Anticorrosion shape memory-assisted self-healing coatings: A review

The escalating demand for metallic components and infrastructures in key industries appears inevitable. These metallic materials are frequently exposed to aggressive environments, leading to various forms of corrosion, which, in turn, results in unexpected failures, casualties, and economic losses. To prevent corrosion, an effective and cost-efficient approach would be the application of polymeric coatings on metal and alloy surfaces. Nonetheless, the integrity of these coatings, crucial for their anticorrosion properties, can be jeopardized by physical damage and degradation over time, making them unsuitable for most applications. Self-healing polymeric coatings have been introduced to moderately address this issue. Nevertheless, the recurring damage to these coatings has undermined their functionality. To alleviate this issue, researchers have explored the application of shape memory functionality in polymeric coatings, enabling them to recover their initial shape after repeated damages. This article presents the anti-corrosion performance of different types of shape memory-assisted self-healing coatings (SMASH) categorized by their healing mechanisms. The downsides and upsides of the different healing processes are discussed. Besides, the anti-corrosion performance of each healing mechanism is also compared. The effect of formation and accumulation of corrosion products at damaged areas on self-healing efficiency is discussed as well as the influence of the corrosive environment and corrosion resistance of metallic substrates on the healing performance of SMASH coatings. Based on the current literature, shape memory polymers provide a remarkable capability for repeatedly repairing damaged coatings. Corrosion inhibition, scratch sealing, and hydrophobicity are complementary anti-corrosion mechanisms employed to improve shape memory coatings' barrier performance. Multi-action coatings offer promising protective performance due to the synergistic effect of various healing mechanisms. However, further investigation is necessary to determine the synergistic/antagonistic effect of different self-healing mechanisms on long-lasting protective performance. Research gaps are specifically highlighted in the literature to gain deeper insights into the steps required to further develop SMASH systems.