Method for measuring localized corrosion rate with a multi-electrode array sensor

• US 20050274628A1
• Filed: 04/08/2005
• Published: 12/15/2005
• Est. Priority Date: 04/09/2004
• Status: Active Grant

• Current Assignee: Southwest Research Institute
• Original Assignee: Southwest Research Institute
• Inventors: Yang, Lietai
• Granted Patent: US 7,309,414 B2
• Time in Patent Office: Days
• US Class Current: 205/775.500
• CPC Class Codes: G01N 17/02 Electrochemical measuring systems for weathering, corrosion or corrosion-protection measurement

Abstract

A method of measuring localized corrosion, using a multi-electrode array sensor. The method eliminates the effect of internal current in corroded electrodes, and thus provides a more accurate corrosion measurement. In one embodiment, the potential of a common node of the sensor is adjusted so that the sensor'"'"'s most cathodic current is close to zero.

Claims

1. A method of using a multi-electrode array sensor to measure corrosion or other heterogeneous electrochemical process at a site of interest, comprising:

exposing the sensor to the process at the site of interest;

wherein the sensor has an array of substantially similar metallic electrodes arranged such that each electrode has a surface area operable to be exposed to the process, and such that each electrode is electrically insulated from other electrodes;

wherein each electrode is operable as an anode or cathode depending on the extent of corrosion at that electrode;

wherein each electrode is electrically connected to a common node, such that the sensor simulates a one-piece electrode surface;

adjusting the voltage at the common node to a value that substantially eliminates the effect of internal current in the electrodes;

measuring voltage across one or more of the electrodes; and

determining a corrosion value based on the results of the measuring step.

2. The method of claim 1, wherein the electrodes are each connected to the common node through a resistor.

3. The method of claim 1, wherein the adjusting step is performed by adjusting the voltage at the common node such that the current associated with the most cathodic electrode is substantially zero.

4. A method of using a multi-electrode array corrosion sensor to measure corrosion or other heterogeneous electrochemical process at a site of interest, comprising:

exposing the sensor to corrosion at the site of interest;

wherein the sensor has an array of substantially similar metallic electrodes arranged such that each electrode has a surface area operable to be exposed to corrosion at the site of interest, and such that each electrode is electrically insulated from other electrodes;

wherein each electrode is operable as an anode or cathode depending on the extent of corrosion at that electrode;

wherein each electrode is electrically connected to a common node, such that the sensor simulates a one-piece electrode surface;

identifying an electrode that is substantially the most corroded electrode;

determining the voltage associated with the most cathodic site on the electrode identified in the preceding step, and placing the electrode at that value;

measuring voltage across one or more electrodes; and

determining a corrosion value based on the results of the measuring step.

5. The method of claim 4, wherein the electrodes are each connected to the common node through a resistor.

6. A method for measuring localized corrosion or other heterogeneous electrochemical process, comprising:

forming an integrated multi-sensor wire beam electrode sensor whose working surface simulates a one-piece metal electrode surface in electrochemical behavior;

exposing the working surface of the wire beam electrode to the localized corrosion or other heterogeneous electrochemical process;

adjusting the voltage at a common node electrically connected to each wire beam to a value that substantially eliminates the effect of internal current in the electrodes;

measuring local electrochemical parameters from local areas of the wire beam electrode surface by means of wires located at these local areas;

calculating local electrochemical kinetics of localized corrosion and other heterogeneous processes based on the results of the measuring step.

7. The method of claim 6, wherein the adjusting step is performed by identifying a terminal that is substantially the most cathodic terminal, and adjusting the voltage at the common node such that the current associated with the most cathodic terminal is substantially zero.

8. The method of claim 6, wherein the measuring step is performed by measuring voltage across one or more of the electrodes.

9. The method of claim 6, wherein the measuring step is performed by inserting a zero resistance ammeter between each selected wire terminal of a wire beam electrode and all other coupled wire terminals to measure the coupling current flowing into or out the selected wire;

using a high impedance voltmeter to measure the electrochemical potential of each temporarily uncoupled wire versus a reference electrode; and

using a polarization resistance measuring apparatus to measure the polarization resistance of each temporarily uncoupled wire.