Plant for the immersion treatment of vehicle bodies, comprising: - at least one skid intended to support a body to be treated; - at least one process liquid tank; - a conveyor line for conveying the skid above the tank; - means for overturning and immersing, inside the tank, the body on the skid which has been positioned over the tank by means of the conveyor line; the skid comprising a base part for support and movement along the conveyor line and a support part for supporting the body, the support part being supported rotatably on the base part by means of a rotatable shaft with an axis arranged transverse to the direction of movement of the skid on the conveyor line so that the support part is rotatable between a first upper position and a second position for immersing the body in the tank, the skid further comprising a toothed wheel which is connected kinematically to the shaft for its controlled rotation and, alongside the tank, there being provided at least one rotation actuating device which comprises a rack which is intended to engage said toothed wheel in order to actuate the rotation of the skid support part by means of the movement of the skid along a section of the conveyor line in region of the rack, characterized in that - the conveyor line comprises parallel travelways of the roller type, arranged on opposite sides of the tank and the skid comprises on its two corresponding opposite sides of the base part, runners which rest on the parallel travelways so as to support and move the skid above the tank; - additional motorized driving means, being arranged so as to engage the skid when the rack is engaged with the toothed wheel, so as to produce an additional driving power during the force for rotation of the body, whereby the additional motorized driving means are motorized rollers that are arranged so as to rest on top of one of the runners of the skid, formed with a suitable upper surface. - at least one skid intended to support a body to be treated; - at least one process liquid tank; - a conveyor line for conveying the skid above the tank; - means for overturning and immersing, inside the tank, the body on the skid which has been positioned over the tank by means of the conveyor line; the skid comprising a base part for support and movement along the conveyor line and a support part for supporting the body, the support part being supported rotatably on the base part by means of a rotatable shaft with an axis arranged transverse to the direction of movement of the skid on the conveyor line so that the support part is rotatable between a first upper position and a second position for immersing the body in the tank, the skid further comprising a toothed wheel which is connected kinematically to the shaft for its controlled rotation and, alongside the tank, there being provided at least one rotation actuating device which comprises a rack which is intended to engage said toothed wheel in order to actuate the rotation of the skid support part by means of the movement of the skid along a section of the conveyor line in region of the rack, characterized in that - the conveyor line comprises parallel travelways of the roller type, arranged on opposite sides of the tank and the skid comprises on its two corresponding opposite sides of the base part, runners which rest on the parallel travelways so as to support and move the skid above the tank; - additional motorized driving means, being arranged so as to engage the skid when the rack is engaged with the toothed wheel, so as to produce an additional driving power during the force for rotation of the body, whereby the additional motorized driving means are motorized rollers that are arranged so as to rest on top of one of the runners of the skid, formed with a suitable upper surface.