Change search
ReferencesLink to record
Permanent link

Direct link
Review—Passive Film Properties and Electrochemical Response of Different Phases in a Cu-Alloyed Stainless Steel after Long Term Heat Treatment
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.ORCID iD: 0000-0002-9045-9696
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
2016 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 163, no 7, C377-C385 p.Article in journal (Refereed) Published
Abstract [en]

In this work the influence of copper (0–4 wt%) on the microstructure, passive film properties and local electrochemical response of 25Cr7Ni-type duplex stainless steel is investigated after long term heat-treatment at 800◦C for 6 months. This heat-treatment was done to promote the formation of different phases which could be studied in terms of passive film properties and electrochemical response. The unique microstructures of the alloys comprise austenite, sigma phase, Cr2N nitrides and, for the 2 wt% and 4 wt% Cu alloys, epsilon-Cu phase. The results show that alloying with Cu increases slightly the amount of isothermal Cr2N nitrides and epsilon-Cu phase, but decreases the sigma phase fraction. The location of pitting corrosion as well as the Electrochemical Potential (EP), or electron work function, measured with Scanning Kelvin Probe Force Microscopy (SKPFM) show that the epsilon-Cu phase has the lowest corrosion resistance. The EP appears to depend more on the composition of the underlying phase than on the thickness of the passive film. Cr-nitrides have the highest EP followed by sigma phase, austenite and epsilon-Cu phase. There is a clear decrease of EP of the austenitic phase when 2 wt% Cu is added in the alloy.

Place, publisher, year, edition, pages
Electrochemical Society, 2016. Vol. 163, no 7, C377-C385 p.
Keyword [en]
Stainless steel, corrosion, passive film, SKPFM, volta potential
National Category
Corrosion Engineering
Research subject
Materials Science and Engineering
Identifiers
URN: urn:nbn:se:kth:diva-186200DOI: 10.1149/2.1101607jesOAI: oai:DiVA.org:kth-186200DiVA: diva2:926100
Note

QC 20160513

Available from: 2016-05-04 Created: 2016-05-04 Last updated: 2016-05-16Bibliographically approved
In thesis
1. Use of local electrochemical techniques for corrosion studies of stainless steels
Open this publication in new window or tab >>Use of local electrochemical techniques for corrosion studies of stainless steels
2016 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The excellent corrosion resistance of stainless steels arises from the presence of a passive film on its surface. Above 10.5wt% Cr a chromium oxide of 1-3 nm is formed on the surface of the metal that in case of damage will reform and hinder further dissolution of the metal. However, the passivity of the stainless steel can be altered by material factors and external factors; such as the composition of the underlying phases, external loads or thermal treatments.

In this work the local electrochemical techniques Scanning Vibrating Electrode Technique (SVET) and Scanning Kelvin Probe Force Microscopy (SKPFM) and the local characterization techniques X-ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES) have been used to investigate corrosion phenomena of stainless alloys based on measurements of corrosion current density, work function, thickness and composition of the oxide.

The effect on work function of the thickness of the passive film and composition of the underlying phases was investigated for 301LN austenitic stainless steel (Paper I) and a heat treated superduplex 25Cr7Ni type stainless steel (Paper II). It was shown that the work function can be an indicator of corrosion resistance of the phases in the microstructure, and that the composition of the underlying phases had a greater effect on the work function than the thickness of the passive film.

External factors such mechanical deformation (Paper I) and welding (Paper III) altered the passivity of the steel and work function. It was found that plastic deformation decreased irreversibly the work function, whereas elastic deformation did not have any permanent effect. Thermal oxides affected the passivity of stainless steels welded joints and were detrimental for its corrosion resistance. Anodic activity, observed with SVET, and pitting corrosion were detected at the heat tint and attributed to the interaction between the composition and the thickness of the oxide. Brushing combined with pickling was recommended for recovering the passivity of stainless steels.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. 68 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2016:24
Keyword
Stainless steel, passive film, thermal oxides, work function, pickling, SKPFM, SVET, XPS, AES
National Category
Corrosion Engineering
Research subject
Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-186206 (URN)978-91-7729-002-5 (ISBN)
Presentation
2016-06-09, sal K53, Teknikringen 28, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 20160516

Available from: 2016-05-16 Created: 2016-05-04 Last updated: 2016-05-26Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textPublisher's website

Search in DiVA

By author/editor
Fuertes, NuriaPettersson, Rachel
By organisation
Surface and Corrosion Science
In the same journal
Journal of the Electrochemical Society
Corrosion Engineering

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 31 hits
ReferencesLink to record
Permanent link

Direct link