through the enclosure 26 the interior walls of the enclosure 26 are preferably coated with a non stick surface treatment or are otherwise formed of a material that inhibits adhesion of the over spray from the spray guns 28 the wire arc spray process is believed to be preferred for use with the invention for example plasma spray processes use nitrogen as the plasma gas but argon is required to start the actual arc necessitating a controlled argon purge to start the plasma gun then switching to nitrogen also the wire arc spray process can immediately start spraying the braze alloy whereas plasma spray processes require a minute or two to warm up before spraying can commence finally the desired coverage for the tube 12 can be difficult to achieve with plasma spray powders necessitating the use of relatively large particles in order to enable accurate metering and control of the powder feed rate finally fig1 and 2 represent the apparatus 10 as preferably including a quenching station 34 and sizing station 36 downstream from the thermal spray enclosure 26 where the tube 12 is cooled and then undergoes a final sizing operation as known in the art the cooling step is preferably carried out in a manner that cools the braze alloy coating on the tube 12 before the surface of the coating oxidizes for this purpose the quenching station 34 may be located immediately adjacent the enclosure 26 or the tube 12 can be continuously enclosed and enveloped by an inert gas up to and through the quenching station 34 fig3 and 4 depict a second embodiment of the invention that differs from the embodiment of fig1 and 2 primarily by the order.