A few weeks ago, I bought some 0.1 micron Iron (Ferrous) Oxide powder from Kremer Pigments. I like it so far, and am using it in two different ways:
(1) A very fine paste for touching up a razor. (I'm experimenting, using this in place of the 0.5 micron Chromium Oxide to "freshen up" an edge.)
(2) A polish for the non-cutting areas of the blade.
Occasionally, someone mentions using Iron Oxide. I am curious whether many others are using it?