Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Hydrophobic and superhydrophobic coatings for corrosion protection of steel
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden.
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Since metals in general, and steels in particular, are vital construction materials in our modern society, the corrosion protection of said materials is of great importance, both to ensure safety and to reduce costs associated to corrosion. Previously, chromium (VI) and other harmful substances were effectively used to provide corrosion protection to steel, but since their use was heavily regulated around year 2000, no coating has yet been developed that, in a fully satisfactory manner, replaces their corrosion protective properties.In this thesis, the use of hydrophobic and superhydrophobic surface coatings as part of corrosion protective coating systems has been studied. Since the corrosion mechanism relies on the presence of water to take place, the use of a superhydrophobic coating to retard the penetration of water to an underlying metal surface is intuitive. The evaluation of corrosion protective properties of the hydrophobic and superhydrophobic surfaces was performed using mainly contact angle measurements and electrochemical measurements in severely corrosive 3 wt% NaCl water solution.First, the differences in corrosion protection achieved when employing different hydrophobic wetting states were investigated using a model alkyl ketene dimer wax system. It was found that superhydrophobicity in the Lotus state is superior to the other states, when considering fairly short immersion times of less than ten days. This is due to the continuous air film that can form between such a superhydrophobic surface and the electrolyte, which can retard the transport of electrolyte containing corrosive ions to the metal surface to the point where the electrical circuit is broken. Since corrosion cannot occur unless an electrical current is flowing, this is a very efficient way of suppressing corrosion.An air layer on an immersed superhydrophobic surface is, however, not stable over long time, and to investigate long-term corrosion protection using hydrophobic coatings a polydimethylsiloxane formulation containing hydrophobic silica nanoparticles was developed. This system showed enhancement in corrosion protective properties with increasing particles loads, up until the point where the particle load instead causes the coating to crack (at 40 wt%). The conclusion is that the hydrophobicity of the matrix and filler, in combination with the elongatedivdiffusion path supplied by the addition of particles, enhanced the corrosion protection of the underlying substrate.To further understand how hydrophobicity and particle addition affect the corrosion protective properties of a coating a three layer composite coating system was developed. Using this coating system, consisting of a polyester acrylate base coating, covered by TiO2 particles (with diameter < 100 nm) and finally coated with a thin hexamethyl disiloxane coating, it was found that both hydrophobicity and particles are needed to reach a great enhancement in corrosion protective properties also for this system.

Abstract [sv]

