This morning I continued to address the rust inside the cabin and, to a lesser extent, the engine bay. Yesterday I used a wirewheel to mechanically attack the rust. Today I used chemical means.
I bought a chemical rust neutralizer from Halon Marketing called Rust Away. The liquid is blue in color and can be used to soak parts, or applied onto rusty areas to convert rust. It uses tannins to convert iron oxide into iron tannate, which is black. I applied it to the footwells of both sides of the floorboards by laying on paper towels and them pouring the Rust Away on. The paper towels held the solution in contact with the rusty spots I was targeting.
The instructions recommend allowing rusty parts to soak for two hours; I allowed for three before removing the still-soaked paper towels from the floorboards. Visually the rust appeared converted.
I repeated the process on the passenger side.
Also the cracked firewall in the brake master cylinder pocket had some rust developing inside. I treated that area by laying paper towels on the engine bay side, then tucking the edges of a couple of towels down into the cracked area.
Then I soaked the paper towels and allowed the solution to work for several hours before removing the towels.
With all of the seam sealer and other adhesives removed, it will be time for one more washing before I begin the bodywork in earnest.