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Three protocols of accelerated startup and shutdown (SU/SD) test were investigated: startup and shutdown with air supply and soak to both anode and cathode (air-SU/SD), hydrogen protected startup and shutdown (H 2 -SU/SD), and hydrogen protected startup and shutdown with a load (H 2 -SU/SD with a load). The performance losses, electrochemical surface area (ECSA) reduction, and catalyst layer degradation were characterized and compared for these SU/SD protocols. Air-SU/SD protocol showed much more severe performance loss and catalyst layer degradation than hydrogen protected ones, which confirmed the benefits of hydrogen protection. The temperature effect on air-SU/SD was significant in a broad range from 20 °C to 70 °C, with low temperature greatly reducing the degradation. The mechanism of H 2 protection and load drawn in alleviating carbon corrosion was explained based on reactions and charge conservation during SU/SD. This paper provides comprehensive test data and failure analysis to quantify the benefits of H 2 protection and load drawn and to facilitate future enhancement of system strategies on SU/SD durability.