The Electrochemical Behavior of Titanium: Effect of pH and Chloride Ions

Abstract

The anodic and cathodic behavior of titanium in sulfuric acid in the absence and presence of chloride ions have been investigated. Two stable corrosion potentials were observed. One was in the active region, the other in the passive region. Neither corrosion potential was appreciably affected by chloride ions or pH changes between pH 0.25 –2.00. The corrosion current of active titanium was not affected significantly by chloride ions up to 3.5% but decreased with increase in pH. Passivation parameters decreased with increase in pH but either remained unchanged or decreased only slightly with addition of chloride ions. The rate of the h.e.r. in the Tafel region was not appreciably affected by chloride ions. The differential capacitance of titanium in solutions of pH 0.25–2.00 ranged from 150 to 200 µf/cm2 at the active corrosion potential and was a reasonably constant value, 25 /µf/cm2, at the passive corrosion potential. For the negative potential range a maximum capacitance, 222 µf/cm2 at which was approximately the primary passivation potential, and a minimum capacitance, 73 µf/cm2 at , were observed. At potentials more positive than the primary passivation potential, the capacitance decreased monotonically with increase in potential and reached a value of 7 µf/cm2 at 3.2V.