An apparatus and method for applying an absorptive coating to a portion of the evacuated enclosure in an x-ray generating device is disclosed. The absorptive coating is applied to the inner surface of the evacuated enclosure to enhance its heat dissipation characteristics, which in turn assists in tube cooling during x-ray production. The absorptive coating is applied atop an intermediate bonding layer. Both the absorptive coating and the intermediate bonding layer are applied to the evacuated enclosure surface by electroplating processes. A plating apparatus comprising the evacuated enclosure portion, a plating fixture, and a base plate is used both to contain the electroplating solution during the plating process, as well as to facilitate its entry into and removal from the evacuated enclosure. A method of employing the plating apparatus to apply the intermediate bonding layer and the absorptive coating is also disclosed.