SCIENCEspond to changes in both pH and chromate ion activity. Relative locations of the electrodes in the cell may have contributed. Ag-15-R was in front of Ag-16-R for Experiment 1 and exhibited higher voltages and more dramatic responses. Ag-14-R later developed unusually high potentials in this same location. The electrode housings were in electrical contact with the autoclave, and corrosion currents cause iR offset voltages when they flow past both the test electrode and the Pt reference. Local heating probably did not contribute, but examining this possibility directly is difficult.Interpretation of these results is neither easy nor unambiguous. Takagi et al. 8 measured the effect of y radiation on the corrosion potential of type 304 SS and reported a positive shift in NWC, negative in HWC. However, there was general consistency among the results of the present experiments, and it appears that:Pt electrodes with a brazed pressure seal operate well in HWC, but can develop a mixed corrosion potential without excess H 2 .Fe/Fe3O4 seemed more stable and may be preferable to Cu/Cu 20 for the reference couple of pH electrodes in a radiation field.Polymer-free Ag/AgCI electrodes are suitable for use in highintensity ionizing radiation, but may require a simple calibration to provide the theoretical reference potential. Transient decreases to stable values that depend on the dose rate probably stem from water radiolysis in the reference chamber. The electrode potential may return to the theoretical value when the reference chamber approaches a true steady-state concentration of chemical species.
ABSTRACTA consequence of corrosion of steel in the presence of oxygenfree carbon dioxide and a water phase is the formation of an iron carbonate (FeCO 3) corrosion scale. This scale provides some protection of the steel from further corrosion. The protectiveness of the scale depends on environmental factors and characteristics of the steel. Information presented here describes structural characteristics of iron carbonate scales and discusses how structure may affect the corrosion mechanism. Examinations of iron carbonate scales revealed two kinds of scales and variations in scale thickness depending on the steel microstructure.
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