SMART COATINGS CONTAINING LINSEED OIL MICROCAPSULES AS SELF-HEALING AGENT

摘要

The aim of this work is the preparation of a smart coating with epoxy resin that is able to repair itself (self-heal) when suffering a mechanical defect. Self-healing mechanism is possible due to the presence of microcapsules, which are dispersed in the resin (clear epoxy coating) and that contain in its core the self-healing agent. These capsules were prepared in an emulsion of linseed oil in water to form micelles and an outer skin of poly (urea-formaldehyde) was formed. For the corrosion resistance and self-healing effect evaluation of the coating, carbon steel plates were coated and tested by electrochemical impedance spectroscopy technique (EIS) in 0.1molL~(-1) NaCl solution and by accelerated corrosion test in salt spray chamber (SSC). After curing of the capsules additivated epoxy based clear coating applied on carbon steel plates, electrochemical impedance measurements were performed on plates with a controlled mechanical defect. A three-electrode cell was used. These measurements were made at 0, 24, 48, hours after making the incision (mechanical defect). For comparison, the same measurements were performed with the plates painted with a non- capsules additivated clear coating of the same total thickness of 120 μm. The results showed that the capsules were broken and released the linseed oil, which indeed have repaired the incision area after at least 24 hours of natural aging. It was found that for the plates coated without a defect, the values of |Z| remained high. However, the coating without the capsules after 24 hours, showed a considerable decrease in |Z|. So, using EIS it was possible to quantitatively assess the mechanism of self-healing of the additivated coating using microcapsules containing linseed oil. The SSC accelerated corrosion tests showed results in close agreement with those obtained by EIS.