Summary for primers for galvanized metal Discussion
Primers for galvanized metal are discussed as a practical painting problem, with the original question asking for a cheap way to make paint stick to galvanized steel, preferably using polyester resin. Ward Barcafer said an acid etch primer can work well if the galvanizer did not apply chromate, and noted that the chromate should be omitted when painting is planned. For large galvanized gates, Ted Mooney recommended an ideal shop phosphatization treatment, but for installed gates suggested scrubbing with trisodium phosphate and using a galvanize primer. Later, another answer noted that waiting for the galvanizing to weather for several years can improve adhesion, and that newer silane-based paints may be applied directly to fresh galvanizing. When asked about avoiding alkyds and water-based coatings, Geoff and Ted pointed toward acrylic/latex primers and silane systems as the remaining options.
Q. Looking for cheap method for priming galvanized metal before painting a way to make paint stick to galvanized metal using preferably polyester resin
Thank for your help
Menier
menier abel
– france
1998
A. Hi, Menier. The answer depends on whether you are a manufacturer wishing to do this in-house on thousands of parts, or an end user trying to paint one object, though. There are primers that are intended to provide good adhesion on galvanized surfaces. But if you are a manufacturer, a zinc phosphate pretreatment system will prove far better than a can of primer. The topic is the subject of a FAQ here. Good luck.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
Need quick confidential answers? $25
Need project assistance? $100/hr.
1998
A. If you already are set-up to paint galvanized, I have had excellent success in the past with using an acid etch primer. Acid etch primers are best used when a chromate is not applied over the galvanized coating. One must specify to the galvanize processor to omit the chromate. There are countless articles on painting galvanized material.
Ward Barcafer, CEF
aerospace – Wichita, Kansas
1998
Q. I need your articles (your best method).
MOON GU,OH
– SEOUL,KOREA
1998
Q. I have got some big galvanized gates to prime and paint. I think there is chromate present in the galv; (it’s shiny!) What’s the best way to prime this surface?
Peter O’Callaghan
building – Charente, France
2007
A. Ideally they would be sent to a shop for a phosphatization process, Peter. This may not be practical for installed gates, leaving you to scrub them with trisodium phosphate
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[affil link]. Good luck.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
Need quick confidential answers? $25
Need project assistance? $100/hr.
2007
Painting a galvanized metal building
Q. Have a 20×40 steel building it looks like it is galvanized. I would like to paint it and would like to know the proper procedure. Thanks
rod beadow
– kingsville ontario canada
December 7, 2014
A. Hi Rod. This has been addressed a number of times here; as mentioned you can start with our FAQ, which links to many of those discussions. I suggest you read them to understand the tricky issue of adhesion to galvanized surfaces.
But the short answer is that, unless you are willing to do truly extensive prep work, including as a minimum: scrubbing with detergent, followed by sweep blasting, followed by T-washing, then careful inspection, followed by immediate priming, success can’t be guaranteed. All that can be proposed otherwise is things that may work. The issue is that, depending on age/weathering, thickness of corrosion products, and whether the surface had a chromate brightening quench, lesser pretreatment may or may not adhere.
I would suggest that you find a small area of your building that you think is representative, wash it with detergent, make sure it’s completely dry, then try a self etching primer. If it hasn’t blistered by spring and can’t be flaked off with a wire brush, you’re probably ready to try that approach. If it comes off, then sweep blasting and T-wash priming would probably be necessary for proper adhesion. Best of luck.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
Need quick confidential answers? $25
Need project assistance? $100/hr.
December 2014
A. Another approach is to use time.
If you wait for galvanizing to weather (it has to be in the weather), then painting can be done with reasonable adhesion. It takes years though, perhaps 4-8 years depending on the environment.
Still another approach is to use one of the newer paints of a silane base which are designed to paint straight onto fresh galvanizing without any pretreatment. I don’t know which countries there are available in, but do know they’re on the market in UK, Belgium, Ireland. There are various brands.
Geoff Crowley
Crithwood Ltd.
Westfield, Scotland, UK
December 7, 2014
Ed. note: Some external links that may be helpful are “Sherwin Williams: Peeling – From Galvanized Metal” at
www.sherwin-williams.com/homeowners/ask-sherwin-williams/problem-solver/peeling-cracking/peeling-from-galvanized-metal/
… and “Environmentally Friendly Anti-Corrosion Primers for Hot-Dip Galvanized (HDG) Steel” at
www.asminternational.org/documents/10192/1849770/05216G_Sample.pdf
Q. You say alkyd primers should be avoided for coating galvanized steel. Assuming water based paints are permeable to water vapor, I believe it would be best to avoid those too. What’s left?
Ross Wilkinson
– San Francisco, California USA
March 17, 2015
A. Hi Ross. My understanding is that the latex primers for this purpose work pretty well. You can put a top coat of something else on after you’ve secured good adhesion.
Geoff suggests investigating silanes, and the ASM article talks about that. The Sherwin Williams article says acrylics. Good luck.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
Need quick confidential answers? $25
Need project assistance? $100/hr.
March 2015