In this paper the main results obtained within different research projects, developed about the applicability of seismic passive control of major-hazard industrial installations are shown. The work has been subdivided into two papers; in this second part the results relating to big steel tanks equipped with floating roof are presented. After a brief discussion about the seismic vulnerability of tanks and the study of the equations of motion of fixed and isolated base tanks, the main results of a series of shaking table tests, carried out on a steel tank with diameter of 4 m and filled with water up to 1m, are presented. The tank has been tested both in fixed base configuration with floating roof and seismically protected with elastomeric and elasto-plastic isolation devices. The results have confirmed the reliability of the simplified models and the high effectiveness of the base isolation systems in reducing the pressure on the tank wall and the relative stresses, also with floating roof. On the contrary, a low increasing of the oscillation amplitude of the liquid surface has been observed, partially compensated by an increasing of damping, which drastically reduces the number of the free oscillations of the floating roof, in the post-earthquake phase.