Prevent windshield rusting

[thistle3585]

I thought I read somewhere about spraying some expandable foam in to the windshield frame to prevent condensation from accumulating from the defrost vents. Has anyone done that? Getting ready to insatall my new windshield and wondered if I should do it. Seems like it sealing it would make the vents more effective since they're not pushing air around the frame.

 

[jammer1]

Windshield frame always has condensation. Expandable foam will just trap the moisture. I coated the inside of the frame with epoxy primer then painted. The only good thing the foam would do is direct and force the warm air out the defroster.

 

[Posi]

x2 on the foam
A coating of Rust Encapsolator on the inside would work as well.

 

[IOPort51]

I was going to try this and didn't.

the moisture is there because the defrost circulates warm humid air from the cab into the cold sheet metal windshield frame which collects inside the frame. IMHO. the biggest worry I would have would be that the foam expanded enough to swell the frame. Kind of hard to prep for paint inside the frame, pealing/chipping paint inside the frame could be quite a mess.

 

[Hedgehog]

But....... Remember there are windshield arms and such swinging back and forth in here along with the hotish air.

 

[PaRenegade]

I don't recommend filling it with foam because that can trap and hold moisture, unless you can ensure it's tight to the metal and no holes get drilled around the top and sides and you treat the pinch weld with something like POR15 or epoxy primer. But I can tell you blocking the airflow will help tremendously. The problem, as already stated, is the warm defrost air circulating the entire frame. It goes up around the top, cools, and then condenses on the cold metal.
In 1996 I replaced my rusted out ws frame and I sprayed primer the best I could inside, which wasn't too well. But I took some sheetmetal and made and air dam for each side of the bottom, past the defrost ducts and linkage path and sealed it in place, all but the bottom, with rtv silicone. Then it got painted with the bc/cc while still just a metal shell. Come 15 years later when I tore it down for a resto-build it had one little spot of rust by one of the inside mounting tab bolt holes. This time I sprayed the inside with Internal Frame Paint and a 2' hose. Should be good for another 15+.
I highly recommend the IF paint with the hose and conical spray tip for any enclosed space of a Jeep. I used it extensively during my body restore.

 

[jammer1]

As I said, I did mine with epoxy primer then paint on the CJ7 . On the CJ8 I did the epoxy primer only. I have epoxy primer on my work truck. When I painted it then wet sanded I exposed the primer (sanded through the paint enough to see the primer). Three years later still no rust. On the windshield frame tape up all the holes but one of the defrost holes (the tub side hole). Mix the epoxy and pour into the frame. Turn the frame slowly is all directions. Let it sit for 5 - 10 minutes and repeat a few times to coat (multi-layers). If you don't want to epoxy, get a good auto paint and use that. I didn't take many pics of the windshield frame but I took pics of the frame. I did the same with the frame except I used a garden spray pump with 6 ft. of fuel hose. I filled it then flipped the frame a quarter turn at a time. On the windshield frame I even had the primer coming out of the seams. This way you get a good coat, not a thin spray.