Biopolymeric Anticorrosion Coatings from Cellulose Nanofibrils and Colloidal Lignin Particles

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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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ACS Applied Materials and Interfaces, Volume 13, issue 34
This study presents a process for preparation of cellulose-lignin barrier coatings for hot-dip galvanized (HDG) steel by aqueous electrophoretic deposition. Initially, a solution of softwood kraft lignin and diethylene glycol monobutyl ether was used to prepare an aqueous dispersion of colloidal lignin particles (CLPs) via solvent exchange. Analysis of the dispersion showed that it comprised submicron particles (D = 146 nm) with spherical morphologies and colloidal stability (ζ-potential = -40 mV). Following successful formation, the CLP dispersion was mixed with a suspension of TEMPO-oxidized cellulose nanofibers (TOCN, 1 and 2 g·L-1) at a fixed volumetric ratio (1:1, TOCN-CLPs), and biopolymers were deposited onto HDG steel surfaces at different potentials (0.5 and 3 V). The effects of these variables on coating formation, dry adhesion, and electrochemical properties (3.5% NaCl) were investigated. The scanning electron microscopy results showed that coalescence of CLPs occurs during the drying of composite coatings, resulting in formation of a barrier layer on HDG steel. The scanning vibrating electrode technique results demonstrated that the TOCN-CLP layers reduced the penetration of the electrolyte (3.5% NaCl) to the metal-coating interface for at least 48 h of immersion, with a more prolonged barrier performance for 3 V-deposited coatings. Additional electrochemical impedance spectroscopy studies showed that all four coatings provided increased levels of charge transfer resistance (Rct) - compared to bare HDG steel - although coatings deposited at a higher potential (3 V) and a higher TOCN concentration provided the maximum charge transfer resistance after 15 days of immersion (13.7 cf. 0.2 kΩ·cm2 for HDG steel). Overall, these results highlight the potential of TOCN-CLP biopolymeric composites as a basis for sustainable corrosion protection coatings.
This research was funded by Technology Industries of Finland/Jane and Aatos Erkko Foundations “Future Makers: Biorefinery Side Stream Materials for Advanced Biopolymer Materials (BioPolyMet)” and Academy of Finland (NoWASTE, no. 297962). Furthermore, this work utilized facilities provided by the RawMatTERS Finland Infrastructure (RAMI) at Aalto University, supported by the Academy of Finland. Additionally, we are grateful for the support by the FinnCERES Materials Bioeconomy Ecosystem. The authors would like to express their gratitude to Jari Aroma for providing expertise on EIS, Antti Markkula and Pasi Väisänen (SSAB Europe Oy) for providing the HDG substrates, and Ville Saarimaa (Top Analytica Oy) for assistance with further characterization of the coatings. Publisher Copyright: © 2021 The Authors. Published by American Chemical Society.
electrochemical impedance spectroscopy, electrophoretic deposition, galvanized steel, scanning vibrating electrode technique, water-borne
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Dastpak, A, Ansell, P, Searle, J R, Lundström, M & Wilson, B P 2021, ' Biopolymeric Anticorrosion Coatings from Cellulose Nanofibrils and Colloidal Lignin Particles ', ACS Applied Materials and Interfaces, vol. 13, no. 34, pp. 41034-41045 .