<p>A method of forming a metal nitride or metal alloy nitride on a corresponding metal or a metal alloy substrate, which method comprises: covering the substrate with an oxygen-reacting composition comprising (a) particles of a metal that oxidizes in preference to the metal or metal alloy substrate and that is unreactive with respect to the metal or metal alloy substrate and (b) particles of an inert material; and exposing the covered substrate to industrial grade nitrogen at an elevated temperature and for a time sufficient to produce the metal nitride or metal alloy nitride on the substrate.</p>
