Analysis of the influence of ambient air contamination on changes in wettability of a metal surface after nanosecond laser ablation

A problem of controlled time-dependent reduction of wettability of rough metal surfaces obtained after laser ablation by means of periodic laser pulses is theoretically studied. The evolution of the wetting contact angle of samples having a hierarchical surface structure after laser treatment is determined by their open-air storage, leading to spontaneous adsorption of an organic impurity. The theory of physical adsorption/desorption with a reversible quasi-chemical reaction in accordance with a linear mechanism supplemented with the Gibbs isotherm and the Young equation at the contact point of three phases is considered. The influence of the equilibrium constant and the fraction of the adsorbed impurity in ambient air on the rate of system transition to the equilibrium state is analyzed. The method used allows one to model the wettability transition mechanism and to calculate the time evolution of the wetting contact angle in the case of adsorption of organic substances on the textured surface of the metal.