Since I bought my car I thought the boot (trunk) floor needed a few touch-ups with a grinder and MIG welder but I figured I could just spot-repair them and then spray some Bully Liner over the top to seal it all.
Then I ran over the whole panel with a grinder fitted with a wire cup, and I saw how badly corroded it actually was.
I mucked in yesterday (Sunday) and chopped the boot floor out, which I will run through below. While it seems simple there are a few tricks to making it easier.
I tried to cut out as little as possible, taking note of challenging areas like the rounded or sloped sections. I also had to avoid cutting through the two rubber body mounts, and not cutting the two supports sitting under the 2 flat sections in the middle of the floor. I used masking tape to set straight lines, which were easy to follow with a 6in grinder using a thin cut-off wheel. It took 2 cut-off wheels to do the entire trunk, working slowly and carefully.
After I cut around the outside I tried to drill out the 20 (approximately) spot welds that hold the centre of the trunk floor to the fuel tank supports under the middle of the trunk. Blunt drill bits killed that idea quickly, so I cut around the supports as the new floor was going to be made in 3 pieces as a way of making it stronger and easier to fit.
It took approximately 30 minutes to get here. It will take a lot longer to fix this up!
It is a bit difficult to see, but the insides of the fuel tank mount are filled with dirt and rust scale. This will clean up easily, but if I had left it there is no double these parts would have rusted, which is concerning given the fuel tank mounts here!
The consensus was made to get the new fuel tank mounted before we weld the floor in, as it will be far, far easier to do this without a trunk floor in the way.
After giving the fuel tank supports a quick wire-wheel I hit them with some Anti-Ox rust converter to get rid of the scale and surface rust.
The replacement floor was made in three sections, Tek-screwed to the remaining metal to test-fit while a door in the floor allows me to pull the fuel pump from the car without dropping the whole tank out, just in case the pump fails.
The boot floor was welded in but I am not happy with the job done, particularly as the seam sealer is very sloppily applied. It will do for the time-being as carpet will be going over the top of this area.