[en] Coating the walls of a vacuum chamber with Be or some other low Z material has been proposed as a possible solution to the problem of high Z impurities in plasmas. The properties of any coating will be highly dependent on (1) the nature of plasma impurity deposition on walls, and (2) radiation-induced solute segregation. The latter process can spontaneously produce low Z coatings in some alloys and drastically alter metallic interdiffusion in a reactor environment. We have studied the required parameters of coatings (thickness, composition, purity, etc.) and possible means of in situ deposition. We present results of a preliminary survey of coatings, substrates, and deposition methods whih are most compatible with reactor operation. We also outline experiments presently underway which will measure the stability of coatings in a radiation environment