Pit growth behaviour of aluminium under galvanostatic control

The pit growth process on (1 0 0) aluminium under anodic pulse current in a mixed solution of 1 M HCl and 0.1 M H2SO4 at 30 °C has been evaluated using potential transient measurements and pit size distributions obtained by scanning electron microscopy. Sustained pit growth is observed for all pits during the initial anodic potential rise before reaching a steady-state etch potential, whereas a substantial fraction of the pits passivate at the steady-state etch potential. The pit growth rate during the initial potential rise is 3.4 μm s−1, which is similar to that at the steady-state etch potential. The growth rates of active pits are potential-independent.

► We focus on potential dependency of pit growth behaviours.
► All of pits keep growing during anodic potential transient.
► A substantial fraction of pits stop growing at the steady-state potential.
► The pits grow at a same growth rate at the differential potentials.
► The constant growth rate is 3.4 μm s−1 in 1 M HCl and 0.1 M H2SO4 at 30 °C.