An Electrochemical Study of the Corrosion Behaviour of T91 Steel in Molten Nitrates

A study of the corrosion behaviour T91 steel in molten 60 wt% NaNO3-40%KNO3 has been carried out at 300, 400 and 500 °C during 1000 h. Employed techniques included potentiodynamic polarization tests, linear resistance (LPR) electrochemical impedance spectroscopy (EIS) measurements. Experiments were complemented by detailed scanning electronic measurements X-ray diffraction studies. Polarization curves revealed existence a passive layer formed onto steel, composed mainly Cr2O3, FeCr2O4, NaCrO4 K2Fe2O4. Corrosion current density values increased, whereas value decreased more than one order magnitude as testing temperature increased. EIS tests indicated charge transfer controlled process, regardless temperature, that double with temperature.