Expressions for calculating corrections to surface tension in nonuniform and nonequilibrium liquid-gas systems are obtained in terms of the thermodynamical properties of equilibrium systems in the framework of van der Waals theory of capillarity. It is shown that the pressure and temperature nonuniformities in the interface lead to significant surface tension corrections at high-rate phase transitions. The effect of thermodynamical instability and dissipation of the liquid-gas interface at intense evaporation is predicted.