MGB & GT Forum

Almost warm enough to start working on the 'bgt.

I ignored the body last year rather working on the suspension, etc. I have rolled the roto back into the garage for some final welding on the body, some mods and a bit of bodywork. Then re assembly.

A couple years back I had the body cleaned and then I sprayed it with a 2 part epoxy.

Did a bit of searching on the i'net and there doesn't seem to be any consensus of having to rough up the area with 80 grit sandpaper before I apply or just leave it.. I am inclined to leave it since I gather the body filler will adhere to the epoxy quite well without the mechanical advantage of what the sandpaper will do.

Thoughts ?

I'd sand it.

Rough it up or remove all ?

I’d sand it as well but assuming the sheet metal is sound and smooth I think 80 grit is too aggressive. If not careful, you’ll expose the metal substrate again defeating the purpose of the epoxy and you may miss some sanding scratches in later steps.

Try using lighter grits in less noticeable areas until you’re comfortable with the resulting tooth.

Thanks !

180 on a DA sander, and a red scotch bright pad by hand.
Sand it just enough for adhesion, not shaping or leveling.
Some people would go with a finer grit.

Perfect.

I will epoxy coat my MGB this summer and have been told that if the epoxy primer is less than seven days no need to sand but if more than that then sanding is essential.

I was told that for painting. Hoping my paint guy doesn't retire before I can get the body ready fir him.?

I can’t believe all the wrong advice! DO NOT SAND THE EPOXY PRIMER. You can skim coat with body mud over the whole thing with the primer and then do your block sanding. Don’t remove the primer if you can avoid it. If you sand through during the blocking that’s ok as long as you recoat those spots. Epoxy primer is amazing stuff. After you have the body straight, apply at least 4 coats of high build primer and do your final long boarding and finessing.

I have no way of knowing what product was sprayed and what its engineers suggest.

I would read the material data sheet for your epoxy and see what it says about topcoating.

Here is a sample from an epoxy primer sold by Summit racing.




Pete

Everything depends on who's epoxy you use. Southern Polyurethanes INC. (SPI) is the best on the market for epoxies, 2K, Clear coats. Established in 1998, Southern Polyurethanes is a two-generation family-owned premium coatings manufacturer. Their Universal Clear has been featured on many world-class restorations include Pebble Beach Concours winners.

This is their statement on how to with their epoxy:


11
Epoxy Primer
2.1 VOC

SPI Epoxy Primer is one of the finest available and great for use on any type of metal if properly
sanded and cleaned. This epoxy eliminates the need for an acid-etch primer. Use this epoxy
on bare fiberglass or SMC before applying body fillers or 2k primers for best long-term results.

Pot Life:
72-120 hours depending on humidity and temperature (stored in a sealed container, never store in
refrigerator)
Prepping the Surface:
When prepping for epoxy always sand with 80 grit DA paper for bare metal, sand with 180-320
for paint or primer. Metal must be clean of all rust, oils, and any films. Never clean metal with
lacquer thinner, acetone or reducers of any kind. Clean surface with SPI 700-1 Waterborne
Wax and Grease Remover and let sit for 45-60 minutes before applying epoxy.

Body Fillers:
On any restoration, it is always best to apply the body filler over the epoxy rather than
applying filler over bare metal for best adhesion and corrosion protection. After applying two
coats of epoxy wait overnight before applying the body filler. The epoxy does not need to be
sanded before applying the body filler for up to 7 days if it does not go outside.
If time allows, it’s always best to apply filler over the epoxy after it has set for 24-48 hours.
If you choose to do the filler work over bare metal, the epoxy can be sprayed over the sanded
body filler.
Seam sealers are typically used over epoxy. Fiberglass filled fillers or other structural products
are used before epoxy primer

Hope this helps

John

I’m not sure how you do things at your shop, but after priming with epoxy primer, the next step is to completely skim coat with filler, which gets sanded until the panel is dead flat. Then it gets high build primer and is sanded with 400 paper on long boards. At this stage s guide coat is applied and sanded with 400 until the orange peel is gone and the surface is super straight and ready for finish. I’ve never heard of going directly from primer to top coat.

Going from epoxy primer directly to top coat works well on peelers.

Ok, what’s a peeler?

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