Chemically induced hydrodynamic pattern formation: Slowly rotating disk electrode under dissolving conditions and genesis of spatial bifurcation

We investigated the system of a dissolving and slowly rotating steel disk electrode in an unstirred, highly concentrated iron(III) chloride solution (3.5 M). Visible convection vortices in the solution beneath the electrode were observed in the range of rotational speed from 0-25 revolutions per minute (rpm). The convection vortices thus observed were correlated with etched patterns on the surface of the electrode. The curvature of these patterns was found to be dependent on the rotational speed. At a certain value of the rotational speed (the transition region), the curvatures changed sign. A spatial bifurcation dependent on the radius was observed.