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Multiscale Analysis of pigment effects on weathering of Polyester Coatings: From Nanoscale Chemistry to Macroscale Performance
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. RISE Research Institutes of Sweden, Division Materials and Production, Department of Corrosion, Kista, Sweden.ORCID iD: 0000-0001-6438-1357
Top Analytica, Turku, Finland.ORCID iD: 0000-0001-6394-0161
SSAB Europe, Borlänge, Sweden.
SSAB Europe, Borlänge, Sweden.
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2025 (English)In: npj Materials Degradation, E-ISSN 2397-2106, Vol. 9, no 1, article id 66Article in journal (Refereed) Published
Abstract [en]

Almost all organic coatings used for corrosion protection contain various types of pigmentation, both for the sake of aesthetics and performance. By focusing on spatially resolved vibrational spectroscopy and electron microscopy, we demonstrate that the type of pigmentation has a fundamental effect on both localized and global degradation processes across the investigated coatings. Samples with white TiO2 pigments display low macroscale chemical degradation across the surface but do experience a significant change in topography. SEM-EDS imaging shows that µm-scale craters are formed around the TiO2 pigments. Nanoscale spatially resolved IR spectroscopy (AFM-IR) suggests that this local erosion is not triggered by reactions seen in coatings with other types of pigments. However, FTIR-ATR chemical imaging of coating cross sections confirmed that the TiO2 pigments also protects material beneath the surface, resulting in very shallow chemical degradation effects as compared to the other systems. Darker coatings, containing carbon black, experience moderate to high chemical degradation across the surface, and additionally the degradation propagates deep into the coatings. Overall, this paper highlights that single criteria should not be used when comparing the degradation of different coatings.

Place, publisher, year, edition, pages
Springer Nature , 2025. Vol. 9, no 1, article id 66
National Category
Analytical Chemistry Polymer Chemistry Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-356717DOI: 10.1038/s41529-025-00617-3ISI: 001504541100001Scopus ID: 2-s2.0-105007526225OAI: oai:DiVA.org:kth-356717DiVA, id: diva2:1914969
Note

QC 20250701

Available from: 2024-11-20 Created: 2024-11-20 Last updated: 2025-08-01Bibliographically approved
In thesis
1. Micro- and nanoscale perspectives on degradation in coil coated materials
Open this publication in new window or tab >>Micro- and nanoscale perspectives on degradation in coil coated materials
2024 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Coil coating is a process where durable organic coatings are applied onto metalsubstrates to prevent corrosion and to add texture or color. Recent rapiddevelopments in coating formulations, often motivated by improvedsustainability, have led to changes in established formulations. A less exploredaspect of these developments is the importance of testing and evaluationmethods. Especially methods to assess and predict long term stability. Thisthesis presents how well established and newly developed techniques can beused together to better understand and quantify degradation processes inorganic coatings. In addition, test results are also used to understand differencesbetween natural and artificial weathering methods. The focus lies on chemicalanalysis methods with spatial resolution on the micro-, and nanoscale.

Spatially resolved infrared spectroscopy shows that additions of renewablediluents or pigments significantly impact degradation, both at the surface andwithin the depth profile. The pigmentation type greatly affects the chemicaldegradation and how deep into the coating the degradation reaches. In addition,the kinetics of water transport are correlated with degradation in the coatingcross-section. Local assessments on the nanoscale using SEM- and AFM-basedtechniques reveal that TiO2 pigments causes local erosion across the surface andvoids inside the coatings. Nanoscale mechanical testing show that weatheringcaused homogenization and an increase in stiffness on the sub-micron scale innon-pigmented coatings. However, no major variation in chemical degradationacross small surface areas is observed.

Abstract [sv]

Bandlackering är en process där stabila organiska beläggningar appliceras på metallsubstrat för att förhindra korrosion samt ge textur och färg åt ytan. Snabba framsteg inom beläggningsformuleringar, ofta drivna av förbättrad hållbarhet, har lett till förändringar i etablerade formuleringar. En mindre utforskad aspekt av dessa framsteg är vikten av test- och utvärderingsmetoder, särskilt metoder för att bedöma och förutsäga långsiktig stabilitet. Denna avhandling visar hur väletablerade och nyutvecklade tekniker används tillsammans för att bättre förstå och kvantifiera nedbrytningsprocesser i organiska beläggningar. Dessutom används testresultat för att förstå skillnader mellan naturlig och artificiell väderpåverkan. Fokus ligger på kemiska analysmetoder med spatial upplösning på mikro- och nanonivå.Spatialt upplöst infraröd spektroskopi visar att tillsatser av förnybara additiv eller pigment visats ha en betydande inverkan på nedbrytning både i ytan och djupt inne i systemen. Vilken typ av pigment som finns i en beläggning kan avsevärt förändra hur mycket kemisk nedbrytning som uppstår, samt hur djupt in i beläggningen nedbrytningen når. Dessutom har en korrelation mellan vattentransport och djupgående nedbrytning observerats. Lokala mätningar med upplösning på nanonivå med SEM- och AFM-baserade tekniker visade att TiO2 orsakar lokal erosion över ytan och mikrometerstora håligheter inuti beläggningarna. Mekaniska tester på nanoskalan visade att även om exponering i natur-liknande förhållanden orsakade homogenisering och en ökning av styvheten hos beläggning över små områden. Trots detta förekom ingen större variation i kemisk nedbrytning på denna storleksskala.

Place, publisher, year, edition, pages
Stockholm, Sweden: KTH Royal Institute of Technology, 2024. p. 72
Series
TRITA-CBH-FOU ; 2024:52
Keywords
Corrosion protection, coil coating, FTIR, AFM-IR, nano-FTIR, hyperspectral imaging, nanomechanical properties, Nyckelord: Korrosionsskydd, bandlackering, vittring, FTIR, AFM-IR, nano-FTIR, hyperspektral avbildning, AFM, nanomekaniska egenskaper
National Category
Chemical Sciences
Research subject
Chemistry
Identifiers
urn:nbn:se:kth:diva-356718 (URN)978-91-8106-134-5 (ISBN)
Public defence
2024-12-18, F3, Lindstedtsvägen 26, https://kth-se.zoom.us/j/61979698033, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Foundation for Strategic Research, FID18-0034
Note

QC 20241126

Embargo t.o.m. 2025-12-18 godkänt av skolchef Amelie Eriksson Karlström via e-post 2024-11-25

Available from: 2024-11-26 Created: 2024-11-24 Last updated: 2026-01-22Bibliographically approved

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Wärnheim, AlexanderJohnson, C. MagnusClaesson, Per M.

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