抄録
The system that spatially measures the distribution of corrosion current density with time by means of the scanning vibrating electrode technique (SVET) has been developed. The SVET system developed has a high resolution of current density, so that the corrosion current at the grain boundary of the bicrystal of Inconel X-750 in 0.1mol/l Na2SO4 solution or that of the corrosion pit of a pure aluminum in water containing 30ppm chloride ion can be measured. This system was applied to make in-situ observations of corrosion damage progression during corrosion fatigue of an offshore structural steel, 3.5% Ni-Cr-Mo-V steel, in synthetic seawater (SSW). Immediately after a specimen was loaded in SSW, localized corrosion was observed along an edge of the exposed area, which gradually spread to the middle part. The localized corrosion area was more localized at higher stress levels than at lower stress levels; the localized corrosion current density generally increased with increasing applied stress. Anodic current was dependent on the distributions of localized corrosion and of small cracks initiated on the surface; the factors controlling the measured current density distribution were discussed.
