Protective coating for substrates that are subjected to high temperatures and method for producing said coating

A method of producing a protective layer on a substrate with the steps of:

• (a) applying on the chromium-oxide-forming substrate having at least one alloying addition selected from the group consisting of manganese, magnesium, and vanadium, a coating consisting essentially of at least one spinel-forming element selected from the group consisting of cobalt, nickel, copper and vanadium,
• (b) forming a chromium oxide layer at the substrate/applied coating interface,
• c) at a temperature of 500° C. to 1000° C. causing the diffusion of the at least one alloying addition through the chromium oxide layer and forming a compound thereof with the least one spinel-forming element diffusing from the applied coating and forming between the chromium oxide layer on the substrate and the applied coating, a uniform, compact, adherent chromium-free gas-tight spinel layer, said alloying addition and said applied coating containing sufficient reservoirs of said alloying addition and said spinel-forming element, respectively to heal any microcracks in the chromium-free spinel layer which forms during operation of a high temperature fuel cell.