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Abstract
Two strategies on the development of novel inhibitive pigment for coatings for corrosion protection were investigated in this work: I. Inhibitive pigment encapsulation with control-release and II. Green inhibitive pigment development. Epoxy coatings formulated with the as-developed novel inhibitive pigments showed enhanced anti-corrosive properties.
I. Smart Anti-corrosive Coating with Control-release of Inhibitive Pigment via Encapsulation
Calcium phosphate was encapsulated into mesoporous silica nanoparticles (MSN). The effect of pH on the structure and morphology of the MSN and the release of calcium phosphate from the MSN was investigated. Epoxy coatings with encapsulated (3 wt.%) and non-encapsulated (3 wt.% and 5 wt.%) calcium phosphate were formulated and their anti-corrosive performance was evaluated by Open Circuit Potential (OCP) and Electrochemical Impedance Spectroscopy (EIS) techniques. Results showed that encapsulation of the calcium phosphate as inhibitive pigment in the coating can enhance the anti-corrosive performance by preventing spontaneous pigment dissolution and controlling the pigment’s release from the coating.
To understand how the encapsulated pigment works in the coating, the changes of the coating microstructure and the leaching behavior of pigment were studied for both the conventionally pigmented coatings and the smart coatings with encapsulated pigment. Leaching of calcium phosphate as an inhibitive pigment from epoxy coatings was tested in 3.5% NaCl solution. Results showed that pigment encapsulation contributes to a more uniform and stable coating microstructure based on the Scanning Electron Microscopy – Energy-Dispersive X-ray Spectroscopy (SEM-EDX) analysis and a higher leaching rate of the inhibitive pigment via the Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) analysis, thereby enhancing both the active corrosion protection and the barrier properties of the coating film.
II. Green Inhibitive Pigment for Anti-corrosive Coating Formulation
A Tannin-based inhibitive pigment, calcium tannate, was synthesized, characterized, and dispersed into an epoxy coating as an inhibitive pigment. EIS was employed to monitor the anti-corrosive performance of the coating formulated with the as-prepared pigment after exposure to the salt spray chamber. Reference coatings with the commercial calcium phosphate pigment and unpigmented coating were also evaluated for comparison reasons. EIS results showed that epoxy coating pigmented with calcium tannate has higher coating impedance after 21 days of exposure compared with reference coatings, either unpigmented or calcium phosphate pigmented coatings. X-ray Photoelectron Spectroscopy (XPS) analysis was conducted for a deeper understanding of the inhibitive action of calcium tannate towards corrosion protection and verified the incorporation of tannate molecules in the protective film formed on the steel substrate under the calcium tannate pigmented coating.
I. Smart Anti-corrosive Coating with Control-release of Inhibitive Pigment via Encapsulation
Calcium phosphate was encapsulated into mesoporous silica nanoparticles (MSN). The effect of pH on the structure and morphology of the MSN and the release of calcium phosphate from the MSN was investigated. Epoxy coatings with encapsulated (3 wt.%) and non-encapsulated (3 wt.% and 5 wt.%) calcium phosphate were formulated and their anti-corrosive performance was evaluated by Open Circuit Potential (OCP) and Electrochemical Impedance Spectroscopy (EIS) techniques. Results showed that encapsulation of the calcium phosphate as inhibitive pigment in the coating can enhance the anti-corrosive performance by preventing spontaneous pigment dissolution and controlling the pigment’s release from the coating.
To understand how the encapsulated pigment works in the coating, the changes of the coating microstructure and the leaching behavior of pigment were studied for both the conventionally pigmented coatings and the smart coatings with encapsulated pigment. Leaching of calcium phosphate as an inhibitive pigment from epoxy coatings was tested in 3.5% NaCl solution. Results showed that pigment encapsulation contributes to a more uniform and stable coating microstructure based on the Scanning Electron Microscopy – Energy-Dispersive X-ray Spectroscopy (SEM-EDX) analysis and a higher leaching rate of the inhibitive pigment via the Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) analysis, thereby enhancing both the active corrosion protection and the barrier properties of the coating film.
II. Green Inhibitive Pigment for Anti-corrosive Coating Formulation
A Tannin-based inhibitive pigment, calcium tannate, was synthesized, characterized, and dispersed into an epoxy coating as an inhibitive pigment. EIS was employed to monitor the anti-corrosive performance of the coating formulated with the as-prepared pigment after exposure to the salt spray chamber. Reference coatings with the commercial calcium phosphate pigment and unpigmented coating were also evaluated for comparison reasons. EIS results showed that epoxy coating pigmented with calcium tannate has higher coating impedance after 21 days of exposure compared with reference coatings, either unpigmented or calcium phosphate pigmented coatings. X-ray Photoelectron Spectroscopy (XPS) analysis was conducted for a deeper understanding of the inhibitive action of calcium tannate towards corrosion protection and verified the incorporation of tannate molecules in the protective film formed on the steel substrate under the calcium tannate pigmented coating.
Original language | English |
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Place of Publication | Kgs. Lyngby |
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Publisher | Technical University of Denmark |
Number of pages | 149 |
Publication status | Published - 2022 |
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Dive into the research topics of 'Novel Inhibitive Pigments for Corrosion Protection'. Together they form a unique fingerprint.Projects
- 1 Finished
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Role of Additives on Corrosion Protection of Metals by Organic Coatings
Lamprakou, Z. (PhD Student), Fedel, M. (Examiner), Gunnarsson, S. (Examiner), Dam-Johansen, K. (Main Supervisor), Bi, H. (Supervisor) & Weinell, C. E. (Supervisor)
01/02/2019 → 09/06/2022
Project: PhD