Do It Yourself Knowledge

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Spray Painting Galvanized Metal

Posted by diynovice on September 16, 2009

I recently made the mistake of promising my future wife that I could easily and cheaply spray paint a galvanized steel lantern we bought from IKEA.  After three cans of spray paint and a couple of lanterns, I found out I was dead wrong.  Now, I know a lot about metals, but I was never told that galvanized steel is difficult to paint.  So, this post is about galvanized steel, and ultimately, the only spray paint that will work on it.  For the readers who don’t care about the details, scroll down to the “**********” and continue reading.

Galvanized steel cannot be painted with normal alkyd-based paints, which almost all spray paints are based on (check the ingredients on the back of the can.  If there is any “alkyd…” don’t even think about using it).  Rust-o-leum is nice enough to put on the back of their spray paint cans to not use their spray paint on galvanized steel.  However, beware, most spray paint companies do not include this warning.

First, what is galvanized steel?  It is steel that has a zinc coating to increase the steels corrosion (rust) resistance.  Most galvanized steel is created by a process called hot-dip galvanization and a common characteristic of these steels is their display of  Spangle.  Spangle is just a fancy word for visibly large crystalline grain size.  Small amounts of lead and other impurities will increase the size of the spangle and make it more noticeable.  You can see the spangle in the galvanized steel guard rail below.
Guardrail
Other galvanization processes used to apply zinc coatings usually do not produce noticeable spangle but instead have a dull gray finish.  These processes are briefly described below (from Grip-Rite fasteners website):
Electrogalvanized – zinc coating applied to steel with an electric charge – offers limited corrosion resistance – typically applied to roofing nails
Mechanically galvanized– zinc applied by tumbling with powdered zinc and glass beads – provides slightly better corrosion protection than electrogalvaized steels.
Hot galvanized – zinc is applied through a heat treatment.  Provides best corrosion protection behind Hot-dip galvanization.

How does the zinc coating work?  The zinc coating provides corrosion protection by actively reacting with the atmosphere to form a thin, tough, inert layer of zinc carbonate to prevent the steel from rusting.  The zinc coating will also provide cathodic protection if the underlying steel is ever exposed (such as by a scratch).   While the zinc will always provide cathodic protection, it takes time for the zinc carbonate to form, and must undergo three transformations.  First, the zinc rich coating will react with oxygen in the air to form zinc oxide.  Second, the zinc oxide will react with oxygen and moisture to form zinc hydroxides.  Third, the zinc hydroxides will react with oxygen, moisture, and carbon dioxide to form zinc carbonate.

Depending on the atmospheric conditions that the galvanized steel is subjected to, the time required for each of these layers to form will vary.  Pure zinc will be present from 0 to 48 hours after the galvanization process; zinc oxides/hydroxides will form anywhere in 24 hrs to 2 years, and zinc carbonate will form in 8 months to 2+ years.  Galvanized steel exposed to the elements will quickly form zinc carbonate (within 8 months) whereas galvanized steel located indoors and not exposed to the elements, can take more than 2 years to fully form the zinc carbonate layer.  As the transformation advances, the surface will start to appear duller, but, the spangle of the surface will not be lost.

This is important for surface preparation, especially if you decide to brush paint and the steel is exposed to the elements.  The zinc oxides and zinc hydroxides are not well adhered to the surface and can easily chip off.  Zinc carbonate bonds well to the underlying zinc and provides an excellent painting surface.  More in depth details on the surface preparation for painting can be found on the American Galvanizers Association (AGA) website (see links at the end).   Rubbing the galvanized surface with a damp, lint-free cloth is most likely all that is required for the average DIY’er.  Oils can be present on the surface from the manufacturing process, however, items for indoor/home use should not have these oils.  Mineral spirits, turpentine, or vinegar can be used especially to remove any surface oils, however, these will leave a residue.  Be sure to thoroughly wash the surface to remove this residue if you choose to clean with one of these.

