A comprehensive review of stimulus-based smart self-healing coatings for substrate protection

Smart self-healing coatings represent a transformative advancement in corrosion protection, offering dynamic responses to environmental stimuli like pH fluctuations, temperature changes, and mechanical damage. This review outlines the evolution of corrosion protection strategies, highlighting the limitations of traditional coatings and the emergence of intelligent systems that autonomously and non-autonomously detect and repair damage. It sets the record straight on the discrepancies between autonomous, non-autonomous, intrinsic, and extrinsic self-healing coatings and their combinations for wholesome self-healing architecture. Central to these innovations are mechanisms like autonomous-intrinsic, autonomous-extrinsic, non-autonomous intrinsic, and non-autonomous extrinsic self-healing coatings, facilitated by reversible bonds, microcapsules, shape memory alloys, nanocapsules, and vascular networks that store and release inhibitors and healing agents upon activation. The review also discusses the synthesis and application of these containers, emphasizing their importance in enhancing self-healing capabilities. Furthermore, the study highlights the next direction in integrating environmentally friendly phytochemical corrosion inhibitors, further underscoring the shift towards sustainable solutions. Economically, smart coatings promise reduced maintenance costs, extended service life, and decreased environmental impact, aligning with industry demands for durability and efficiency. Market analysts project significant growth, with the self-healing coatings market expected to reach approximately USD 10 billion by 2028, driven by applications across automotive, construction, and aerospace sectors. This review consolidates current knowledge on smart self-healing coatings, elucidating their mechanisms, benefits, challenges, and potential to redefine standards in corrosion protection, making it a valuable resource for researchers and professionals in materials science and engineering. It also discusses future directions for development and application in various industries.