Mon, 19 April, 2021
GeoHex expert from University of Leicester (ULEIC) will be presenting some interesting results at Corrosion Virtual Conference and Expo 2021.
Development of superhydrophobic suspension plasma sprayed TiO2, CuO and Fe3O4 coatings for corrosion mitigation in geothermal heat exchangers
Presentation schedule: Monday (4/26/2021) 9am - 9:25amEST
Corrosion, together with scaling, is one of the main threats to the lifetime and efficiency of geothermal heat exchangers as they are in contact with. Geothermal fluids, containing non-condensable gases, ions, and cycling temperature conditions. Coatings provide a means of mitigating corrosion by acting as a barrier. Ceramic coatings are preferred due to their better resistance to corrosion, oxidation and wear at higher temperatures. Besides, these coatings can be altered to exhibit better compressive strength and hardness than metallic and organic coatings. Suspension plasma spray is a thermal spray technique used as coating method that has been successfully employed to deposit ceramic materials from liquid feedstock. In this study, different coatings of TiO2, CuO and Fe3O4 were developed on carbon steel using the suspension plasma spray method for single-phase heat transfer application in geothermal heat exchangers. All suspensions contained 5 wt.% of solid phase dispersed into water. The torch-to-substrate standoff distance was varied to optimize the coating properties, as it plays a vital role in determining the coating microstructure. The deposited coatings were analysed for microstructure and morphology by using SEM/EDX and for surface wetting characteristics by contact angle measurements. Results showed that due to the surface roughness CuO and Fe3O4 were hydrophobic.
Development of Solution precursor plasma spray TiO2/Al2O3 composite coatings for heat-exchanger application
Presentation schedule: Friday (4/23/2021) 9am - 9:25amEST
Surface modification of the metal components involved in heat transfer is one of the passive methods used to enhance their heat transfer efficiency. Coatings with micro- or nano-scale features are widely employed to modify surfaces due to their enhanced surface area, which increases the number of boiling nucleation sites, leading to the generation of a higher number of bubbles. In geothermal power generation, due to the aggressive nature of the working fluid and chemistry of the geothermal brine, ceramic coatings are preferred. Along with having good compressive strength and hardness, ceramic coatings can protect the surface against corrosion, oxidation and wear. The coating deposition method has a specific impact on the coating microstructural characteristic as well as performance, which define its application. Among these, plasma-spraying has been widely used to deposit ceramic materials, due to its high jet enthalpy and the excellent corrosion and wear resistance of the obtained coatings. In this work, solution precursor plasma sprayed coatings of TiO2/Al2O3 composite were developed on carbon steel for boiling heat transfer applications in geothermal heat exchangers. The effect of plasma current and stand-off distance variation on the microstructural properties of coated samples were assessed. The morphology of the final coatings was compared using SEM/EDX. Further, the surface wetting property was analyzed through a drop sample analyzer and found that with spray parameters the water contact angle and diiodomethane contact angle fluctuate.