Water under paint? What now?

I had a piece of trim on my 2008 Silverado that was starting to come loose. I figured I'd be a good owner and pull it off and fix it. Under every piece of trim on all four doors I found some degree of this.

It's water bubbles between the paint and primer. Not rust through, no rust at all actually, but leaving it like this seems like a bad idea.
So what's the suggestion? Sand it flat, prime, sand, paint with sometjing to protect and them implement that awesome two tone vinyl stripe idea that I've been toying with?

I have nothing of value to add, but I do have this: I own a 1985 C-30 Silverado Duallie that has been repainted once--basecoat/clearcoat. The clear is peeling badly, and every time it rains, I see areas similar to the bubbles you have there. One of these days, I'm going to do something about it.

How long do you plan on keeping the truck and what's your budget?

The truck will be around for another decade, selling it has been forbidden by Mrs. Deuce. At that time it will be 20 years old and have 250-300k miles on it. Even though it looks pretty good now, I can't see inventing much more than driveway level money into keeping up appearances.

It's not visible with the trim on? Sand, paint with por-15, replace trim? Total layout should be about $40 if you already own a brush.

I'm with Huckleberry. Sand out and brush paint on. Trim will cover it all anyway.

I'm mostly interested in how TF did it get there....

Crackers wrote: I'm mostly interested in how TF did it get there....

And that's kind of the issue. It appears that water was getting trapped behind the trim and some voodoo was happening and water ended up between the paint and primer. I don't know how, but it's not like GM is known for their excellent paint adhesion. I worry if I put the trim back on I'll just be waiting for more bubbles.

Another vote for sand and paint with por15. Then you can cover it up with vinyl or the original trim.

So, for Future Voodoo Prevention is there any way to drill holes at intervals along the lower edge of the trim so water can escape? If not, I'm thinking maybe careful repair + the awesome two-tone vinyl stripe idea has merit, if you're really planning on ten more years.

Lets say there wasn't any trim going back on to cover it up. Same procedure, but sand it the POR-15 smooth and primer over it? Actually getting it repainted is out of the budget for now.

Asking for "a friend" who procrastinated and didnt roll their fenders and finally the tire berkeleyed up the paint and its separating from the body with winter (salt) approaching.

I don't get it. How can water get between paint and primer?

... or is thought there was water on it when they sprayed the paint?

In reply to NordicSaab:

Your guess is as good as mine. Factory paint, I've owned the truck since new. It's only that bad on one door, maybe 10% of that on the other three.

So it is probably pretty low on the vehicle, right? I'd take all the trim off, sand, then throw bed liner on from about 1-2 inches higher than that trim line. The entirety of the vehicle.

dumb question but are you sure its behind the paint and not just behind the clear coat? it may be hard to notice the difference on a black truck. the clear on the bedside of my truck is coming off pretty bad and when it rains it makes nice little water pockets between the clear and the paint.

not that it helps much...

I don't really have much to add here other than what I learned from living in the rust belt. If you press on a bubble and it's squishy, it's paint. If it's slightly crunchy it's clearcoat, and if it's really crunchy, it's rust. Hopefully it's only slightly crunchy.

Could that be blistered from the Texas heat?

It just occurred to me this is the same body style as my 2010 Silverado... and I have trim like yours... hopefully this isn't hiding under mine as well.

I'm sure it has something to do with blistering (heh) Texas heat and the water getting trapped. Not a great picture because I'm sitting in the car rider line picking up the Deucelings, but this is what happens when you open one up. Water comes out, paint falls off, primer is still firmly stuck to the galvanized metal.

And it's ONLY under the trim. Even the paint on the hood and roof is still good.

Call gm?

patgizz wrote: Call gm?

I've had enough of talking to manufacturers for a while.

Hang with me while I try to figure out how it happen. Osmotic Pressure. Water got behind the trim, it was really hot and no where for it to go and was pushed through the paint. Any takers?

Googling Osmotic pressure and paint seems like that's how it happens.

If water passively seeped in a void and was then under pressure, wouldn't logic dictate that it would take the path of least resistance and go out the way it came in rather than working its way through a (supposedly) impermeable membrane i.e. the paint?

Could it have been moisture trapped when the paint was applied and the trim did not allow it to outgas and cure like the exposed paint? Just spit balling here..

In reply to Apis Mellifera:

Certainly could be that the paint under the trim didn't cure as well, but having water trapped against it by the trim is probably the real culprit. The paint on the truck has always been fairly terrible. Soft and absurdly easy to scratch with inconsistent orange peel. It's GM paint. They've done worse.

I would go with the Rhino Lining except I hate that look with the white hot intensity of 1000 suns. Tomorrow I'll break out the sanding block. I have 500 grit wet/dry, I assume that'll work to knock it down? This is the first time I've ever intentionally sanded paint.

That GM paint is permeable. As you suspect, water trapped under the trim has migrated under the paint. I would sand it with 400 grit, use etching primer ( available in spray cans from Rustoleum or DupliColor ) and then paint it before applying the trim or vinyl stripes.

I would be interested in taping a desiccator over a few of the blisters and seeing what happened.

My personal experience with micro blisters has been boats, and it is a no-fun expensive gel-coat repair.

If the truck is a keeper and the damage is covered by the trim, I would remove a minimum of the paint that is there. I would scuff the surface and then go buy a can of matching paint in a spray can. My paint shop will mix two part automotive paint and put it in a spray can. You need to use the stuff the same day.