A study of the time of passivation of gold has
been made in a series of hydrochloric acid solutions.
For a given concentration of hydrochloric acid the
equation (i - i₀)T = K holds for all current densities
provided the solution is vigorously stirred. This
equation is similar to that obtained by Shutt and
Walton working at lower current densities.
A linear relation has been found to exist between
i₀, the limiting current density and the acid concentration.
A similar relation also holds between the constant K
and the hydrochloric acid concentration.
The results obtained have been interpreted on
the basis of a diffusion theory. The time of passivation
is taken to be the time required to set up a diffusion
layer at the electrode surface. The reduction of
the chloride concentration at the electrode surface
to nearly zero is assumed to be necessary before
the passivation of the electrode can take place.
Two methods have been given whereby the thickness
of the diffusion layer at the electrode can be determined
The results are in reasonable agreement with each other
and are of the order normally encountered in diffusion
phenomena.
A reason for the non-application of sand's
equation has been suggested
