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Microstructure influence on corrosion behavior of a Fe-Cr-V-N tool alloy studied by SEM/EDS, scanning Kelvin force microscopy and electrochemical measurement
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
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2013 (English)In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 66, 153-159 p.Article in journal (Refereed) Published
Abstract [en]

Microstructure influence on corrosion behavior of an N-based tool alloy (Fe-Cr-V-N) has been studied. Electron microscopy analysis showed two types of hard phases in the alloy. One-pass mode scanning Kelvin force microscopy (KFM) was used to investigate relative nobility of the hard phases. Volta potential mapping indicates higher nobility for the hard phases than the alloy matrix, and, the V- and N-rich particles exhibit the highest Volta potential. Post-polarization analysis by SEM revealed localized dissolution initiated in matrix regions adjacent to hard phase particles, and the boundary region surrounding the Cr- and Mo-rich particles is more prone to localized corrosion.

Place, publisher, year, edition, pages
2013. Vol. 66, 153-159 p.
Keyword [en]
A. Alloy, B. AFM, B. Polarization, B. SEM, C. Hardening, C. Passivity
National Category
Other Chemical Engineering
URN: urn:nbn:se:kth:diva-118136DOI: 10.1016/j.corsci.2012.09.013ISI: 000313383800018ScopusID: 2-s2.0-84869502402OAI: diva2:605048
Swedish Foundation for Strategic Research

QC 20130213

Available from: 2013-02-13 Created: 2013-02-12 Last updated: 2013-10-25Bibliographically approved
In thesis
1. Nanocomposite films for corrosion protection
Open this publication in new window or tab >>Nanocomposite films for corrosion protection
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis describes technical and scientific aspects of new types of composite films/coatings for corrosion protection of carbon steel, composite films with nanometer thickness consisting of mussel adhesive protein (Mefp1) and ceria nanoparticles, and polymeric composite coatings with micrometre thickness consisting of conducting polymer and ceria nanoparticles in a UV‐curing polyester acrylate (PEA) resin.

The influence of microstructure on corrosion behaviour was studied for a Fe‐Cr‐V‐N alloy containing micro‐sized nitrides with different chemical composition spread in martensitic alloy matrix. The Volta potential mapping suggested higher relative nobility for the nitride particles than the alloy matrix, and the nitrides with higher amounts of nitrogen and vanadium exhibited higher nobility. Potentiodynamic polarization measurements in a 0.1 M NaCl solution at neutral pH and ambient temperature showed passivity breakdown with initiation of localized corrosion which started in the boundary region surrounding the nitride particles, especially the ones enriched in Cr and Mo.

Mefp1/ceria nanocomposite films were formed on silica and metal substrates by layer‐by‐layer immersion deposition. The film formation process was studied in situ using a Quartz Crystal Microbalance with Dissipation (QCM‐D). The film grows linearly with increasing number of immersions. Increasing Mefp1 concentration or using Mefp1 with larger size leads to more Mefp1 being deposited. Peak Force Quantitative Nanomechanical Mapping (Peak Force QNM) of the composite films in air indicated that the elastic modulus of the film increased when the film deposited had a higher Mefp1 concentration. It was also noted that the nature of the outermost layer can affect bulk morphology and surface mechanical properties of the film.

The QCM‐D study of Mefp1 on an iron substrate showed that Mefp1 adsorbs at a high rate and changes its conformation with increasing adsorption time. The QCM‐D and in situ Peak Force QNM measurements showed that the addition of Fe3+ ions causes a transition in the single Mefp1 layer from an extended and soft layer to a denser and stiffer layer. In situ ATR‐FTIR and Confocal Raman Microscopy (CRM) analyses revealed complex formation between Fe3+ and catechol groups in Mefp1. Moreover, optical microscopy, SEM and AFM characterization of the Mefp1/ceria composite film formed on carbon steel showed micron‐size aggregates rich in Mefp1 and ceria, and a nanostructure of well dispersed ceria particles in the film. The CRM analysis confirmed the presence of Mefp1/Fe complexes in the film. Electrochemical impedance microscopy and potentiodynamic polarization measurements showed that the Mefp1/ceria composite film can provide corrosion protection for carbon steel, and that the protection efficiency increases with exposure time.

Composite coatings of 10 μm thickness composed of a UV‐curing PEA resin and a small amount of conductive polymer and ceria nanoparticles were coated on carbon steel. The conductive polymer (PAni) was synthesized with phosphoric acid (PA) as the dopant by chemical oxidative polymerization. The ATR‐FTIR and SEM analyses confirmed that the added particles were well dispersed in the coatings. Electrochemical measurements during long exposure in 0.1 M NaCl solution, including open circuit potential (OCP) and EIS, were performed to investigate the protective performance of the coatings. The results showed that adding ceria nanoparticles can improve the barrier properties of the coating, and adding PAni‐PA can lead to active protection of the coating. Adding PAni‐PA and ceria nanoparticles simultaneously in the coating can improve the protection and stability of the composite coating, providing excellent corrosion protection for carbon steel.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. xi, 63 p.
Trita-CHE-Report, ISSN 1654-1081 ; 2013:37
corrosion protection, nanocomposite, coating, tool alloy, layer‐by‐layer, polarization, passivity, nanomechanical, topography, Mefp‐ 1, ceria nanoparticle, PAni, UV‐cure, AFM, Peak Force QNM, EIS, SEM, CRM, QCM‐D, ATR‐FTIR
National Category
Corrosion Engineering
urn:nbn:se:kth:diva-132240 (URN)978‐91‐7501‐850‐8 (ISBN)
Public defence
2013-11-01, Kollegiesalen, Brinellvägen 8, KTH, Stockholm, 10:00 (English)

QC 20131024

Available from: 2013-10-25 Created: 2013-10-24 Last updated: 2013-10-25Bibliographically approved

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