Contents lists available at ScienceDirect Progress in Organic Coatings journal homepage: www.elsevier.com/locate/porgcoat Biofriendly vegetable oil healing agents used for developing self-healing coatings: A review Shahla Ataei, Saied Nouri Khorasani ⁎ , Rasoul Esmaeely Neisiany Department of Chemical Engineering, Isfahan University of Technology, Isfahan, 84156-83111, Iran ARTICLE INFO Keywords: Self-healing Coatings Vegetable oils Biofriendly Encapsulation ABSTRACT Corrosion in the metallic structures has been a significant economic concern, with corrosion degradation esti- mated to cost between 2–5% of the gross national product of all countries each year. There have been several methods proposed and deployed to reduce and mitigate corrosion damage. Among the various approaches, applying an organic coating to cover the surface of the metallic structure has risen to prominence due to their effectiveness, cost efficiency, and the relatively benign environmental impacts associated with their use. However, the main drawback related to the use of such organic coatings is their sensitivity to aggressive en- vironments, which damages the coatings and compromises their protective performance. Self-healing coatings, part of an advancing field of polymer science, has shown remarkable development over the recent number of years and demonstrated great promise in extending the service life, reducing maintenance costs, thereby im- proving the durability and reliability of conventional protective organic coatings over metallic structures. Of the strategies used to imbue self-healing capabilities in the next generation of organic coating materials, the in- corporation of healing agents has been widely acknowledged to be the most applicable approach to realizing autonomous self-healing performance. In particular, the deployment of vegetable oils as healing agents has received considerable attention due to their ecologically-safe nature. Therefore, a comprehensive review of the developments in the scientific literature on bio-friendly vegetable oils as healing agents is presented in this paper. The paper will first describe and define self-healing in polymeric materials, then subsequently delve into the introduction and classification of the various vegetable oils and their healing applications. The methodol- ogies for achieving the encapsulation of healing agents in various structures such as nano/microcapsules are then reviewed, with the healing performances of the various healing agents presented and evaluated. Lastly, at the conclusion of the review article, the challenges of using vegetable oils as healing agents will be discussed, along with a brief perspective on the future of vegetable oil based self-healing in scalable industrial im- plementation. 1. Introduction One of the major concerns for all industries globally is the effect of structural corrosion on the economy of the societies. From the myriad proposed methods, to overcome the problem, covering the metallic surfaces by a polymeric coating has been known as the most economical and effective method [1,2]. Polymers and polymeric composites owning to their excellent properties such as lightweight, facile processibility, and chemical stability in many environments are used in various ap- plications including transport vehicles, civil engineering, sporting goods electronics, etc. [3–5]. When they are subjected to the hostile environment such as mechanical, thermal, chemical and the radiation of UV or combination of these effective factors, polymeric components get damaged, and they lose their protective performance. Consequently, the corrosion of the metallic substrate will be initiated and accelerated [6]. Traditional repair techniques such as patching and welding are limited to visible damages. Since the methods are neither autonomic nor instantaneous, it was necessary to find a better approach to repair the created microcracks [7,8]. Microcracking is one of the serious generated deteriorations in the coatings, which dramatically truncates the lifetime of the coated structures. Furthermore, the detection and repair of the inside damages within the bulk of materials are relatively impossible. To overcome the above-mentioned limitations, the first-generation of successful self- healing materials was introduced in 2001. In that research, White et al. microencapsulated Endo-Dicyclopentadiene as a healing agent within https://doi.org/10.1016/j.porgcoat.2019.01.012 Received 23 September 2018; Received in revised form 8 December 2018; Accepted 6 January 2019 ⁎ Corresponding author. E-mail address: saied@cc.iut.ac.ir (S.N. Khorasani). Progress in Organic Coatings 129 (2019) 77–95 0300-9440/ © 2019 Elsevier B.V. All rights reserved. T