Development of Scanning Laser Enhanced Electrochemical Microscope for Hydrogen Detection

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The research of hydrogen enbrittlement has needed a new system to detect the positional distribution of hydrogen concentration in/on high strength steels and the other metals. For the purpose, we have developed the Scanning Laser Enhanced Electrochemical Microscope for Hydrogen Detection (H-SLEEM). The principle of this system is described in the following : Ar laser is introduced to an optical microscope through glass fiber. The laser is converged by an object lens, and is irradiated to the metal through the layer of aqueous solution. Two electrochemical cells are attached to the metal. Acid or neutral solution is in the one cell to introduce hydrogen. The introduction of hydrogen can be promoted by electrochemical method. In the other cell, the metal is anodically polarized in alkali solution. Permeation rate of the hydrogen diffused from the hydrogen introduction side of the metal can be obtained by monitor the anodic current. In the case that the converged laser is irradiated to the anodically polarized metal surface of hydrogen detection side, the anodic current may increase due to thermal acceleration of hydrogen oxidation process at very small irradiation site. The current increment by laser irradiation may depend on hydrogen content on the hydrogen detection surface. Therefore, it is expected to obtain two-dimensional hydrogen distribution on the hydrogen detection surface in the solution in-situ by scanning the converged laser. The following was made clear in this study : The system was established in this term. The current increment by unconverged laser irradiation is almost linearly dependent on the hydrogen detection current. The converged laser also induced current increment of hydrogen detection. Scanning the converged laser from hydrogen detection area to the area covered by an insulator provided the mono-directional distribution in current increment relating to the hydrogen detection current at the small irradiation site.