In this study, small amounts of either Ir or Ru (up to 22 mu g cm(-2).) were added to 85 mu g cm(-2) Pt by either co-sputtering or over-layer sputtering onto 3M Company's NSTF catalyst support, which was grown on glassy carbon electrodes for the purpose of simulating fuel cell start-up and shut-down with rotating disk electrode techniques. The transient cathode potentials caused by fuel cell start-up, shut-down and operating conditions were simulated with a combination of potentiostatic and galvanostatic holds. Constant potential was used to simulate fuel cell run, rest and idle, and constant current was used to simulate the start-up and shut-down events. Over the course of an experiment, the catalyst would experience potential as low as 0.650 V-RHE (run) and as high as 1.53-1.8 V-RHE (dependent on the behavior of the composition) under the galvanostatic holds. All compositions including either Ir or Ru lasted significantly longer than for pure Pt under repeated start-up/shut-down. The stability of the over-layer Ir-Pt compositions was significantly higher than for the co-sputtered deposition. The compositions containing 9 and 22 mu g cm(-2) Ir over-layer on Pt showed no ORR activity decrease over the course of 1400 SU/SD simulations (2800 potential peaks >1.5 V-RHE) (c) 2014 The Electrochemical Society. All rights reserved.