Micro- and nanoscale perspectives on degradation in coil coated materials
Time: Wed 2024-12-18 10.00
Location: F3 (Flodis), Lindstedtsvägen 26 & 28, Stockholm
Video link: https://kth-se.zoom.us/j/61979698033
Language: English
Subject area: Chemistry
Doctoral student: Alexander Wärnheim , Yt- och korrosionsvetenskap, RISE Research Institutes of Sweden, Department of Corrosion
Opponent: Professor Carita Kvarnström, University of Turku, Finland
Supervisor: Professor C. Magnus Johnson, Yt- och korrosionsvetenskap; Doktor Dan Persson, RISE; Professor Per M. Claesson, Yt- och korrosionsvetenskap
QC 20241126
Embargo t.o.m. 2025-12-18 godkänt av skolchef Amelie Eriksson Karlström via e-post 2024-11-25
Abstract
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.