Establishing a New Solution Based on Hydrochloric Acid/Sodium Thiosulfate for Detecting and Measuring Degree of Sensitization of Stainless Steels Using Double-Loop Electrochemical Potentiodynamic Reactivation Method

New High-Resolution Solution for Measuring Degree of Sensitization of Duplex Stainless Steel 2205 Using Double-Loop Electrochemical Potentiodynamic Reactivation Technique

“…The fact that increasing the thiosulfate concentration up to level 3 decreases the resolution is the cathodic reaction of reduction of thiosulfate to sulfur. This reaction was reported previously 44 and it was shown that the redox potential of this cathodic reaction is high enough to form adsorbed sulfur on the surface in the anodic potentials. Increasing the amount of thiosulfate ion increases the current density of this cathodic reaction and, hence, masks the anodic current density formed during the reactiva- tion stage.…”

“…One of them is the thiosulfate ion in the form of sodium thiosulfate salt (Na 2 S 2 O 3 ), which is reported previously by authors as a depassivator agent in the DL-EPR method. 44 The other one is chloride ions in the form of NaCl salt that was previously introduced for the DOS measuring of DSS2205. 45 The results of both sensitized specimens show that the depassivating effect of the thiosulfate ion is higher than that of the chloride ion.…”

“…The mechanism of depassivation of the thiosulfate ion is previously reported. 44 Here, in brief, the thiosulfate ion in acidic solutions and on the surface of metal reduced to adsorbed sulfur on the surface and the adsorbed sulfur itself reduced to H 2 S. The H 2 S then breaks down the passivity of iron (in the depleted areas) and has no influence on the passivity of chromium (inside the grains). On the other hand, the effect of chloride ion on the passivity of stainless steels is well known and the passivity in presence of chloride is more deteriorated than its absence.…”

Magnetic and Electrochemical Techniques as Tools to Detect Deleterious Phases in Duplex Stainless Steels

“…The electrochemical potentiokinetic reactivation technique with double loop (DL-EPR), was first used to detect chromium carbides in austenitic stainless steels. [1][2][3][4][5][6][7][8][9][10][11][12] Later on, several groups adapted this technique to other materials and extended its scope of identification. [13][14][15][16][17][18][19][20][21][22][23][24][25][26] The use of the DL-EPR technique has been proposed for duplex stainless steels (DSS) to detect several phases, such as sigma, chi, and others.…”