.
Auto paints for galvanized steel are also very good, but these pieces may be too large for that to be practical.
Etching the metal before the primer is necessary. People often leave galvanized surfaces unpainted for a year, and let the weather do the prep. Auto body shops cant wait that long and so use a special etching solution.
Joe Gwinn
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Jameko wrote:

Treat it with vinegar first, then prime and paint. Make sure that there is no oil on the surface before you apply the vinegar.
--
Gary Brady
Austin, TX
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The phosphoric acid, "Metal Prep" is very effective, but be sure NOT to leave it on the galvanized sheet too long. It will completely remove the galvanizing, given enough time, and enough time is not very long for thin electrogalvanizing. Try out a small sample first.
awright
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The traditional method is allow it to get a year old or to acid etch. I picked up a can of latex galvanized primer expecting to be disappointed and able to chalk up another latex product that did not work well with steel.
I was quite pleased and surprised that it did an excellent job on some sheetmetal pipe guards. ___________________________ Keep the whole world singing. . . . DanG

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40-some years ago, I worked for a paint contracter, summers, to make money for college. We always used latex as a primer for galvanozed gutters and down-spouts. Worked well.
Ken
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