Why cars rust
Cars since the mid-80's have less corrosion problems because they started using galvanized steel in body panels. This was to use thinner metal to save weight (better mileage) and the old method of "let her rust from the inside" wouldn't have outlasted the warranty, all the short-sighted bean counters cared. They had trouble getting paint to stick initially, which is why you see many with flaking paint, which was repeated in the late 90's from changed solvents mandated by EPA. Almost all trim is now plastic, which fails from uV but not corrosion.
What causes rust?
#1 Salt. Besides salted roads, I cringe at the ads in the 70's of a car driving on the beach at the waterline splashing salt water underneath, plus the cars we saw parked on the Fla beaches whose owners forgot about the tide.
#2 Leaks.
From rain or bad heater cores. This usually just rusts the floors since the carpet stays wet. This happens even on the west coast.
#3. Condensation. A car sitting outside, even if covered, can get condensation all over each morning if the surface temperature falls below the air dew point. This is less a problem out west. Even in Seattle when drizzling, the air feels drier than in the East. Cars don't seem to corrode terribly in the NW, despite the rain.
#4. Cheap and minimal paint inside doors and underside. The factory barely sprayed inside the doors in the 60's and almost no paint at the tops or in the crevices. Treat those whenever you have the door panels off. Scrape and use rust converter paints.
I really agree with this. I have lived in Seattle besides a short stint of living in L.A. my whole life, so have my parents and we have had numerous 60's and 70's cars and one 50's car.
I think it has more to do with mainenance and upkeep, and a little bit of watching what your driving in.
My parents bought a 64 Custom 880 and a A108 68 Dodge van brand new. the car was a daily driver till 1988, the van was a daily driver till 2005.
The car was never driven in snow, the van was taken to the mountains skiing all the time in the winter. The car was completly undercoated, the van wasnt.
Both were garaged most of their lives, the van till 2005, and the car till 82, when my parents bought a K car, then the 880 sat outside.
The van when sold did not have any rust on it, anywhere, the car, with the undercoating, had started getting rust around the rear quarters, typical of mopars. I think the undercoating which is meant to save the body actually contributes to the rust by eventually holding the grunge in and letting it corrode.
My Coronet is undercoated completely on the bottom, its probably helped it last 40 yrs, but it too has the rust around the lower quarters where all the crap on the road gets thrown and gets stuck in the undercoating.
The Satellite i had was done in by the leaking wiper pivots as the floors were rusted and i think the trunk leaked too and it rusted through from the leak above and not the water below.
I agree with the humidity statement too, even if your car leaks inside, like mine, the Coronets drip rail molding is bad, so the water runs down the gutter, right into the door gap and into the drivers footwell, it will dry and be fine, and not mold or stay damp like a more humid states carpet would, i think that has a lot to do with the corossion starting too. Just my thoughts
