Chapter 7 - Hydrogenation and Corrosion Investigations of Titanium Under Attack by an External Cathodic Current

Abstract

The cathodic activation of titanium occurs in sulfuric and hydrochloric acids in the presence of air. This chapter discusses hydrogen and corrosion of titanium under attack by an external cathodic current. Detailed investigations of the hydrogenation and corrosion of titanium under the conditions of attack by an external cathodic current were performed in a saturated chlorine solution of 260 g/l NaCl, i.e., the chloranolyte and in a 1 g/l NaCl chlorine-saturated solution. Hydrogen absorption (hydrogenation) was measured by the radioisotopic method by using a tracer of radioactive tritium. The titanium samples, after being polarized in the tritium-labeled solution (14–50 mCi/ml), were washed with distilled water and dissolved in 40% H2SO4 at 98°C. The evolving hydrogen was oxidized with CuO at 300°C. The amount of hydrogen absorption (hydrogenation) was determined by the radioactivity of the water obtained. The dependence of the hydrogenation on time, obtained in acid solutions, is characterized by a gradual slowing down of the growth in the hydride layer. In the case under consideration, the hydrogen absorption increased rapidly during the first hour of polarization at a current density of 20 mA/cm2 and then sharply decreased, which may just be connected with the dissolution of the hydride layer. After 2–3 h of polarization, the hydrogenation remained constant, thereby indicating that the rates of formation and dissolution of the hydride layer had equalized.