Metallic superhydrophobic surfaces coatings

The application of the coatings by dipping the roughened aluminium samples in a diluted polymer solution seems to be suitable and effective to provide large aluminium sheets with superhydrophobic surface properties. Coating films to control the surface properties, e.g. the wetting behavior, and to prevent metal substrate... 

In recent years, due to a plethora of potential applications of superhydro-phobicity in daily life, many elforts have been taken to fabricate artificial superhydrophobic surfaces. Depending on the application and material, different methods have been employed to create superhydrophobic smfaces [8], Most of these methods involve either creating a micro/ nano-structme on an inherently hydrophobic material [9,10] or treating a specific micro/nano-structure with a hydrophobic coating [11-14]. For instance, for metallic materials, roughened surfaces have to be coated with low surface energy materials. 

In order to prepare hydrophobic and superhydrophobic surfaces, femtosecond laser was used to pattern the metallic surface and after irradiation the surface was subjected to silanization using dip coating in order to reduce its surface energy and make it inherently hydrophobic. Details on the silanization method used can be found elsewhere [27]. 

Superhydrophobicity is usually a result of hydrophobic (low surface energy) coating (e.g. wax or Teflon) combined with the roughness that magnifies the effect of the coating. However, superhydrophobicity has been reported also for intrinsically hydrophilic (metallic) surfaces. In this case, superhydrophobicity arises from the surface roughness only. The typical size of roughness details in superhydrophobic surfaces is of the micron scale. 

Azim S. S., Sathiyanarayanan S. and Venkatachari G. (2006), Anticorrosive properties of PANI-ATMP polymer containing organic coating , Ptxrg. Org. Coatings, 56,154—8. Bai H., Li C. and Shi G. (2008), Electrochemical Fabrication of Superhydrophobic Surfaces on Metal and Semiconductor Substrates , J. Adhes. Sci. TechnoL, 22,1819-39. 

Stable superhydrophobic surfaces obtained after applying the listed coatings onto different metals and semiconductors are presented in the references given in Table 4. 

These experiments show that the performance of superhydrophobic surfaces on metals can be improved by an additional application of a low-energy polymer coating and infusion with lubricants. The lubricant infusion method is particularly interesting for the maintenance of superhydrophobic properties under special ambient conditions (e.g., high pressure or high temperature). 

Direct fabrication of superhydrophobic coatings on metal surfaces has indeed brought new research trends to the corrosion problem. Two main approaches have been developed... 

Zhang et al. [58] developed superhydrophobic aluminum alloys by one-step spray coating of an alcohol solution consisting of hydrophobic silica nanoparticles (15-40 nm) and methyl silicate precursor on etched aluminum alloy with pitted morphology. The as-sprayed metal surface showed APCA of 155° and ROA of 4°. In their study they used many different mechanical durability tests that we will describe in the next section and... 

Table 5 Comparison of the Performance of Superhydrophobic Metal Surfaces without and with Additional Coatings (Fadeeva, 2014)...

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