Science & Technology
Superhydrophobic Coating on Metallic Surfaces
- 17 Mar 2020
- 4 min read
Why in News
- A team from the Indian Institute of Technology (Indian School of Mines), Dhanbad, and Ohio State University has created a superhydrophobic coating to save steel from rusting.
- The coating was made from polyurethane and silicon dioxide nanoparticles.
Superhydrophobic Surfaces
- The term hydrophobicity is derived from two greek words that are hydro (water) and phobos (fear). It is the ability to repel water.
- Superhydrophobic coating is a nanoscopic surface layer that repels water.
- Adding a superhydrophobic coating makes a surface liquid and water repellent, easy to clean, and boosts its anti-icing performance (ability to delay the formation of ice for a certain period of time)
- Super-hydrophobic coatings are also found in nature; they appear on plant leaves, such as the Lotus leaf, and some insect wings.
- Apart from steel the coating can be done on other metallic surfaces, such as aluminum, copper, brass. The coatings have also been developed for glass, cloth, paper and wood.
- Developing an antimicrobial superhydrophobic coating for biomedical applications is also being worked on.
- Without this, the coating tends to easily peel off due to smoothness of steel.
- The spin coating was found to be more advantageous and cost-effective compared to immersion coating and spray coating.
- Spin coating dried quickly and the thickness of the coat could be controlled easily
Silicon dioxide
- Silicon dioxide (SiO2), also known as silica, is a natural compound made of two of the earth's most abundant materials: silicon (Si) and oxygen (O2).
- Silicon dioxide is most often recognized in the form of quartz. It's found naturally in water, plants, animals, and the earth.
Polyurethane
- Polyurethane is a polymer composed of organic units joined by urethane links.
- It is a plastic material, which exists in various forms.
- They are used in a wide variety of applications to create all manner of consumer and industrial products that play a crucial role in making our lives more convenient, comfortable and environmentally friendly.
Properties of the Coating
- Chemically Stability: Stable in both acidic (pH 5) and alkaline (pH 8) conditions for more than six weeks.
- Thermal Stability: Stable up to 230 degree C.
- Mechanical Stability: Highly stable when tested with water jet, floating, bending, sand abrasion tests.
- Self-cleaning
- When water droplets were made to fall on an uncoated surface they stuck to it and made a messy surface.
- However, in the case of a coated sample, water droplets roll away while collecting dust from the surface.
- Easy to make
- The chemicals used to make the coating are easily available and are also environmentally friendly.
- The cost of coating will further reduce when mass-produced on commercial scale.
