The colour of oxidized steel substrates covered with polymer layers

Veerle Goossens, Sake Van Gils, Robert Finsy, Herman Terryn

Research output: Chapter in Book/Report/Conference proceedingChapterpeer-review

2 Citations (Scopus)

Abstract

A commercially available aqueous acrylic dispersion was used in this chapter. The dispersion was characterized to determine its particle size, stability and chemical composition. The dispersion is then spin-casted on oxidized interstitial free steel surfaces. The steel surfaces were mechanically polished and subsequently thermally oxidized in an oven at 250°C. At this temperature 2 iron oxide layers are stable: hematite and magnetite. Raman spectroscopy was used to characterize the composition of the oxide layers. When the substrate was oxidized in atmospheric conditions a duplex layer with an inner layer of magnetite and an outer layer of hematite was grown. When the substrate was oxidized in an oxygen depleted atmosphere a single magnetite layer was grown. These samples were measured by spectroscopic ellipsometry and their optical constants were determined accordingly. The acrylic dispersion was only cast on the oxides grown under atmospheric conditions.
Two experiments were devised. In the first experiment the oxide thickness was kept constant, but the acrylic concentration in the dispersion was changed. In the second experiment the acrylic concentration in the dispersion was kept constant and the oxide layer thickness was varied. These samples were measured by spectroscopic ellipsometry. Using the optical constants obtained from previous investigations, an optical model was constructed to extract the layer thickness from the raw data. A parabolic relationship was observed between the acrylic concentration in the dispersion and the acrylic layer thickness in the first experiment. In the second experiment a downward relationship was observed between the acrylic layer thickness and the oxidation time. This could be linked to the wettability of the surfaces.
In order to evaluate the optical model and the results obtained, the colour of the samples was investigated. The colour measured by a spectrophotometer was compared to the colour generated from the optical model. The good correlation between both colours indicates that the optical model is physically correct.
Original languageEnglish
Title of host publicationNew Research on Thin Solid Films
EditorsMaria G. Benjamin
PublisherNova Publishers, New York
Pages249-274
Number of pages26
ISBN (Print)1-60021-454-1
Publication statusPublished - 2007

Bibliographical note

Maria G. Benjamin

Keywords

  • colour
  • appearance
  • steel
  • thin films
  • oxide
  • modeling

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