Semiconducting behavior and bandgap energies of oxide films grown on alloy 600 under PWR simulated primary water conditions with different dissolved hydrogen contents

Alloy 600 samples were oxidized under different simulated PWR primary water conditions, with varying contents of dissolved hydrogen. The photoelectrochemical techniques, used to characterize the semiconducting behavior and bandgap energies of oxide films have shown that the scale has several components. The first ones, exhibiting photocurrents at photon energies lower than 2.5 eV behave as n-type semiconductors, whereas the analyze of the photocurrents measured at higher energies suggests that other components are either n-type or insulating, depending on the hydrogen partial pressure tested: <0.01, 0.3 and 6.5 bar (<1, 30 and 658 kPa). Furthermore, a novel approach developed recently by our group allowed us determination of the number of semiconducting components in the scales and assessment of the bandgap energy for each of them. These results revealed that the composition, as well as the semiconducting properties of the scales, were influenced by the hydrogen partial pressure used in the corrosion test.