Fig. 4: Schematic and results from computational model of O2 diffusion and consumption.

a Schematic of the rotationally symmetric surface film, in which the diffusion of O2 from the sample border and its consumption at the Mg alloy surface is modelled. The respective equations and boundary conditions are indicated. The dashed line delineates the radius of the central region that was evaluated for comparison with the experiments. b Model output for different values of the ORR rate k in the central region. The simple diffusion case is shown in grey.