The dehydrogenation kinetics of air exposed samples of MgH2/Mg2Cu and MgH2/MgCu2 have been studied with in situ time resolved X-ray powder diffraction. The X-ray setup enabled the recording of full diffraction patterns within 150 s, thereby allowing the study of structural changes combined with simultaneous extraction of kinetic parameters. Phase fractions as a function of time and temperature were derived from series of consecutive diffraction patterns by numerical integration of selected diffraction peaks. The apparent activation energy for the dehydrogenation of the MgH2/Mg2Cu, and MgH2/MgCu2 sample was found to be 108 kJ/mol and 160 kJ/mol, respectively. Furthermore, substantially improved dehydrogenation kinetics of MgH2 and resistance towards oxidation of Mg due to the presence of Mg2Cu/MgCu2 are discussed in relation to previous work.