Portable, hand-held, in-situ electrochemical sensor for evaluating corrosion and adhesion on coated or uncoated metal structures

• US 6,054,038 A
• Filed: 06/08/1998
• Issued: 04/25/2000
• Est. Priority Date: 06/08/1998
• Status: Expired due to Fees

• Current Assignee: Dacco SCI, Inc.
• Original Assignee: Dacco SCI, Inc.
• Inventors: Davis, Guy D., Dacres, Chester M.
• Primary Examiner(s): Warden, Sr., Robert J.
• Assistant Examiner(s): Olsen, Kaj K.
• Application Number:
  US09/093,001
• Time in Patent Office: 687 Days
• Field of Search: 205/775.5, 205/776.5, 205/777, 205/791, 205/791.5, 204/404, 204/434, 324/71.2, 324/693, 324/700, 73/86
• US Class Current: 205/776.5
• CPC Class Codes: G01N 17/02 Electrochemical measuring systems for weathering, corrosion or corrosion-protection measurement
• CPC Class Codes: G01N 33/32 Paints; Inks

Abstract

A hand-held and flexible corrosion sensor is described that uses electrochemical impedance spectroscopy (EIS, also known as AC impedance) to detect coating degradation and corrosion of coated and uncoated metals. The hand-held and flexible corrosion sensor is pressed against the surface of the structure of specimen to be inspected, and may be either straight in structural configuration in the form of a pen or bent in a curved or angled manner to achieve better access to the structure. An EIS spectrum can than be obtained in the field or under arbitrary conditions and the degree of coating or material degradation can be determined from the resultant spectrum. There are no restrictions on the configuration of the structure being inspected. The area of detection is controlled by moderating the extent and degree of wetness of the surface. A dry surface will provide a localized measurement; a wet surface will allow inspection of the wetted area.

Claims

1. A method for early detection of electrochemical corrosion of a coated or an uncoated surface of a metal structure utilizing electrochemical impedance spectroscopy, comprising the steps of:

(a) providing an electrochemical impedance spectrometer, said spectrometer comprising a computer controlled potentiostat and a sensor device which comprises a metal tip, said sensor device functions as both a counter and reference electrode;

(b) placing the metal tip of the sensor device directly onto the top surface of the coated or uncoated surface of the metal structure;

(c) wetting the surface of the metal structure around the metal tip with an electrolyte, the metal tip and the area covered by the electrolyte thereby defining a controlled detection area;

(d) applying an AC voltage from the potentiostat across the metal tip and the metal structure to be tested, the metal structure thereby functioning as a working electrode;

(e) measuring the resulting AC current thus obtaining a first reading;

(f) performing steps (d) and (e) at different frequencies of AC voltage to obtain multiple readings;

(g) calculating an impedance magnitude and phase for each obtained reading, thereby generating an impedance spectrum over the entire applied frequency range;

(h) comparing the generated impedance spectrum of the controlled detection area with the impedance spectrum of previously determined measurements of metallic structures in different stages of known surface corrosion to determine the stage of surface corrosion of the metal structure being tested.