Hydrogen Entry Behavior on Steel Materials Exposed to Wet-dry Cyclic Corrosive Environment Using Surface Potential Measurement

The surface potential measurement has been applied for elucidation the hydrogen entry behavior of pure iron under wet-dry cyclic corrosive environment. The hydrogen detection side was electroplated with Ni to prevent any changes of the surface due to a long-time experiment. Distilled water was used in the corrosion test after adding the droplet of NaCl solution in the first cycle. Although the first cycle gave the surface potential change immediately after the surface dried, after 2 cycles the change occurred while the surface was still wet. The potential change area corresponded to the area that showed metallic luster. The surface potential further decreased in the drying process, and the change area also was expanded. In the third cycle, the surface potential changed even on the back side of the surface covered with the corrosion product. It is possible to two-dimensionally detect and visualize the change in permeated hydrogen with time under atmospheric corrosive environment by the surface potential measurement.