Subframe reinforcement finishing coats, opinions needed.

[bavarian3]

Context: Purchased my car with "subframe reinforcement done"...meaning only plates of course. I'm doing a full rear-end overhaul with topside reinforcement. I have everthing removed at the moment, turns out whatever the previous owner finished the plates with wasn't sufficient and there's some surface rust on the plates that crept under the factory undercoating.

My question: what does everyone recommend for coating these correctly after I clean em' up.

I see different methods but narrowed it down to two. In order of application from bare metal...

option 1 - rust paint(por15 or other) -> undercoating -> spray top coat/color
option 2 - etch primer -> high build primer -> seam sealer -> undercoating
option 3 - seam sealer -> etch primer -> sem ez coat

concerns:
-rust paint supposedly doesn't do well on smooth surfaces. worried about it as a first coat flaking off.
-durable primers like 2k's have nasty shit in em'. I can't move the car and don't have proper ventilation of a pro shop.
-using seam sealer on bare metal no good as it traps moisture?

we overthink things perhaps, but nothing worse than doing a job like this to find out a better way after...

[bmwfnatic]

Etch primer is sort of antiquated at this point, and lots of things will have trouble sticking to it.

I would clean everything up properly with clean and strip discs and wire wheels, then go a bit further than the previous owner did and rough up the surface around the bare metal that is still original e-coat / seam sealer.

Then spray the aforementioned area with a good few coats of 2k epoxy primer, opposed to etch primer, epoxy sticks to pretty much about anything, to avoid breathing in nasty shit get a painting respirator, they’re not that expensive.

Then afterwards you can apply a spray on seam sealer if you desire so, make sure to rough up the epoxy primer a bit for optimal adhesion.

[Cubieman]

For the Vincebar I used a few coats of rustoleum after scuffing the bar/gusset cups, installed everything, protected the interiors even more so than during installation added seam sealer and shot it with POR-15 Silver which eneded up looking damn close to factory paint.

I too was worried about rust so any portion that was not epoxied was painted.
I sure hope the seam sealer doesn't trap moisture enough to cause rust, I suppose you would really never know until it got really bad.

[D-O]

I put on Por-15, followed by brushable seam sealer, and finished up with SEM EzCoat.

[nahvkolaj]

When I did mine (Vinceskins and Vincebar + gusset cups, all epoxy/rivet products):
- cover stuff you don't want paint on with tape/plastic
- Clean
- scuff
- 3M seam sealer on all seams and every rivet
- clean
- 2k epoxy primer
- light sand
- clean
- Rustoleum enamel top coat (interior/topside)
- Rustoleum undercoat (exterior/bottom side)

My car was up on Quick Jacks so I set up a box fan to exhaust air out of the garage. I set it in the trunk opening for interior painting and under the rear bumper for exterior painting. Yes it got some paint of it but it's a $20 fan. I wore a 3M respirator for the spray painting.