# Painting new galvanized duct work



## joecaption (Nov 30, 2011)

Skip the water and use straight vinegar to etch it.
123 should work.
I'd be using a foam roller for a smoother faster finish.
What's this duct for?


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## Gymschu (Dec 12, 2010)

Anything galvanized can be a crap shoot to put paint on. SW makes a primer specifically for galvanized metal called GalVite. The reason a special primer is needed is because galvanized metal has a waxiness to it that keeps most paints from bonding. It will look great for a year or so then pull off in great sheets. I would definitely go to your local paintstore and get some advice from an experienced store manager. New products come out all the time and perhaps there is a less toxic metal primer other than Galvite that would work.

Now, having said all of that, I have had a job or two where paint has failed using the Galvite primer. I've also had success using Rust-Oleum oil-based paint for metal WITHOUT USING PRIMER. So, like I said, it can be a crap shoot. Hopefully, Ric Knows Paint comes along with some more quality info.


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## poppameth (Oct 2, 2008)

We always etch with phosphoric acid. Then prime and paint with a high quality acrylic DTM. No issues even on a roof. It's all about removing the micro refined oil it's coated with. After that it's just zinc and acrylics work fine.


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## ToolSeeker (Sep 19, 2012)

Gymschu said:


> Anything galvanized can be a crap shoot to put paint on. SW makes a primer specifically for galvanized metal called GalVite. The reason a special primer is needed is because galvanized metal has a waxiness to it that keeps most paints from bonding. It will look great for a year or so then pull off in great sheets. I would definitely go to your local paintstore and get some advice from an experienced store manager. New products come out all the time and perhaps there is a less toxic metal primer other than Galvite that would work.
> 
> Now, having said all of that, I have had a job or two where paint has failed using the Galvite primer. I've also had success using Rust-Oleum oil-based paint for metal WITHOUT USING PRIMER. So, like I said, it can be a crap shoot. Hopefully, Ric Knows Paint comes along with some more quality info.


yea Ric hasn't been around for a while.


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## Jmayspaint (May 4, 2013)

I've painted plenty of it with just a vinegar wash and good acrylic. One building we did 15+ years ago I drive by all the time. It's faded as heck, but no peeling. 

There is a certain kind of galvanized metal that cannot be coated with anything. Passivated galvanized has to have special, intensive prep (a lot more than a vinegar wash) work for any coating to stick to it. I've only encountered passivated metal on roofs and lintels, but it is used in other applications as well.


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## Will22 (Feb 1, 2011)

Oil primers or paint applied directly to galvanized surfaces may delaminate due to a condition called saponification, which causes peeling (if you scratch the underside of the peeled surface, it actually smells like soap, which is a compound derived from the combination of the zinc in the galvanizing with the alkyd binder). An acrylic industrial (DTM) metal primer (like Devflex 4020) is a good primer, considering that the galvanized surface is cleaned thoroughly of any passivation and grease.


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## kkeith (Oct 4, 2011)

I have found a primer from Sherwin Williams that is part of their Industrial and Marine line that works great for adhesion on aluminum and galvanized metal that is called simply DTM Wash Primer. It is not on the show floor so you have to ask for it. It is a semi transparent watery primer, but bonds great and fast. As for cleaning the metal I have found that when I pressure wash the house after applying a non chlorine cleaner such as Krud Kutter house and siding cleaner, that is sufficient for degreasing the metal and further etching is not beneficial and has even caused some problems down the road.
This question prompted me to do a little research. I primarily come across galvanized metal just when painting new gutters and downspouts. Sherwin Williams outlines the preparation according to the standard SSPC-SP1 which is solvent cleaning with a degreaser, or water and a detergent. The standard also recommends letting the metal weather for 6 months, and another week after cleaning before priming and painting. In the real world we have to paint for the customer shortly after the gutters are installed.


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