The effects of a high-frequency electric field (44 MHz, 60 V peak-to-peak no-load amplitude) on surface free energy components and zeta potentials of an alumina (Al2O3) surface were studied. The samples of alumina with preadsorbed OH-, H+, Ca2+, Mg2+, La3+ and Al3+ ions were also investigated. All these ions essentially reduce the electron donor component of the alumina surface, and the most drastic changes occurred in the presence of La3+ and Mg2+ cations. The radio frequency (RF) field caused further changes in the free energy components, electron donor and electron acceptor, of the surface with the preadsorbed ions. These changes can be explained based on thermodynamic functions of the ion hydration. The RF field also affected the zeta potential of an alumina suspension in water or a solution of the investigated cation. After 15 min of the suspension irradiation with the field, its zeta potential fluctuated, even up to 50 min. If the suspension was outgassed prior to the zeta potential measurements (with a help of water pump), the RF field effect was much smaller. It supports the literature observations that nanosize bubbles present in the system are responsible for so-called "memory effect" presence, which may last even a couple of hours after the field removal. However, in the presence of trivalent La3+ and Al3+ cations in the outgassed suspension the RF field effect was still present. Therefore, it was concluded that the memory effect must be also due to the field energy absorption, which causes a disturbance in the adsorption-desorption equilibrium at the surface/solution interface. Return to the equilibrium state ran in a fluctuating way. Also, a static electric field (24 kV de) caused a decrease in the negative zeta potential of an alumina suspension exposed to the field for 20 min, which lasted during 45 min of the experiment. More experiments are needed to explain the observed RF field effects.