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Improved corrosion properties of hot dip galvanized steel by nanomolecular silane layers as hybrid interface between zinc and top coatings

Vuori, Leena ; Ali-Löytty, Harri ; Lahtonen, Kimmo ; Hannula, Markku ; Lehtonen, Elina ; Niu, Yuran LU and Valden, Mika (2017) In Corrosion 73(2). p.169-180
Abstract

Thin organic coatings (TOC) or paints on hot dip galvanized steel (HDGS) improve the corrosion properties and create visually pleasing surfaces. Delamination of these coatings leads to corrosion and peeling of the paints. Hence, a novel method for improved adhesion and corrosion properties for HDGS surfaces is introduced. It is shown how the fabrication of a nanomolecular silane film as an interfacial layer between the HDGS and TOC or paint improves the corrosion properties of HDGS in different pH regimes. Understanding the corrosion behavior of ultra-thin silane layers under differing pH is crucial, as subsequent coatings have different pHs. By varying the silanization parameters, two different nanomolecular surface structures of... (More)

Thin organic coatings (TOC) or paints on hot dip galvanized steel (HDGS) improve the corrosion properties and create visually pleasing surfaces. Delamination of these coatings leads to corrosion and peeling of the paints. Hence, a novel method for improved adhesion and corrosion properties for HDGS surfaces is introduced. It is shown how the fabrication of a nanomolecular silane film as an interfacial layer between the HDGS and TOC or paint improves the corrosion properties of HDGS in different pH regimes. Understanding the corrosion behavior of ultra-thin silane layers under differing pH is crucial, as subsequent coatings have different pHs. By varying the silanization parameters, two different nanomolecular surface structures of aminopropyl trimethoxysilane (APS) on HDGS were fabricated: well-ordered monolayers with approximately 1 nm thickness and highly clustered APS films with a thickness in the range of 5 nm to 8 nm. To verify the nanomolecular APS structures, photoelectron spectroscopy and contact angle measurements were used. The corrosion properties of HDGS and silanized HDGS were studied with linear sweep voltammetry and electrochemical impedance spectroscopy. It is shown that at pH 5 and 7, passivation behavior is observed on silanized samples, but the most significant improvement in corrosion resistance is found at pH 10, where the corrosion currents of silanized samples are up to two orders of magnitude lower than on uncoated metallic samples. Also, it is demonstrated that the corrosion inhibition of APS is not only dependent on the thickness of the silane film, but also the molecular ordering at the surface. The thin, well-ordered APS monolayer is more resistant toward corrosion in NaCl solution (pH 7) than thicker clustered APS layer. This indicates that the highly ordered nanomolecular surface structure protects the HDGS/silane interface from the Cl- adsorption better than the thicker, but more randomly ordered, APS layers. Nanomolecular interfacial silane films for enhanced corrosion and adhesion properties on HDGS are transferrable to industrial production lines providing a low cost and environmentally friendly method for improved HDGS products.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Coatings, Corrosion resistance, Electrochemical impedance spectroscopy, Hot dip galvanized steel, PH changes and effects, Silanes, X-ray photoelectron spectroscopy, Zinc
in
Corrosion
volume
73
issue
2
pages
169 - 180
publisher
Elsevier Limited
external identifiers
  • scopus:85070740987
ISSN
0010-9312
DOI
10.5006/2206
language
English
LU publication?
yes
id
74a7375f-0e76-4468-970d-bff48be425ff
date added to LUP
2019-09-12 15:50:15
date last changed
2020-01-13 02:21:35
@article{74a7375f-0e76-4468-970d-bff48be425ff,
  abstract     = {<p>Thin organic coatings (TOC) or paints on hot dip galvanized steel (HDGS) improve the corrosion properties and create visually pleasing surfaces. Delamination of these coatings leads to corrosion and peeling of the paints. Hence, a novel method for improved adhesion and corrosion properties for HDGS surfaces is introduced. It is shown how the fabrication of a nanomolecular silane film as an interfacial layer between the HDGS and TOC or paint improves the corrosion properties of HDGS in different pH regimes. Understanding the corrosion behavior of ultra-thin silane layers under differing pH is crucial, as subsequent coatings have different pHs. By varying the silanization parameters, two different nanomolecular surface structures of aminopropyl trimethoxysilane (APS) on HDGS were fabricated: well-ordered monolayers with approximately 1 nm thickness and highly clustered APS films with a thickness in the range of 5 nm to 8 nm. To verify the nanomolecular APS structures, photoelectron spectroscopy and contact angle measurements were used. The corrosion properties of HDGS and silanized HDGS were studied with linear sweep voltammetry and electrochemical impedance spectroscopy. It is shown that at pH 5 and 7, passivation behavior is observed on silanized samples, but the most significant improvement in corrosion resistance is found at pH 10, where the corrosion currents of silanized samples are up to two orders of magnitude lower than on uncoated metallic samples. Also, it is demonstrated that the corrosion inhibition of APS is not only dependent on the thickness of the silane film, but also the molecular ordering at the surface. The thin, well-ordered APS monolayer is more resistant toward corrosion in NaCl solution (pH 7) than thicker clustered APS layer. This indicates that the highly ordered nanomolecular surface structure protects the HDGS/silane interface from the Cl<sup>-</sup> adsorption better than the thicker, but more randomly ordered, APS layers. Nanomolecular interfacial silane films for enhanced corrosion and adhesion properties on HDGS are transferrable to industrial production lines providing a low cost and environmentally friendly method for improved HDGS products.</p>},
  author       = {Vuori, Leena and Ali-Löytty, Harri and Lahtonen, Kimmo and Hannula, Markku and Lehtonen, Elina and Niu, Yuran and Valden, Mika},
  issn         = {0010-9312},
  language     = {eng},
  number       = {2},
  pages        = {169--180},
  publisher    = {Elsevier Limited},
  series       = {Corrosion},
  title        = {Improved corrosion properties of hot dip galvanized steel by nanomolecular silane layers as hybrid interface between zinc and top coatings},
  url          = {http://dx.doi.org/10.5006/2206},
  doi          = {10.5006/2206},
  volume       = {73},
  year         = {2017},
}