Rechroming / Gold Nitriding
Fork legs (pr) / Shock shaft
While Rechroming will repair forks that are not too badly corroded,
pitted or scored, Nitride treatment to forks does not make a substantial difference to performance.
While the surface is a lot more slippery, it doesn't produce
massive real-world differences. It also means you can't repair stone damage - it just will not polish up like chrome, it's too hard.
The surface treatment demands closer tolerances, better alignment or the advantages will be mostly lost in a sloppy front end.
So if you want the best in low friction and you put a high end coating on,
then the rest of the fork must be brought up to a similar high end level of engineering.