'69 Windshield Frame
The only place that I think that the windshield frame INTERIOR could be accessed is through the pillar posts. By removing the kick panels and the speakers and spraying UPWARD through the speaker opening in the pillar post I could see where it would be THEORETICALLY possible to to spray rust inhibitor up and into the windshield frame. Just how much coverage would occur would be hard to determine. Certainly, the side frames (which are an integral part of the pillar posts) would receieve coverage. The header and lower windshield frame elements are "open" to the side frames, but I don't know how much of the inhibitor would get in those areas.
Beyond all this, I'm not sure how much good that any rust inhibitor will do if the area already suffers from significant corrosion. Once the structure is weakened by corrosion, a rust inhibitor will not "repair" the damage. And, if significant corrosion has gotten started, I don't see a normal rust inhibitor stopping it. A product like "Extend" might arrest further corrosion, though, but I don't think that it's sprayable.
I know it is too late when the rust is already creating holes in the metal and that I only can slow down that process, never reverse it. This is why I want to spray 'anti corrosion fat' (or 'grease' I am not sure how to translate Korrosionsschutzfett) into the frame. According to the german rust prevention forum (which does not exist any more, probably rusted away) this is the best method to slow down further rusting. That stuff is very similar to what Mercedes and BMW (and probably many other brands) spray into their new cars body cavities to prevent rusting.


I have looked and felt up in the windshield pillars (as far as I can reach and haven't found any rust, so I haven't tried spraying anything up there.
Unfortunately the only sure way to completely stop rust is to cut it out and replace the metal. Most paint, and undercoating will only retard it slightly.
Phosphoric acid is supposed to convert the rust from iron oxide into iron phosphate (I think) and prevent it from further growth. I think POR-15 and Corless also use some form of chemical conversion to stop rust.