***********
Why can’t galvanized steel be spray painted?  Alkyld-based spray paints will react with the zinc during any stage of the galvanized layer, in a process called saponification.  The alkyd-base interacts with the zinc to form a soap at the interface.  This will result in poor paint adhesion and paint peeling.  Cold galvanizing spray paints will adhere to galvanized steel because of their high zinc content, however, top-coats of regular spray paints still will not adhere, and the colors of cold-galvanizing spray paints are very limited.

LatexMany brush-on paints exists to cover galvanized steel, but spray paints appear to be non-existent.  After much research, I finally found the solution.  Acryllic latex will adhere to galvanized steel with minimal surface preparation.  Therefore, the solution is Krylon’s H2O Latex spray paint.  It is an acrylic latex that will not chemically react with the galvanized surface.  [Krylon is one of the companies that does not include a warning against using their regular spray paints on galvanized steel.  Don’t be fooled.  All of their alkyd-based spray paints cannot be used on galvanized steel.  And, I don’t think they realize that they have the only spray paint that can be applied to galvanized steel.]  The spray paint costs about the same as any other spray paint and since it is a latex paint, it is more environmentally friendly.  It is difficult to find in stores.  I found it at Ace Hardware, but you can also find it from online retailers.  This spray paint is less viscous (more watery or runny) than the average spray paint, so use multiple light coats to prevent the paint from running and pooling on your project (I learned this the hard way).  DO NOT try to cover it in one coat.  The paint dries in about 15 minutes, however, the paint will not fully cure for about 7 days.  Also, do not use the Krylon H2O Latex primer.  It is alkyd-based (so technically, not a latex spray paint) and will not adhere, just like any other spray paint.

Hopefully, this information will help any future DIY’ers with their projects.  For more information, and more in depth explanation, visit the American Galvanizers Association’s (AGA) website at http://www.galvanizeit.org/ and check out their free publications on painting galvanized steel.

For general painting of galvanized steel, here is an excellent list of paints and their compatibility with galvanized steel.  This table comes from “Duplex Systems: Painting over Hot-Dip Galvanized Steel” which is available on the AGA’s website.

Type (paint base)…..Compatible…..Comments

Acrylics …….Sometimes……If the pH of the paint is high, problems may occur due to ammonia reacting with zinc
Aliphatic Polyurethanes…..Yes…..If used as a top coat for a polyamide epoxy primer, it is considered a superior duplex system
Alkyds…..No…..The alkaline zinc surface causes the alkyds to saponify, causing premature peeling
Asphalts…..No…..Petroleum base is usually not recommended for use on galvanized steel
Bituminous…..Yes…..Used for parts that are to be buried in soil
Chlorinated Rubbers…..Yes…..High VOC content has severely limited their availability
Coal Tar Epoxies…..Sometimes…..Rarely used, only if parts are to be buried in soil
Epoxies…..Sometimes…..If paint is specifically manufactured for use with galvanized steel
Epoxy-Polyamide Cured…..Yes…..Has superior adherence to galvanized steel
Latex-Acrylics…..Yes…..Has the added benefit of being environmentally friendly
Latex-Water-based…..Sometimes…..Consult paint manufacturer
Oil Base…..Sometimes…..Consult paint manufacturer
Portland Cement in Oil…..Yes…..Has superior adherence to galvanized steel
Silicones…..No…..Not for use directly over galvanized steel, can be beneficial in high temperature systems w/ base coat
Vinyls…..Yes…..Usually requires profiling, high VOC’s have severely limited their availability
Powder Coating…..Yes…..Low temperature curing powder coatings work exceptionally well over galvanized steel

Works Cited
American Galvanizers Association. (n.d.). Duplex Systems: Painting over Hot-Dip Galvanized Steel.Retrieved from American Galvanizers Association: http://www.galvanizeit.org 

American Galvanizers Association. (1999). Practical Guide for Preparing Hot Dip Galvanized Steel for Priming. Retrieved from American Galvanizers Association: http://www.galvanizeit.org 

Avallone, Eugene A., Theodore Baumeister III, eds. Marks’ Standard Handbook for Mechanical Engineers. 10th ed. New York: McGraw-Hill. Pgs. 6-93 & 6-110.

Grip-Rite. (2008, june). Grip-Rite Fasteners Catalog. Retrieved from http://www.grip-rite.com/fasteners.asp

Malone, J. F. (1992). Painting Hot Dip Galvanized Steel. Materials Performance , 31 (5), 39-42: http://www.galvanizeit.org

Peeling – From Galvanized Metal. (n.d.). Retrieved from Sherwin Williams: http://www.sherwin-williams.com/pro/problem/problems/peeling_galvanized/index.jsp

Painting Galvanized Steel. http://www.galvanizingasia.com/pdfs/page65-69.pdf

Why does Rustoleum Rusty Metal Primer say not to use on galvanized metal?
. (2008, May 8). Retrieved from Handy Man Club: http://www.handymanclub.com/Community/Forums.aspx?g=posts&t=38018

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55 Responses to “Spray Painting Galvanized Metal”

  1. Donna said

    Oh my gosh, do you miss grad school or something? Why are you writing these research papers on your blog? AHHH!

  2. coatings said

    I have previous coatings in my garage floor. How can I remove it to install a new one?

    • Jim said

      You might try a furniture stripper, like “stripeeze”, comes in gallons, or navel jelly, not very practical in such a large area, but will strip about anything down to the base & washes off with water.

  3. w e kenyon said

    Your article is excellent. Thanks for putting it up. And for even including a photo-example of spangle. Now I know (among other things) why galvanized items spangle brightly in the store and only dully when they’re old.

  4. Lauren said

    Thanks so much for this article! I also just purchased a galvanized steel lantern from Ikea a few days ago for my wedding and was hoping to paint it white. Now I know!

  5. [...] Quite interesting scientific background of galvanization is presented on Do It Yourself Home Repair blog. [...]

  6. Ike Herbst said

    i am so grateful that was the best coz i am in the look out to refurbish some guardrails, thank you thank you, very interesting blog.
    cheers Ike (Swaziland, Africa)

  7. Woody McTootle said

    I beg to differ from all of the above. I took two galvanized fenders off my boat trailer, rusted to beat shit. I soaked them in a big bucket with a 50% solution of phosphorous for an hour, pulled them out and sanded them, put them back in for an hour. When I pulled them out I had bare metal. I rinsed them clean for about 5 minutes. The next day I lightly sanded the flash surface rust with 250 grit sandpaper, then put 2 coats of rustoleum primer on top of it. The next day I painted them with black rustoleum. Wet sanded between three coats. My fenders have been on the trailer for 6 months now and look just as good as the day that I painted them. Phosphorous etches the metal so that primer will stick to it.

    • Andrew said

      You just defeated the purpose of the galvanising !!! You want to paint over it not remove it

    • Jerri Sue Dawson AKA Gillmore said

      Hi Woody, So you got a boat and you’re Florida? Funny!

    • Steve said

      Yup…you ‘de-galvanized’ the fenders with the phosphoric acid bath…so when you primed and painted, you were working with bare, non-galvanized steel…as evidenced by the flash rust you found the next day.

  8. Thank you for the wonderful ideas on Spray Painting Galvanized Metal.

  9. How timely that I found this.
    I just bought two nice outdoor light fixtures, but they are galvanized metal. So, seeing the labels on Rustoleum spray paint, I asked the clerk if I could use some kind of primer. She found a brush-on primer for galvanized metal.
    It’s acrylic based grey and also made by Rustoleum.
    Comes in a quart can though, so seems like a waste if I can find the spray paint you mention, in a color I like! One step- less cost. And we have an ACE store downtown.

  10. Gitmoir said

    Great explanation. I would be curious of using “rust converter” products on galvanized with rust breakthrough and of using “hammered” paints on galvanized (which Rust-Oleum licensed for its spray cans). I have used “hammered” spray paints on a variety of metals with excellent results, it bonds with rust, what it does on galvanized I do not know yet.

    A relative reported that the “Grip-it” product sold by Home Depot bonds well to galvanized permitting a top coat with most any paint desired.

    I have tried a variety of automotive paint products including “engine enamel” all of which eventually peeled sometimes in a little as two week sometimes up to 10 years, but eventually all peeled.

  11. Gitmoir said

    I tried painting a galvanized steel door with the Krylon H2O product, it bubbles and peeled within 6 hours and absolutely did not stick to the galvanized at all. Maybe Krylon has changed its formula since this article above was written. Krylon does offer an H2O Primer though it makes no mention of galvanized.

    At this point I’m totally stripping the door and will use an airless sprayer to apply “Gripper” a Glidden product specifically rated for galvanized metal. It could just as easily be applied with a fine finish roller.

  12. Kari said

    Thanks for this! We were wondering why the galvanized wash tub we need to make black wasn’t cooperating. We looked at the H2O at the store, and thought it wouldn’t be right for our needs–so thanks for setting us straight!

  13. Tom said

    Dude! You knocked this topic out of the park for me! Your article explained the problem and solution in perfect detail… I’ve got galvanized joist hangers I’m using for a pergola and want them to blend into the beams, so I will take this great information to heart and see about the Krylon H2O.

  14. Ciara said

    wow! thanks. we just bought some galvanized brackets to build our fence and decided to spray paint them a bronze color. when we went to the spray paint section, we couldn’t find anything and the guy at the store couldn’t think of any solutions.

    do you think this stuff will hold up through the rainy portland seasons?

    thanks so much!

    –ciara.

  15. adrian catalano said

    there is a paint made for galvanized metal. this is the website.

    http://www.zrcworldwide.com/p_zrc.asp

  16. M said

    I wish I had found this article an hour ago. I just bought a 17 gallon galvanized steel wash tub and literally just spray painted it an hour ago with Rustoleum’s Ultra Cover. I was reading the back to see how long until it’s dry and just realized it said do not use on galvanized steel. So i googled to learn why, now I know. How long before it starts to peel and do not need to strip this paint off before I apply the acrylic latex spray paint?

  17. Chuck said

    I just called Rust-oleum product support. I wanted to use their Rusty Metal Primer on galvanized — they confirmed you can’t (generally) spray paint galvanized metal. Their solution: use a “latex primer” on the galvy, then “any kind” of spray paint over that. Specifically they recommended Zinsser Bullseye 1-2-3 spray latex primer, and said I could use any kind of Rust-oleum spray paint over that — I want to use Rust-oleum hammered finish and they said that would work fine.

  18. Myles said

    Wow! found this in the nick of time. doing some Reno work in an old warehouse. For what reason I don’t know they have Galvanized I-Beams running through the place. The owner is going for a whole open concept which exposes all mechanical piping and so forth. Anyhow, he wants everything painted. This is a good start.

    Thanks!

  19. Ashkey said

    A scrapbook company I took a class from said they spray painted chalkboard paint onto the galv. Steel boards I bought from them. I just don’t remember if they primed or not? They looked really good . What do u think?

  20. crystal said

    Does the spray paint you mentioned have a color that looks galvanized. I borrowed a friendscarrier and it got damaged by humidity (it does not do well with humidity and amonia from rabbit urine.

  21. mike emm said

    I tried and liked the results with H2O on galvanized metal and was just informed by Krylon that they are discontinuing the product…..probably because people don’t know how to use it correctly. (it is a lot “runnier” than ordinary spray enamels). So you will find the product on sale ($3.99 at our local Ace). Stock up.

  22. Dude! You knocked this topic out of the park for me! Your article explained the problem and solution in perfect detail… I’ve got galvanized joist hangers I’m using for a pergola and want them to blend into the beams, so I will take this great information to heart and see about the Krylon H2O.

  23. Ali said

    Thank you for this article, informative, clear and well structyred.The best I found covering the subject withot technical details

  24. raquel chaparro said

    Thank you! I really needed this!

