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Corrosion protection and nanomechanical properties of waterborne acrylate-based coating with and without nanocellulose on carbon steel
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.ORCID iD: 0000-0003-2151-2913
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Corrosion protection is commonly achieved by applying a thin polymer coating on metal surfaces. In this doctoral thesis, a waterborne hydroxyacrylate-melamine copolymer coating was used for this purpose. The first step was to find the optimal curing conditions. To this end the effect of curing time at 180 °C on the conversion of the cross-linking reaction, surface topography, nanomechanical and nanowear properties were investigated using atomic force microscopy, AFM. The results demonstrated that optimal performance required 10 min curing at 180 °C. This resulted in 80% conversion of the cross-linking reaction, as well as good barrier performance with polarization resistance of the order of 109Ω·cm2during 35 days in 0.1 M NaCl solution as determined by Electrochemical Impedance Spectroscopy (EIS). It also resulted in minor surface roughness and high surface elastic modulus in the order of GPa. 

 

This waterborne coating and its nanocomposite containing 0.5 wt.% cellulose nanocrystals (CNC) were systematically studied, focusing on their corrosion protection performance and the effect of environment and localized wear on the properties of the top surface. The results show that both coatings have high polarization resistance, Rp. For the matrix coating the polarization resistance displays a slightly decreasing trend with time, as expected for a barrier coating. In contrast, the CNC nanocomposite coating exhibits an unusual and unexpected increase in polarization resistance with time. The difference in the time dependence of Rp can be attributed to the reinforcement effect of CNC, which form strong hydrogen bonding interactions with the matrix coating. Further, the appearance of a second time constant in the corresponding EIS spectra implies formation of a more protective second layer at the metal-coating interface. The presence of this compact layer also contributes to the corrosion protection offered by the CNC nanocomposite coating. In addition, both coatings show only limited water-uptake during long term exposure to 0.1 M NaCl. The water up-take is too small to measurably change the coating capacitance, as studied by EIS. However, AFM studies of surface nanomechanical properties show that for the CNC nanocomposite some water penetration occurs, which irreversibly renders the surface softer.

 

Inspired by the CNC nanocomposite coating and its favorable corrosion protective properties, 0.5 wt.% cellulose nanofibrils, CNF, nanocomposite coatings were also studied using the same methodologies. The results revealed that the CNF nanocomposite coating cannot provide efficient corrosion protection performance even over a period of 24 h. The measured polarization resistance decreases rapidly over time, and consistently water uptake is readily observed by analyzing coating capacitance using EIS technique. The substantial difference in corrosion protective properties of the CNC nanocomposite and the CNF nanocomposite are explained mainly from the perspective of microstructure, matrix-CNC or matrix-CNF interactions by using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The results show the presence of defects on the surface and in the bulk and absence of strong hydrogen bonding interactions between matrix and CNF. These are two reasons for why the CNC nanocomposite performs well in terms of corrosion protection, whereas the CNF nanocomposite does not. 

 

In real applications good barrier coatings may also fail due to external forces such as erosion by wind and water, impact of solid particles or sliding motions against other objects, which may destroy the coating integrity. This motivated further studies of the matrix and the CNC nanocomposite, by focusing on their nanomechanical and nano-wear properties using local measurements by means of AFM. The effect of applied normal load, ranging from 50 – 400 nN, scanning speed, ranging from 1 – 20 µm/s, operating environment including air and water, as well as exposure to corrosive 0.1 M NaCl solution, were systematically studied and discussed.

