Frame Rust Treatment

[Iamscotticus]

Hello,

Im sure this has been covered ad nauseam.

 

I have neglected my 1996, storing it in less than ideal conditions, in sheds on concrete slabs, but in humid environments.

 

As expected, much of the Powder Coat (PC) is not good. I have to do something to stop the spread, especially internally so 1246 can live on.

 

At this time, I not a fan of PC. Partly because I would rather be able to spot repair a painted surface for chips, damage, alterations, etc.

Painting is the easy decision.

Black or grey is the hard paint decision...

 

What I have to decide is how to treat the frame inner surfaces? I have read glowing reports for products like WoolWax, Dinitrol, AFC50, Rust Encapsulator, Chassis-In-One, Cosmoline RP-342, and good old farm equipment MARC Rust Away. Too many to list all of them.

 

I need to choose a treatment that will flow to all points, work on existing internal rust regardless the severity, without any prep, prevents future corrosion and is paint safe or paintable, if necessary.

 

Which is another point, to treat internals before or after external painting? If I paint the exterior first, then I can use almost anything internally. If I use a paintable treatment inside first, if it doesn't interfere with painting, it may not be the most effective treatment. If I use a waxy treatment inside first, It may be the most effective treatment,

but seepage may interfere with exterior painting...Therefore, is painting the exterior first then treating interior with a waxy creeping coating the way?

 

I need to get some opinions. Arch is a hop across the Atlantic so Im doing this project myself. I can build a chassis rotisserie for the project. Rub the frame with spices and bake it. Lemon herb....mmmmm

[SLR No.77]

You've mentioned a rotisserie so are your intending to strip the chassis completely, back to tubes and panels?

Stu.

[Iamscotticus]

I am seriously considering it.  I must do all I can to preserve the frame. Thankfully, other than a bent lower basket stay, all is in good order.

Engine is coming out for a refresh and a T9, fuel tank for clean out, axle for paint and possibly a LSD and Rakeway kit, if they make more.  Very busy, shaping up the frame seems logical.

No frame, no car.

[SLR No.77]

I've not come across a rotisserie being used for a Caterham. I have one for my Mini but when a Caterham is stripped it's pretty easy for two people to simply turn a whole bare chassis over. When I refreshed my Caterham though a pair of mobile axle stands did prove very useful.

To treat rust on the chassis it's better to use an acetic acid based rust remover rather than a rust converter, then when the rust is fully removed cover initially with a high zinc content primer then finish with a suitable chassis paint such as Eastwood Chassis Black or POR15 (POR15 is also good for spot repairs).

The biggest problem is any areas where there's corrosion between the aluminium skin and the chassis tubes, ideally these need separating to treat both but that's not always practical.

When done treat the inside of the tubes with a suitable wax, Dinitrol etc, and also treat as much as you can where the skin is pressed against the tubing, eg. the outside lower chassis rails can have wax forced into the gap from above. I treated the inside of the tubes by trimming a rivet to fit the end of my wax sprayer, then removing rivets to spray the wax inside ... I managed to force around 3 litres inside the tubing which now makes a break for freedom on really hot days!

Stu.

[Iamscotticus]

Yes a set of wooden stands would work.

 

I read the details of many wasy rust inhibitors that prevent further rust, but they don't claim to convert surface rust like an oxidation (rust is oxidation). whatever it does, it turns rust black and claims to stop the process like these:

Corroseal

Permatex 81849-12PK

Evapo rust

FDC Rust Converter Ultra

https://www.carbibles.com/best-rust-converter/

[SLR No.77]

I've used both rust converters and removers (such as Bilt Hamber Deox Gel), my experience is that rust converters only hold the rust back for a limited time before it's spread enough to be evident again on the surface. An advantage of the remover is that zinc rich primer can then be applied directly over bare metal rather than to the converted rust, this seems to be the key to holding back future rust.

Stu.

