The Use of EPR-DL Technique to Determine the Degree of Sensitization of Modified AISI 316 Stainless Steel

摘要

The Double Loop Electrochemical Potentiokinetic Reactivation (EPR-DL) technique was used to determine the degree of sensitization (DOS) of AISI 316 type alloys where the molybdenum content was replaced both partial and totally by vanadium. The double loop potentiokinetic polarization curves in 0.5 M H_2SO_4 with the addition of 0.01 M KSCN at 25°C were obtained to calculate the DOS via reactivation and passivation charges ratio (Ca/Cp). Before the electrochemical experiments were carried out, the alloys were heat treated at 680°C for 1.5 and 10 hours to produce a sensitized microstructure with chromium and molybdenum depleted zones close to the grain boundaries. The results showed that the 1.5 hour heat treated partially modified alloys displayed less DOS than the totally modified ones, while the 10 hour heat treated totally modified alloys showed less DOS than the partially modified ones. The results are consistent with a beneficial effect of vanadium when it replaces the molybdenum in the alloys. Transmission Electron Microscopy was used in order to correlate the electrochemical and microstructural results.