Emission characterization and X-ray diffraction analysis of flow-acceleration corrosion of steels in secondary circuits of pressurized water reactors

Flow-accelerated corrosion (FAC) (also known as corrosion-erosion) is a typ ical case of generalized corrosion which affects, in particular, carbon and low-alloy steels in a fluid stream at temperatures above 150 degreesC. Thi s phenomenon occurs in the secondary circuit of the PWR (Pressurized Water Reactor) powerplants and leads to a material loss process and, at the end, to a failure of the in-service components. The present work is devoted to t he characterization of the thin iron oxide layers formed on the carbon stee l components under the chemical and hydrodynamical conditions prevailing wi thin the secondary circuit of the PWR powerplants (deaerated and alkalinize d turbulent water or wet steam at 235 degreesC). Experiments using low-ener gy electron induced X-ray spectrometry (LEEIXS), X-ray diffraction (XRD), s canning electron microscopy (SEM) and atomic force microscopy (AFM) have al lowed to get information on the nature and structure of the surface oxide l ayer and to put in light the influence of the alkaline reducing agent (hydr azine) added to the feedwater. Other experiments carried out by glow-discha rge optical spectrometry (GDOS) have allowed to gain additional data and to show the complementarity of the methods used in this study.