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 potentiostatic 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.

The crevice corrosion of Alloy 22 in the Yucca Mountain nuclear waste repository

“…They found that when the applied torque is too low, the determined E R,CREV tend to be inordinately high, but for a torque higher than 0.98 N·m (0.1 kgf·m) the measurement becomes stable. The same tendency was displayed for Alloy 22 PCA specimens tested in 1 M NaCl solution 11 with PTFE tape covered ceramic crevice former, but in this case the E R,CREV became stable for a torque higher than 3.4 N·m in 1 M NaCl at 90°C.…”

“…or the crossover of the reverse and forward scans (E RCO ) ( Figure 1). Other tests are the Tsujikawa-Hisamatsu Electrochemical (THE) method, for which a round-robin matrix of results is under discussion in ASTM, 11,12 and the potentiostatic (POT) test, which does not have an ASTM standard. 9,13 In the THE method the repassivation potential (E R,CREV ) is the potential at which the anodic current ceases to increase in the potentiostatic decreasing steps (Figure 2).…”

Susceptibility of 316L stainless steel to crevice corrosion in submersible solenoid valve

“…In recent years, various electrochemical techniques, such as cyclic potentiodynamic polarization [4][5][6][7][8][9], potentiostatic polarization [4][5][6][7], galvanostatic polarization [10], tsujikawa-hisamatsu method [11], electrochemical noise method [12,13] and dynamic electrochemical impedance spectroscopy [14], are being used to asses the crevice corrosion process. The effects of variables, such as crevice former materials, applied torque on crevice formers, chemical elements and crevice geometries on crevice corrosion behavior, have been studied [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21].…”

“…The effects of variables, such as crevice former materials, applied torque on crevice formers, chemical elements and crevice geometries on crevice corrosion behavior, have been studied [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21].…”

“…It indicates that the values of repassivation potential are approximately the same when the applied torque is high. However, when the applied torque is low, the repassivation potential slightly increased, probably because a larger gap was established between the crevice former and the tested specimen [7,8,11]. The effects of nitrogen and nickel on the crevice corrosion resistance are studied in different chloride solution [15][16][17].…”