  The modification of the wetting properties of marble surfaces upon
multi-scale texturing induced by ultrafast laser processing (340 fs pulse
duration, 1030 nm wavelength) has been investigated with the aim of evaluating
its potential for surface protection. The contact angle (CA) of a water drop
placed on the surface was used to assess the wettability of the processed
areas. Although the surfaces are initially hydrophilic upon laser treatment,
after a few days they develop a strong hydrophobic behavior. Marble surfaces
have been irradiated with different scan line separations to elucidate the
relative roles of multi-scale roughness (nano- and micro-texture) and chemical
changes at the surface. The time evolution of the contact angle has been then
monitored up to 11 months after treatment. A short and a long-term evolution,
associated to the combined effect of multi-scale roughness and the attachment
of chemical species at the surface over the time, have been observed. XPS and
ATR measurements are consistent with the progressive hydroxylation of the laser
treated surfaces although the additional contribution of hydrocarbon adsorbates
to the wettability evolution cannot be ruled-out. The robustness of the results
has been tested by CA measurements after cleaning in different conditions with
very positive results.
