Rustproofing the frame (on car..)?

[4regt4]

OK, rustproofing is a strong word here, as 100% protection is difficult even with body removed.

I'm just wondering if there are some preventative measures that can be done without removing the body. Specifically, I'm talking about a 1969 Plus 2.

Waaaay back, when I was a kid working in a car dealership, it was common to undercoat new cars. There was some argument about what to use. Many customers wanted a thick tar like coating, while others argued that such coating could seal in gaps in the various seams and welds thus possibly creating a pocket for corrosion. A thin coating had a chance to flow into such gaps. Or so the theory went.

A number of years ago, I built a Lotus 7 clone. I painted the frame and rear axle assembly with POR-15. It is tough as nails, and I suspect quite good a preventing corrosion long term.

But what about painting/coating/spraying the frame on a fully assembled (i.e. body on) Plus 2? This is assuming that the frame is in reasonably good shape and not needing replacement. Perhaps a bit of surface rust here and there. I'd guess something thin that would flow would be good, and perhaps not even a paint type coating, but rather something oily that may need to be reapplied periodically. Just speculating. If I knew, I wouldn't ask!

Hans.

[mbell]

I cleaned and painted the accessible parts of my chassis with POR-15. Given how well it sticks and stays stuck I can't think of a much better solution for protecting the existing chassis.

[h20hamelan]

permatex rust converter comes in a spray. it has withstood 15 years here in a salty road environment.
I think because it is a converter, it actually bonds by chemically.
corroseal is better maybe, not as available I believe.

[USA64]

I daily drove mine for a couple of years and then, having failed inspection (emissions), it sat for 35 years. When disassembled the only chassis (subframe) rust was on the horizontal flange at the bottom of the spine; much dirt had accumulated there. The upper part of the spine still had the factory undercoat, easily removed with sub-turp.
I think the problem you would have trying to under coat it in stu would be getting the surface clean. Without a clean surface I think you would be wasting your time.

[2tmike]

I did this in the summer on my S4 just raised up on axle stands. It was a bit of a faff, using petrol, scrapers,etc to clean down the accessible parts but it was possible, resulting in a clean, dry and pretty rustfree chassis. The upward facing flanges of the chassis under the body were nicely oil covered so I left those alone. I re-coated the rest using Dinitrol 4941 from aerosol cans which was easy to do but needed lots of masking up. The finished result looked very good BUT as engine leaks applied their own covering over a few months it washed off a lot of the Dinitrol off. Very annoying !!!!!

[derek uk]

Worth a watch https://www.youtube.com/watch?v=lyWHF4NoNVk
Project Farm tests a wide range of stuff and can sort the wheat from the chaff. Most expensive often doesn't get the win.
Bar and chain oil gets the nod by some people. I guess it depends if your OCD allows the car to be oily all over the underside.

[pharriso]

I have this controlled oil leak device installed between the Y of the chassis at the front... Oil then spreads backwards coating most of the chassis ensuring that nothing rusts....

[mikealdren]

The problem with my original +2 chassis was rust at the base of the uprights on the chassis at the front to the top suspension mounts, sadly engine oil doesn't get there.

[MrBonus]

I've always cleaned up the frames on my (old) cars and sprayed them with Corrosion X. Theoretically, it should need to be reapplied regularly but since my Lotus sees such infrequent use and never in the wet/rain, one coating should last the rest of its useful life.

It's a lot easier to do than to go through the laborious and messy process of applying POR-15.

[My72Sprint]

Hey Phil,
The engine in my Elan Sprint 0183K was always "externally lubricated" as well preventing chassis rust and hard to remove chassis, engine mount bolts etc.
Very help full when removing the body from the subframe during restoration.
Tim

[Bigbaldybloke]

Unless you do a lot of journeys at speed in reverse, the front cross member and uprights are the areas to concentrate on as any engine oil leaks won’t get to these parts! Specifically inside the front towers and ensure the drain hole is clear if you have the standard Lotus chassis/subframe. Mine has been powder coated and I know that lots on here are weary of that, but I’m happy with it. There is a chain of thought that suggests the thick rubbery under seal is beneficial on the inside of the wheel arches to minimise any possible effects of stones flying up, hitting the fibreglass and causing star cracks in the paint. If I was going to do something with the body on I’d probably use Waxoyl or similar.

[4regt4]

Thanks.

I think it was the Permatex brand rust converter that my father used on some rusty metal at his (former) house on the Oregon coast - right on the beach. Interesting stuff. Seems to chemically alter the rust and add protection.

POR - 15 was the first thought that came to mind. For those who have not used it, the name stands for Paint Over Rust. You have to do a reasonably half assed job of cleaning the surface, but once loose dirt and rust are removed, it sticks very well to surface rust.

Anyway, I appreciate the comments. I'll be looking into the Corrosion X, Waxoyl and Dinitrol also.

Hans.

[USA64]

One more thought; I had excellent results from the old, fish oil based, Rustoleum (AH Sprite) when I first heated the area with a propane torch. The vapors that came off the rust, and it was a door frame, suggest that the rust is quite porous. The products work well on rust but not water, grease, solvents, etc. Make sure it is really clean and dry.

[3261R]

Don't know if it's available down there but there is a good product here in Canada - Rust Check (https://www.rustcheck.com/). My last "daily driver" went 17 years and 360K km without rust perforations. It can be done professionally - they know where to drill holes to get into all the nooks & crannies. Holes are plugged with plastic caps.
Their data base might not include vintage sportscars, but you can probably work out where you need to get inside. Spray cans of the stuff can be purchased at retail outlets and you can do the work yourself. It has great creep properties.
I can see there being problems with the outside of the backbone where it's covered with the felt sound deadening, in that area I would go with POR15.
Jon.

[Bigbaldybloke]

Surprisingly, when I replaced my chassis many years ago, the one area with no rust at all was the central chassis backbone under the sound deadening felt! The felt seemed stuck to the paint of the chassis. In contrast, the front towers and crossmember were badly corroded and were why I changed the chassis (or subframe for the pedantic!)
When replacing the chassis i coated this central section with black bitumastic paint and applied the felt to it while it was still wet.
Obviously haven’t taken it off to check but am not expecting problems.