Superhydrophobic coating to save metallic surfaces

Created with polyurethane and silicon dioxide nanoparticles, the coating can be easily spin-coated on steel

March 14, 2020 07:41 pm | Updated March 15, 2020 02:39 pm IST

Repels water:  In the case of a coated sample, water droplets roll away leaving the surface free of dust.

Repels water: In the case of a coated sample, water droplets roll away leaving the surface free of dust.

Fascinated by the beauty of water rolling off a lotus leaf, a team of chemical engineers has now created a similar superhydrophobic coating that can be used to save steel from rusting.

The team from the Indian Institute of Technology (Indian School of Mines), Dhanbad, and Ohio State University used polyurethane and silicon dioxide nanoparticles to create the coating which can be easily spin-coated on steel.

“Not just steel, the coating can be done on other metallic surfaces, such as aluminum, copper, brass. We have also successfully developed superhydrophobic coatings for glass, cloth, paper and wood,” explains Aditya Kumar from IIT (ISM) Dhanbad and one of the corresponding authors of the work published in the journal Philosophical Transactions of the Royal Society A.

Treated surface

Before applying the coating, the team created a roughness on the steel using a chemical etching process to improve the adhesion strength. Without this, the coating tends to easily peal off due to smoothness of steel.

The team also tried different methods for the application of the coat on steel and found that spin coating was 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.

The surface of the coating was found to have superhydrophobic property. The coating was also chemically stable in both acidic (pH 5) and alkaline (pH 8) conditions for more than six weeks. It also exhibited thermal stability up to 230 degree C.

The mechanical stability of the coating was tested with water jet, floating, bending, sand abrasion tests and was found to be highly stable.

Self-cleaning coating

Another useful property exhibited by the coating was of 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 in our country and they are environmental friendly too. When mass-produced on commercial scale, the cost of coating will further reduce,” adds Mukesh Kumar Meena, first author of the paper who completed his M.Tech from IIT (ISM) Dhanbad.

Now the team is working on developing an antimicrobial superhydrophobic coating for biomedical applications.

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