Why do some Mopars rust all to hell, and others go for decades with no major issues?

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jos51700

jos51700

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To be clear, I'm not talking about your typical rust in a quarter panel or floor. I'm talking rust EVERYWHERE on a car; the rust leaves a car as swiss cheese, where there's not much to work with.

Background: I'm in Missouri. We salt our roads. I know how much rust my cars get every year, but some of my cars...I wonder if they lived in a lead-acid battery plant before I got them. My '75 Valiant is an absolute rust bucket. The tops of the quarter panels have rusted out. The friggin' dashboard rusted out. It seems like it's continued to rust despite being mostly parked for a decade.

My '72 Dart on the other hand, has sat for more time, I've owned (and not maintained) it longer than the Valiant, the top rotted off exposing the unpainted roof to the elements, and it hasn't really rusted much at all through the years.

I have two '92 Dakotas....Same thing; one truck had the frame rust through where the rear cross member bolted up. The upper windshield frame has rusted through in places. It's just RUSTY. The other truck...clean. Nothing more than surface rust, and that's even limited. They've both been in Missouri for the last 25 years.

So, I've heard everything from "thinner sheetmetal after '72 to save weight for fuel economy" to "St. Louis vs. Hamtramck vs. wherever", to "the battery ground is hooked up poorly or wrong so the body is being used like a sacrificial anode". I understand that region plays a huge role, but all of my cars have been in my possession in the same area for 20+ years. I've owned my Dart and Valiant since the mid '90's, and the Valiant floorboard was rusted out even then.

What say you guys? This "Daytona Superbird" is a good example. Even the chrome is rotted off the bumper! The deck lid is roached. It looks like it was driven through a puddle of battery acid. The car has clearly seen a repaint, but WHY is the rust so aggressive on this versus other cars?
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Northern cars vs Southern cars. It's really that simple, it's all the road salts fault. Everything is rust free around here and seeing work trucks from the 60s still being used Isn't rare
 
DumpsterFire said:
Northern cars vs Southern cars. It's really that simple, it's all the road salts fault. Everything is rust free around here and seeing work trucks from the 60s still being used Isn't rare
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I guy could make a living bringing those old rust-free "work trucks" here to the rust belt. Cars too.....
 
North Carolina is filled with rust buckets. The state sprays liquid brine on all of the roads. Check out Jeeps or any other "metal" vehicle not covered in plastic. Rocker panels hide the salt damage real well.
 
Rust is brutal. I bought a '68 Barracuda Convertible 17 years ago, and found a sliver dollar sized hole in the trunk. It went all the way through the sheet metal, but I was able to treat the edges and put a plastic body plug in it.

I drive it year-round, so I've been keeping an eye out for any other signs of rust, especially on the floors but haven't found any since.

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I've driven my Dart on salted roads. It's not ate up like the Valiant, and I've never driven the Valiant in the snow. Road salt doesn't eat chrome off a bumper like the 'Bird in my OP.
 
In my opinion there are two variables: dirt and moisture. Ever notice how dirty cars seem to rust faster? Dirt allows moisture to adhere to the surface, thus allowing the electrochemical process of corrosion to occur, either "easier", or at a faster rate (I'm not sure which is the correct term I want to use here).

And once corrosion (rust) starts, it's pretty hard to contain. And impossible to reverse. "("Rust never sleeps"....)

I don't buy into the whole "different assembly line = different amounts of rust" theory, as no one who has said that has ever done a Control (one car from both, kept in the same conditions, etc, etc). But I do think there's something to be said for the fact that with cars bought used/previously owned, there is no way of knowing how clean the PO kept the vehicle. One wash at Time of Sale, even on a relatively new car, does not equate to good ownership, IMO. And a car from a dirty "first owner" doesn't stand a chance against one from a "good" first owner.

Somewhat related to this: In High School Chemistry I was taught that fire was a chemical process, and the only one that couldn't be undone. Well, I thought about that for a couple of days, while driving my completely rotted-out POS Ford Maverick, and when I asked my Science Teacher about rust, he said something like, "Well, that as well".
 
