Floor Pans- Rust prevention and Tunnel treatement, advice needed Options

[highways]

Hi all,

I'm working on my floor pans... I have them wire brushed down to bare metal. They are in overall decent shape though there is some rust around the perimeter where they meet the longitudinals. These corners seem innaccesable to all but a small wire brush (toothbrush size). Question is:

1. Should I apply POR 15 Surface Prep, then POR 15 to get in cracks, then Seam Sealer, then maybe another coat of POR 15 over Seam Sealer?

2. Or, should i just do Seam Sealer first over bare metal, partial rust areas around the perimeter? Then follow with POR 15?

Second question... the smaller 'cross tunnel'.. the one where the front seat adjustment bracket mounts, is in poor shape. Rust inside it looks bad... some of the lower edges are gone but it's still largely inaccesable to any tools or painting. I think my options are:

A. Drill some holes in top, blow it out, and spray as much paint in there as I can and call it a day.

B. Cut it out and weld in replacement. But is this part even available? And still how do you paint the bare metal inside after you've welded a new piece in?

Any advice would be appreciated.

[r_towle]

I picked up a gallon of phosphoric acid which seems to be the base of all of these rust stopper products.
It is just the acid used to clean floors and such at HD in the cleaning isle.

I sprayed it on a section that was covered in surface rust (underside of a roof on another car) and it did what I expected...it turned all the rust to dark black.

It may be a good thing to use inside the tunnel...at least as one of the first steps to stop any further rust from spreading.

My philisophy is simple, if its rusted, cut it out and replace it.
In the case of the tunnel, that has a few more challenges, but I have removed the floor underneath the tunnel and cleaned that way with some success.



Rich