Patent ID: 8859116

Claim:
A multilayer coating for a metal containing surface of an interconnect of a solid oxide electrolytic device, the coating comprising at least two layers: a first layer in direct contact with the metal containing surface of the interconnect and a second layer in contact with the surrounding atmosphere, wherein both the first and second layers comprise an oxide; and wherein the first layer has a tracer diffusion coefficient for cations M m+ , wherein M is a scale forming element of the metal, and the second layer has a tracer diffusion coefficient for oxygen ions O 2− satisfying the following formula: ∫ In ⁢ ⁢ p ⁡ ( O 2 ) in In ⁢ ⁢ p ⁡ ( O 2 ) ex ⁢ ( D o + m 2 ⁢ D M ) ⁢ ⁢ ⅆ ln ⁢ ⁢ p ⁡ ( O 2 ) < 5 · 10 - 13 ⁢ ⁢ cm 2 ⁢ / ⁢ s wherein p(O 2 ) in is the oxygen partial pressure in equilibrium between the metal containing surface and an oxide of M, p(O 2 ) ex is the oxygen partial pressure in the reaction atmosphere, p(O 2 ) is the equivalent oxygen partial pressure, D M is the tracer diffusion coefficient of the metal cations M m+ in the first layer, and D O is the O 2− tracer diffusion coefficient in the second layer, wherein the first layer comprises an oxide having a perovskite structure, and the second layer comprises an oxide having a spinel structure, a rock salt structure, a corundum structure, or a wurtzite structure, and wherein the first layer, the second layer, or both, comprises a graded composition such that the composition varies through the layer.