Which primer first?

[ebmbiker]

Good day folks,

I'm at the stage where I'm ready to respray my 1983 911 SC.

I've got a mix of surfaces: bare metal, existing paint, body filler [bondo] and factory underseal, as in the stuff that protects the sills and is in the engine bay. I'm doing the outside, in the cabin, and the engine bay.

My local auto paint supplies shop suggests using 2k epoxy primer as the first primer. Just seeing what you guys think?

Cheers, JB

[962porsche]

over the bare metal areas you should spray a coat of epoxy primer.
in most cases with epoxy primers you can go wet on wet. this means you let the epoxy flash off for 15 to 20 minutes and then you can spray your filler / build primer.
beside to make sure you can go wet on wet with you epoxy primer before you try doing so.
the epoxy will or should do two things for you one is give better adhesion for the filler primer to bite into the other is give better metal protection than the filler primer will.
there is no need to spray everything with the epoxy it's only needed over the bare areas so you wouldn't need to buy as much of the epoxy if you only have a few areas of bare metal.
you would want to spray the epoxy on areas bigger than the size of a US quarter.

you also have the option of not using the epoxy and using a DTM filler primer.
DTM= Direct To Metal.
personally I'm not to into DTM filler primers they in most cases will not give you the best metal protection. they are made more for collision shops to speed up cycle times to get the collision repair out the door.

[mhurwitz]

JB,
962 Porsche is right on. The only thing I feel differently about is that I would spray the complete body with and epoxy primer. I feel, when used as a primer/sealer, it is good “shell” to protect the different substrates (original paint, existing paint and bondo) from “shrinking” differently. It creates a good base to start with your building primer. It would be good if you could use a wet on wet system as epoxy primer is not easy to sand. When you are blocking the building primer on your car, make sure to stop when you hit the epoxy layer. I’m sure you already know how to use a guide coat when blocking.
Good luck,
Mark

[ebmbiker]

Originally Posted by mhurwitz

JB,
962 Porsche is right on. The only thing I feel differently about is that I would spray the complete body with and epoxy primer. I feel, when used as a primer/sealer, it is good “shell” to protect the different substrates (original paint, existing paint and bondo) from “shrinking” differently. It creates a good base to start with your building primer. It would be good if you could use a wet on wet system as epoxy primer is not easy to sand. When you are blocking the building primer on your car, make sure to stop when you hit the epoxy layer. I’m sure you already know how to use a guide coat when blocking.
Good luck,
Mark

Thanks guys. mhurwitz, your advice ties in with what my local paint supplies bloke said.

[962porsche]

there really I no reason to spray epoxy over the hole car. it will not aid adhesion to things like plastic body filler or old paints and primers it will not give you the needed metal protection thru the body fillers or old paints and primers either.
if your trying to use an epoxy to help stop the filler or build primer from shrinking in then your build or filler primer and or your prep of the substrate is wrong.

[mhurwitz]

962,
From my experience, epoxy primers, when used a a sealer, seem to “attack” the different substrates less and create a great “shell” before using polyester/building primers. You don’t have to take my word for it.....although I did paint cars that were shown at Pebble Beach and 1 (a Scarab) that ended up in the Collier Museum in Naples. 😁

[962porsche]

yup us too have built many high quality show cars that have been to many high profile shows that have won and placed very well.
I was also a factory paint tech rep and work for Porsche AG as one of the coating department heads for years. all this is big **** and who cars.

the fact that a sealer will still shrink simply means you need to no rely on the sprayable products and worry about making the substrate right. if not nothing will or could shrink in.

[mhurwitz]

I guess the bottom line is .....it best just to work with the original paint. If the car has been repainted at least get rid of the repaint cuz you never know what they used.

[mhurwitz]

962,
You obviously know what you’re talking about. You still at it or retired?

[962porsche]

I closed the big shop some years ago still own the building and all the equipment is as it was when I was operating the business everything was bought and paid for a 1000 times over.
for about a year I didn't do much woke up late had coffee on our porch and screwed around restoring our old victorian farm house. this got old and we own a small 5000 SQ FT building as my wife and I both race and we do about 50 to 60 events a season to keep myself busy I do some work for customers out of this shop and do lots of race car builds and fabrication work.
I come and go as I please and if the customer is in a big rush I just pass on the job. most days I will come to the shop and work 3 to 4 hours or so and play around with our cars getting them ready to go to the tracks.

I know what your saying about giving the car a good base to put a primer over and to a point your correct!
how ever the difference is what type of primer your using over the top of the epoxy.
if your using a primer surfacer AKA none high build then spraying a sealer coat is more than fine to do and at times needed.
if your opting for a high build or ultra high build then coating the hole car with epoxy really is not a needed thing.
this comes down to also just what your substrate is like and what products it's comprised of.
please don't get me wrong I'm not saying it's the wrong thing to do.
but often it's not needed and your spending money on more product then you would need to.