(1) Hydrogen embrittlement damage of titanium belongs to hydride type hydrogen embrittlement damage. The characteristic of hydride type hydrogen embrittlement is that brittle fracture occurs only under high-speed deformation, and it does not usually exhibit hydrogen embrittlement sensitivity when deformed at low speed. When the hydrogen content in titanium is higher than 0.03%, the section shortening rate will be affected, and when the hydrogen content is lower than 0.05%, the tensile strength, yield strength and elongation will not change at all. This indicates that the conventional mechanical properties are not sensitive to the hydrogen embrittlement of titanium.
(2) The location where titanium is scratched and contaminated by iron, because the surface of titanium is inlaid with iron particles, which is often the trigger point for pitting corrosion, and it is also the breakthrough point for hydrogen to enter. The impurity iron dissolved in titanium, or even the iron-rich phase as the second phase, is not sensitive to pitting corrosion, hydrogen absorption, and hydrogen embrittlement.
(3) The hydrogen embrittlement sensitivity of titanium is the same as that of pitting corrosion, and the surface pretreatment condition has a great influence. Anodized or thermally oxidized surfaces are the most resistant to hydrogen absorption and hydrogen embrittlement, pickled (nitric acid plus hydrofluoric acid) or annealed surfaces are second, and mechanically polished or mechanically sandblasted are resistant to hydrogen absorption and hydrogen embrittlement. The worst ability. This indicates that titanium in an active state always simply absorbs hydrogen, and the intact oxide film on the surface of titanium is a useful barrier to prevent hydrogen absorption and prevent hydrogen embrittlement.
(4) Hydrogen absorption of titanium is usually produced through the following paths: (a) high temperature (>300 degrees) hydrogen atmosphere or hydrogen-containing atmosphere; (b) nascent hydrogen generated during crevice corrosion or reductive inorganic acid corrosion; (c) ) Hydrogen generated during galvanic corrosion or cathodic maintenance; (d) Titanium in seawater electrolysis is in cathodic condition (potential <0.70V). For this reason, in order to ensure that titanium does not absorb hydrogen, the potential of titanium in seawater should be controlled above 0.70V.
(5) In the pH scale of 3-12, the oxide film of titanium is stable and it is a useful barrier for hydrogen permeation. In the above pH scale, the short-term cathodic hydrogen charging experiment did not find the appearance of hydrogen absorption. If the pH value is outside the above-mentioned scale, it is estimated that the oxide film is unstable, so the maintenance effect is very weak, and the maintenance of the oxide film is not good for hydrogen to enter the titanium matrix. Long-term experiments have shown that in neutral brine, the cathode potential can cause hydrogen absorption when the cathode potential is lower than 0.7V. At a very large cathode current density (the electrode potential is more negative than -1.OVSCE), it can accelerate hydrogen absorption and eventually cause hydrogen embrittlement at room temperature.
www.crnmc.com 