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Coastal and FL cars rust from the top down as the salt is in the rain.
Not unusual at all to see drip rails and fender tops rusted out down here.
It's WAY worse on vinyl top cars, and I can't stress that enough...WAY worse.

Certain body styles and years rust differently.

What I've found on most A body cars is the cowl and vent stacks go.
This seems more pronounced on earlier cars, the earlier, the worse.
After that, rockers.
That's odd to me being a B body guy, as we almost never see rusted rocker panels.

Lower rear quarters go on almost any car.
 
jbc426 said:
Rust is brutal. I bought a '68 Barracuda Convertible 17 years ago, and found a sliver dollar sized hole in the trunk. It went all the way through the sheet metal, but I was able to treat the edges and put a plastic body plug in it.

I drive it year-round, so I've been keeping an eye out for any other signs of rust, especially on the floors but haven't found any since.

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In the northeast a convertible gets garage kept if not they leak and the floors trunk are gone. Now if you are not in the rust belt they probably last pretty good.
 
I'm sure if you park on dirt not asphalt you will get water trapped in the car coming up from the ground. Up here in winters some people store their cars on the grass and cover with a tarp. Worst thing you can do.
 
1 of my parts cars came out of Oregon it too fell victim to the peeling bumpers. It was a very well optioned car

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ProjectBazza said:
Somewhat related to this: In High School Chemistry I was taught that fire was a chemical process, and the only one that couldn't be undone. Well, I thought about that for a couple of days, while driving my completely rotted-out POS Ford Maverick, and when I asked my Science Teacher about rust, he said something like, "Well, that as well".
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That's a good point, but I might make the argument that the rusting of a car is the undoing of the chemical process. We have to chemically process the iron into the steel before we can use it, and rusting is the reversal (undoing) of that process.
YY1 said:
Coastal and FL cars rust from the top down as the salt is in the rain.
Not unusual at all to see drip rails and fender tops rusted out down here.
It's WAY worse on vinyl top cars, and I can't stress that enough...WAY worse.

Certain body styles and years rust differently.

What I've found on most A body cars is the cowl and vent stacks go.
This seems more pronounced on earlier cars, the earlier, the worse.
After that, rockers.
That's odd to me being a B body guy, as we almost never see rusted rocker panels.

Lower rear quarters go on almost any car.
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That is a really interesting observation! I haven't spent a lot of time near coasts. I've never seen a drip rail rusted out on any car.
 
YY1 said:
Coastal and FL cars rust from the top down as the salt is in the rain.
Not unusual at all to see drip rails and fender tops rusted out down here.
It's WAY worse on vinyl top cars, and I can't stress that enough...WAY worse.

Certain body styles and years rust differently.

What I've found on most A body cars is the cowl and vent stacks go.
This seems more pronounced on earlier cars, the earlier, the worse.
After that, rockers.
That's odd to me being a B body guy, as we almost never see rusted rocker panels.

Lower rear quarters go on almost any car.
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Agreed. As a lifelong MN resident, it's rather odd buying a car from, say, Florida or the SE Texas/Louisiana area, as they seem to rot-out from the top down.
 
A56 said:
North Carolina is filled with rust buckets. The state sprays liquid brine on all of the roads. Check out Jeeps or any other "metal" vehicle not covered in plastic. Rocker panels hide the salt damage real well.
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Maybe in the hills but everywhere else it doesn't happen enough to make a difference
 
DumpsterFire said:
Maybe in the hills but everywhere else it doesn't happen enough to make a difference
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Get on marketplace and checkout cars for sale throughout NC. They salt roads from Sanford to Raliegh and points beyond. lmao, they salt when one inch of snow is threatened. Check out vehicles out of Wilmington and Hampstead. Plenty of salt from the ocean air.
 
We have rust buckets here in Florida too, beach cars or for that matter anyone who lives near the beaches and hurricane flooded cars.
 
