Study of zinc passivation in chromium(VI)-containing electrolytes with short-term impedance measurements

The development of a passivating layer on zinc in an acidic chromium(VI)-containing solution is studied by measuring electrical impedance. After examining the passivated electrode in its stationary state, a method is derived to study the pre-stationary state (having, by definition, time-dependent properties). Three hypotheses concerning the layer development are introduced, and their possible relevance is examined by comparison with experimental proof or known literature data. With one of these hypotheses, accordance with all available data is obtained, thus identifying this model as possibly valid. Based upon this model, some further growth characteristics of the passivating layer are derived.