The Inhibition of Pitting Corrosion in Stainless Steel 304 L During Proton Irradiation
In 0.1M sodium chloride, proton irradiation resulted in a 220mV increase in the pitting potential of stainless steel 304L (0.425 vs 0.644V saturated calomel electrode). In addition, the passive region of the polarization curve during irradiation was associated with a drop in metastable pitting activity by a factor of 100. Mott–Schottky experiments in pH 1.6 H2SO4 found that irradiation was associated with an increase in oxygen vacancy concentration (VO=2.94×1021 vs 3.41×1021cm−3 ). However, electrochemical impedance spectroscopy experiments found that the Warburg coefficient (σ) increased during irradiation (47kΩcm2/s0.5 vs 118kΩcm2/s0.5 ). An increase in film impedance was also observed. Given that σ is inversely proportional to VO , one would expect that an increase in VO would result in a decrease in σ. This apparent dichotomy, an increase in oxygen vacancies in the space charge region at the film/solution interface and a corresponding increase in σ, can be explained if the film is composed of inner Cr-rich p-type and outer Fe-rich n-type semiconducting layers. It is proposed that changes in the inner Cr-rich layer of the oxide are responsible for the observed increase in pitting potential during irradiation.
Lillard, Robert, "The Inhibition of Pitting Corrosion in Stainless Steel 304 L During Proton Irradiation" (2008). Chemical and Biomolecular Engineering Faculty Research. 460.