Investigation of the anticorrosion performance of lignin coatings after crosslinking with triethyl phosphate and their adhesion to a polyurethane topcoat

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Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2020-01-01
Major/Subject
Mcode
Degree programme
Language
en
Pages
9
762-770
Series
AGRONOMY RESEARCH, Volume 18, issue Special Issue 1
Abstract
This study investigates the anticorrosion properties of sustainable organic coatings, which were prepared by dissolution of two different types of technical lignins-organosolv lignin (OL) and kraft lignin (KL)-in an organic solvent and applied onto iron-phosphated steel by air-assisted spray coating. Influence of triethyl phosphate (TEP) as a crosslinking agent for lignin and its effect on the anticorrosion properties of coatings during 24 h of immersion in 3.5% NaCl were investigated. Results obtained from electrochemical impedance spectroscopy (EIS) of coated steels suggest that the initial protection performance (1 h immersion) of non-crosslinked OL is higher than that of KL. Nevertheless, KL coatings that contained TEP and were heat-treated at elevated temperature (180 °C) demonstrated the best overall anticorrosion performance. In contrast, a similar trend was not observed for OL coatings, which indicates that the structural properties of lignin may be a crucial factor in applicability of TEP as a crosslinking agent. In addition, a layer of polyurethane was applied on all the different types of lignin coatings prepared and their adhesion characteristics were studied by crosscut adhesion measurements (ISO 2409). These adhesion results revealed that neither KL-TEP nor OL-TEP coatings demonstrate proper adhesive characteristics with a polyurethane (PU) topcoat and consequently these coatings are not suitable for utilization as a primer coating for the PU topcoat studied.
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Keywords
Corrosion protection, Kraft lignin, Organosolv lignin, Sustainable coatings, Triethyl phosphate crosslinker
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Citation
Dastpak , A , Wilson , B P & Lundström , M 2020 , ' Investigation of the anticorrosion performance of lignin coatings after crosslinking with triethyl phosphate and their adhesion to a polyurethane topcoat ' , Agronomy Research , vol. 18 , no. Special Issue 1 , pp. 762-770 . https://doi.org/10.15159/AR.20.061