EIS assessment of critical pitting temperature of 2205 duplex stainless steel in acidified ferric chloride solution

•Critical pitting temperature estimated by impedance measurement in FeCl3 solution.•Results verified by ASTM G48, zero resistance ammeter and polarisation methods.•A new fast and reliable critical pitting temperature evaluation is proposed.

In this study, critical pitting temperature (CPT) of 2205 duplex stainless steel (DSS2205) was assessed using electrochemical impedance spectroscopy (EIS) in ferric chloride solution. In order to verify the results other methods such as ASTM G 48, potentiodynamic and potentiostatic polarisation and zero resistance ammeter (ZRA) were also employed. The results show a strong close relation between the results of this method by those of previous methods. CPT of the alloy is 40 °C based on standard method and 44 °C, 49 °C according to the ZRA and potentiostatic methods. Both potentiodynamic and EIS methods give an almost identical CPT value.