Electrochemical Noise Analysis On Corrosion Process Of Nuclear Plant Materials

In recent years, nuclear power plant has played an important role in our nationalenergy resource developmental strategies. However, corrosion is still great problem ofthe nuclear industry materials. In this paper, researching the methods of analyzingelectrochemical noise (EN) and studying the corrosion process of nuclear materials indifferent environment was considered as the main line.The corrosion process of304stainless steel in2mol/L alkaline chloride solutionwas measured for about40h by electrochemical noise(EN). In order to identify thedifferent pitting states, the results of principal component analysis(PCA)/clusteranalysis(CA), shot noise theory, wavelet analysis and surface micrographs werecompared. According to the results, PCA/CA can be used in analyzing the EN data inthis experiment. The pitting process were classified by the K-means CA to three states.The results of wavelet analysis can account for the three different states, i.e. theinduction of pitting, the meta-steady state and the steady state.Electrochemical noise (EN) monitoring technique was applied to characterize thetemperature effect on the corrosion evolution process of304stainless steel in hightemperature water. The principal component analysis(PCA)/cluster analysis(CA), aswell as noise resistance (Rn) and wavelet transform, have been employed to analyzethe EN data. As temperature increased, the protective property of the flm degradedand structure varied from one stage to another. Effect of temperature on the protectiveproperty and the growth mechanism of the oxide film was discussed.The effect of thiosulfate ions on the electrochemical behavior of alloy800wasinvestigated in simulated neutral steam generator crevice solutions by usingelectrochemical noise, potentiodynamic polarization and potentiostatic polarizationtechniques. The results showed that thiosulfate and chloride containing solution wasmore corrosive than solution containing only thiosulfate or chloride ion. Under thesynergistic effect of S2O32-and Cl-ions, chloride and thiosulfate ions could besuccessively absorbed into the alloy surface, impeded the passivation of alloy800anddecreased the corrosion resistance of alloy800.