Rust treatment

W

wilkinson92

Member
So

My 3500S has accumilated some surface rust on the outer sills and various other places. The underseal is also coming away in places and in terrified of it getting muxh worse!

My question is, whats the best method of tackling surface rust? I read somewhere that using a wire brush can sometimes make it worse in the long term, so im not really sure what to do. Ive also read on this very forum that things like hammerite arent the best option for rust treatmrnt, so what is recommended?

Thanks
 
Hi
Apart from sand blasting it off, scrap off underseal till you get to clean paint/metal.
A selection of good quality wire brushes for an electric drill does do a good job/ always try to remove as much rust as poss.
As for rust paint, i have used Bonda primer red oxide type paint with zinc for many years on all my restos.
Can get it on Ebay from superpaintexpress.
Cheers,
Clive.
 
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Poly carbide "strip and clean" discs are great and gentle to the parent metal. You can get them for grinders or drills, and there's no chance of wire brush arrows flying at you as they wear!
Jim
 
Firstly get rid of underseal. It will eventually lift and it will trap water and salt eventually regardless of how careful you are. There really is no reason it use it in 2016 as there are loads of better options; this stuff belongs in the 1950s. Hammerite will chip. The modern, environmentally friendly formulation is even worse than before. As rockdemon say, epoxy mastic 121 is brilliant stuff. It sticks like anyones business and it an utter bugger to remove afterwards (do mask/cover the floor carefully!). If you don't believe me try it, let it cure and then attack it with a wire brush and see how much of a fight it puts up. You can get a really good-looking finish if you brush it on to ensure you get completely coverage and then go over it with a foam roller to even it out. I use grey and then black for two coats and I can see everything is covered or if it gets damaged. You might want to give a light covering of black stonechip because epoxy breaksdown on the surface with UV exposure and goes "milky/powdery"

I do the following for my rust treatments. Takes a good weekend to do.

1. Clean everything up and that includes complete degreasing of any accessible surfaces
2. Coat everything with FE-123 rust converter from rust.co.uk - you can pump this inside sills/box sections too.
3. Paint everything with mastic 121 or equivalent (chemically they are all pretty much the same - often you can get it from a swimming pool supplier, it's what they paint the floor with)
4. Dinitrol ML products (couple of options probably MF3125) - this is the liquid stuff that creeps into seams. Spray on surfaces and inside sill/box sections.
5. Dinitrol heavier wax probably to 1000.

Not rust treatment however good is maintenance free. You need to clean and inspect annually and reapply it in some areas. You will likely need to remove trim and maybe drill an extra hole or two for access.

The P6 is probably one of the easiest cars to do a really good good on by removing the the wings and the cover sills - the inner sill structure is simple and a couple access holes drilled from the inside will do the job. The only truly awkward spot is the d-pillar Don't forget the "A" pillars.
 
^^^ WHS ^^^

If you're only patching up and don't have the time for a full underseal removal, find an area of rust, remove the underseal around it so you have at least 25mm of good steel. Wire brush the rusty bit until as much of the rust possible is gone, you shouldn't be able to see any left. Paint some of the FE123 onto the rusty bit and let it cure - it will go black. Don't paint it onto good steel as it won't do anything and it isn't a brilliant primer. When fully cured apply the 121 mastic (It's a paint really, not a mastic).

I painted Sparky with black onto the vulnerable areas, then coated the whole underside with a coat of cream 121, then another black.
 
Ok one last question....

What's the best way of removing the old under seal? Presumably a scraper or some other tool but I'm open to Suggestions :)
 
The tool for removing paint from windows which uses a stanley knife blade sideways for large, flat areas. sharpened screwdriver or chisel for smaller areas. Lots of white spirit to remove the residue.
 
PeterZRH said:
The tool for removing paint from windows which uses a stanley knife blade sideways for large, flat areas. sharpened screwdriver or chisel for smaller areas. Lots of white spirit to remove the residue.
Click to expand...
You left out the big barrel of elbow grease......
 
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