APPLICATION OF DOUBLE-LOOP ELECTROCHEMICAL POTENTIODYNAMIC REACTIVATION TEST TO AUSTENITIC AND DUPLEX STAINLESS-STEELS

Double loop electrochemical potentiodynamic reactivation (DLEPR) tests are performed on an austenitic (317L) and an austeno-ferritic (UNS S3 1803) stainless steels. In order to optimise results, the standard ele ctrochemical solution has been modified by adding NaCl to the composit ion and by increasing the concentration of H2SO4. Results show a high resistance to intergranular corrosion of the 317L heat treated at 675 degrees C for 30 min to 24 h. On contrast, the duplex stainless steel corrosion resistance decreases with time of sensitisation. Low exposur e time (1 h at 675 degrees C) provides low reactivation current densit y whereas longer exposure time (10 h) shows an increase in the value o f this reactivation current, which is due to the formation of chromium carbides and sigma phase at grain boundaries leading to more chromium depleted areas. Heat treatment at 900 degrees C shows a high reactiva tion proportional to sigma-phase precipitation. The aim of this work i s to validate the DLEPR technique for detecting susceptibility to inte rgranular corrosion of duplex stainless steels. This test is not yet n ormalised and could be used for on-site measurement. (C) 1997 Elsevier Science S.A.