Coating against limescale: Imparting scalephobicity with rational microtexturing of soft materials
In thermal power plants, limescale deposits significantly reduce the efficiency of the plants: a layer of limescale just 1 mm thick in the pipes of the heat exchangers reduces the efficiency of electricity production by around 1.5 %. To compensate for the Europe-wide loss, an additional 8.7 million tons of hard coal would have to be burned.
A research team from ETH Zurich and the University of Berkeley has invented a special coating that prevents the adhesion of lime crystals. The team investigated the interaction between growing lime crystals, the surrounding water flow and the surface on a microscopic level. Based on this, coatings made of various materials were developed and tested.
The most effective coating turned out to be a polymer hydrogel, the surface of which the researchers had provided with microscopically small ribs. Its microstructure is based on shark scales, whose ribbed structure suppresses the formation of surface deposits. In the kettle or boiler, the ribs ensure that the lime crystals have less contact with the surface, cannot adhere and are carried away by the water flowing over the hydrogel and through the ribbed structure. The passive removal of the microscopic crystals prevents them from coalescing into a stubborn layer. In experiments, up to 98% of all limescale crystals previously grown on a hydrogel-coated surface with a size of around 10 μm were removed. In contrast to previous descaling methods, some of which still use toxic and aggressive chemicals, the hydrogel is biocompatible and environmentally friendly.
This research has been published in Science Advances, Vol 9, Issue 51.
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