Smart protection provided by epoxy clear coating doped with polystyrene microcapsules containing silanol and Ce (III) ions as corrosion inhibitors

• Polystyrene microcapsules release encapsulated corrosion inhibitors by mechanical triggering.
• After a mechanical damage the doped system shows better performance due to the self-healing effect.
• The protection offered by the microcapsule-doped coating was markedly better than the non-doped.

Polystyrene microcapsules loaded with octylsilanol and Ce (III) ions as core materials have been synthesized by solvent evaporation method from a double emulsion. The obtained microcapsules were doped into an epoxy clear coating and applied on carbon steel. A mechanical defect was done on the coating, in order to evaluate the self-healing effect.The self-healing effect provided by this system was studied by electrochemical impedance spectroscopy (EIS), scanning vibrating electrode technique (SVET) and accelerated corrosion tests in salt spray chamber (SSC) of the coated samples with a clear epoxy coating formulated with 30% w/w of polystyrene microcapsules.For the samples with artificial defect, the performance of the microcapsule-formulated coating was better than the formulated without microcapsules, due to the release of the inhibitors, even after 120 h of immersion in 0.05 molL− 1 NaCl solution. The SVET results are in good agreement with the EIS results, showing the corrosion inhibition in the artificial defects done in coated samples and endorsed the marked self-healing effect. The accelerated tests in salt spray chamber have shown less corrosion products and minor blistering around the scratch for the coating formulated with inhibitor containing microcapsules after 144 h of exposure.

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