Sensitization of as Rolled and Stable Annealed Alloy 625

Alloy 625 is used as cladding material in the oil and gas industry. Different annealing conditions are used, these are stable annealed and as rolled. Both conditions have been isothermally sensitized in a laboratory resistance furnace. The annealing temperature was up to 1050 °C and the annealing time up to 10 h. Susceptibility to intergranular corrosion has been investigated by means of a conventional immersion tests according to ASTM G28A and the Double Loop—Electrochemical Potentiokinetic Reactivation Test (DL-EPR method). Scanning electron microscopy (SEM) was used to evaluate microstructure and type of attack after testing. The chemical composition of precipitated phases was characterized by SEM and Transmission Electron Microscopy (TEM). High-resolution investigations with concentration profiles proved high molybdenum precipitates to determine the degree of sensitization.