Sealing Back Side of Corvette Image Panels

[Patricia Brown]

Hi everyone,

I have read of people occasionally having issues with paint blistering on high-quality, press-molded, aftermarket panels, such as those from Corvette Image. It seems it is still up for debate as to what, exactly, is causing the problem, whether it is the panels still a bit green and oozing contaminants, or whether it is moisture working through the panel from the backside, etc. The panels now come with gel coat applied to the outside surface. I am not clear whether this has absolutely solved the problem or not.

After reading of these occasional issues and wanting very much to do what I can to avoid them, coupled with the fact that I live near Seattle, WA where our humidity (never mind rain!) is very high nearly all the time (it's lower today at 80%), I am considering spraying some kind of waterproof sealer on the BACK SIDE of the panels, for extra protection.

I spoke to Jerry at Corvette Image, telling him I would like to coat the back side of the panels, and he recommded either gel coat or a catalyzed urethane sealer.

My question is: Do I stand a chance of trapping moisture or a contaminant (if the panel is still a bit "green") within the glass by coating the back side? After receiving the new panels, should I let them sit some extended period of time prior to spraying them to be sure they're fully cured? Will our atmospheric humidity here (of late around 90% most of the time) cause the panel to absorb that moisture and then I will trap it by spraying the backside? And, finally, does it really matter if I DO trap something in the glass? Is the gel coat such an amazing barrier that it will contain any moisture or "green" contaminants within the glass and prevent any paint blistering?

Any help much appreciated!
Patricia ('72)

[Patrick T.]

Re: Sealing Back Side of Corvette Image Panels

I've never had that problem with two front clips, but in both cases I had bonded the clip on the car and let it "gas out" for a year. Both my painters asked me how old the panels were.

I would not seal the inside of a new panel, except for the blackout in the engine area. If there are VOC's or vapors in the fiberglass, it needs somewhere to escape and you don't want it going through the painted side. PT

[Joe R.]

Re: Sealing Back Side of Corvette Image Panels

Gentlemen & Ladies,

Corvette Image gives a great explanation of how to finish their panels BEFORE the paint is applied. It comes with every panel they sell. DO NOT use anything but a polyester sealer and primer!!!!!! Using a two part epoxy primer and sealer will doom you to failure.

We are talking POLYESTER fiberglass here so use POLYESTER products for sealers and primers.

Sealing the back side of fiberglass panels it NOT necessary and may lead to premature failure by sealing the gasses between two sealed surfaces.

Regards,

JR

[Richard S.]

Re: Sealing Back Side of Corvette Image Panels

We used Corvette Image panels on my 67 coupe. After bonding to the car they cured for two summers in the sun. We then gelcoated all top surfaces before painting. Last summer,two years after painting and completion of the car,I had some work done to my garage. I made the mistake of double covering the car with heavy covers while I left the car outside for two weeks while the workmen were in the garage. It got very hot and humid for 10 days and when we uncovered the car the rear panels had very small blisters in the paint. I have been told that it is possible that the humidity and moisture came through the back side of the panels because we did not treat the backs of these panels in any way. They were left in the natural state in which they came from Corvette Image.

[Wayne W.]

Re: Sealing Back Side of Corvette Image Panels

Rick, Many have had the same problems with original panels exposed to the same conditions. I am curious to know how long ago that was. Were the panels the old style or the new, with gelcoat.

[Patricia Brown]

Re: Sealing Back Side of Corvette Image Panels

Rick, I remember reading about your sad story. I plan to really drive this car, and it will get wet. It is also VERY humid here. I did talk to Jerry at Corvette Image about coating the backside, and he stated to use gel coat or a catalyzed urethane, but now I am concerned with the possibility of trapping moisture or gases within the panel between both coatings of gel coat. I am really surprised you had moisture still blister the paint, even though you had applied gel coat to the topside. I guess gel coat is pretty good but not fool-proof. So have you repainted? Have you treated the back side of the panels or done anything differently this time around?

Patricia

[Patrick T.]

Re: Sealing Back Side of Corvette Image Panels

Rick, the gelcoat on the outside surface acts as a firewall, which should have prevented any gaseous or solvent substances from penetrating through to the paint. Any lacquer or catalyzed urethane paint which is shot on a correctly prepped fiberglass surface and baked should not have any problems as far as outside ambient temperature and humidity are concerned.

The paint on my car is one year old and the painter shot it in a downdraft spray booth with an oven and baked it at 160 degrees for an hour. I was told the oven's at St. Louis were 800 degrees, though the painted bodies only ran through there for 2 minutes.

I'm not an expert, but I'll offer my two cents. The problem with your car's paint was in the preparation of the surface or the sealers or mixing of the paint. Mixing DuPont with PPG products are many times incompatible and can end with disastrous results. In other words, from my perspective, the fault lies with the person who bought the paint ingredients and shot the car. Again, just my opinion.

[John H.]

Re: Sealing Back Side of Corvette Image Panels

St. Louis (midyear era) ovens were:

Prime: 60 minutes @ 280*F
Sealer and First Color: 30 minutes @ 160*F
Second Color: 30 minutes @ 160*F
Final Color: 45 minutes @ 250*F