Corrosion protection of AA2024 by sol–gel coatings modified with MBT-loaded polyurea microcapsules

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Vol. 283; pp. 1108 - 1117
• Main Authors: Maia, F., Yasakau, K.A., Carneiro, J., Kallip, S., Tedim, J., Henriques, T., Cabral, A., Venâncio, J., Zheludkevich, M.L., Ferreira, M.G.S.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.01.2016
• Subjects: Controlled release; Corrosion inhibitor; Corrosion protection; Polyurea microcapsules; Sol–gel coating; Corrosion protection; Corrosion inhibitor; Controlled release; Polyurea microcapsules; Sol–gel coating
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2015.07.087

[Display omitted] •Successful encapsulation of 2-mercaptobenzothiazole in polyurea microcapsules.•Encapsulation reduces the detrimental interaction between corrosion inhibitor and sol–gel matrix.•Loaded microcapsules suppresses corrosion activity and improves the adhesion of sol–gel coatings to the metal substrate.•Self-healing corrosion protective coatings for AA2024 based on modified sol–gel coating with MBT@PU-MC. In this work we report the synthesis of polyurea microcapsules loaded with corrosion inhibitor 2-mercaptobenzothiazole (MBT) for corrosion protection of 2024 aluminum alloy. The microcapsules were prepared by interfacial polycondensation. The resulting capsules exhibit spherical shape, with diameter ranging between 100nm and 2μm. The loading content of MBT was found to be 5wt% and release studies showed that MBT is preferentially released under acidic and alkaline conditions and follows a Fickian diffusion model. This pH dependency seems suitable for protection of metallic alloys where corrosion processes are accompanied by local pH changes. Furthermore, the microcapsules were added to a hybrid sol–gel coating and its performance assessed by electrochemical and accelerated standard tests. The results obtained indicate that capsules loaded with MBT do not affect negatively the barrier properties of sol–gel coatings, and contribute for the enhancement of adhesion of coatings to the metallic substrate. More relevant, these additives impart active corrosion protection suppressing corrosion activity at defect sites, which opens prospects for application of polyurea microcapsules as additives for high-performance coatings.