General and localized corrosion rate measurements
AssigneeBaker Hughes Incorporated
InventorsRaymond Paul Gill, Vladimir Jovancicevic, Wai Yeung Mok, Paul Hammonds
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Abstract
Simultaneous determination of general corrosion and localized corrosion rate measurements is achieved with polarization applied by the electrodes themselves rather than externally applied polarization. Two or more working electrodes may be galvanically coupled. A localized pitting corrosion event on one of the electrodes will lead to a potential transient. The area within the potential transient is measured with the baseline being the initial starting potential. This gives localized corrosion as a function of time. The relationship Rp=ΔV/ΔI is calculated, where Rp is the polarization resistance of the working electrodes and is a measure of generalized corrosion rate.
Claims13
A method for measuring generalized corrosion and localized corrosion rates comprising:
- (a) placing at least three electrodes in proximity to one another, where
- i. at least two working electrodes are galvanically coupled via a zero- or low-resistance ammeter used to monitor the potential of the electrodes, and
- ii. a reference electrode of a material resistant to localized attack used to monitor the potential of the galvanically coupled electrodes;
- (b) detecting transients in potential data for a localized corrosion event and calculating an area within the transient having units of volts-time;
- (c) calculating the change in the magnitude of the current data passed during the potential transient for the same time period as (b) and giving it a value with units of current-time (coulombs);
- (d) dividing the volts-time by the current-time to give the polarization resistance (Rp) as a measure of general corrosion rate;
- and
- (e) doubling the charge in (c) to calculate the metal loss caused by the localized corrosion event.
A method for measuring generalized corrosion and localized corrosion rates comprising:
- (a) placing at least three electrodes in proximity to one another in a corrosive acid solution, where
- i. at least two working electrodes are galvanically coupled via a zero- or low-resistance ammeter used to monitor the potential of the electrodes, and
- ii. a reference electrode of a material resistant to localized attack used to monitor the potential of the galvanically coupled electrodes;
- (b) detecting transients in potential data for a localized corrosion event and calculating an area within the transient having units of volts-time;
- (c) calculating the change in the magnitude of the current data passed during the potential transient for the same time period as (b) and giving it a value with units of current-time (coulombs);
- (d) dividing the volts-time by the current-time to give the polarization resistance (Rp) as a measure of general corrosion rate;
- and
- (e) doubling the charge in (c) to calculate the metal loss caused by the localized corrosion event.
Dependencies are inferred from the claim text.