Liquid-core polyelectrolyte nanocapsules produced by membrane emulsification as carriers for corrosion inhibitors

Polyelectrolyte capsules loaded with the mixture of two inhibitors: 2-methylbenzothiazole (BT) and 2-mercaptobenzothiazole (MBT), were successfully produced by a membrane emulsification process. The capsules diameter was about 3-4 mu m allowing introduction of about 10 wt% of BT and 0.5 wt% of MBT to the dry epoxy coating. Anti-corrosive coatings were prepared on the surface of AA2024T3 alloy, scratched by a steel blade, and tested for the occurrence of the self-healing action by electrochemical impedance spectroscopy in 0.05 mol dm(-3) NaCI solution. Some worsening of the barrier properties of the coatings due to the introduction of the capsules was observed, which however was to some extent compensated by the leaking of the inhibitor from the capsules. The coating showed the self-healing action only when contacted with the restricted volume of the NaCl solution, which was ascribed to the washing-out of the inhibitor from the surface in the case of the large volume of the electrolyte. (C) 2016 Elsevier B.V. All rights reserved.