The growth and chemical interaction of both aluminum and chromium interfaces with chemically etched (100) oriented mercury cadmium telluride (MCT) has been studied using x-ray photoelectron spectroscopy (XPS). It is shown that the EVICT is chemically passivated with the deposition of Cr, and that there is no outdiffusion of Te and no loss of mercury, as has often been observed. It was found that Cr followed a laminar growth mode with an escape depth of 21 Angstrom. In contrast, the deposition of aluminum onto the etched (100) MCT surface induced an increase in the Te and Cd XPS intensities of approximately 100% and 34%, respectively, of the zero coverage value. This coincided with a rapid loss of mercury from the interfacial region. At high coverage a reacted Tr component was observed. A structural model is introduced and is used to account for the trends observed in the core level intensities of the postetched surface. Mathematical expressions derived from this model are utilized to fit the core level intensities as a function of overlayer thickness. We report the success of the model, with excellent fits obtained for both the Cr-MCT and AI-MCT systems and, as a result of this study, a method of chemically passivating the system.