markyerger

What is the problem with C3 frames rusting out?
My 1972, recently purchased from e-bay, recently thoroughly burned on, because the seller was not really truthful, has a rusty frame.
Was it cheap metal? Bad design?
Just need to know.

GrandSportC3

There's nothing specificly bad or good about Corvette frames.. Just like other cars frame - if the car sits outside most of the time and gets driven in all types of weather... one day they will rust through..
My 68 has a close to perfect frame.. It had been garaged most of it's life...

:cheers:

Olivier

a454corvette

Gotta disagree...Being of box section, the problem is worse than many other cars with c section frame rails. Corvette was not alone in use of this, though. Many GM (and other makes) cars used the same general design, and in fact it is still in use today, albeit with much better corrosion protection than was ever used in the '50s through the '80s.

The cars were never designed to last 30+ years, we should be happy ANY are left :thumbs:

GrandSportC3

Interesting... I've seen so many classic cars with rusted frames of all brands and models... I always thought that it only depended on how the car was cared for... Never knew about the design differences..

:cheers:

Olivier

a454corvette

Early Chevelles, for example, are bad about rotting at the rear kick-up, because it's guess what, box section, even though the main perimeter rails are open c section. Chevy pickups use mostly c section frames, and don't have as many problems.

Living in a coastal region likely aggrevates the problem, regardless of design, due to the salt air and uncoated insides of the rails.

Robert N

I think the issue is a mix of the design and care. Unless a frame is designed without any areas where water, road salts etc can collect, there will be weak points.

Mystery Machine

So, is it safe to say that the only way to prevent rust on oneof these cars is to remove the body and powdercoat the frame?

I have been all under my '73 and there is MINIMAL rust...if any really, that is visible anyway. However I have seen a small spot on the side portion of the frame (below the door) and I was thinking of removing the rockerpanel and grinding it down. Is that worhwhile or a waste of time and effort?

jerryp58

I have an interesting Corvette Fever article (December 1999) that sounds just like what a454corvette is talking about. Here are a couple of excerpts...

"To save weight and material cost, many full-frame cars utilized "C" channels (three sided members) instead of boxed channels (four-sided members.) But for maximum resistance to deflection, torsional rigidity, durability, and the like, there was no substitute for the fully boxed chassis sections utilized with the Corvette."

"Those same boxed side rails that imparted so much strength to the chassis had an inherent shortcoming. They contain various openings necessary for the production process and for components to mount to. Water, dirt, road salt, and other contaminants easily entered ijnto the rails through these openings."

"...rear corners of both side rails have drain holes..."

"...drain holes functioned as they were intended to, but only fro a time..."

"...debris inside the rails effectively close(s) off the drains..."

"With no place for the dirty and sometimes salty water to go, it remained inside the rail and, over time, induced or at least accelerated corrosion."

Time for me to check those drain holes :eek:

markyerger, the articles talk a little bit about repairing the frame. If you want them, just email me and I'll send them to you.

Paul Borowski

We are fortunate too many frames are available for our cars, even new ones that some vendor is reproducing. Yeah, $3995 and up, but at least they are there. :yesnod: :steering:

Blues77

jerryp, Could you send those articles my way as well? I have some rot spots to weld up.

All - Why dont vendors make aluminum frames? Has anyone done that?

a454corvette

Many autobody suppliers make rust inhibitors that will slow down the spread by sealing off oxygen/moisture. 3M version is a waxlike sustance sprayed with a flexible wand about 3-4 feet long that coats the inside of inaccessible rails. Commonly used on new cars (that black you see on your new truck's frame), and in my industry to prevent corrosion where frame rails have been sectioned.

mrvette

ONe of the best things you can do it when it's on a lift....or far enough in the air, is take a fit-up of brake line on to your air jet...compressor needed, and blow out all the frame holes untill the dust/dirt/crap is blown out.....in Florida that means SAND also.....
I drive my car on the beach sometimes too...and blow it out periodically....
keep the drain holes clean, IF you see an accumulation you need worry about...blow it out also and drill a drain hole in the spot so as not have it again.....

GENE

mengbar

Hi Mystery:

I've used quiet a bit of powder coating in nasty enviroment applications. My problem with powder coating a boxed frame is....how do I visually inspect it without doing a cross-sectional cut? You could use a fiber scope and inspect through the drain holes but.....where could I rent that?

Don't take me wrong, I'm a bonified powder coating kinda guy. Doing a whole frame would be expensive, and I'm not sure you would be gaining a lot of mental security. I think I would prefer to dip that frame in ioniziation tank, give it one hell of a nice paint job in epoxy, and pump a gallon of break fluid through the drain hole periodically.

Good Day... :D

blue72lt4sc

i had nothing but just a bit of surface rust on my 72....the plan is to have it blasted, dipped, weld all seams in the frame instead of leaving the factory spot welds as they were (increases frame strength) powder coat and then eastwood sells a wand that will allow me to spray some kind of sealer in side the frame rails.....then i will fill parts of the frame with high density-high expansion foam (mostly for frame strength)......this will insure that i wont have to worry about the frame again. cost....$600 for all...powder coating and the dipping cost me only $340, i bought a sears 10gal sand blaster setup for $60 and a couple of bucks for sand...then the welding cost me $50, and the wand foam and sealer cost about another $100-150.... :chevy

75 BBC Stingray

I like all those ideas, but the foam still concerns me. I would be worried that moisture would condense on the inside surface of the metal and get trapped by the foam up against it.... Maybe I'm just being a worry-wart, and probably the coating on the inside of the frame would be more than adequate, but if for some reason it wasn't... How do you get the foam out to work on the frame?!?!?! Can it be heated w/ a torch and melted out?

MassVette

We used to use an inorganic zinc paint in the maritime industry to coat the inside of salt water ballast tanks with. Worked GREAT!
:yesnod: :yesnod:
P.S.
I wouldn't fill a frame with foam....too many condensate problems, and it'll only accelerate corrosion.

carl a

i por -15 the exterior of the frame on my 73- then took it to z-bart and they did the inside of the frame( only because z-bart wouldnt spray por -15 thru there spray wand)- i did this before starting the restoration http://www.geocities.com/carlclub2