SUPERHYDROPHOBIC COATING
Where it comes from? A team of IIT from Dhanbad and Ohio created to save some metal’s surfaces like steel, brass, aluminum, copper, etc…. using this superhydrophobic coating. It may be found by nature like plant leaves, lotus leaf and insect wings. This coating was made-up of some nanoparticles like silicon dioxide and polyurethane. The word hydrophobicity was comes from Greek words. Hydro means water and Phobos means fear. It means ability to repel the water. That coating make a nanoscopic surface layer, it repels the water. Uses of adding this coating is to makes a liquid surface, cleaning is very easy and also it boosts the anti-icing performance. Anti-icing is to delay the formation of ice in a mention period. The coatings are also produced for wood, glass, cloth and paper. Antimicrobial superhydrophobic coating is developed for biomedical applications. If steel’s surface is very smooth, the coating is very easy to peel off. The spin coating is compare to immersion and spray coatings, it have more advantages and also cost effective. Spin coating thickness was controlled very easily at the same thing easily dried.
PROPERTIES
1. Chemical stability – It have a stability in both ways acidic and alkaline. This conditions works more than six weeks.
2. Thermal stability – It have a stability maximum of 230 degree Celsius.
3. Mechanical stability – When we goes to some test with water jet, sand abrasion test and bending, it have a high stability.
4. Self-cleaning – When water droplets are made to fall on the uncoated surface, then they stuck to it and made a messy surface. While collecting dust from the surface for a coated sample, water droplets are roll away.
5. East to make – Easily available and environmentally friendly chemicals are used to making this coating. The mass production is commercial one. So, the cost of the coating will be reduce.
CORROSION PROTECTION
Metals and materials are mainly affected by corrosion, it also restricts the metals utilization. Superhydrophobic coating is contact metal surface angle of above 150 degree. It may be used as a protection film on the metal surface. So, this coatings are gives anticorrosion ability of the material. It may be a substitute of chromate containing coatings to protect the metal surfaces. Two fabrication methods are there. 1. Top down, 2. Bottom up. The top down method is create a roughness and texture on the surface using the removal of surface material. Using the hydrophobic chemicals with low surface energy, the surface may be coated. Plasma treatment, lithography, machining, chemical etching are some of the methods in top down. Bottom up includes electrochemical deposition, chemical vapor deposition, layer-by-layer deposition and sol-gel method. This fabrication method is versatile and produced for corrosion resistance on surfaces. It gives chemical stability in different pH, abrasive resistance and good corrosion resistance.
In general case, corrosion cannot be stopped completely, it takes some methods to decrease the corrosion of metals. Example- anodic and cathodic protection. Air layer is created between the metal surface and corrosive environment. This layer protect the metal surface from the corrosive ions. Air layer is reduce the real contact between the metal surface and corrosive electrolyte and also increase the corrosion protection. When superhydrophobic coatings are exposed to environment, they lost their original characteristics. So, they have not long time stability. It is very difficult to improve the chemical stability.
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