2016 Volume 56 Issue 3 Pages 478-482
Surface potential measurement has been applied to visualize hydrogen permeation behavior through steel materials. The measurement system consists of the surface potential measurement device, X-Y stage and personal computer, and the detective probe and X-Y-Z stage are installed to acrylic container. The hydrogen entry was accelerated by galvanostatic polarization in 0.1 M NaOH solution. The hydrogen evolution was observed only at the small exposed area. The surface potential directly beneath the exposed area shifted to a less noble direction compared with the initial potential during hydrogen charging. The surface potential gradually moved to the original potential after stop of the hydrogen charging. No red rust was observed on the surface of hydrogen detective side after surface potential measurement. The area of negative surface potential expanded in the surface potential distribution over time, and the area was gradually reduced after 3 hours. The location was nearly the same as the exposed area of mild steel at the entry side. The behavior of surface potential change was also correspondent with the hydrogen release behavior from the steel materials. It is concluded that the surface potential measurement can be a powerful tool for the visualization of the hydrogen permeation behavior.