Patent ID: 7390582

Claim:
A method of producing a protective coating on an interconnector for a high temperature fuel cell comprising a chromium oxide forming substrate, which comprises the step of: on a surface of the chromium oxide forming substrate, consisting essentially of CoO, MnO, and CuO in suspension to said surface, or applying powdered CoO, MnO, and CuO to said surface; at a temperature of 500 to 1000° C., to form a protective coating on the chromium oxide forming substrate, said protective coating consisting essentially of a uniform, gas-tight, compact, adherent chromium free spinel layer on which is coated a metal oxide layer of CoO, MnO, and CuO, said metal oxide layer containing sufficient reserves of the reactive elements in the CoO, MnO, and CuO to heal any microcracks in the chromium free spinel layer which form during operation of a high temperature fuel cell. wherein the uniform, gas-tight, compact, adherent chromium-free spinel layer has the composition Co 3-x-y Cu x Mn y O 4 in which 0<x<1.5, 0<y<3 and (x+y)<3.