Abstract: The inventions refer to method of product surface treatment, technological line and device for hot applying the coating on lengthy products. Line for applying the coating on lengthy product comprising supplying device, product surface preparing unit, devise for continuous applying the coating, cooling camera and final product acceptance unit. Device for applying the coating comprises camera (13) for applying the coating, fixed above the tank (14) with melt. In cover (16) of camera (13) there is an outlet 19 for creating pressure discharge, and in cover (21) of tank (14) there is an inlet (22). Camera (13) is provided with intake vertical passage (20) plunged into the melt of the tank. In the walls of camera (13) there are passages (23) and (24) for product (2) transporting. In working state the melt in the tank (14) and in the camera (13) occupies levels (25) and (26) correspondingly.