Mapping currents at the corroding surface/solution interface
Corrosion is electrochemical in nature. The kinetics of the processes taking place are controlled by the potential of the metal in its environment. The potentials of corroding metals can be measured against a reference electrode in virtually all cases. However, the currents and corrosion rates are generally difficult to determine directly. The flow of current in solution depends on the corrosion processes taking place. When the corrosion is uniform, then conceptually there need not be currents flowing in solution as the anodic and cathodic reactions take place at the same sites on the surface. This may be the case for both very high or low corrosion rates. In acidic solution, where rapid corrosion takes place, models which envision migration of separate anodic and cathodic sites have been proposed. With passive surfaces, the anodic and cathodic sites are considered to be separated by the thickness of the passive layer which acts as a mixed electrolyte, conducting both ions and electrons. This is similar to the processes taking place during high temperature oxidation. Direct measurement of these currents have not been made. It is generally necessary to produce changes in the system, by applying external voltages, to ascertain the behavior of the currents through measurement of changes in the net current. This can only be done on small areas of metal. Corrosion rates can then be determined by extrapolation back to the open circuit potential. This paper describes studies in current density mapping for the understanding of corrosion.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States)
- Sponsoring Organization:
- USDOE Office of Energy Research, Washington, DC (United States)
- DOE Contract Number:
- AC02-76CH00016
- OSTI ID:
- 456356
- Report Number(s):
- BNL-64019; CONF-970332-9; ON: DE97004073; TRN: 97:002328
- Resource Relation:
- Conference: Corrosion 97. 52. annual corrosion conference of the National Association of Corrosion Engineers: economics and performance - bridging the gap and NACExpo, New Orleans, LA (United States), 9-14 Mar 1997; Other Information: PBD: 1997
- Country of Publication:
- United States
- Language:
- English
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