Oxidation kinetics of 304L stainless steel in hot concentrated nitric acid

摘要

The oxidation kinetics of 304L stainless steel (SS) was studied in hot and concentratednitric acid solution. The investigations were performed with long term potentiostaticexperiments in the passive domain allowing different parameters to be characterizedas a function of time. The metal dissolution was determined via weight lossand via solution analyses with inductively coupled plasma atomic emission spectroscopy(ICP-AES). Corrosion morphology was observed by optical microscopy and surfacecomposition (oxide layer and underlying metallic layer) was characterized byXray photoelectron spectroscopy (XPS). The oxide layer thickness was independentlyestimated from electrochemical impedance spectroscopy (EIS) measurements.During the first 50 hours of polarization, the passive film properties together with themetal dissolution rate evolve. Then an apparent steady-state establishes with a lowand constant dissolution rate (15 μm/ year). It was also shown that the metallic speciesdissolve uniformly and that a uniform nanometer oxide layer enriched in chromiumforms. A Ni enriched underlying metallic film is also observed, the chemical compositionof which seems to be not uniform in the whole surface of the SS.