Dear Pablo Gonzalez, it depends on the nature of the solid surface. There are many factors involved in deciding about the interface solid-liquid. The following references deal with such factors. My Regards

https://doi.org/10.1007/s11172-016-1259-5

https://doi.org/10.1021/acs.langmuir.8b02875

Thanks for your answer.

The pH of water (and its surface tension) changes differently under the influence of various alkaline and acidic additives, inorganic or organic. Inorganic pH regulators can increase the contact angle (CA) of water on an inert polymer. Conversely, in the presence of an organic base or acid, the CA may not change or decrease. The same refer to the surface tension of alcaline/acidic water too. Also, the direction of the CA change depends on how the surface of your polymer behaves depending on the pH of the aqueous solution.

Thanks