Pronounced internal corrosion attack is often found when analysing structural components, which failed during service. Lifetime for high-temperature applications in corrosive environments is hardly predictable since usually mutual interactions between mechanical damage evolution and internal corrosion are not taken into account. In this study the creep behaviour of the Ni-base superalloy Nicrofer 7520 Ti was studied in a nitrogen-based atmosphere, where external oxide scale formation was suppressed. On the one hand internal nitridation depth increases with increasing creep elongation and on the other hand crack initiation and propagation is promoted by the formation of a brittle internal nitridation layer. A quantitative description of these internal corrosion processes is generally possible by a combination of a numerical treatment of the transport processes and computational thermodynamics.