Anodic Behaviour of Lead inPerchloric Acid: I. Continuous and Interrupted Polarisation

the passivation time (t_p) of polycrystalline lead anodes in perchloric acid has been studied over a range of current densities (i).

When diffusion is the only mode of mass transport, the equation: i√t _p = C _p √α is obeyed where Cp is the concentration of metal ions at the anode at the onset of passivity. The effect of an interruption (at time t₁ for a period t₂) during the polarisation (at i₁) followed by further polarisation (at iy₂) until passivation occurs (t ₁ + t ₂ + t ₃) is considered. The relationship:

i ₂√t ₃ − i ₁(√t ₁ + t ₂ + t ₃ − √t ₂ + t ₃) = C _p√α is derived theoretically and shown to apply in practice.