Prime Coat for PVC Columns

      What kind of coating will stick to PVC plastic pipe? January 29, 2009

Question
I have a guy who will be bringing me four PVC columns to be painted that will be going into a bathroom. The columns will be about 5-6" diameter and 6' tall. What would you recommend for a primer that would adhere to these well. I figure I will need to scratch them up with some 150-220 grit sandpaper before anything. Can I use MLC Clawlock on these? Or will it bite too hard. I'm sure the top coat will be some sort of latex.

Forum Responses
(Finishing Forum)
From contributor G:
Are these decorative or functional? And what do you mean by Clawlock biting too hard?



From contributor A:
BIN shellac primer would be your safest bet, considering they will be topcoated with latex. At the end of the day any decent acrylic waterborne primer should do the trick.


From contributor S:
Just about any hardware store carry's the Krylon brand "Fusion" for plastic. It works very well on PVC, and at $4 an aerosol can, it is cheap for as little surface as you have to do. It also comes in lots of colors and sheens.


From the original questioner:
To contributor G: As you might know Clawlock is an acid catalyst activated primer. I was wondering if it might melt it.


From contributor G:
According to my info, the solvent for PVC is called Tetrahydrofuran, which is an ether. I doubt the acid in the Clawlock would touch PVC, but perhaps the solvent in the thinner might. I would think this may help the bond rather than eating through the material. The reason I asked about function is that decorative use may allow use of a simpler primer. If I wanted it bulletproof, I'd likely use XIM, or go to an automotive paint store.


From contributor L:
Make sure to clean the columns. If they still have mold release agents on them, you may have problems regardless of the primer chosen.


From contributor C:
Be very careful here. I've seen guys do the above things and a month later the finish peeled off. I use an auto plastic bumper primer, aka super flexible and sticks like stink. Then after that anything will stick to the primer and stay.


From contributor J:
Akzo Nobel makes a variety of primers for plastics/PVC.


From the original questioner:
I ended up using Clawlock. I did a test piece first (of course) and this is the schedule. First of all these were not columns per say. They were PVC tubing, 4" ID 1600 PSI rated and they were blue, not white. So I am not sure if this was a dye in the PVC or a different formulation.

1. Random Orbit Sand with 120 grit to knock down the extruded lines and marks.
2. Scuff sand to 220 to knock down some fuzz.
3. Wipe down with MLC standard lacquer thinner. Basically a tack rag. There was tons of static.
4,5,6. Spray on 2 coats of Clawlock primer sanding 220 between coats.

I did an adhesion test. Cut a grid of 3/32 squares and used silver foil tape to try to pull off the finish. Pressed it on real good and ripped it off quick and I did it a second time. I had an excellent adhesion. One small speck in 1 grid came off. The rest were not touched. I would call it a success. This test was performed after 24 hour dry time. So if you ever need to coat PVC, this will work.



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