The wetting behavior (hydrophobicity/hydrophilicity) of atmospheric plasma sprayed (APS) and suspension plasma sprayed (SPS) TiO_2 coatings was investigated. The effect of different spraying process parameters on the water contact angle (WCA) of these coatings was studied using a Taguchi method for design of experiments. It was found that by controlling the spraying parameters, coatings can be developed with WCAs as high as 140° despite the natural hydrophilicity of TiO_2. SEM imaging showed that these coatings have a hierarchical (dual scale) roughness that provides the hydrophobicity of their surface by enhancing water repellency and mobility on the surface.
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