Dave Tracy

I have had some issues with the primer/build coats separating from the car in the deep crevices. I have stripped all of the paint off of my '64 coupe. This was done chemically. Gelcoat was applied, sanded and cleaned. This was followed with PPG epoxy primer and K36 high build primer. The car has been in primer for a couple years. In the areas of the cowl and the deep crevices on the side louvers, the primer has lifted off. It appears to be between the gelcoat and epoxy primer. Some of the areas that have lifted are at a fiberglass/epoxy primer interface where I have dealt with this issue before. My thoughts are some sort of contamination in those tight areas or the material lifting after the application of the material. What would you all who have been there and done that recommend. As always, thank you for your responses.

vetman1

Is the gelcoat shiny where the other prime broke loose. Maybe those areas were not able to be sanded enough to make a good bond to the gelcoat. What grit sandpaper was use to sand the gelcoat?

Dave Tracy

After the gel coat was put on, I used a 3M pad with lacquer thinner to clean off the waxy layer. I then used, if I can remember that far back, 180, 220 and then 320 grit paper. This was followed with DP40 epoxy primer and K36 primer. This has been sanded to contour with 400 grit. The gel coat does not appear shiny. I have been sanding down to glass, through the gel coat in all of these problem areas.

CF6873

The lifting could be caused by several things. I've seen cars that were chemically stripped that still had some residual stripper in the glass and over time it gassed out causing primer lift.

Also if the primer coats were put on too thick without long enough flash time between coats. Primers will shrink as they dry and cure and if they are too thick they can pull up out of a crevice.

And as was already mentioned, make sure you have the areas sanded properly.

Good Luck,

Craig

Dave Tracy

Thank you all! The deep crevices could be collection areas for a thickening of the material. I'll make sure to keep it light when I touch up the spots.