A review on corrosion-protective extrinsic self-healing: Comparison of microcapsule-based systems and those based on core-shell vascular networks

Corrosion is a natural phenomenon which significantly deteriorates metal properties. The existing corrosion protection methods are costly and require a regular replacement of sacrificial metals or inevitable use of toxic chemicals. So far, various extrinsic self-healing approaches have been attempted to prevent metal corrosion, which have facilitated the corrosion protection at a reasonable cost and non-toxicity level. Here, we review the existing and the recent novel corrosion-protective extrinsic self-healing technologies, focusing on the capsule-based and the fiber-based self-healing approaches, while looking at the pros and cons of these methods. In addition, by introducing potential ways, this review aims to provide insights for the further development of extrinsic self-healing technologies.