Apparatus and method for detecting the degradation of a coating using embedded sensors

• US 6,911,828 B1
• Filed: 05/23/2002
• Issued: 06/28/2005
• Est. Priority Date: 05/23/2001
• Status: Active Grant

• Current Assignee: Southwest Research Institute
• Original Assignee: Southwest Research Institute
• Inventors: Brossia, Christopher S., Dunn, Darrell S.
• Primary Examiner(s): Nolan, Jr., Charles H.
• Application Number:
  US10/153,996
• Time in Patent Office: 1,132 Days
• Field of Search: 324/649, 324/663
• US Class Current: 324/649
• CPC Class Codes: G01N 17/02 Electrochemical measuring systems for weathering, corrosion or corrosion-protection measurement

Abstract

A system and method for monitoring the effectiveness of a coating on a substrate surface and indicating the failure of the coating to adequately protect the surface from corrosion, degradation, and the like. The system includes a sensor array positioned in contact with the coating utilizing a number of sensor electrodes connected to a single integrated circuit or a number of separate individual sensor circuits. The electrodes of the sensor array make measurements of the electrochemical impedance characteristics of the coating and provide such data by way of telemetry to a data interrogation device that is periodically be placed in proximity to the sensor array. The interrogation device may serve to both power the sensor array and trigger it to acquire data. A nominal parameter N′, which is the product of the impedance magnitude and the phase angle, is utilized as a direct indication of the resistance and capacitance characteristics of the coating and therefore a direct indication of the coatings effectiveness.

Claims

1. A system for monitoring the effectiveness of a coating on a substrate surface, the system comprising:

(a) a sensor array positioned in contact with said coating, said sensor array comprising;

(i) a plurality of sensor pins in contact with said coating;

(ii) at least one sensor circuit connected across at least two of said sensor pins, said sensor circuit comprising signal generation circuitry for generating an electromagnetic signal across said at least two sensor pins, response signal metering circuitry for measuring a response electromagnetic signal across said at least two sensor pins, and first telemetry circuitry; and

(iii) at least one power supply circuit; and

(b) a data interrogation device positioned in proximity to said sensor array, said interrogation device comprising second telemetry circuitry for data communication with said first telemetry circuitry of said sensor array.

2. The system of claim 1 wherein said at least one sensor circuit of said sensor array further comprises digital signal processing circuitry.

3. The system of claim 1 wherein said plurality of sensor pins are electrically insulated from said substrate.

4. The system of claim 1 wherein at least one of said plurality of sensor pins is electrically connected to said substrate.

5. The system of claim 1 wherein said sensor array comprises a plurality of discrete sensor packages, each of said sensor packages comprising at least two of said plurality of sensor pins, one of said sensor circuits, and one of said power supply circuits, said plurality of discrete sensor packages arranged in an ordered matrix in contact with said coating.

6. The system of claim 1 wherein said plurality of sensor pins are arranged in an ordered matrix in contact with said coating and are each connected to a single one of said sensor circuits.

7. The system of claim 6 wherein said plurality of sensor pins are discretely connected in parallel to said sensor circuit.

8. The system of claim 6 wherein said plurality of sensor pins are connected in at least one series circuit with said sensor circuit.

9. The system of claim 1 wherein said first telemetry circuitry and said second telemetry circuitry each comprise radio frequency wireless telecommunication circuits.

10. The system of claim 1 wherein said first telemetry circuitry and said second telemetry circuitry each comprise infrared signal wireless telecommunication circuits.

11. The system of claim 1 wherein said first telemetry circuitry and said second telemetry circuitry each comprise hard wired data telecommunication circuits.

12. The system of claim 1 wherein said at least one power supply circuit comprises an on-board electrical fuel cell.

13. The system of claim 1 wherein said at least one power supply circuit comprises an electromagnetic wave receiver and said data interrogation device further comprises an electromagnetic wave transmitter, power to said sensor array being transmitted from said interrogation device.

14. The system of claim 5 wherein said discrete sensor packages are dispersed within said coating and are generally insulated electrically from said substrate surface.

15. The system of claim 14 wherein said discrete sensor packages each comprise a spherical shaped semiconductor device, wherein said sensor pins comprise exposed contact surfaces on said semiconductor device and said at least one sensor circuit and said at least one power supply circuit comprise semiconductor integrated circuits.

16. The system of claim 15 wherein said spherical shaped semiconductor device comprises a silicon based microsphere capable of being incorporated into the coating material prior to or during application to said substrate.

