Thermodynamic and electrochemical predictions on the formation of secondary phases in CO2 containing atmosphere on the La0.6Sr0.4Co0.2Fe0.8O3 +/-delta(LSCF-6428) surface have been carried out utilizing the CALculation of Phase Diagram (CALPHAD) approach. The effect of temperature, CO2 partial pressure, O-2 partial pressure as well as the cathode composition on the formation of secondary phases have been investigated and correlated with the previous investigations in the literature. It is predicted that SrCO3 has the possibility to form on the surface as a result of CO2 exposure to the system. In addition, it is seen that LSCF-6428 experiences higher degradation due to the larger amount of segregated phases than LSM20 at the same operating condition. (C) 2016 Elsevier B.V. All rights reserved.