Researchers develop self-healing fluid-based coating

Researchers from Illinois-based Northwestern University have developed a new coating strategy for metal that self-heals within seconds when scratched, scraped or cracked.

Pipeline structures can often rupture due to hard-to-detect corrosion in tiny cracks, scratches and dents.

“Localized corrosion is extremely dangerous,” said Jiaxing Huang, professor of materials science and engineering in Northwestern’s McCormick School of Engineering, who led the research.

“It is hard to prevent, hard to predict and hard to detect, but it can lead to catastrophic failure.”

Huang’s patent-pending system readily flows and reconnects when damaged by scratches and cracks. The researchers have demonstrated that the material can heal repeatedly, even after scratching the same location over 200 times.

 The study has been published in academic journal, Research, which was recently launched by the American Association for the Advancement of Science (AAAS) in collaboration with the China Association for Science and Technology (CAST).

Although self-healing coatings already exist, these systems typically only work for nanosized damages. However, Huang’s team looked to fluids to upscale the technology to work on millimetre sized damages.

“When a boat cuts through water, the water goes right back together. The ‘cut’ quickly heals because water flows readily. We were inspired to realize that fluids, such as oils, are the ultimate self-healing system,” said Huang.

Huang and his team required a system with two contradicting properties: fluidic enough to flow automatically but not so fluidic that it drips off the metal’s surface.

The challenge was solved by a network of lightweight particles to thicken the oil: graphene particles. It prevents the oil from dripping but also releases the oil when the network is damaged by a scratch or a crack.

Huang said that the material can be made with any hollow, lightweight particle, not just graphene.

“The particles essentially immobilize the oil film,” Huang said. “So it stays in place.”

The coating sticks even in underwater and harsh conditions such as acid baths. Huang has stated that the coating could be painted onto bridges and boats that are naturally submerged in water as well as on metal structures near highly corrosive liquids.

Graduate student Alane Lim and Chenlong Cui, a former member of Huang’s research group, served as the paper’s co-first authors.

You can watch a video of the coating here.