Abstract [sv]

Korrosionsskydd uppnås vanligtvis genom att applicering av en tunn polymerbeläggning på metallytan. I denna doktorsavhandling studerades först en vattenburen hydroxyakrylat-melamin-sampolymerbeläggning för att hitta de optimala härdningsförhållandena. Effekten av härdningsbetingelserna, t ex längd på härdningstiden vid 180 °C, på omvandling av tvärbindningsreaktion, yttopografi och nanomekaniska egenskaper och nanodegrarderingsegenskaper undersöktes med användning av AFM. Resultaten visar att det optimala härdningsförhållandet är vid 180 ° C under 10 min, vilket kan ge 80% omvandlingen av tvärbindningsreaktionen, liksom goda barriärprestanda med en polarisationsresistens i storleksordningen 109Ω·cm2under lång tids exponering under 35 dagar för 0,1 M NaCl-lösning utvärderat med elektrokemisk impedansspektroskopi (EIS). Mindre ytråhet och hög ytelastisk modul i storleksordningen GPa uppnås också för prover under optimalt härdningsförhållande.

 

Vidare studerades ovan vattenburen beläggning och dess nanokomposit innehållande 0,5 viktprocent cellulosa nanokristaller (CNC) systematiskt med fokus på deras korrosionsskyddsprestanda. Mätningarna utfördes med elektrokemisk impedansspektroskopi (EIS) teknik i 0,1 M NaCl-lösning. Resultaten visar att båda beläggningarna har hög polarisationsbeständighet i storleksordningen 108- 109ohm · cm2. För matrisbeläggningen uppvisar polarisationsmotståndet en svag minskande trend medan CNC-nanokompositbeläggningen uppvisar en ökande trend. Skillnaden i Rp-beteenden kan delvis tillskrivas förstärkningseffekten av CNC där starka vätebindningar bildas mellan CNC och matrisbeläggningen. Dessutom innebär närvaron av en andra tidskonstant i motsvarande EIS-spektra att ett mer skyddande andra skikt bildats, troligen vid gränsytan mellan metallen och beläggningen. Närvaron av detta kompakta skikt bidrar också till de korrosionsskyddande egenskaperna hos CNC-nanokompositbeläggningen. Dessutom uppvisar båda beläggningarna endast begränsat vattenupptag under långvarig exponering, vilka är för obetydliga för att mätbart förändra beläggningskapacitansen, vilket studerades med EIS.

 

Inspirerad av CNC-nanokompositbeläggningen och dess gynnsamma korrosionsskyddande egenskaper studerades också 0,5 vikt-% CNF-nanokompositbeläggningar på samma sätt. Resultaten avslöjar att CNF-nanokompositbeläggningen inte kan ge effektivt korrosionsskydd ens under 24 timmar. Det uppmätta Rp-värdet minskar snabbt över tiden och därigenom ökar vattenupptaget över tiden, vilket studerades med EIS. Den väsentliga skillnaden i korrosionsskyddande egenskaper hos CNC-nanokompositen och CNF-nanokompositen förklarades huvudsakligen från perspektivet av mikrostruktur, matris-CNC eller matris-CNF-interaktioner genom att använda svepelektronmikroskopi (SEM) och Fourier transform infraröd spektroskopi (FTIR). Resultaten visar att närvaron av defekter på ytan och i bulk och frånvaro av starka vätebindningar mellan matris-CNF i den beredda CNF-nanokompositbeläggningen bidrar till de dåliga barriäregenskaperna.

 

I själva verket kan en bra barriärbeläggning också förstöras på grund av yttre krafter som infallande fasta partiklar eller glidande rörelser mot andra föremål, vilket förstör beläggningens integritet. Därför studerades CNC-nanokompositbeläggningen ytterligare med fokus på dess nanomekaniska och nano-nötnings egenskaper med användning av (atomkraftsmikroskopi) AFM-teknik. Effekten av applicerad normal belastning från 50 - 400 nN, skanningshastighet från 1 - 20 um/s, typ av omgivning inklusive luft och vatten, samt exponering för korroderand 0,1 M NaCl-lösning, studerades och diskuterades systematiskt.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2019. , p. 53
Series
TRITA-CBH-FOU ; 2019:62
Keywords [en]
Hydroxyacrylate-melamine copolymer, cellulose nanocrystals (CNC), cellulose nanofibrils (CNF); Electrochemical impedance spectroscopy (EIS), atomic force microscopy (AFM); corrosion protection performance, water uptake, nanomechanical and nano-wear properties, coating, nanocomposite.
Keywords [sv]
Hydroxyakrylat-melamin-sampolymer, cellulosananokristaller (CNC), cellulosananofibriller (CNF); Elektrokemisk impedansspektroskopi (EIS), atomkraftsmikroskopi (AFM); korrosionsskyddsprestanda, vattenupptag, nanomekaniska egenskaper och nano-slitage, coating, nanokomposit.
National Category
Natural Sciences
Research subject
Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-262709ISBN: 978-91-7873-349-1 (print)OAI: oai:DiVA.org:kth-262709DiVA, id: diva2:1362225
Public defence
2019-11-22, M3, Brinellvägen 64, Lecture Hall M3, KTH campus, Stockholm, Sweden., Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 2019-10-18