Eftersom metaller, och då särskilt stål, är viktigta konstruktionsmaterial i vårt moderna samhälle är korrosionsskydd av stor betydelse, både för att garantera säkerhet och för att minska kostnader som uppkommer i samband med korrosion. Tidigare har sexvärt krom och andra skadliga ämnen använts för att på ett effektivt sätt skydda stål från korrosion, men efter att deras användning kraftigt reglerades runt år 2000 har ännu ingen beläggning utvecklats som helt kan ersätta krombeläggningarna med avseende på funktion.I denna avhandling har hydrofoba och superhydrofoba ytbeläggningar och deras möjliga applikation som en del av ett korrosionsskyddande beläggningssystem studerats. Eftersom korrosionsmekanismen är beroende av närvaron av vatten, är användandet av en superhydrofob beläggning för att fördröja transporten av vatten till den underliggande metallytan intuitiv. De korrosionsskyddande egenskaperna hos superhydrofoba ytbeläggningar utvärderades här främst med hjälp av kontaktvinkelmätningar och elektrokemisk utvärdering i korrosiv lösning bestående av 3 vikts% NaCl i vatten.Först undersöktes skillnaden i korrosionsskydd som uppnås vid användandet av ytbeläggningar med olika hydrofoba vätningsregimer med hjälp av ett modellsystem bestående av ett alkylketendimer vax. Det konstaterades att superhydrofobicitet i Lotusregimen är överlägset bättre än de andra hydrofoba vätningsregimerna, i alla fall när man ser till relativt korta exponeringstider, typiskt mindre än tio dagar. Detta beror på att den kontinuerliga luftfilm som kan bildas på en sådan typ av superhydrofob yta kan minska transporten av elektrolyt (som innehåller korrosiva joner) till metallytan till den grad att den elektriska kretsen bryts. Eftersom korrosion inte kan ske utan en sluten elektrisk krets är detta ett mycket effektivt sätt att förhindra korrosion från att ske.Ett luftskikt på en superhydrofob yta nedsänkt i vatten är dock inte stabilt under lång tid. För att undersöka möjligheten till korrosionsskydd under längre tid med hjälp av hydrofoba beläggningar utvecklades en hydrofob ytbeläggning bestående av polydimetylsiloxan och hydrofoba nanopartiklar av kiseldioxid. Detta system visade en förbättring av korrosionsskyddet vid ökat partikelinnehåll upp till den koncentration (40 wt%) där i stället sprickbildning i ytbeläggningen observerades. Från detta system kunde slutsatsen dras att matrisens och partiklarnasvihydrofobicitet i kombination med den längre diffusionsvägen som partiklarna orsakade förbättrade korrosionsskyddet av den underliggande metallen.För att ytterligare förstå hur hydrofobicitet och partikeltillsatser påverkar en ytbeläggnings korrosionsskyddande egenskaper har dessutom ett treskikts kompositbeläggningssystem utvecklats. Genom att använda detta beläggningssystem, som består av en basbeläggning av polyesterakrylat, ett lager TiO2-partiklar (med en diameter på <100 nm) slutligen belagt med ett tunt ytskikt bestående av hexametyldisiloxan så kunde slutsatsen dras att både en hydrofob matris och partiklar behövs för att nå en markant förbättring av ytbeläggningens korrosionsskyddande egenskaper.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. , xvi, 57 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2015:54
Keyword [en]
Superhydrophobic coating, hydrophobic coating, corrosion protection, contact angles, electrochemical measurements, surface characterization
National Category
Engineering and Technology
Research subject
Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-175405ISBN: 978-91-7595-703-6 (print)OAI: oai:DiVA.org:kth-175405DiVA: diva2:860828
Public defence
2015-11-06, F3, Lindstedsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Foundation for Strategic Research , 2005:0073/13
Note

QC 20151015

Available from: 2015-10-15 Created: 2015-10-14 Last updated: 2015-10-15Bibliographically approved
List of papers
1. The effect of superhydrophobic wetting state on corrosion protection - The AKD example
Open this publication in new window or tab >>The effect of superhydrophobic wetting state on corrosion protection - The AKD example
Show others...
2013 (English)In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 412, 56-64 p.Article in journal (Refereed) Published
Abstract [en]

Corrosion is of considerable concern whenever metal is used as construction material. In this study we address whether superhydrophobic coatings could be used as part of an environmentally friendly corrosion-protective system, and specific focus is put on how the wetting regime of a superhydrophobic coating affects corrosion inhibition. Superhydrophobic alkyl ketene dimer (AKD) wax coatings were produced, using different methods resulting in hierarchical structures, where the coatings exhibit the same surface chemistry but different wetting regimes. Contact angle measurements, ESEM, confocal Raman microscopy, open circuit potential and electrochemical impedance spectroscopy were used to evaluate the surfaces. Remarkably high impedance values of 1010Ωcm2 (at 10-2Hz) were reached for the sample showing superhydrophobic lotus-like wetting. Simultaneous open circuit potential measurements suggest that the circuit is broken, most likely due to the formation of a thin air layer at the coating-water interface that inhibits ion transport from the electrolyte to the metal substrate. The remaining samples, showing superhydrophobic wetting in the rose state and hydrophobic Wenzel-like wetting, showed less promising corrosion-protective properties. Due to the absence of air films on these surfaces the coatings were penetrated by the electrolyte, which allowed the corrosion reaction to proceed.

