Turbulent mass transfer in a rotating shallow electrochemical cell was investigated experimentally. Six local miniprobes embedded in the cathode were used to measure the local mass transfer rate and to detect unsteady turbulent convection. The mass transfer rates were nondimensionalized and correlated. A critical parameter was obtained to describe the onset of transient and turbulent conditions in the rotating electrochemical cells. The transient and turbulent phenomena in the rotating system are more complex than natural convection in vertical enclosures because of gravity-gradient effects.