Available from: 2019-10-18 Created: 2019-10-18 Last updated: 2019-10-22Bibliographically approved
List of papers
1. Nano-scale mechanical and wear properties of a corrosion protective coating reinforced by cellulose nanocrystals: initiation of coating
Open this publication in new window or tab >>Nano-scale mechanical and wear properties of a corrosion protective coating reinforced by cellulose nanocrystals: initiation of coating
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Organic coatings are commonly used for protection of substrate surfaces like metals and wood. In most cases they fulfil their purpose by acting as a barrier against unwanted substances such as oxygen, water or corrosive ions. However, with time coatings fail due to degradation caused by chemical reactions or wear by wind, water, impact of solid particles or sliding motions against other solid objects. In this work we focus on a nanocomposite coating having a hydroxyacrylate-melamine matrix and being reinforced by a small amount (0.5 wt.%) of cellulose nanocrystals. This nanocomposite is of interest as it has shown favourable corrosion protection properties on carbon steel. Here we investigate the nanomechanical and nanowear properties of the coating in air and in water, and we also explore how these properties are affected by exposure to a corrosive 0.1 M NaCl solution. Our data show that the nanomechanical properties of the coating surface is strongly affected by the environment (air or water), and that exposure to the corrosive solution affects the coating surface well before any deterioration of the corrosion protective properties are found. We suggest that our experimental methodology constitutes a powerful way to investigate and understand the initiation of coating degradation.

Keywords
Nanomechanical properties, nanowear, nanocomposite, coating degradation, scanning probe microscopy, hydroxyacrylate, cellulose nanocrystal
National Category
Physical Chemistry
Research subject
Chemistry
Identifiers
urn:nbn:se:kth:diva-262698 (URN)
Note

QC 20191023

Available from: 2019-10-17 Created: 2019-10-17 Last updated: 2019-10-23Bibliographically approved
2. Corrosion protective properties of cellulose nanocrystals reinforced waterborne acrylate-based composite coating
Open this publication in new window or tab >>Corrosion protective properties of cellulose nanocrystals reinforced waterborne acrylate-based composite coating
Show others...
2019 (English)In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 155, p. 186-194Article in journal (Refereed) Published
Abstract [en]

The present investigation highlights corrosion protection of carbon steel by a waterborne acrylate-based matrix coating, with and without reinforcement by cellulose nanocrystals, by using electrochemical impedance spectroscopy in 0.1 M NaCl solution over a period of 35 days. Interactions between cellulose nanocrystals and the matrix coating were demonstrated by Fourier transform infrared spectroscopy. The results show that both coatings have high barrier performance but different protective characteristics during long-term exposure. The differences can be attributed to the reinforcement effect of cellulose nanocrystals caused by hydrogen bonding interactions between cellulose nanocrystals and the matrix coating.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Waterborne organic coatings, Cellulose nanocrystals, Electrochemical impedance spectroscopy, IR spectroscopy, Interfaces, Corrosion protection performance
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-262694 (URN)10.1016/j.corsci.2019.04.038 (DOI)000471086500018 ()2-s2.0-85065617813 (Scopus ID)
Note

