Role of Thiosulfate on Chloride Breakdown Potential of Heat Treated Ni 18Cr 6Fe Alloys

Volume 6, Issue 3 (March 2009)

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ISSN: 1546-962X
CODEN: JAIOAD
Published Online: 12 March 2009
Page Count: 10

Role of Thiosulfate on Chloride Breakdown Potential of Heat Treated Ni-18Cr-6Fe Alloys

Ezuber, Hosni M.
College of Engineering, University of Bahrain,

(Received 21 February 2008; accepted 3 February 2009)

Abstract

The breakdown potentials of mill-annealed Ni-18Cr-6Fe alloys were measured in wide range of chloride concentrations (0.001–1 M NaCl) and various concentrations of thiosulfate ranging from 0–0.25 M (Na₂S₂O₃) at 80°C using the potentiodynamic technique. These potentials were compared with heat treated alloys for one or five hours at 900°C (and quenched). This work aimed to study the effect of sensitization on the pitting characteristics of this alloy in chloride-thiosulfate solutions. The anodic polarization curves revealed that sensitized alloys became more susceptible to chloride and thiosulfate pitting attack, or both. Addition of thiosulfate was potentially detrimental to chloride pitting resistance and the aggressiveness of thiosulfate species was found dependent on the ratio of chloride to thiosulfate concentration as the overall ionic strength is varied. A thiosulfate to chloride ratio of 1:40 (S₂O^2–₃ / Cl^–=0.025) was found be the most aggressive, regardless of ionic strength or heat treatment duration.

Keywords:

Paper ID: JAI101709
DOI: 10.1520/JAI101709
ASTM International is a member of CrossRef.

Author Title Role of Thiosulfate on Chloride Breakdown Potential of Heat Treated Ni-18Cr-6Fe Alloys Symposium Advances in Electrochemical Techniques for Corrosion Monitoring and Measurement, 2007-05-23 Committee A01

		SEDL / Journals / Journal of ASTM International (JAI) / Citation Page Volume 6, Issue 3 (March 2009) Click here to download this paper now for $25 PDF (352K) View License Agreement ISSN: 1546-962X CODEN: JAIOAD Published Online: 12 March 2009 Page Count: 10 Role of Thiosulfate on Chloride Breakdown Potential of Heat Treated Ni-18Cr-6Fe Alloys Ezuber, Hosni M. College of Engineering, University of Bahrain, (Received 21 February 2008; accepted 3 February 2009) Abstract The breakdown potentials of mill-annealed Ni-18Cr-6Fe alloys were measured in wide range of chloride concentrations (0.001–1 M NaCl) and various concentrations of thiosulfate ranging from 0–0.25 M (Na₂S₂O₃) at 80°C using the potentiodynamic technique. These potentials were compared with heat treated alloys for one or five hours at 900°C (and quenched). This work aimed to study the effect of sensitization on the pitting characteristics of this alloy in chloride-thiosulfate solutions. The anodic polarization curves revealed that sensitized alloys became more susceptible to chloride and thiosulfate pitting attack, or both. Addition of thiosulfate was potentially detrimental to chloride pitting resistance and the aggressiveness of thiosulfate species was found dependent on the ratio of chloride to thiosulfate concentration as the overall ionic strength is varied. A thiosulfate to chloride ratio of 1:40 (S₂O^2–₃ / Cl^–=0.025) was found be the most aggressive, regardless of ionic strength or heat treatment duration. Keywords: Paper ID: JAI101709 DOI: 10.1520/JAI101709 ASTM International is a member of CrossRef. Author Title Role of Thiosulfate on Chloride Breakdown Potential of Heat Treated Ni-18Cr-6Fe Alloys Symposium Advances in Electrochemical Techniques for Corrosion Monitoring and Measurement, 2007-05-23 Committee A01