EFFECT OF HYDROGEN PEROXIDE AND DISSOLVED OXYGEN ON THE CORROSION RATE OF TITANIUM IN GEOLOGICAL DISPOSAL ENVIRONMENTS

摘要

The corrosion rate of pure-titanium (Ti) was measured in a simulated ground water that contained small amounts of hydrogen peroxide (H2O2) up to 200 μ mol /l, or was saturated with oxygen (O2) gas. The corrosion rate was measured under the Ti specimen being freely immersed as well as catholically polarized conditions; in the latter case, the H2O2 concentration of the solution was precisely controlled by a H2O2-stat we designed. The H2O2 accelerated the corrosion rate of the Ti specimen when it was freely immersed in the solutions; the rate was around 3μm/year in the solutions that included about 200μmol/l of H2O2. The dissolved O2, however, produced greater effect when the Ti specimen was catholically polarized conditions. It was as high as 7.5μm/year when the specimen was polarized at - 677mV vs Ag/AgCl in the oxygen saturated solution of which pH was 12. It could be considered that the higher corrosion rate in the O2 - saturated solution caused by the concentrated H2O2 that was generated by the cathodic reaction of O2 on the specimen.