Keyword
Alkyl ketene dimer (AKD), Corrosion protection, Superhydrophobic coating, Wetting state
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-136081 (URN)10.1016/j.jcis.2013.09.006 (DOI)000326665700009 ()2-s2.0-84885028398 (Scopus ID)
Funder
Swedish Foundation for Strategic Research , 2005:0073/13 RMA08-0044
Note

QC 20131204

Available from: 2013-12-04 Created: 2013-12-03 Last updated: 2017-12-06Bibliographically approved
2. Towards superhydrophobic polydimethylsiloxane-silica particle coatings
Open this publication in new window or tab >>Towards superhydrophobic polydimethylsiloxane-silica particle coatings
2016 (English)In: Journal of Dispersion Science and Technology, ISSN 0193-2691, E-ISSN 1532-2351, Vol. 37, no 9, 1375-1383 p.Article in journal (Refereed) Published
Abstract [en]

Hydrophobized silica nanoparticles of different sizes, from 16 to 500 nm, were used to impart roughness to a hydrophobic polydimethylsiloxane (PDMS) coating with the aim of obtaining superhydrophobic properties. The particle silanization process and the curing process of the PDMS coating were optimized to increase the contact angle of the particle containing coating. The evaluation of the coatings, by means of water contact angle measurements and scanning electron microscopy imaging, show that superhydrophobicity in the adhesive rose state was achieved using combinations of two differently sized particles, with an excess of the small 16 nm ones. Superhydrophobicity in the Lotus state was obtained when the filler concentration of 16 nm particles was 40 wt%, but under such conditions the coating was found to partially crack, which is detrimental in barrier applications. The preference for the rose wetting state can be explained by the round shape of the particles, which promotes the superhydrophobic rose wetting state over that of the superhydrophobic Lotus state.

Place, publisher, year, edition, pages
Taylor & Francis, 2016
Keyword
Silica particles, silanization, particle functionalization, superhydrophobic coating, wetting, rose state, Lotus state
National Category
Other Chemistry Topics
Research subject
Chemistry
Identifiers
urn:nbn:se:kth:diva-175401 (URN)10.1080/01932691.2015.1101610 (DOI)000374897300017 ()2-s2.0-84963606497 (Scopus ID)
Funder
Swedish Foundation for Strategic Research , 2005:0073/13
Note

QC 20160530

Available from: 2015-10-14 Created: 2015-10-14 Last updated: 2017-12-01Bibliographically approved
3. Corrosion protection by hydrophobic silica particle-polydimethylsiloxane composite coatings
Open this publication in new window or tab >>Corrosion protection by hydrophobic silica particle-polydimethylsiloxane composite coatings
2015 (English)In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, no 99, 89-97 p.Article in journal (Refereed) Published
Abstract [en]

In this study, the time-dependent corrosion protection ability of 10–15 µm thin polydimethylsiloxane -nanoparticle composite coatings was evaluated using mainly open circuit potential and electrochemical impedance spectroscopy measurements. The best result was obtained for the coating containing 20 wt% hydrophobic silica nanoparticles, where it was possible to achieve protection for almost 80 days in 3 wt% NaCl solution. The protective properties offered by this coating are suggested to be due to a synergistic effect of the hydrophobicity of the polydimethylsiloxane matrix and the prolonged diffusion path caused by addition of hydrophobic silica particles.

Keyword
Carbon steel, organic coating, EIS, electrochemical calculation, polymer coatings
National Category
Metallurgy and Metallic Materials
Research subject
Chemistry
Identifiers
urn:nbn:se:kth:diva-175400 (URN)10.1016/j.corsci.2015.06.018 (DOI)000362619900007 ()2-s2.0-84941805107 (Scopus ID)
Note

QC 20151015

Available from: 2015-10-14 Created: 2015-10-14 Last updated: 2017-12-01Bibliographically approved
4. Long-term corrosion protection by a thin nano-composite coating
Open this publication in new window or tab >>Long-term corrosion protection by a thin nano-composite coating
Show others...
2015 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584Article in journal (Refereed) Published
Abstract [en]

