Application of thermally sprayed coatings of the type WC/CoCr in reverse osmosis processes for seawater desalination

Seawater desalination based on the reverse osmosis process requires a variety of hydraulic systems. The material concepts of these hydraulic systems are designed to reliably resist the corrosive properties of seawater and brine as well as the tribological loads. Strong tribological loads typically occur during the start-up and shutdown of multi-stage high-pressure pumps. Thermally sprayed coatings can be used to increase the wear resistance and also the tribological properties of bearings. Also in pressure exchangers for energy recovery, high tribological loads occur on the surfaces of rotors which operate with a clearance gap of 40-100 mu m. Today, thermally sprayed coatings are used for the surface protection of these rotors. To resist the various tribological loads, the material pairs are optimized for each case. Thermally sprayed coatings with high surface hardness have proven to be particularly successful. A coating system, based on a CoCr matrix, has been developed especially for these applications.