  25. CJ said

    Excellent Article, I now know all I ever wanted to about Galvanized steel. Thank you!
    Now, I have a galvanized chain link fence around my pool area. The actual chain link is black and the posts and crossbars are just galvanized steel colored. My wife wanted a new fence due to the two different colors so I suprised her and spray painted the posts and crossbars. The rustoleum at Lowes had the “do not use on galvanized metal” warning so I asked the “paint expert” who recommended Lowes brand because it sticks to anything. There was no warning so I tried it. Four cans and 3 months later it still looks great. I used the Valspar gloss black spray paint. I guess only time will tell if it’s going to last but if I can get 2-3 years out of it with minimal touch up I will be happy. (BTW the fence is about 20 years old with no rust). $15 poorer but happy!!

  26. sal said

    FYI…Rust-o-leum has a customer support phone number on their spray can to assist with paint questions. Prime with a water base and then use either an oil base or water base top coat. Just spoke to them this a.m.
    Question: once galvaized metal rusts, is it still galvanized? Can you sand the galvanized out of galvanized metal?

  27. Rick said

    Our church has recently decided to paint the outside of building and would like to know we are on the right track. The building is sheeted with galvanized material. The front side was powder-coated probably in the factory, while the back side is bare. We were told to treat/prep the bare material with a solution of acid diluted with water 20 to 1. This was the the advice of Sherman Williams pain store. This will allow the primer to adhere to the metal. Next we were told we can get the same life from a water based acrylic latex as with an oil based paint when applied correctly. Please advise. Thank you.

  28. RG said

    I can’t find this stuff anywhere. I spoke to someone at a Sherwin-Williams about the H20 Latex, They were supposed to carry it, but no luck. He did say however, that all of the Krylon acrylic latex paint could be used on galv. Can anyone confirm?

  29. stephen paul said

    After struggling to replace an old suspention unit on my trailer I am pleased to read your article that makes it easy to put a uniform finnish on the whole of the underside, wood metal ang galvanized steel. Thanks

  30. Thad said

    Just ran across this post while trying to find a suitable solution to paint galvanized joist hangars and post caps for a patio cover.

    After much searching for the Krylon H20 in my local area, I came up empty. So I started looking on the internet for places that would ship it. This stuff is EXTREMELY difficult to find!
    The solution I found is much simpler. Instead of the consumer level Krylon H20, I found that Krylon makes an “Industrial” line of paints, including latex based spray paints.

    You cannot find them on the main Krylon website but instead on http://www.krylonindustrial.com/. From there search for Eco-Guard™ Latex Spray Paint Enamels.

    These turned out to be much easier to find (although still online) than the H20 line.

    I ended up buying from Grainger, and did NOT need a contractors license or account to do so.

  31. Frank said

    I read your info on painting galvanized steel. You mentioned that there are many brush on types, but I only found the spray type. Could you tell me what are the brush on types? Send response to: some1else1@msn.com. Put PAINT in the subject line. Thanks.

  32. Krakus said

    Thank you for posting your article. I built an EMT conduit fixture stand for my aquarium, and it’s time to paint it. My search for prep/treatment brought me here several times.

    I just hacked my way through the myriad of mis/information on the web, and in retail stores, trying to figure out next steps. So, admittedly, I did not contact a paint retailer like Sherwin, CIL et al. But I was

    I ended up buying a product at Canadian Tire called “Armor Coat Galvanized Metal Primer” (~$4/340g spray can). I can’t find anything on the internet about the brand, so I wrote CT about the product. CT Customer Support referred me to Rust-Oleum Consumer Brands Canada @ (800) 387-3625 (currently closed eh!). The only indication that the primer is oil based is the instructions say to soak the nozzle in paint thinner if it becomes clogged.

    I also bought a 340g can of Krylon Outdoor Spaces for a top coat. The only indication on the can that it’s oil based is the instructions say to use paint thinner to clean over spray (immediately after spraying).

    News at 6

  33. Smoke said

    Dude, Zinsser Bulls Eye 123…you can put that sh*t on anything. It even specifies in the specs that galvanized metal (interior and exterior) is a surface it covers. I used to paint for money, and that was always my go to primer. Great price for the product also.

