Magnitude of surface tension vanishes at

The surface tension is the excess free energy associated with the area of the interface between two phases. If the surface tension is positive , the system minimizes the free energy cost by minimizing the area of contact. This leads, for example, to the spherical shape of a water droplet in coexistence with water vapor.
The surface tension tends to be 0 is quite an unrealistic situation.For example the between water and water vapour at the critical point the surface tension vanishes.But here there is contradiction as there is no two distinc surface at critial point.So its rare to have 0 surface tension