Rust inhibitors or just epoxy primer?

[Bez]

Posted in the paint section, but not as much action so sorry for the double post...

Restoring a '71E targa that is 95% rust free...only significant rust in the front suspension pan that will be replaced entirely.

I'm doing a bare metal repaint, that is, bare metal on all outside panels, door jams, etc. (will prime & paint over orginal factory finish on undersides of hoods, lids, etc.). Also, undercarriage & wheel wells are in good shape, so I'm not planning on stripping these down. I succumbed to peer pressure from this board and stripped the tar material from the interior floor boards, so this will need to be refinished.

Here's my question...

There are a few areas of surface rust on the floor boards, windshield frame, targa bar and various spots underneath the car (where the undercoating has cracked).

Should I use POR-15 / Zero-Rust or other product on all these spots and then cover in epoxy primer OR should I just clean out as much of the rust spots and just epoxy prime?

I've done some searching on this board and 101autobody and have heard both options put forward, though the most recent threads suggest that catalyzed epoxy primers are maybe more effective than these rust inhibitors in the long term.

Appreciate thoughts on this.

[LakeCleElum]

Bez: I've painted 9 cars/trucks over the years and in the process of painting my Toyota P/U right now.......A little off subject, but if I can relay an experience I had, it could save you a lot of grief.

Years ago, I took my 912 down to bare metal and used a special "epoxy primer. I failed to follow the instructions and put on paint right away. My reason was to continue to smooth out some panels.

After it was all done, I could take my fingernail and scrap paint off the car.......Since I had not put the paint on the primer within "X" number of hours, it failed to adhere.

So, I would say, use the epoxy primer and then follow up with the paint right away....Good luck....

[calling911]

Originally Posted by LakeCleElum

Bez: I've painted 9 cars/trucks over the years and in the process of painting my Toyota P/U right now.......A little off subject, but if I can relay an experience I had, it could save you a lot of grief.

Years ago, I took my 912 down to bare metal and used a special "epoxy primer. I failed to follow the instructions and put on paint right away. My reason was to continue to smooth out some panels.

After it was all done, I could take my fingernail and scrap paint off the car.......Since I had not put the paint on the primer within "X" number of hours, it failed to adhere.

So, I would say, use the epoxy primer and then follow up with the paint right away....Good luck....

I would like to say.... from experience.. I would never ever paint over epoxy primer. I would always prime the epoxy primer with a build primer, block sand it and then paint.

Im just sayin this from experience..

[calling911]

Originally Posted by Bez

Posted in the paint section, but not as much action so sorry for the double post...

Restoring a '71E targa that is 95% rust free...only significant rust in the front suspension pan that will be replaced entirely.

I'm doing a bare metal repaint, that is, bare metal on all outside panels, door jams, etc. (will prime & paint over orginal factory finish on undersides of hoods, lids, etc.). Also, undercarriage & wheel wells are in good shape, so I'm not planning on stripping these down. I succumbed to peer pressure from this board and stripped the tar material from the interior floor boards, so this will need to be refinished.

Here's my question...

There are a few areas of surface rust on the floor boards, windshield frame, targa bar and various spots underneath the car (where the undercoating has cracked).

Should I use POR-15 / Zero-Rust or other product on all these spots and then cover in epoxy primer OR should I just clean out as much of the rust spots and just epoxy prime?

I've done some searching on this board and 101autobody and have heard both options put forward, though the most recent threads suggest that catalyzed epoxy primers are maybe more effective than these rust inhibitors in the long term.

Appreciate thoughts on this.

I would use acid on that rust until its gone and then prime it. I never leave rust.

[GaryR]

Originally Posted by calling911

I would like to say.... from experience.. I would never ever paint over epoxy primer. I would always prime the epoxy primer with a build primer, block sand it and then paint.

Im just sayin this from experience..

Absolutely! And follow directions on the Epoxy for drying/respray times..

[Bez]

Originally Posted by GaryR

Absolutely! And follow directions on the Epoxy for drying/respray times..

Yep, my painter is recommending epoxy then body filler, prime and top coat (same as the Hernandez 101 sticky in paint forum). My question is if I should use POR15 or Zero Rust on interior floorboards, undercarriage spots, etc. as an 'extra' layer of protection beneath the epoxy primer?

I will definitely be removing as much rust as I can see anyway. I want all the rust protection I can get, but don't want to have adhesion issues between the rust inhibitors and epoxy primer. Thanks!

[Porsche-O-Phile]

If you look on POR-15's web site they recommend removing as much of the rust as you can and prepping the surface with Metal Ready (I think it's really just Phosphoric Acid or some derivative thereof). Then apply the POR-15, then use their primer on top of that (it will bond to the POR-15). Then you should be able to paint whatever you want on top of it.

[Scott R]

POR is a great product, I restored a 72' Land Cruiser with my brother about five years ago, all of the repaired floor sections were painted with POR, as well as the entire frame and axles and such. Not a spot of rust has surfaced since then. We painted bed liner over a lot of it, and paint over other sections, no issues at all.

Just try to not get any on your hands...

[rw7810]

While I have used POR15, it is a great product, but I wouldn't use it on a Porsche. There are more elegant solutions to your needs. Certainly an epoxy primer is in line. I would use PickleX for treat the surface rust. See here details and procedures.. http://www.autobodystore.com/forum/index.php.