I’m a believer that after that rust has gotten to that point, it is a MAJOR job trying to patch back that roof skin with welding in new strips of metal
Yes the salt air of living near the ocean will speed up that rust in that area BIG TIME! It rusts from the inside with the roof condensation mixing with the salt air - and it runs down into that sandwiched metal of the drip rail seam.
I had shipped my ‘67 to Hawaii for a few years and boom! Got rust bubbles there in a otherwise solid roof. Damn.
I vowed to save the roof, get it completely sealed up so no rain could get in from the outside, AND seal up that seam all across the front of the roof on the inside. I started with the hardest part - the inside.
Cleaned out all the heavy scale in that wedge area of the interior roof. Cleaned it out good, vacuumed it, blew it out, wiped it clean with damp rags. You can actually look into that area with a flashlight if you try. I used a flexible hacksaw blade to chip out the big rust scales. It was just surface rust and holes when I was through!
But not a pleasant job.
Now the scary part…. I pressed in TAR with my fingers to completely seal that wedge area from ANY future moisture. The tar applied to that seam prevents any moisture from ever hitting that metal again. I put alot in there, and its not visable from the cabin. Your fingers and that goopy tar will seal it and halt the rusting.
Of course as you know, the outside drip rail is completely cleaned out. Tar will have squeezed out the holes, I let it harden up a bit and then shear it off flush. Do your body work on the outside, I used the tar, up to level, in the drip rail too.
Going down the street, you can barely notice the sealed up roof rot - depending on how neatly you do the cosmetics on the outside drip rail.
That was my hack, an my
FWIW
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