  34. Max Osterhasi said

    Thank you for very much for summarizing this information, very useful indeed.
    Questions:
    A) You state that ” Acryllic latex will adhere to galvanized steel with minimal surface preparation.” Will Valspar’s Latex Enamel brush-on paints (sold at Lowes, for example) also adhere to galvanized steel? (it does’t say “Acryllic latex” on the label, only Latex Enamel).
    B) If so, would it be enough of a surface prep to wipe it down with vinegar on paper towels?

  35. wayne said

    Someone asked “why are you posting this”? I want to say thank you, thank you, this is first-class information. I was just about to make a screen door kick plate with galv. and spray it brown, but just from the look and feel of the material I suspected the material wouldn’t easily hold paint, and you confirmed that. Thank you, and the details on the galv. process are also very useful.

  36. Michelle said

    Thank you.

  37. John said

    This is an OUTSTANDING resource material you’ve provided. Thank you for sharing your trials helping the rest of the world save time and money! ;)

  38. John said

    You rock! I especially appreciate the curiosity apparent in your quest to learn ‘why’ – and that you shared it with us in such detail! Thanks!

  39. Steve said

    You can use a product called T-Wash which is a liquid solution that will etch into the galv then use a primer coat then top coat, or alternatively use Etch Primer this does exactly the same as the T-Wash then base coat the galv then top coat.
    Simple :-)

  40. Robert said

    This is a great blog and great information.
    I have owned a sheet metal shop for 25 years and when we have need to paint galvanized metal that is non-paint grade. We rub it down or dip it in vinegar. After it dries, it is ready to paint. Very seldom do we have a problem with it flaking.

  41. sawndra said

    hi! Any help would sooooo greatly be appreciated! i teach 2nd grade and need to paint a galvanized trash can (that will be used outside) for a school carnival project. ICK! i am an artist, but no NOTHING about galvanized metal. I am planning on painting it a base color and then have students paint on it various designs and their name. Am i able to use the Krylon H2O latex on the trash can? If so, what kind of paint can i purchase for the students to do their work on top of the Krylon H20? Could I have them use permanent markers? Don’t laugh! hahahaha Thank you!

  42. I make metal art. I want to put a clear over galvanized to keep it shiny and use the natural zinc color as a decorative element alongside copper or brass. Rustoleum has a latex clear and I may try water based polyurethane clear.

  43. Glenn said

    I never knew about how a zinc coating protects the underlying metal. Thanks for a very informative article and a good, um, primer, on the subject!

  44. Ruben said

    Thank you, this was very informative. I’m going to bury a galvanized pole to mount a security camera and I want it to last as long as possible for the customer. Thanks again.

  45. […] you can’t spray paint galvanized steel. If you’re a nerd, you can read all about why here.  Otherwise, just trust me on it. So we ended up using Martha Stewart’s Metallic Paint […]

  46. Dane Of the house of McHadden said

    Great write-up. Page is bookmarked. I am refurbishing an antique boat,motor,trailer. The whole package is original from 1979 and the trailer is galvanized and in great shape. I am planing on painting it white and stenciling the thunderbird emblem from decal onto the fenders. This post has given me the information to be 100% confident in the process and practice of doing such a thing. I too have had failiures in painting galvanized items in the past, but, no more.

    Thanks again.

  47. Adam said

    Very good….got a good knowledge through your theory …I tried acrylic paintt over galvanized dipped paint and it worked out quite well and that was in Fiji back in 1990s …

  48. Johne267 said

    Thanks for the sensible critique. Me &amp my neighbor were just preparing to do a little research about this. We got a grab a book from our area library but I think I learned more clear from this post. I am very glad to see such wonderful info being shared freely out there. agadebbddcak

  49. […] Spray painting galvanized metal « do it yourself knowledge […]

  50. Kaylene said

    I’m pretty pleased to discover this website. I wanted to
    thank yyou for your time for this wonderful read!!

    I definitely loved every little bit of it and i also have you saved to fav to look at new stuff on your blog.

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