It’s hard to believe that even the tiniest cracks in the metal may one day lead to the destruction of entire structures. However, the examples do not need to go – falling bridges, exploding pipelines, and many other disastrous consequences are often corrosion, resulting in tiny cracks, the scratches and dents that are very difficult to detect. The most common method of corrosion control is the application of protective coatings, insulating the metal surface from the damaging effects of the environment. The problem is that a violation of this coating loses its effectiveness.
A group of scientists from northwestern University under the leadership of Jiaxing Huang has developed a coating for metal, capable of damage to regenerate itself in seconds, preventing the transformation of these subtle defects in the localized corrosion, which in turn can lead to the collapse of the entire structure. The new material is resistant to extreme environmental conditions and it can even be applied under water.
“Local corrosion is very dangerous. It is difficult to predict, prevent and detect, but it can lead to disastrous consequences,” says Jiaxing Huang.
According to the developers, their patented coating has the most optimal properties of fluidity and potential of self-healing. During the experiments, the researchers demonstrated that the coated metal 200 times rebuild their structure after repeated damage and is not subjected to corrosion in hydrochloric acid solution.
About the new development reported in the article of the journal Research. Brief information about the study published in a press release at northwestern University.
On the market there are several options for self-healing coatings, but they are note examined, generally suitable for recovery of damages, no larger than a few nanometers. To address the issue of larger damage a few millimeters in size, scientists turned to liquid properties.
“Once the boat cuts the water surface, the fluid regains its original state. “Cut” quickly “heals” due to the flow property of water. We decided that the most effective basic for samoustraniajutsia coverage will be the liquid, so decided to use silicone oil (polymerized siloxane),” says Huang.
The scientist adds that the low viscosity allows the material to recover quickly, however, such fluids poorly retained on the surface of the metal. Too viscous coating or not able to recover, or do so very slowly. The opportunity to combine these two contradictory properties in the new coating has allowed the combination of silicone oil (responsible for fluidity) of a coating and microcapsules of the recovered graphene oxide, which are responsible for the viscosity of the substance. Graphene microcapsule absorb oil, form a connected structure. At its violation, oil out of the capsules and restores the connection between the damage. According to Huang, they decided to use graphene, but as a binder you can use any light particles.
The inventors note that even a small concentration of binding particles is able to significantly improve the oil viscosity — five % of the total mass of the microcapsules increased it a thousand times. The particles are heavier liquid, so it does not run down even a vertical surface. It can be applied to the surface with any geometry, and even in the water without trapping the air bubbles or the liquid. In addition, the stability of the oil with graphene microcapsules to mechanical damage checked also in acid. Its efficiency was at the same high level.
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