Salt is brutal. Did yall see that car @GTX JOHN had that sat close to the beach for years? One side looked good. The side toward the beach, not so much. The car is very repairable, mind you, but you can get a good idea about what's goin on by lookin at that car. Some cars get like a heavy surface rust and seem to go no further. Stay like that for decades and they remain solid. Beats me.
 
Part of the equation is also condensation. Salt can't do much on it's own, it needs to be in solution to do much to metal. This is why dry climates tend to be nicer to vehicles.
Condensation happens whenever the car is colder than the dew point of the air surrounding it. Being parked in a place that gets regular sun can help heat the car up enough that condensation is driven off (evaporated) versus if it is in the shade where it stays cool and then condensation forms every morning and every evening. If there is condensation on the outside, there's condensation anywhere the car is cool - wheel wells, rocker panels, etc.
Each time the condensation re-wets the salts, it starts another attack. Do this a few dozen or hundred times each year and it begins to take a toll.
Another part of the equation is freezing weather. Water is incompressible and expands when it freezes. If there's a blemish in a coating like paint or chrome then water can get in and freeze which can lift the edges. Each freeze-thaw cycle advances this failure region. I have an old jeep which had a bird-**** spot in the clear and water got under it and blew the rest of the clear off the whole hood as a result!
Salts are also not just de-icing salts. There is plenty of other salts and other minerals in dust. Some are used as a dust control, but they do so by absorbing water from the atmosphere - so even if your car never gets wet those salts can suck up their own water and start to attack the steel!
There is plenty of junk in road dirt which can also contribute. Brakes create a lot of iron dust which can stick to a car and help create a corrosive entry point on various parts of a car. Other things like smoke, ash, and even rain water can contain junk which acidifies water and cause increase reactivity. Water spots on glass are a very visible reminder of the 'stuff' that's often found in water at any given time. Rain water sucks up nitrogen as it falls and becomes mildly acidic. Soot and ash from wood fires can do similar, or the opposite but either can cause accelerated chemical attack. Remember cars have a lot of plated parts too. Aluminized exhaust, zinc coated parts, zinc coated brake discs etc. When those coatings wear or react, that stuff is strewn about in trace amounts on roads and highways. When it comes in contact with a car, it can build up and help create small anodic or galvanic cells. Vehicle electrical systems, static electricity (which can get generated just driving down the road), and even regional weather can have a greater or lesser impact on corrosion once those cells are setup.
Something else to consider is what types of products are used on a car. Waxes, polishes, oils and such can help repel water but also seal metal surfaces to prevent moisture attack and slow or eliminate rust from forming. Lots of newer car washes and polishes have polymer additives which stick to things and effectively 'shrink wrap' the car.

There's really a lot of things which can contribute, all of which are extremely regional and variable. The best thing to prevent rust and corrosion is to keep the entire car warm and dry and clean. If a car is going to see water from any source, then protections like undercoating or waxes or oils should applied to clean surfaces to keep them from being able to attack the metal. I like using things like LPS3 or the old boshield but have had good luck with fluid film and even WD40 in some cases.
 
Another issue in cowel and lower front fenders is dirt, leaf, pine needle build-up blocking water drainage through lower cowel.
 
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Bad, Bad, Bad

They rust because they have been neglected and have been sitting outside. Nobody took the time to seal them up internally, most people don't even have a clue on how to do it.

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Yes, that a GTS.... Buldge Hood, all rusted out.


☆☆☆☆☆
 
This one was sitting behind a auto shop in south Fl. Drug it to the front and it just started pulling apart in pieces !

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Has anyone ever tried using a sacrificial anode like they do on ships?
 
Location location location.

Colorado salts their roads with mag chloride.

Not to many east coast style rust buckets here.

My so Cal dart lived all but the last 8 years 1-2 miles from the ocean and the chrome shows it. But there is very little rust on the car. None in any of the seams. A few pinholes drivers and pass floor.

The car was daily driver 25 years and 300,000 miles.

It was also garaged every night.

And factory under coat.

Add it all up and I go back to location.

But circumstances plays a role
 
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