We report and discuss the corrosion protective properties of a thin nano-composite coating system consisting of an 11 μm thick polyester acrylate (PEA) basecoat, covered by an approximately 1 - 2 μm thick layer of TiO2 nanoparticles carrying a 0.05 μm thick hexamethyl disiloxane (HMDSO) top coat. The corrosion protective properties were evaluated on carbon steel substrates immersed in 3 wt% NaCl solution by open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) measurements. The protective properties of each layer, and of each pair of layers, were also evaluated to gain further understanding of the long term protective properties offered by the nano-composite coating. The full coating system showed excellent corrosion protective properties in the corrosive environment of 3 wt% NaCl-solution for an extended period of 100 days, during which the coating impedance, at the lower frequency limit (0.01 Hz), remained above 108 Ωcm2. We suggest that the excellent corrosion protective properties of the complete coating system is due to a combination of i) good adhesion and stability of the PEA basecoat, ii) the surface roughness and the elongated diffusion path provided by the addition of TiO2 nanoparticles, and iii) the low surface energy provided by the HMDSO top coat.

Place, publisher, year, edition, pages
Elsevier, 2015
Keyword
Liquid flame spray, corrosion, corrosion protection, carbon steel, plasma coating, impedance spectroscopy
National Category
Condensed Matter Physics
Research subject
Chemistry
Identifiers
urn:nbn:se:kth:diva-175402 (URN)10.1016/j.apsusc.2015.09.238 (DOI)000366219700131 ()2-s2.0-84957029673 (Scopus ID)
Note

QC 20160115

Available from: 2015-10-14 Created: 2015-10-14 Last updated: 2017-12-01Bibliographically approved
5. Comparison between AFM-based methods for assesing local surface mechanical properties of PDMS-silica composite layers
Open this publication in new window or tab >>Comparison between AFM-based methods for assesing local surface mechanical properties of PDMS-silica composite layers
Show others...
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Local surface mechanical properties of polymeric nanocomposites play a significant role in theirperformance. Atomic Force Microscopy (AFM) can be used to perform measurements of suchproperties with high lateral resolution. The interphase between filler and matrix, and how it can becontrolled by means of surface chemistry is of particular interest. In this work we compare threeoperating modes of AFM: Tapping mode, PeakForce QNM (Quantitative Nanomechanical Mapping)and Intermodulation AFM (ImAFM), for their ability to capture the tip-surface force and to extractlocal mechanical properties by applying different contact mechanics models. Layers ofpoly(dimethylsiloxane) (PDMS) with and without 20 wt.% of hydrophobic silica nanoparticles werestudied employing these AFM modes. We show that tapping mode AFM can provide qualitativeinformation, but it is insufficient to accurately and quantitatively discriminate surface propertiessince this mode does not allow extraction of the tip-surface force. Quantitative mapping ofmechanical properties is possible with both PeakForce QNM and ImAFM. However, it remained achallenge to evaluate the data for soft PDMS layers with PeakForce QNM. Local surface mechanicalproperties could be more reproducibly assessed via ImAFM. We show that the Tapping modeimages for pure PDMS report a relatively homogeneous surface, but as we utilize PeakForce QNMand ImAFM more details appear and the inhomogeneous nature of the surface layer becomesapparent. Incorporation of silica particles in the PDMS layer results in a significant increase in theapparent stiffness of the matrix. All imaging modes allow visualization of the hard particles in thesoft matrix. However, we were most successful with imaging the interphase using ImAFM.

Keyword
Nanomechanical properties, nanocomposites, Atomic Force Microscopy, Scanning probe microscopy, intermodulation, PDMS, elastic modulus, viscoelasticity
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-175404 (URN)
Note

QS 2015

Available from: 2015-10-14 Created: 2015-10-14 Last updated: 2017-03-15Bibliographically approved

Open Access in DiVA

Hydrophobic and superhydrophobic coatings for corrosion protection of steel - Lina Ejenstam(1978 kB)2680 downloads
File information
File name FULLTEXT01.pdfFile size 1978 kBChecksum SHA-512
71b9efdd763ab36b93e0d8a2542b77227934b8069f256c3fa27955a2aeba4b5b5847f51499c8da4dfe18c417bbfaf60b3693478b5a0620c7172b590e029915e6
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Ejenstam, Lina
By organisation
Surface and Corrosion Science
Engineering and Technology

Search outside of DiVA

GoogleGoogle Scholar
Total: 2680 downloads
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

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 666 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf