Boron is diffused 10-250µm in the alloy where it makes borides (of Fe, Ni, and minor alloying elements). Whether you want to call it a chemical reaction, I don't care.
Removing it should be difficult. It's comparable with carburizing. Remove the surface of the metal part - but mechanical parts often get unusable then. Boriding serves often against wear, and most wear parts need very accurate dimensions.