Inhibiting Effects of Nitrates on the Passive Film Breakdown of Alloy 22 in Chloride Environments
| Autor: | G. E. Gdowski, Christine A. Orme, J. J. Gray, Joel Hayes |
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| Rok vydání: | 2006 |
| Předmět: |
Renewable Energy
Sustainability and the Environment Inorganic chemistry Alloy Oxide engineering.material Condensed Matter Physics Chloride Surfaces Coatings and Films Electronic Optical and Magnetic Materials Dielectric spectroscopy Corrosion chemistry.chemical_compound symbols.namesake chemistry Materials Chemistry Electrochemistry engineering symbols medicine Raman spectroscopy Dissolution Crevice corrosion medicine.drug |
| Zdroj: | Journal of The Electrochemical Society. 153:B156 |
| ISSN: | 0013-4651 |
| Popis: | The influence of nitrates and chlorides on the passive film of alloy 22 (Ni-Cr22-Mol3-W3-Fe3) in chloride-containing solutions (1 and 4 m NaCI) from pH 5 to - 1 at 60 and 90°C is characterized. The combination of nitrates and chlorides in low pH solutions leads to a variety of different corrosion states, including: active, passive, active/passive, and transpassive. For each corrosion state, electrochemical impedance spectroscopy (EIS) is utilized to characterize the passive film properties. Active corrosion is a sensitive function of the nitrate-to-chloride ratio, rather than the total amount of anions in solution. At pH < 0, transpassive dissolution is initialized in all nitrate solutions independent of the tested temperatures and nitrate-to-chloride ratios. Raman spectroscopy analysis shows that Mo is a significant dissolution product during the initial stages of transpassive dissolution. The dissolution is attributed to a transformation from an insoluble Mo oxide to soluble Mo complexes at high open-circuit potentials and low pH. Finally, the results are correlated with critical nitrate/chloride ratios that lead to crevice corrosion in occluded volumes. |
| Databáze: | OpenAIRE |
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