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MG MGB Technical - Underbody Treatment

I am rebuilding a '72 Roadster, and have replaced numerous panels (many more than originally intended - of course ! )floors, sills, boot-floor etc. I am now wondering what the best primer/paint/underseal combination would be to use - any thoughts?? Main priority is corrosion-resistance, never going to be concours!
Adrian

A couple of recent threads on the matter:

http://www2.mgcars.org.uk/cgi-bin/gen5?runprog=mgbbs&access=&mode=archiveth&subject=71&subjectar=71&thread=2003101818143226592

http://www2.mgcars.org.uk/cgi-bin/gen5?runprog=mgbbs&access=20930895007008&mode=archiveth&subject=71&subjectar=71&thread=2003102514502314643

Which bit of the Midlands are you from?

hth,
--
Olly
Oliver Stephenson

Yo Adrian,

Sorry I just had to do that.

Anyhow what an experienced body-prep individual told me to do and I did was to use roofing wet/dry plastic cement. Yes the same stuff roofers use to patch up areas on your roof.

The wet/dry type is at a consistency where you can virtually brush it on, may take some heating of the can though.

After the product hardens (several months) you can even paint it.

In a nutshell, it is inexpensive and appears to be more effective than a spray type rocker guard available at most auto product retailers.

I am currently restoring another LBC and will use same when it comes to undercoating.

For Your Info, Dino
Dino

I have considered "Snow Coat" which produces a flexible 1/16-1/8th thick completely watertight elastomeric membrane ( Ace, HD, Lowes). I used a reapply of the "undercoat" sprayon rubber on the LE after 3 wash downs with engine degeaser and a pressure washer and forced drying over 3 days. FWIW, the dealer applied ( assumed) undercoat had kept the undercarriage sans-rust, and both floor panels are perfect. The new coat looks spiffy, and for certain overkill, I'm gonna try some waxoyl squirted on via Wagner pot airless, cause I have a bunch left.Concern over chip damage and water harboring seem speculative to me. The stuff on the LE was 24 years old and absolutely impervious as of last week. After the degrease and pressure wash, almost none broke loose. Hey, just my experience boys ( before the flameon).
vem myers

Certainly standard Waxoyl in the box-sections, and Finnigans Underbody Seal on most of the underbody areas as it is tougher but resilient. Behind the wheels can get quite a bit of abrasion, though. 'Solid' underbody seals make me think of the rubberised stuff that manufacturers and dealers used to put on, which was fine for a couple of years until it started to crack and unstick with body flexing, which lets in water and salt, which accelerates corrosion. Whether things that seem to be available in the USA, something called 'bed liner' seems to be another, are available in the UK is another question. I think it depends on the usage, no winter salt driving needing lighter protection than full all year round use.
Paul Hunt

On bare metal or cleaned metal I like to use a product called POR 15 which may be available in GB. You can also do a search for 'moisture cured urethane' which it is. I use the silver primer putting on 2 coats, and then top it off with semigloss black. Then I use waxoyl on top of that for the undercarriage. In the cockpit I would use the same paint but apply a bedliner paint on the floors which, if applied correctly, will be completely waterproof and it hardens which permits it to be painted body color if you so desire.

There's also a product called 'schutz' which can also be applied providing you prime the metal first. It's a hard textured finish that can be painted and is frequently used on newer cars as it takes a lot of abuse.

I get nervous about applying rubberized undercoatings as I have seen what they can do when they harden and crack. The only place I would used that is in the wheel wells because it is very visable and you can see any cracks forming or undercoat peeling.

I also get nervous about any sound deadening mats like dynomat etc unless the edges are thoroughly sealed using silicone or other sealant. I have seen what happens to factory floors in which an asphalt based sound deadener is applied and it ain't pretty, especially in convertibles that leak. However, I plan on using the sound deadener on the verticle surfaces and on the tranny tunnel and battery cover (possibly).

If I were you I'd do some research and then you can decide what you'd like to use.
Mike MaGee

While welding up the sills, I sprayed all of the concealed surfaces with zinc rich weld-through primer from a can then shot some catalyzed epoxy based paint over each section when that stage of the welding was done. You may find that the weld through primer yields slightly dirtier welds and splatter, so you could just grind away the paint in just those areas and then paint the edges and all around as best you can once it is done. Then waxoyl the inside of the sills, and externally prime, seam seal all of the joinst, and finally top coat.

Zinc rich epoxy primer is tough stuff and the zinc acts as a rust inhibitor (sacrificial anode?) but requires ventilation because it is catalyzed. Yummmmmm Polyisocyanites. Respirator is below minimum lung protection (but people do it) while the right job is an outside fresh air supply. I always wondered if a scuba tank would work for this?? probably gum up the regulator.

I'm not done yet so I still don't know what is going on the underside.

Regards,


Brian
Brian Corrigan

Adrian-
I'm surprised that nobody has mentioned P.O.R.-15. The stuff is practically bulletproof. It's manufacturer, Restomotive Labrotories, makes everything you need, including the fillers and sealers. They even have a primer that you can shoot over it so that you can hide it with normal paint (just the thing for Purists). They have a website at http://www.por15.com/
Steve S.

POR-15 Find it on the WEB in your search engine

Cec
Cec

POR 15 is the stuff to use. It is as good as they say it is. Just don't paint anything with it that you don't want to stay painted.... itis hard/impossible to remove...
Moe

POR-15 is similar to spraying your panels with Rhinoliner. NOT the same stuff, but equally as tough ~ tough in resistance to road rash, and tough as hell to get off if you ever need/want to. But both are good protection for their intended uses.

As for protection when working around these things with welding equipment, I tend to wait for an opportunity to push the car or work outside and then use a typical box fan blowing its stream of air across the work and between the work and myself. If possible, I also position things so that the fan's stream runs with the prevailing wind to blow as much of the toxic fumes away from me and to dissipate it as quickly as possible (the neighbors, you know). I also then wear a face respirator as well, just for whatever protection it provides. However, a scuba mask with pressurized clean air would not be a bad idea.

The fumes are not just the isocyanates but also the toxic fumes from zinc rich materials as well (if you have used them) In some ways, they are even more deadly and a bit faster acting.

I found that a side benefit of using plug welds was that the exposure to heat on a body panel SEEMED to be a bit less than bead welding and less fumes appeared to be generated from panels I had treated very much as Brian did his. They can be more tedious, but then everything has its compromise. FWIW
Bob Muenchausen

Cheers guys. I will contact the usual suppliers to see if I can get some POR 15 over this side of the pond - it seems to come highly recommended!

Olly, thanks for the links - hope you've got that 'B patched up now. (I'm in Staffordshire by the way)

Thanks Again..

Adrian

I don't have a copy of their catalog handy, but I think I remember seeing POR-15 in Frost's catalog.

http://www.frost.co.uk
Derek Nicholson

I used POR 15 on the insides of my wheel arches and the underside after I replaced the floors. Good stuff although it never keeps once you open the tin. I found the finish very, very glossy and smooth so I sprayed over it with rubbery underseal stuff from a spray can. Gives a dull finish and provides a bit of sound dampening perhaps. The POR 15 doesn't need any protection though. It is very strong stuff.

Oh yeah, don't get it on yourself. It won't come off until it wears off!

Simon
Simon Jansen

This thread was discussed between 09/12/2003 and 17/12/2003

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