Thiosulfate pitting corrosion of stainless steels in paper machine environment

Dissertation

Research output: ThesisDissertationCollection of Articles

1 Citation (Scopus)

Abstract

Thiosulfate pitting corrosion of austenitic stainless steels of types UNS S30403 (AISI 304L) and UNS S31603 (AISI 316L), and duplex stainless steel of type UNS S31803 (22Cr DSS) was studied in simulated paper machine environments containing chloride, sulfate and thiosulfate by cyclic polarization scans, scratch tests, Contact Electric Resistance (CER) technique and by corrosion coupon tests performed in a real paper machine. The formed pits and crevice corrosion were examined by Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS). The surface films were also analyzed by Electron Spectroscopy for Chemical Analysis (ESCA) and Secondary Ion Mass Spectrometry (SIMS). Thiosulfate and chloride clearly have a synergistic effect in inducing localized corrosion. Thiosulfate is able to prevent passivation of an active stainless steel surface and able to stabilize metastable pits initiated below the actual pitting corrosion potential. The role of chloride is to initiate corrosion pits. Thiosulfate increases the possible potential range of corrosion pits to grow by lowering the repassivation potential. Hydrogen sulfide originating from thiosulfate is proposed to accelerate the anodic dissolution inside corrosion pits and crevices by forming sparingly soluble metal sulfides and by acidifying the local environment. The compositions of the black deposit enriched inside thiosulfate pits and corrosion crevices were similar to the compositions of the low-resistance surface films. Pitting Resistance Indices (PRE) of the test materials increased in the order of UNS S30403 (PRE 19 - 21), UNS S31603 (PRE 24 - 25) and UNS S31803 (PRE 35) in accordance with the observed localized corrosion resistance in both the laboratory and field tests. All the materials corroded technically significantly in corrosion coupon tests performed in a paper machine. The bulk environment of the paper machine was very mild, but the chloride and thiosulfate ions concentrating up to high levels created favourable conditions for corrosion.
Original languageEnglish
QualificationDoctor Degree
Awarding Institution
  • Aalto University
Supervisors/Advisors
  • Hänninen, Hannu, Supervisor, External person
Award date3 Dec 1999
Place of PublicationEspoo
Publisher
Print ISBNs951-38-5543-0
Electronic ISBNs951-38-5544-9
Publication statusPublished - 1999
MoE publication typeG5 Doctoral dissertation (article)

Fingerprint

Thiosulfates
Stainless Steel
Pitting
Corrosion
Chlorides
Chemical analysis
Surface resistance
Hydrogen Sulfide
Acoustic impedance
Electron spectroscopy
Sulfides
Austenitic stainless steel
Secondary ion mass spectrometry
Passivation
Sulfates
Corrosion resistance
Energy dispersive spectroscopy
Dissolution
Deposits
Metals

Keywords

  • pitting corrosion
  • austenitic stainless steels
  • thiosulfate
  • pulp and paper
  • paper machines
  • duplex stainless steel
  • tests
  • corrosion resistance
  • theses

Cite this

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title = "Thiosulfate pitting corrosion of stainless steels in paper machine environment: Dissertation",
abstract = "Thiosulfate pitting corrosion of austenitic stainless steels of types UNS S30403 (AISI 304L) and UNS S31603 (AISI 316L), and duplex stainless steel of type UNS S31803 (22Cr DSS) was studied in simulated paper machine environments containing chloride, sulfate and thiosulfate by cyclic polarization scans, scratch tests, Contact Electric Resistance (CER) technique and by corrosion coupon tests performed in a real paper machine. The formed pits and crevice corrosion were examined by Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS). The surface films were also analyzed by Electron Spectroscopy for Chemical Analysis (ESCA) and Secondary Ion Mass Spectrometry (SIMS). Thiosulfate and chloride clearly have a synergistic effect in inducing localized corrosion. Thiosulfate is able to prevent passivation of an active stainless steel surface and able to stabilize metastable pits initiated below the actual pitting corrosion potential. The role of chloride is to initiate corrosion pits. Thiosulfate increases the possible potential range of corrosion pits to grow by lowering the repassivation potential. Hydrogen sulfide originating from thiosulfate is proposed to accelerate the anodic dissolution inside corrosion pits and crevices by forming sparingly soluble metal sulfides and by acidifying the local environment. The compositions of the black deposit enriched inside thiosulfate pits and corrosion crevices were similar to the compositions of the low-resistance surface films. Pitting Resistance Indices (PRE) of the test materials increased in the order of UNS S30403 (PRE 19 - 21), UNS S31603 (PRE 24 - 25) and UNS S31803 (PRE 35) in accordance with the observed localized corrosion resistance in both the laboratory and field tests. All the materials corroded technically significantly in corrosion coupon tests performed in a paper machine. The bulk environment of the paper machine was very mild, but the chloride and thiosulfate ions concentrating up to high levels created favourable conditions for corrosion.",
keywords = "pitting corrosion, austenitic stainless steels, thiosulfate, pulp and paper, paper machines, duplex stainless steel, tests, corrosion resistance, theses",
author = "Tarja Laitinen",
note = "Project code: V9SU00146",
year = "1999",
language = "English",
isbn = "951-38-5543-0",
series = "VTT Publications",
publisher = "VTT Technical Research Centre of Finland",
number = "399",
address = "Finland",
school = "Aalto University",

}

Thiosulfate pitting corrosion of stainless steels in paper machine environment : Dissertation. / Laitinen, Tarja.

