Accession Number : ADA331114

Title :   High-Resolution Microbial Pitting Corrosion Studies Utilizing a Two Dimension Scanning Vibrating Electrode Microscope (SVEM) System, Tri-Service Committee on Corrosion Proceedings

Corporate Author : TRI-SERVICE COMMITTEE ON CORROSION WRIGHT-PATTERSON AFB OH

Personal Author(s) : Angell, Peter ; Luc, Jiunn-Shyong ; White, David C.

PDF Url : ADA331114

Report Date : JUN 1994

Pagination or Media Count : 15

Abstract : Traditionally, electrochemical techniques used in corrosion studies have been limited by their lack of spatial and temporal resolution. Microbial corrosion is often evidenced as pitting in which small anodes and correspondingly large cathodes are formed. Techniques such as electrochemical impedance spectroscopy, which are unable to differentiate the anode form the cathode, therefore underestimate the rate of corrosion due to the fact that it averages both anodio and cathodic processes. Vibrating micro-electrodes allow mapping of the current densities over a corroding metal surface where the resolution is determined by the height of the electrode above the surface (resolution =twice the height) and the number of measurements made. This theoretical value is approached by vibrating the electrode in the vertical plane as well as the horizontal plane helping to smooth out irregularities in the surface topography. By scanning such an electrode over the surface, a current density map can be generated showing the size and location of both the anodic and cathodic regions with time. Due to the rapid nature of the scans (<5 minutes), the temporal resolution is also enhanced. A system giving a resolution of approximately 300 micrometers has been coupled with a microscope (resolution better than 1 micrometer) and a photon counting imaging system capable of detecting the light produced by a single luminescent bacterium. This system allows the congruent mapping of bacterial locations and activity (bioluminescence) with the resultant current densities. It has been shown that anodic regions are formed below colonies of bacteria. Manipulation of these colonies of bacteria have shown that 1,000.00 of cfu /sq cm are necessary to form an anodic region.

Descriptors :   *CATHODES, *ELECTRODES, *MICROORGANISMS, METALS, POSITION(LOCATION), CORROSION, SPECTROSCOPY, BACTERIA, COUNTING METHODS, ELECTROCHEMISTRY, CURRENT DENSITY, TOPOGRAPHY, VERTICAL ORIENTATION, IMAGES, PHOTONS, MAPS, HORIZONTAL ORIENTATION, IMPEDANCE, LUMINESCENCE, DETERMINATION, ANODIC COATINGS, COLONIES(BIOLOGY), ANODES, BIOLUMINESCENCE.

Subject Categories : Microbiology
      Electrical and Electronic Equipment

Distribution Statement : APPROVED FOR PUBLIC RELEASE