A new coating developed by researchers at Northwestern University and the Korea Institute of Geoscience and Mineral Resources can self-heal in seconds when scratched, scraped or cracked. The material could prevent such tiny defects from evolving into localized corrosion, which can cause major structures to fail. A paper on the development is published in the journal Research.

Available self-repairing coatings typically work for nanometer- to micron-sized damage, but the new oil barrier coating can heal larger scratches in the millimeter-scale. A network of graphene capsules was used to thicken and immobilize low viscosity oil and prevent it from dripping off the target surface. When cracked or otherwise damaged, the network releases the oil to flow readily and reconnect.

(a) An aluminum foil boat placed on 2 M HCl solution is damaged after just 8 minutes, indicated by the leakage of methylene blue solution, and completely dissolves away after 20 minutes. (b) Another aluminum boat coated with reduced graphene oxide/oil film stays intact after a day, when the dye solution has dried out, showing that the coating is stable on metal surface with complex geometry and sharp corners. Source: Northwestern University(a) An aluminum foil boat placed on 2 M HCl solution is damaged after just 8 minutes, indicated by the leakage of methylene blue solution, and completely dissolves away after 20 minutes. (b) Another aluminum boat coated with reduced graphene oxide/oil film stays intact after a day, when the dye solution has dried out, showing that the coating is stable on metal surface with complex geometry and sharp corners. Source: Northwestern University

The coating adheres underwater, in harsh chemical environments and to complex geometries on metal surfaces. The U.S. and Korean researchers envision its use as a protective coating for bridges and boats, and for metal structures in contact with highly corrosive fluids.

Self-healing materials are artificial or synthetically created substances with the inherent ability to automatically repair damage to themselves without any external diagnosis of the problem or human intervention. Since the appearance of the first self-healing concepts in the early 2000s the field of self-repairing coatings has significantly evolved.

MIT chemical engineers previously designed a polymer material that can grow, strengthen and repair itself by reacting with carbon dioxide from the air. The material continuously converts CO2 into a self-reinforcing carbon-based material, which could one day be used for construction, repair or protective coatings.

Likewise, a self-healing, durable hydrophobic coating engineered at the University of Michigan has potential applications ranging from clothing to roofs to ships. The fluorinated polyurethane elastomer material is easily sprayed onto virtually any surface.

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