Hi,

Im looking to do some experiments on w123 underbody metal. Im looking to apply a bunch of different rust treatment methods to the metal pieces, but I do not desire to do this to my car, as I am afraid of solvent action damaging the OE thick white/black rubber coating.

Could someone cut me some squares from a rocker panel or similar that has a good coating of the rubber bonded to it? Ill do the rust control tests on bare steel and the chemical compatibility tests on those "coupons" and then report back. I could probably get away with a square foot of it, and I can cut it into small sections...

Thanks!

__________________
Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (113k)
1991 350SD (206k)
1991 300D (228k)
1993 300SD (291k)
1993 300D 2.5T (338k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (265k)

Past Diesels:
1983 300D (228K)
1985 300D (233K)

I'll tell you the absolute BEST you can do...

1/ clean everything back to bare metal.

2/ spray it with drinking water.

3/ leave to rust for 7 days.

4/ paint LIBERALLY with 30% phosphoric acid, which converts the rust to black iron.

5/ paint with 2 pot epoxy marine steel yacht primer.

6/ build up paint thickness with more of #5

7/ build a thick and soft covering of a good underbody treatment like waxoyl.

provided it doesn't get perforated by stones etc, it will rust out from the inside first.

steel treated this way will last 20 years at the high tide line.

waxoyl is better than krown?

__________________
Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (113k)
1991 350SD (206k)
1991 300D (228k)
1993 300SD (291k)
1993 300D 2.5T (338k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (265k)

Past Diesels:
1983 300D (228K)
1985 300D (233K)

Slight correction,
The phosphoric acid converts the rust to iron phosphate, a rut inhibitor & then you put a protective coating on it. A mix of 50/50 ortho phosphoric acid and glacial acidic acid works much better. Be careful with it, it is that reactive that it would get the devil out of hell !! Most commercial rust treatments work this way. It is critical to properly degrease the metal before you start.

__________________
Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving

Clean off all loose rust scale and paint it with POR. Steel painted with POR can not rust so long as the POR is not damaged. Can not be used in places where sun light will get at it as UV will damage it. It can be eroded by sand and gravel grit from the road, but it is really great stuff for the bottom side. It is "anhydrous" and it takes water to cure it.

__________________
Junqueyardjim
Christianity, if false, is of no importance, and if true, of infinite importance. The only thing it cannot be is moderately important. C.S. Lewis



1983 Mercedes W123 240D 4 Speed 285,000 on the road with a 617 turbo, beautiful butter yellow, license plate # 83 240D INDIANA

2003 Jaguar Type X, AWD. beautiful, good mileage,
Mom's car, but I won't let her drive it!

no idea, don't think we can get krown here....

slightly OT...

here I *used* to be able to buy proper red lead, you know, the gallon tin had a metal strap, cos anything weaker and it would break.

this new environmentally friendly "red lead" paint is purest ****e by comparison.

the only "good" waxoyl is the black stuff you have to paint on because it contains something like 5% bitumen.

Ok, should have been a bit more clear. Both my cars have ZERO rust. I just want to be proactive (though my cars don't see salt), and protective coatings in certain spots is key. Problem is making sure all materials are compatible, and given that the rust treatments have solvents, I want to be sure I don't damage the oe coatings...

__________________
Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (113k)
1991 350SD (206k)
1991 300D (228k)
1993 300SD (291k)
1993 300D 2.5T (338k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (265k)

Past Diesels:
1983 300D (228K)
1985 300D (233K)

por has no solvent that can dissolve once cured. it is impenetrable.
and it is NOT a problem to use it in sun exposure areas, it will protect just as well, but it does not retain it's shine in uv exposure.

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

I'm not using por, have no reason.

I'm looking at krown, Eastwood anti-rust, amsoil metal protector and similar products... Proactive products to use on rust free cars to prevent rust from ever forming... I use this kind of stuff on my cars routinely, but not on my w123s which have that nice thick undercoat.

This is only for proactive protection, and I want to make sure the undercoat will not be damaged by its use.

__________________
Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (113k)
1991 350SD (206k)
1991 300D (228k)
1993 300SD (291k)
1993 300D 2.5T (338k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (265k)

Past Diesels:
1983 300D (228K)
1985 300D (233K)