a spraying device for applying a coating material such as anticorrosion oil to the internal surfaces of hollow bodies comprises a spray gun provided with a front piece which is inserted into the hollow body during operation of the device . furthermore , the device comprises a pump for feeding the spray material to the gun and a control device for controlling the gun , the pump and the introduction of compressed gas into the front piece . this gas is introduced in order to further atomize the spray material ejected through an atomizing nozzle of the gun and in order to support the transport of the spray material through the front piece . the control device comprises means for controlling the rate of introduction of spray material into the gun . as a consequence , the degree of atomization of the spray material leaving the front piece is variable .