Measuring the Repassivation Potential of Alloy 22 Using the Potentiodynamic-Galvanostatic-Potentiostatic Method

Abstract

Traditionally, the susceptibility of Alloy 22 (N06022) to suffer crevice corrosion has been measured using the Cyclic Potentiodynamic Polarization (CPP) technique (ASTM G 61). When the alloy is not very susceptible to crevice corrosion, the values of repassivation potential obtained using the CPP technique are not highly reproducible. To circumvent the large uncertainty in the values of the repassivation potential by the CPP method, the repassivation potential of Alloy 22 may be measured using a slower method that combines sequentially potentiodynamic, galvanostatic, and potentio-static treatments (this method is called the Tsujikawa-Hisamatsu Electrochemical or THE method). In the THE method the anodic charge is applied to the specimen in a more controlled manner, which avoids driving the alloy to transpassivity and therefore results in more reproducible repassivation potential values. Results using THE method under various testing conditions are presented. A new standard has been prepared for ASTM balloting for the THE method. The round robin matrix results are also discussed.

Synthesis and characterization of ZA-27/SiC nanocomposites and study of its anticorrosion performance in a 3.5% NaCl medium

“…The corrosion of MMNCs generally initiates at sites having a chemical or physical heterogeneity because of the discontinuity and the changing in the structure such as grain boundary, matrix/reinforcement interface and defect or inclusion (Kanayo Alaneme and Apata Olubambi, 2013; Spataru and Muntean, 2003). The increase of SiC content is accompanied by the increase of matrix reinforcement interfaces which are considered as preferential sites for corrosion initiation (Evans et al , 2007; Mishra et al , 2007). Thus, this will cause a reduction in corrosion resistance of MMNCs.…”

Environmental Degradation of Engineered Barrier Materials in Nuclear Waste Repositories

“…Alloy 22 is extremely resistant to pitting corrosion but may suffer crevice corrosion, especially in pure chloride solutions and at temperatures higher than 60 C [69,70]. Figure 36.2 shows the effect of chloride concentration and temperature on the repassivation potential of alloy 22, obtained using the Tsujikawa-Hisamatsu electrochemical (THE) method (ASTM G 192).…”

“…Figure 36.2 shows the effect of chloride concentration and temperature on the repassivation potential of alloy 22, obtained using the Tsujikawa-Hisamatsu electrochemical (THE) method (ASTM G 192). The higher the temperature and chloride concentration, the lower the resistance of the alloy to localized corrosion [70]. The crevice corrosion susceptibility of alloy 22 is only promoted by the presence of chloride ions, and it can be fully inhibited by the presence of other anions in solution such as nitrate, bicarbonate, sulfate, fluoride, phosphate, and so on [71][72][73].…”

The Effect of Anions on the Passive Film Properties and Localized Corrosion Behavior of Alloy C-22

“…Dunn et al [1] studied corrosion behavior of alloy C-22 in 1M NaCl at 95 °C found the repassivation potential to be 300 mVsce whereas Rebak et al [2] who studied the alloy C-22 properties at 50 °C in the same environment found it to 100 mV higher, at 400 mVsce. Evans et al [3] who studied alloy C-22 in a multi-ionic electrolyte of K + (3,400 mg/L), Na + (40,900 mg/L), Mg 2+ (1,000 mg/L), Ca 2+ (1,000 mg/L), Cl -(24,250 mg/L), NO 3 -(23,000 mg/L), SO 4 2-(38,600 mg/L) and silicon (40 mg/L) found that it was not susceptible to localized corrosion in both aerated and deaerated environments.…”

“…Kehler et al [6] tested alloy C-22 as a function of temperature and pH in concentrated lithium chloride and found that crevice corrosion susceptibility decreased as the chloride to combined sulfate + nitrate ratio decreased from 100 to 1. Evans et al [3] who studied alloy C-22 in 5M CaCl 2 found that at anodic potentials the alloy suffered localized corrosion and underwent massive corrosion at 90 °C. They also found that a solution consisting of Cl -:NO 3 ratio of 10:1 inhibited this localized corrosion.…”