Condensing steam into water is an important step in many systems for power generation and desalination. To accelerate the process, hydrophobic coatings are added to the condenser surface, but over time the performance of these coatings can degrade. Researchers at MIT though have developed a new coating that shows negligible degradation during endurance tests.
When steam touches the condenser surface, heat will be pulled away from it, causing it to condense, and ideally the liquid water will then fall off of the surface, so the process can repeat. This is where a hydrophobic coating comes in, as it will encourage the formation of drops, but as the coating degrades, a film of water will cover the surface, and impair the heat transfer by a factor of seven. This new, polymer coating and a ceramic coating discovered earlier this year, showed little, if any degradation when put through an accelerated endurance test. Modern coatings will start to degrade after just a minute of the test.
These two coatings have different properties, which will influence where they are used. The ceramic can withstand higher temperatures than the polymer, but the polymer can be made cheaper and can be made so thin that the properties of the underlying material are unaffected by its presence.