QC 20191018

Available from: 2019-10-17 Created: 2019-10-17 Last updated: 2019-10-18Bibliographically approved
3. Comparative study of CNC and CNF as additives in waterborne acrylate-based anti-corrosion coatings
Open this publication in new window or tab >>Comparative study of CNC and CNF as additives in waterborne acrylate-based anti-corrosion coatings
Show others...
2019 (English)In: Journal of Dispersion Science and Technology, ISSN 0193-2691, E-ISSN 1532-2351Article in journal (Refereed) Published
Abstract [en]

Nanocomposite coatings are of great interest as barrier coatings since synergy effects between matrix and additive properties can be achieved. This, however, requires favorable additive-matrix interactions to provide a strong interphase (interface region). In this work we elucidate the properties of two environmentally benign nanocomposite coatings based on a waterborne acrylate formulation with additives from renewable sources, i.e. either cellulose nanocrystals, CNC; or, alternatively, cellulose nanofibrils, CNF. We focus on the corrosion protective properties of these coatings and discuss the reason why the nanocomposite with CNC displays favorable corrosion protection properties whereas that with CNF does not. To this end we utilized scanning electron microscopy, water contact angle measurement, Fourier transform infrared spectroscopy and electrochemical impedance spectroscopy techniques to investigate the microstructure, surface wetting, interactions between cellulosic materials and matrix as well as corrosion protective properties of both composite coatings.

Place, publisher, year, edition, pages
Taylor & Francis, 2019
Keywords
Composite coating, corrosion protection, cellulose nanocrystals, cellulose nanofibrils, electrochemical impedance spectroscopy
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-257650 (URN)10.1080/01932691.2019.1647229 (DOI)000479890700001 ()
Note

QC 20190904

Available from: 2019-09-04 Created: 2019-09-04 Last updated: 2019-10-18Bibliographically approved
4. Nano-scale mechanical and wear properties of a waterborne hydroxyacrylic-melamine anti-corrosion coating
Open this publication in new window or tab >>Nano-scale mechanical and wear properties of a waterborne hydroxyacrylic-melamine anti-corrosion coating
Show others...
2018 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 457, p. 548-558Article in journal (Refereed) Published
Abstract [en]

Corrosion protection is commonly achieved by applying a thin polymer coating on the metal surface. Many studies have been devoted to local events occurring at the metal surface leading to local or general corrosion. In contrast, changes occurring in the organic coating after exposure to corrosive conditions are much less studied. In this article we outline how changes in the coating itself due to curing conditions, environmental and erosion effects can be investigated at the nanometer scale, and discuss how such changes would affect its corrosion protection performance. We focus on a waterborne hydroxyacrylic-melamine coating, showing high corrosion protection performance for carbon steel during long-term (approximate to 35 days) exposure to 0.1 M NaCl solution. The effect of curing time on the conversion of the crosslinking reaction within the coating was evaluated by fourier transform infrared spectroscopy (FTIR); the wetting properties of the cured films were investigated by contact angle measurement, and the corrosion resistance was studied by electrochemical impedance spectroscopy (EIS). In particular, coating nanomechanical and wear properties before and after exposure to 0.1 M NaCl, were evaluated by atomic force microscopy (AFM). Fiber-like surface features were observed after exposure, which are suggested to arise due to diffusion of monomers or low molecular weight polymers to the surface. This may give rise to local weakening of the coating, leading to local corrosion after even longer exposure times. We also find a direct correlation between the stick-slip spacing during shearing and plastic deformation induced in the surface layer, giving rise to topographical ripple structures on the nanometer length scale.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Waterborne anti-corrosive coating, Electrochemical impedance spectroscopy, Nanomechanical property, Nanowear, Fast fourier transform analysis
National Category
Other Chemistry Topics
Identifiers
urn:nbn:se:kth:diva-235097 (URN)10.1016/j.apsusc.2018.06.284 (DOI)000441872300065 ()2-s2.0-85049824578 (Scopus ID)
Funder
Swedish Research Council, 2015-05080
Note

QC 20180917

Available from: 2018-09-17 Created: 2018-09-17 Last updated: 2019-10-18Bibliographically approved

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