This study combined scratch testing and fracture-mechanical analysis to characterize the interfacial adhesion of catalyst coating on electrolyte polymer in microfuel cell. Scratch testing was used to determine the critical load for interfacial failure, while fracture-mechanical analysis was used to quantify the adhesion between Nation (the electrolyte polymer substrate) and Pt/Ru alloy (the catalyst coating). Especially, it is appropriate to establish a relationship between interfacial toughness and adhesion failure by scratching because the failure mechanism by electrochemically induced swelling and shrinking at this interface is very similar to that of scratch testing. We also proposed a key of solving ambiguous problems in indentation crack testing by determining geometric information from crack propagation and critical points, as for a hard porous coating on a soft substrate. Finally, three kinds of process manufacturing the catalyst layer for anode were compared to verify our new test algorithm qualitatively. (c) 2006 Elsevier Ltd. All rights reserved.