painting galvanized metal

[My Old Tools]

3 years ago when we remodeled the wife wanted a fancy new front door, the heavy architectual metal variety that are made in Mexico mostly. 3 years later and the paint is coming off in sheets. It is galvanized under the paint. She's not happy and it has to be refinished. I've read a number of articles on washing with vinegar, priming, etc for painting galvanized. Now I'm looking for first hand experience.

 

[My Old Tools]

pictures, a couple of months ago, worse now.

 

[TonyG109]

The easiest way to paint galvanized metal is to clean it using a water based cleaner and then prime with an acrylic based primer designed specifically for galvanized metal. These are sometimes labeled "aluminum and galvanized metal" primer. A color topcoat can then be applied.

Oil/alkyd paints are assumed to stick to anything, but won't adhere long term to galvanized metal. A reaction called saponification occurs between the paint and metal which caused the flaking off of the paint. I see this frequently along highways on galvanized light poles and sign post.

I painted a galvanized lacrosse goal this way and it sat out in the weather for years and is in perfect condition. Well, the metal, at least. The net is another story...

 

[strutaeng]

Yes, oil won't last on galvanized. But are sure it's galvanized? Galvanized is more expensive vs mild steel...I wonder if it's really galvanized. I think the little texture/color you see in galvanized is called "splangle?" Do you see any of that? Can't see it in your photo.

Anyway, back to your question: I've had good luck with Bullseye 123 primer. I give the surface a scuff with a Scotchbrite pad, mainly to remove any of the white powdery stuff it forms from weathering.

https://www.rustoleum.com/~/media/D...1_Bulls_Eye_1-2-3_Water-based_Primer_TDS.ashx

 

[nadogail]

I have always believed that galvanized should be pickled with a mild acid solution before painting. Vinegar is what I have been led to believe was the most common and convenient.

 

[shopnut]

I learn something new on this website everyday... No oil-based paint directly on galv. steel. Thanks guys!

 

[Hunt2871]

Waterbased paint, if it stays on long enough (it probably wont) will rust galvanized steel. I did a sandwich shop once and used galvanized gas lights I converted to electric lights and the owner painted the pipe ran on the ceiling of the shop with acrylic latex. Looked great for about a year and then it turned orange LOL. That pipe had been on that ceiling for a long time without any issues and rusted until it was almost gone in places in 12 months.

 

[Grimpala]

https://www.sherwin-williams.com/ho...eeling-cracking/peeling-from-galvanized-metal

 

[MoonRise]

Well, you certainly have a failed paint situation.

Whether that is related to the (possible) galvanized (zinc) layer on the steel or to other surface contaminants is up to you to determine.

No matter what, the surface to be painted has to be 'clean'. No dirt or crease or oil, some metal-treatments are incompatible with some paints as well.

Some info on painting hot dip galvanized steel:

https://galvanizeit.org/knowledgeba... wash primer, or self,mixed just prior to use.

btw, the 'white powdery stuff' on zinc coated/plated steel is "zinc oxide". Same stuff as old-school 'white' sunblock.

And "spangle" is usually just apparent on hot-dipped galvanized steel. Zinc electro-plated steel still has the zinc surface layer, but usually much more 'even' and uniform and just not as thick as a typical HDG coating. It will still oxidize to zinc oxide and will still possibly interfere with paint adhesion.

 

[metalmagpie]

Are you sure that isn't powder coated? If it is, you have a problem. The whole lot would need to be removed and sandblasted and then refinished.

Hot dip galvanized steel can be painted without etching primer if you wait a year after it is dipped.

I would like to know where in Mexico you bought that door.

metalmagpie

 

[My Old Tools]

The door was bought locally, but made in Mexico we believe. From a web search, just about all of their doors do this after a year or two. Of course they don't warant the finish at all. I wanted to have it powder coated, but it is foam filled. Also removal would be an issue.

https://irondoorsplus.com/finishes/

"All of our steel products from the heavy forged steel doors to the hot rolled metro series receive the highest standard anti-rust treatment. We use heavy duty sandblasting, pure hot zinc galvanizing and premium zinc primer. We also use only superior quality and environmental friendly magnetic paint for top coating and hand faux finishing. All of our field technicians can paint directly on the job or in our 10,000 sq ft Texas facility."

 

[rustyjames]

When I used to paint galvanized stuff I would just clean it thoroughly with lacquer thinner and give it a few coats of Dupont Velvaseal and then topcoat. Never had a problem.

Most manufacturers will print right on the instructions about what type of substrates the product is intended.