Superhydrophobic Coating on Metallic Surfaces

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.

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.

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.

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