Effects of minor additions of ruthenium on the passivation of duplex stainless-steel corrosion in concentrated hydrochloric acid solutions

The effects of minor additions of ruthenium (0.14%, 0.22%, and 0.28%) on the passivation of duplex stainless-steel (DSS, Fe-22%Cr-9%Ni-3%Mo) corrosion in 2 M HCl solutions have been studied using open-circuit potential (OCP), potentiodynamic cyclic polarization, potentiostatic current-time, electrochemical impedance spectroscopy (EIS), and weight loss measurements. OCP measurements showed an increased shift in the corrosion potential to more positive values with increasing Ru content. Polarization and EIS experiments indicated that the presence of Ru and the increase of its content decrease the corrosion rate, critical and passive current density, and polarization resistance. Moreover, it shifts the corrosion and pitting potentials to more positive values. Current-time measurements at -100, -50, and 50 mV versus Ag/AgCl also confirmed that the severity of pitting corrosion decreases with an increasing Ru content. Weight-loss time data showed good agreement with the electrochemical measurements.