Hydrophobic coatings obtained from perfluoropolyethers and metal oxides for fouling mitigation on heat transfer surfaces

The scope of this research is to develop hydrophobic coatings for fouling protection on heat transfer metal surfaces. α-ω substituted perfluoropolyethers (PFPE) were used for obtaining nano-range fluorinated layers on steel surfaces; static and dynamic contact angle measurements attested the obtainment of hydrophobic surfaces (water contact angle 120°-145°), with a relatively high hysteresis (6-14°). In order to assess the coatings efficiency in fouling mitigation a heat exchanger pilot plant has been built. Mitigation of crystallization fouling was studied by considering the thermodynamic performance of a coated heat exchanger respect to an uncoated one. Results obtained shown a significant increase in heat transfer resistance due to scaling on the uncoated heat exchanger respect to the coated one. Further studies are developing about the possibility to obtain anti-fouling metal oxides coatings; siloxane-TiO2 coatings for metal surfaces have been prepared and surface investigation attested coatings superhydrophobicity (CA>150°) and very low hysteresis (about 1°). Resistance tests in liquid media highlighted very high resistance of this metal oxide coatings to chemical aggressive environments, but low resistance to high temperatures.