What Does Self-Healing Coating Mean?
Self-healing coatings are coatings that possess the internal capability to repair sustained damage by themselves, or with some outside stimulation.
Self-healing coatings are used in automotive refinish coatings, with OEM clear-coat and in plastic clear-coat formulations. Smartphones now use a self-healing polymer coating on the back.
Many self-healing coatings are produced by the addition of substances to existing materials. This is defined as "extrinsic" healing. Polymer coating has extrinsic healing properties. This coating has the ability to sense cracks, and repair is initiated when microcapsules of resins contained in the coating rupture and react.
Corrosionpedia Explains Self-Healing Coating
Self-healing coatings heal both surface scratches and mesoscopic damage (e.g., micro-cracks and cavitation). Self-healing is a two-step process: gap closure, followed by healing. The self-healing functionality allows for a high degree of scratch repair and gloss recovery, even in repeatedly damaged areas.
For example, self-healing epoxies can be incorporated into metals in order to prevent corrosion. A substrate metal showed major degradation and rust formation after 72 hours of exposure, but after being coated with the self-healing epoxy, there was no visible damage after 72 hours of the same exposure.
These coatings can intrinsically correct damage, reducing inefficiency over time caused by degradation, as well as preventing costs incurred by material failure.
The ability of self-healing coatings to self-repair local damage caused by external factors is a major factor contributing to their attractiveness. Self-healing coatings use:
- Polymer layers
- Silica-organic layers
- Conversion layers
- Metallic layers
- Ceramic layers
These coatings intelligently respond to mechanical or chemical damage caused by the external environment and to reproduce their original properties, including their adhesion to the substrate and integrity. The self-healing ability is a particularly vital property for coatings designed to protect the material of a construction against corrosion.
Self-healing anti-corrosion coatings are produced using:
- Macromolecular compounds
The properties of such coatings are activated by appropriate stimuli such as:
- Temperature changes
- pH changes
- Pressure changes
- Mechanical action