Painting Over polyurethane

[marklit]

I have recently had the top sides on my Millkraft 45 painted. Original paint was 2 pack poly which was about 4 years old in OK condition. The painter I employed recommended using awl grip enamel and did what I thought was a good job at the time. Nine months after the job was complete the paint started bubbling in certain sections and coming off in small chips. I raised this with the painter and he tells me that it is because the enamel has caused some sort of chemical reaction with the poly which has caused the poly to separate from the old original undercoat. Has anyone heard of something like this happening before?

[Panacea]

Originally Posted by marklit

I have recently had the top sides on my Millkraft 45 painted. Original paint was 2 pack poly which was about 4 years old in OK condition. The painter I employed recommended using awl grip enamel and did what I thought was a good job at the time. Nine months after the job was complete the paint started bubbling in certain sections and coming off in small chips. I raised this with the painter and he tells me that it is because the enamel has caused some sort of chemical reaction with the poly which has caused the poly to separate from the old original undercoat. Has anyone heard of something like this happening before?

Hate to break it to ya, but your "painter" is the problem. Awlgrip is a 2 part polyurethane, not an enamel. Painting 2 part poly over 2 part poly requires only cleaning/degreasing with a surface prep solvent and then sanding/scuffing to a 320 grit profile. The bubbling you describe can occur when there are contaminants on the substrate that have not been removed properly with the surface prep solvent.

Anybody can apply paint. A skilled painter will do the prep necessary for a lasting finish.

[marklit]

Hi Panacea
Sorry I checked the name of the paint again and it is Altex regatta gloss enamel.
It's not bubbling under the recently applied paint. It is under the 4 year old poly and its undercoat.

[bayview]

I'm confused. was the original a two part coating or not? Can you tell from the chips which surface is separating?

[Capt.Bill11]

Originally Posted by marklit

Hi Panacea
Sorry I checked the name of the paint again and it is Altex regatta gloss enamel.
It's not bubbling under the recently applied paint. It is under the 4 year old poly and its undercoat.

I wouldn't think enamel would cause poly to lift. The other way around I can see it happening maybe.

Could be a heat issue.

[bayview]

the solvents in two part coatings are very strong and will lift a lot of stuff but usually immediately. Enamel????? Haven't heard of that in years.

[sean9c]

Looks like that Altex is a one part poly. If your painter knew this he should have removed it all, back to something solid, before applying Awlgrip. Lousy prep. Doesn't really matter now. Only fix is to do what I just said, sand it all back to something solid and start again.

[Panacea]

Yeah in this case the painter should have removed the old enamel completely. It is plausible to prime with epoxy over the enamel, but I've only done this over 1 part interlux brightside... not enamel. I believe enamel is oil based, but I could be wrong. Sorry for the grief!