IN-SITU FLUORESCENCE IMAGING OF LOCALIZED CORROSION WITH A PH-SENSITIVE IMAGING FIBER

A fiber-optic pH-imaging sensor array capable of both visualizing remo te corrosion sites and measuring local chemical concentrations at thes e sites was applied to realtime corrosion monitoring. The imaging fibe r's distal face, containing an immobilized pH-sensitive fluorescent dy e, was brought into contact with metal surfaces submerged in aqueous b uffers and fluorescence images were acquired as a function of time. He terogeneous fluorescence signals were observed due to both pH increase s at cathodic surface sites and pH decreases at anodic surface sites. These fluorescence signals showed both localization and rates of corro sion activity. Three corrosion processes were investigated, galvanic c orrosion at a copper/aluminum interface and crevice corrosion and pitt ing at a stainless steel surface. The spatial resolution of the techni que was limited by proton/hydroxide diffusion and the diameter of the individually clad optical fibers comprising the imaging bundle.