Development of Corrosion Crack Initiation Monitor Based upon Scanning Vibrating Electrode Technique

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The monitor, which can evaluate the initiation and growth rate of localized corrosion including corrosion pit and corrosion crack in aqueous solution, has been developped. It spatially measures distributions of corrosion current density with time by using the computer controlled scanning vibrating electrode system. Distributions of current density on the samples including high-tensile strength steel weldments and model pit, i.e., austenitic stainless steels with spots filled with solder, are measured, and are displayed in three-dimensional plots and contour maps. The influences of differences between a sample and a micro-electrode on measured corrosion current density, and spatial resolution of anodic sites which correspond to localized corrosion are discussed. We also emphasize that computer image processing techniques provide powerful tools to analyze distributions of corrosion current density to extract localized corrosion sites.