Impedance Studies on the Anodic Passivity of Titanium in Aqueous Media of Different pH

Impedance measurements for a mechanically polished titanium electrode at different passivation potentials were used in assessing the dependence of the series resistance and capacitance on frequency, for values ranging from 0.2 to 15 KHz. The variation of the two impedance components with the passivation medium, type of prevailing gas, and concentration of electrolyte were used in testing the applicability of Young's theory. The limited conditions under which the theory applied was interpreted essentially due to deviations in the passive layer resistivity, caused by a varying valency of titanium ions and/or by anion incorporation in the oxide matrix. The passive layer does not represent an ideal dielectric. The presence of a simple charge capacitance is assumed for the passive layer formed in HCl where as in NaCl and NaOH there is an indication of the presence of shallow and deep donor levels.