Longevity of materials, especially technological parts, is influenced by microstructure development during long-time annealing of such parts during their industrial service. Important relations between the volume fractions of phases and the time of service, especially the precipitation of intermetallics need to be revealed. The present study describes the time dependence of the structure development of two corrosion resistant steels with chromium content of 27 and 32 wt.% and various additions of nickel, molybdenum, manganese, silicon, copper and nitrogen. The microstructure was studied on samples annealed at 700 °C for 500, 3 188 and 6 170 h, revealing the kinetics of the equilibrium process. The homogeneity of samples was checked before heat treatment. The experimental microstructures are compared with the predicted phase composition. The effect of using different databases is also discussed.