To patch or not to patch?

[dhanna]

'ALAS! Poor Yorick' and all that
HI EVERYBODY! (I do an amazing Dr. Nick impression)

So I went into complete beast mode last night and finished removal of:
-Rear windshield
-Wiring (all of it in one piece!)
-Dash (all of it no damage)

I now have a bare shell ready to go into paint and body! I'm so EXCITE! (not a typo)

Here's a full album of the resto to date:
https://goo.gl/photos/9Da5k7VLZdq55kNMA

Buhuhuhuhuhuhuhut I have now to decide about a small rust patch I mean like the only major rust I've been able to find on the car see pics below at end of post. even the surface rust in the front of the trunk. The only worse spot of Rust is the spare tire area.

Near as I can tell there is only some bad pitting and NO RUST THROUGH but pitting none the less. Is this a major structural concern?

DO I:
-Cut and patch?
-Clean and fill with Lead (Pb)?
-Just clean and prime?

Lastly is the water that pooled here in this corner indicative of trouble elsewhere?
How do I follow the rust to a leak source / path?
Is this a commonly understood trouble spot on the E9?

I want to dip and coat the car rather than sand blast and then do the metal work and prime by end of Q1 FY 2017
There was a place in Santa Ana, CA called Strip Clean Co but IDK if they're still in business. (not picking up the phone this week for some reason)
Their reputation was pretty good as they were one of the few places that put the bare chassis in a protective phosphate coat of some kind to keep it from rusting for several months after. I had gotten a quote from them years ago for a mustang project (I still have that project)

Your advice is greatly appreciate (not a typo)

Angle grinder with a scouring pad / disc worked a treat...

 

[HB Chris]

You've made fantastic progress, congrats. BTW, that is an e3 A/C panel, they don't fit well in an e9, different side contour and radio sits much lower. I'm not a big advocate of Por15 but it would work well on your rear floor, it needs a bit of rust to adhere.

 

[eriknetherlands]

Wow, your link shows quite some serious tear down. Nice to see you have the place and tools for it.

For what you show I would grind off the top layer with a flap disc. It will remove 90% of all rust. What you then have left is rust in pits that are too deep. Go chemical there. treat it with a rust converter to attack that as well. If you don't treat it it will come right back from those pits upward; taking just 3-6 months for the first bubbles to appear.

Mind you the rust in my coupe was worse under the seat reinforcement 'hump' then next to this bump. I expect it to be worse under your seat reinforcement then the surfaces on your pics. In order to check, shine a light through the 2 large holes at the front of the 'hump' and check for notorious brown colour.
Also the seams where the hump connects to the floor and where the floor connects to the sill are usually worse then just the flat, visible bits.

If you don't want to take all of that apart, which indeed means years instead of months work, treat these seams with something that is very viscous like fluid film or a thin wax. Being on the EU side of the pond I have no POR15 experience.
Erik