17. A system for monitoring the effectiveness of a coating on a substrate surface, the system comprising:

(a) a sensor array positioned in contact with said coating and proximate to said substrate surface, said sensor array comprising a plurality of discrete sensor packages, each of said sensor packages comprising;

(i) a plurality of sensor pins in contact with said coating electrically insulated from said substrate;

(ii) a sensor circuit connected across at least two of said sensor pins, said sensor circuit comprising signal generation circuitry for generating an electromagnetic signal across said at least two sensor pins, response signal metering circuitry for measuring a response electromagnetic signal across said at least two sensor pins, digital signal processing circuitry, data storage circuitry and first telemetry circuitry, said first telemetry circuitry comprising radio frequency wireless telecommunication circuitry; and

(iii) at least one power supply circuit, said at least one power supply circuit comprising an electromagnetic wave receiver; and

(b) a data interrogation device positioned in proximity to said sensor array, said interrogation device comprising second telemetry circuitry for data communication with said first telemetry circuitry of said sensor array, said second telemetry circuitry comprising radio frequency wireless telecommunication circuitry, said data interrogation device further comprising an electromagnetic wave transmitter, wherein power to said sensor array is wirelessly transmitted from said interrogation device to said at least one power supply circuit.

18. A method for monitoring the effectiveness of a coating on a substrate surface, the method comprising:

positioning a sensor array within said coating and proximate to said substrate surface;

generating an interrogating electrical signal and directing it into said coating from said sensor array;

measuring electrical impedance by measuring signal magnitude and phase angle values from said interrogating electrical signal, wherein said signal magnitude is indicative of the resistivity of said coating and said phase angle is indicative of the capacitance of said coating; and

multiplying said impedance magnitude and phase angle values to establish a nominal parameter N′

, the magnitude of said nominal parameter N′

providing a direct indication of the resistance and capacitance of said coating and therefore of the effectiveness of said coating on said substrate surface.

19. The method of claim 18 further comprising the steps of:

retaining said measured impedance data in at least one signal storage device positioned in conjunction with said sensor array;

positioning a data interrogation device in proximity to said at least one signal storage device; and

transferring said measured impedance data from said signal storage device to said data interrogation device.

20. The method of claim 19 wherein said step of transferring said measured impedance data comprises wirelessly transmitting a radio frequency signal from said signal storage device to said data interrogation device.

21. The method of claim 19 wherein said step of transferring said measured impedance data comprises wirelessly transmitting an infrared signal from said signal storage device to said data interrogation device.

22. The method of claim 19 wherein said step of transferring said measured impedance data comprises transmitting an electrical signal from said signal storage device to said data interrogation device across a hardwired connection.

23. The method of claim 18 further comprising the step of providing a power source for said sensor array.

24. The method of claim 23 wherein said step of providing a power source comprises providing a battery in direct association with said sensor array.

25. The method of claim 19 further comprising the step of providing a power source for said sensor array.

26. The method of claim 25 wherein said step of providing a power source comprises providing a battery in direct association with said sensor array.

27. The method of claim 25 wherein said step of providing a power source comprises transmitting an electromagnetic wave from said data interrogation device to said sensor array.

28. The method of claim 18 wherein said step of generating an interrogating electrical signal comprises generating an AC signal and said step of measuring electrical impedance data comprises measuring such data at a plurality of distinct signal frequencies.

29. The method of claim 28 wherein said measurement of impedance data is carried out for at least three distinct frequencies.

30. A method for monitoring the effectiveness of a coating on a substrate surface, the method comprising:

positioning a sensor array within said coating and proximate to said substrate surface;

generating an interrogating AC electrical signal and directing it into said coating from said sensor array;

measuring electrical impedance by measuring signal magnitude and phase angle values from said interrogating electrical signal at a plurality of distinct frequencies;

retaining said measured impedance data in at least one signal storage device positioned in conjunction with said sensor array;

positioning a data interrogation device in proximity to said at least one signal storage device;

providing a power source for said sensor array by wirelessly transmitting an electromagnetic wave from said data interrogation device to said sensor array;

transferring said measured impedance data by wirelessly transmitting a radio frequency signal from said signal storage device to said data interrogation device; and

multiplying said impedance magnitude and phase angle values to establish a nominal parameter N, the magnitude of said nominal parameter N providing a direct indication of the effectiveness of said coating on said substrate surface.