What's the issue? These films are very complex chemistry, locked into unstable crystal structures at quench via fast cooling. Some are stable, some are weak, some are brittle, and they are microns thin. They lay over each other like potato chips. Some are stuck to the base material more strongly.
Energy of any form will release some of these structures from their temporary state. Rubbing, UV, solvents, heat, they'll all break the potato chips.
At some point they have to equilibrate. But if you are vibrating atoms with UV energy, some are going to move around.
No one ever mentions it on these discussions, but quench chemistry can be very exciting stuff.
I thought the Doc Gaddy articles showed the film to be relatively simple chemistry arranged in a unique way. The colored film that forms might not be so unstable, some colors show centuries later if they are protected.
I'm not following what the temporary state is that is going to equilibrate. Aren't the colors primarily iron oxide and separate from the thin case of steel that was formed that may or may not be hardened. I don't think you need to quench to form iron oxide, but the quench seems to arrange the iron oxide in the way that shows as gun case colors.
I think there are things that affect the appearance of the colors, but I think all that means is it isn't always the toughest most resistant surface finish not that it's tearing itself apart to release stress. Even after the colors are long gone, there could still be a hard steel case on the part.
