Extremely sensitive on-line detection of metal ions concentration was used to investigate potential-resolved platinum dissolution from commercial fuel cell electrocatalyst. The experiments were carried out in an electrochemical flow cell connected to inductively coupled plasma mass spectrometer. Avariety of electrochemical treatments using different voltage scan rates confirmed the previously observed primary platinum degradation mechanism - the so-called "transient dissolution". Importantly, the redeposition of dissolved platinum is now shown to play an important role in the overall effective Pt dissolution. Pt redeposition trends exhibit a significant dependence on voltage scan rate. (C) The Author(s) 2018. Published by ECS.