Espoo : VTT Technical Research Centre of Finland, 1999. 101 p.

Research output: ThesisDissertationCollection of Articles

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T2 - Dissertation

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N2 - Thiosulfate pitting corrosion of austenitic stainless steels of types UNS S30403 (AISI 304L) and UNS S31603 (AISI 316L), and duplex stainless steel of type UNS S31803 (22Cr DSS) was studied in simulated paper machine environments containing chloride, sulfate and thiosulfate by cyclic polarization scans, scratch tests, Contact Electric Resistance (CER) technique and by corrosion coupon tests performed in a real paper machine. The formed pits and crevice corrosion were examined by Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS). The surface films were also analyzed by Electron Spectroscopy for Chemical Analysis (ESCA) and Secondary Ion Mass Spectrometry (SIMS). Thiosulfate and chloride clearly have a synergistic effect in inducing localized corrosion. Thiosulfate is able to prevent passivation of an active stainless steel surface and able to stabilize metastable pits initiated below the actual pitting corrosion potential. The role of chloride is to initiate corrosion pits. Thiosulfate increases the possible potential range of corrosion pits to grow by lowering the repassivation potential. Hydrogen sulfide originating from thiosulfate is proposed to accelerate the anodic dissolution inside corrosion pits and crevices by forming sparingly soluble metal sulfides and by acidifying the local environment. The compositions of the black deposit enriched inside thiosulfate pits and corrosion crevices were similar to the compositions of the low-resistance surface films. Pitting Resistance Indices (PRE) of the test materials increased in the order of UNS S30403 (PRE 19 - 21), UNS S31603 (PRE 24 - 25) and UNS S31803 (PRE 35) in accordance with the observed localized corrosion resistance in both the laboratory and field tests. All the materials corroded technically significantly in corrosion coupon tests performed in a paper machine. The bulk environment of the paper machine was very mild, but the chloride and thiosulfate ions concentrating up to high levels created favourable conditions for corrosion.

AB - Thiosulfate pitting corrosion of austenitic stainless steels of types UNS S30403 (AISI 304L) and UNS S31603 (AISI 316L), and duplex stainless steel of type UNS S31803 (22Cr DSS) was studied in simulated paper machine environments containing chloride, sulfate and thiosulfate by cyclic polarization scans, scratch tests, Contact Electric Resistance (CER) technique and by corrosion coupon tests performed in a real paper machine. The formed pits and crevice corrosion were examined by Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS). The surface films were also analyzed by Electron Spectroscopy for Chemical Analysis (ESCA) and Secondary Ion Mass Spectrometry (SIMS). Thiosulfate and chloride clearly have a synergistic effect in inducing localized corrosion. Thiosulfate is able to prevent passivation of an active stainless steel surface and able to stabilize metastable pits initiated below the actual pitting corrosion potential. The role of chloride is to initiate corrosion pits. Thiosulfate increases the possible potential range of corrosion pits to grow by lowering the repassivation potential. Hydrogen sulfide originating from thiosulfate is proposed to accelerate the anodic dissolution inside corrosion pits and crevices by forming sparingly soluble metal sulfides and by acidifying the local environment. The compositions of the black deposit enriched inside thiosulfate pits and corrosion crevices were similar to the compositions of the low-resistance surface films. Pitting Resistance Indices (PRE) of the test materials increased in the order of UNS S30403 (PRE 19 - 21), UNS S31603 (PRE 24 - 25) and UNS S31803 (PRE 35) in accordance with the observed localized corrosion resistance in both the laboratory and field tests. All the materials corroded technically significantly in corrosion coupon tests performed in a paper machine. The bulk environment of the paper machine was very mild, but the chloride and thiosulfate ions concentrating up to high levels created favourable conditions for corrosion.

KW - pitting corrosion

KW - austenitic stainless steels

KW - thiosulfate

KW - pulp and paper

KW - paper machines

KW - duplex stainless steel

KW - tests

KW - corrosion resistance

KW - theses

M3 - Dissertation

SN - 951-38-5543-0

T3 - VTT Publications

PB - VTT Technical Research Centre of Finland

CY - Espoo

ER -