Removing Iron Oxide from a Floppy Disk?
I have to say thank you to Maurice for his suggestion to use more concentrated HCl. I took the same pieces of floppy disk that I used before and increased the acid concentration by a factor of 10 and let them sit for another week.
At first I was disappointed, because there was no visible change in the plastic or the solutions. But when I took the pieces out of the acid and cleaned them off with an alcohol soaked kimwipe, the remaining Iron Oxide came right off. It's not perfectly clean, most likely because I had taped the pieces into my notebook after the first treatment, and I didn't clean the tape residue off before the second treatment. This is also probably why the remaining absorbance at 700 nm is so variable. But I think this method works as long as I don't get the plastic covered in tape goo. The acid treated plastic also might feel a little less stiff than the 0 M control, but this is subjective.