Linseed oil-filled microcapsules containing drier and corrosion inhibitor – Their effects on self-healing capability of paints

•UF shell microcapsules were prepared with core material: linseed oil, Co-octoate and octadecylamine.•Combination of linseed oil, Co-octoate and octadecylamine was optimized for fast drying.•Self-healing was monitored on mild steel plates with complex (primer and topcoat) paint.•Electrochemical impedance spectroscopy measurements were carried out in NaCl solution.•Self-healing efficiency was improved by encapsulated corrosion inhibitor and drier.

Core–shell microcapsules of urea-resorcinol-formaldehyde shell and linseed oil (LO) core material as paint additives for self-healing coatings were prepared. The capsules contained LO either with or without Co-octoate as drier material and/or octadecylamine (ODA) as corrosion inhibitor. The microcapsules embedded in a commercial paint were applied on sandblasted mild steel sheets. After scratching the coated surface, the inhibition efficiency of core–shell microcapsule-containing coat, dipped into corrosive media, was followed visually and evaluated numerically by electrochemical impedance spectroscopy (EIS). In separate experiments, to optimize for the self-healing process, the composition of the core material, the effect of the drier and/or the inhibitor ODA on drying process of LO films were monitored by infrared spectroscopy. Pure LO needed 6–7 days to dry completely. The drying period could be shortened (to 5 h) via application of a dryer, but the addition of the corrosion inhibitor alone increased significantly the time needed for solifidication. To minimize the drying period we have found the proper combination of the ODA and the dryer of the LO.The EIS measurements, in accordance with the drying tests, resulted in the next order of self-healing ability: LO < LO(+ODA) < LO(+Co-octoate) < LO(+ODA+Co-octoate).