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

    TY - THES

    T1 - Thiosulfate pitting corrosion of stainless steels in paper machine environment

    T2 - Dissertation

    AU - Laitinen, Tarja

    N1 - Project code: V9SU00146

    PY - 1999

    Y1 - 1999

    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 -