High aluminum zeolite coatings on metals in general, and on aluminum and aluminum alloys in particular are useful for adsorption applications, such as in air conditioning and air separation devices. It is known that high conductivity metals, such as aluminum and aluminum alloys are preferred as heat exchanger parts (e.g., hot coils and chilled coils, and fins) in an air conditioning system. One way of improving the performance of an air conditioning device is to increase the heat transfer efficiency for both the cooling coil and heat rejection coil by coating the heat exchanging surfaces (i.e., aluminum or aluminum alloys) with a coating that can selectively adsorb moisture from air. It is generally known that high aluminum zeolites including X, Y, A and many others are useful as adsorbents for moisture adsorption.
The present invention is a composition of matter including a substrate of a metal that is susceptible to corrosion in a high pH alkaline solution, a corrosion-resistant base layer disposed on the surface of the substrate, the base layer having a pure or high silica zeolite having a silicon:aluminum atomic ratio of at least about 100, a middle mixed zeolite layer disposed on the surface of the base layer, and a top hydrophilic layer disposed on the surface of the middle layer, the top layer having a high aluminum zeolite having a silicon:aluminum atomic ratio of less than 5. The middle mixed zeolite layer includes a zeolite having a silicon:aluminum atomic ratio range that is between the silicon:aluminum ratio of the pure or high silica zeolite of the base layer and of the high aluminum zeolite of the top layer.
|United States Of America||Issued Patent||7,179,547||02/20/2007||2004-165|