INFLUENCE OF CHLORIDE IONS AS CONTAMINANTS ON THE CORROSION BEHAVIOR OF ALLOY 718 IN POOL WATER OF NUCLEAR POWER PLANTS

摘要

The electrochemical behavior of alloy 718 in a chloride-containing boric acid solution wasstudied to determine the influence of chloride ions as contaminants of pool water of nuclearpower plants on the corrosion behavior of the alloy. Experiments were performed at 20°C and60°C with chloride concentrations from 1.5 to 15 000 ppm, using stationary measurements i.e.OCP versus time measurements and plotting of current-potential curves. After the electrochemical tests, the samples were observed using optical microscopy. Immersion tests inchloride-containing boric acid solutions were also carried out: samples were immersed for a timeas long as 17 weeks at open circuit potential and their residual mechanical properties were measured. Results showed that, whatever the chloride concentration, there was no corrosion forsamples immersed at open circuit potential. However, when the samples were polarized at highpotentials, intergranular corrosion might be observed in occluded zones.