The only thing you can do is to bond a coating to the metal. You can’t touch it, as an ablatable surface.
Mustard? Try molybdenum disulphide spray (moly spray). Give it a light pass, let it dry, give it another pass, let it dry, run a bunch of speed tests and clean off with alcohol, or similar.
Moly spray is the most affordable to play with. If you get great at it and you can turn a buck, buy a proper laser spray.
The 3D print creator channel on YouTube, one of his videos he spreads mustard on a pair of scissors and engraves his name on the metal.
I did read in the comments section he said that a certain brand he uses works better than others.
CRC’s Dry Moly will cost $10USD, leaves a very uniform surface, dries quickly, makes a great bonded image that won’t come off, and lasts a long time. Of course, if you also want to make Bolonga sandwiches…
I should also add that the unexposed Dry Moly cleans off easier than dried on mustard.