AbstractDirect evidence for the interstitial analogue of the reverse Kirkendall effect has been found in experiments of carbon diffusion through platinum membranes. The carbon diffusion was accompanied by the formation of protrusions and depressions in the carburized and decarburized surfaces respectively. The magnitude of the counter-flux of platinum atoms suggests that some of the carbon atoms are strongly bound to vacancies. An analysis based on Lomer's equation yields a vacancy–carbon atom binding energy Ev-cB0·5eV.MST/32