If your seat pan was made of aluminum you could use Alodine to chemically etch it. The stuff basically pre-corrodes aluminum leaving behind a nice brown layer that stays on, we paint over it all the time. You could probably use poly clear over it. Or use nothing if you use the Alodine by the directions it will stay just like that forever and not wipe off on your ass and not corrode anymore. Alodine doesn't do shit to steal though. Cool thing is you can put the Alodine in a spray bottle hit the piece you want anyway you want and when it is brown enough to your liking use water to neutralize it and stop the chemical reaction.
Pain is weakness leaving the body.