Hydrogen Embrittlement Of Titanium In Sea Water Under Cathodic Polarization

General corrosion behaviors of titanium in sea water and effects of temperature, surface roughness of the samples on cathodic hydrogen evolution have been studied by dynamic polarization, transient linear polarization, weak polarization and coulostatic method. The results show that the anti-general corrosion property of titanium in sea water is excellent and its corrosion is controlled by the surface oxide film which causes to its low corrosion rate of a value less than lO4mmla.Hydrogen evolution on titanium is retarded .Temperature has little effect on the corrosion potential but with it rising and surface roughness increasing, hydrogen evolution becomes more easily. Hydrogenation of titanium has been studied under cathodic polarization with electrochemical test technique x-ray diffraction , SEM and single tension experiment. It is displayed that hydrogen ingress weakens the stability of surface passive film and its anodic dissolution current density increases. Cathodic polarization may cause hydride formation on titanium in sea water and the growth of the hydride layer occurs by the diffusion of hydrogen atoms through the layer to the hydride-metal interface. With time of charging , the concentration of TiH2 on the surface increases, instead the diffusion of hydrogen becomes more difficultly. The concentration grad of active atomic hydrogen on the surface of titanium and potential grad are driving force to the hydrogen diffusion . A value of 6.8x 10cm2/s has been obtained for the diffusion coefficient of hydrogen in titanium at room temperature.TiH can not be found on the surface charging at 500mV for two days and the tensile strength and yield strength have little change. But there are more cleavage planes and cleavage steps. Cathodic polarization will result in hydrogen embrittlement susceptibility.