INVESTIGATION OF INTERCRYSTALLINE CORROSI ON OF DUPLEX STAINLESS-STEELS USING THIOACETAMIDE AS AN ACTIVATOR FOR EPR-TEST

To evaluate susceptibility of the duplex stainless steel (DSS) X2CrNiM oN22-5-3 to intergranular attack (IGA) using double-loop (DL)-EPR-test , thioacetamid (TA) instead of KSCN has been taken as activator. TA ha s to suppress selective ferrite corrosion by keeping up good IGA-detec tion. Solution annealed rolled samples were hold at 650 degrees C, 750 degrees C and 850 degrees C over 3 to 600 min. Conditions: 0.5 M H2SO 4 + 0.01 M KSCN, 70 degrees C or 2.5 x 10(-4) to 1 x 10(-2) M TA; 50 d egrees C, 60 degrees C and 70 degrees C. For test evaluation the ratio i(R)/i(P) respectively q(R)/q(P) has been used in connection with res earch of microstructure. Using optimal parameters TA enables EPR-test to detect IGA on DSS produced by chi- and sigma-phase precipitations. The mechanism of effect of TA is discussed.