Method of evaluating the corrosion rate of metal

Details Method of evaluating the corrosion rate of metal Method of evaluating the corrosion rate of metal

1978-10-10

1980-02-26

Weisstuch, Aaron

Chemistry: electrical and wave energy

Processes and products

204195C, G01N 2746, G01N 2730

Patent

active

041905024

ABSTRACT:
A metal test piece is disposed in a cell filled with a test solution. The metal test piece is electrically charged instantaneously through a counter electrode so as to have a few millivolts polarization potential .eta..sub.t. The charge consumed by the corrosion reaction of the test piece is measured by a potential recorder in the form of a variation of the polarization potential .eta..sub.t with respect to time t. The measured (.eta..sub.t -t) relation is analyzed to obtain a polarization resistance R.sub.P of the metal test piece. After the potential of the metal test piece returns to its natural potential Ecorr, the test piece is charged again until its polarization potential .eta..sub.t rises to 50 millivolts or more, and the (.eta..sub.t -t) relation is measured in the same way as mentioned above. Based on this relation, the Tafel slope .beta..sub.a of the anodic reaction is obtained. After the potential of the metal test piece has returned to its natural potential Ecorr, the test piece is so charged for the third time as to have its polarization potential .eta..sub.t lowered to -50 millivolts or less, and the (.eta..sub.t -t) relation is measured. This relation is analyzed to obtain the Tafel slope .beta..sub.c of the cathodic reaction. Based on the polarization resistance R.sub.P, Tafel slopes .beta..sub.a and .beta..sub.c, the corrosion current density I.sub.corr is obtained, from which the corrosion rate V is calculated.

REFERENCES:
patent: 4056445 (1977-11-01), Gauntt et al.
patent: 4130464 (1978-12-01), Kanno et al.
S. Barnartt, "Two-Point & Three-Point Methods for the Investigation of Electrode Reaction Mechanisms", Electrochimica Acta, vol. 15, pp. 1313-1324 (1970).
P. Delahay, "Coulostatic Method for the Kinetic Study of Fast Electrode Processes, I. Theory", J. Physchem., vol. 66, pp. 2204-2207 (1962).
J. L. Ord et al., "The Anodic Oxidation of Iron: Overpotential Analysis for a Two-Phase Film", J. Electrochem. Soc., vol. 123, pp. 1876-1882 (1976).
M. Prazak, "The Polarization Resistance Method for Corrosion Testing", Werkstoffe und Korrosion, vol. 25, pp. 104-112 (1974).
P. J. Moreland et al., "Technique & Instrumentation for Polarization Resistance Measurements", Br. Corrosion Journal, vol. 12, pp. 72-79 (1977).

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