[Iamscotticus]

I think something has been lost here, The exterior isn't the issue, I want suggestions what to use inside the frame tubes to stop and prevent rust. Many products claim to prevent future rust, but they don't claim to stop the present rust. No assumptions here. So far, by reading labels and claims , it appears that only a phosphoric acid solution converts rust to a different element and stops the progression. My current thinking is to first do a phosphoric acid wash internally, dry, repeat, dry, prep and paint exterior with a zinc primer and a top coat of POR15, then apply an internal waxy preventative like Waxoyl or Cosmoline. That seems like a lot of trouble but my 7 is probably the only one I will ever have.

[SLR No.77]

I think you might be overplaying the level of rust that will exist on the inside of the chassis tubes and the effect it will have. Theoretically there could be a mass of surface rust eating away 24/7, in practice this doesn't really happen. Much of the inside of the tubing will still have the oily finish that exists on raw steel tubing (I haven't a clue what it actually is or is called) and other than the braised/welded joints this can hold back rust quite well. A phosphoric clean might not help.
A much bigger concern is that holes have been drilled in the chassis for the insertion of aluminium rivets to retain non-protected aluminium panels, plus the rivets used are not a sealed head type so the tubes can effectively "breath" through the rivets heads, moisture in, moisture out. Each hole is likely to rust quicker than the inside of the tube itself. Short of a full strip down of the chassis and a rebuild using methods more akin to the aerospace industry, there's not much you can do other than treat the tubes inside with a rust inhibitor such as Dinitrol and keep on top of any subsequent rust spots caused by damage to the outside.

Stu.

[Iamscotticus]

Thanks, Stu and I hope you're right. A few things I haven't said yet. The car has sat for the last 10 years. Of those, about 4 years in a shed about 100 yards from water, relocated temporarily for a hurricane, stored again a few more miles inland but still endured another hurricane and the flood of the century, three floods that came close to the car but didn't. This car is very lucky to mot be destroyed by now. I have just barely managed to keep it above water wherever I've kept it. I live in a very humid and stormy place, Houston Texas. This is a horrible city to own a 7. I wasn't living there when I got it, I followed a job there. but I truly love the car and its staying.

[timb2117]

Totally understand Stu's comments and totally understand yours having lived in tropics too. For my "opinion" I'd say you aren't far wrong, presumably the oily internal does suffer a tad around welds and as mentioned electrolytic oxidization is a pest when two dissimilar charged surfaces come together.

If it were me, strip, clean external and internal as much as can be reached. Nylon flapwheel in angle grinder the outside replace if holed through, phospohorus treat anything left, internal too if you can. I do love hammercoat heavy thick coat paints but it will chip in stone spray areas, and it will spoil tight tolerances. Then wash through with well warmed and thinned waxoyl, turn over and do again.

Just my take 'aint no expert. Oh and bravo for realizing the value and importance of the car and taking these steps, they're to be cherished, even throughout natures worst....

 

[TomB]

If your willing, you can undrill the many rivets holding the inside panels and rear bulkhead, then clean with flapwheel all the grotty rust and powder coat and paint which which ever rust treatment looks best. You could then take the engine / box out and do the same in the engine bay, but that less incessible than the frame behind the interior panels. 

By removing the internal side panels you can access the infamous ‘grot’ trap, which is the area where moisture, grit, inaccessibility and bimetallic corrosion all combine to be the main corrosion spot on a Caterham chassis. 

[Wrightpayne]

Perhaps get some pictures of key chassis parts and ally/chassis interfaces when you are with the car next. Post up here and we'll give you a view on its condition and suggested next steps.

Ian

[Iamscotticus]

 Apologies for the upload orientations.

[Wrightpayne]

I dont think that looks too bad at all. Few bits of localised rust to treat. I'd be inclined to remove the inner panels and treat any rust then wax incl squirting in the rivet holes. Pay attention to getting between the ally and steel wherever possible. Hot day and wax aerosol in hot water to make it as runny as possible.
 

Ian