Exploring the frontiers of self-healing layered double hydroxides in corrosion: innovations, challenges, and applications

Corrosion causes significant environmental damage, safety hazards, and economic losses exceeding US$2.5 trillion each year. Traditional anticorrosive coatings often fail due to issues like localized electrochemical corrosion and microcracks. Self-healing anticorrosive coatings have emerged as a promising solution that can autonomously repair damage and restore functionality. These coatings are composed of self-healing agents or corrosion inhibitors encapsulated in their dormant phase in suitable carriers, mostly nanocarriers. Layered double hydroxides (LDHs) have attracted significant attention as nanocarriers for self-healing coatings owing to their layered structure, ion-exchange capacity, tunable composition, and stimuli responsiveness. In LDH matrices, inorganic and organic corrosion inhibitors are incorporated either as interlayer ions (e.g., BTA − /MBT − /Cys − /8HQ − /PO 4 3− /VO 4 3− /NO 3 − /NO 2 − /MoO 4 2− ) or as metal cations (Al 3+ /Mg 2+ /Ce 3+ /Zn 2+ /La 3+ /Y 3+ ), providing anodic and cathodic protection. The literature survey suggests that more than 70% of the articles on LDH-based self-healing coatings have been published in the last five years, underscoring the rapid growth of LDH-based nanocarriers in this field. This review also highlights the pH and heat change, ion-exchange, and mechanical damage activation of LDH-based nanocarriers and subsequent release of active agents to provide anodic, cathodic, or mixed protection. The literature survey also shows that LDH-based self-healing coating enhances barrier properties, corrosion inhibition (>95–99.9%), and durability (hundreds to thousands of hours). This article examines LDH-based self-healing anticorrosive coatings applied to various substrates: magnesium, aluminum, iron, copper, and zinc-based alloys. It focuses on interfacial chemistry, release kinetics, and self-healing efficiency, while also addressing challenges such as scalability, long-term stability, dispersion uniformity, premature release, and future design strategies. • This review critically describes LDH-based self-healing anticorrosive coatings. • LDHs are notable nanocarriers due to their layered structure, ion-exchange ability, adjustable composition, and stimuli-responsiveness. • Corrosion inhibitors are encapsulated as interlayer anions or synergistic metal cations, providing protection. • LDH-enabled coatings exhibit >95–99.9% inhibition, enhanced barrier properties, and durability. • The healing mechanisms, challenges, and future design strategies for LDH-based systems are described.