Corrosion detecting and monitoring apparatus

• US 4,019,133 A
• Filed: 12/29/1975
• Issued: 04/19/1977
• Est. Priority Date: 12/29/1975
• Status: Expired due to Term

• Current Assignee: Chevron Research Company (Chevron Corp.)
• Original Assignee: Gulf Research & Development Company
• Inventors: McCoy, John D., Manley, Robert E.
• Primary Examiner(s): Krawczewicz, Stanley T.
• Application Number:
  US05/644,968
• Time in Patent Office: 477 Days
• Field of Search: 324/65 CR, 324/71 E, 324/71 R, 73/86
• US Class Current: 324/700
• CPC Class Codes: G01N 17/00 Investigating resistance of materials to the weather, to corrosion, or to light
• CPC Class Codes: G01N 27/041 of a solid body
• CPC Class Codes: G01R 27/02 Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant by measuring phase angle only G01R25/00

Abstract

A corrosion detector for determining the corrosivity of a fluid and the ability of a metal to withstand the corrosive tendencies includes a tubular test specimen and a reference specimen. The two specimens are of the same composition and configuration over the length of the test specimen over which measurements are made. Means are provided for maintaining the two specimens at a temperature within less than 1° F. of each other. The corrosive fluid is passed through the test specimen. An alternating current is passed through the test specimen and reference specimen and the change in resistance of the test specimen relative to the reference specimen is measured in a phase sensitive Wheatstone bridge circuit to determine the extent of corrosion.

Claims

1. Apparatus for measuring the rate of corrosion of a ferromagnetic metal by a flowing fluid comprising a tubular test specimen of the ferromagnetic metal, means for flowing the fluid through the test specimen, a tubular reference specimen of the ferromagnetic metal adjacent to the test specimen, said reference specimen being of substantially the same length, diameter and wall thickness as the test specimen, electrical insulation separating the test specimen and the reference specimen, a housing enclosing the test specimen and the reference specimen, thermal insulation within the housing around the test specimen and the reference specimen adapted to maintain the temperature of the specimens within 1°

F. of one another, an alternating current source connected to the test specimen and the reference specimen to pass a current therethrough, and electrical leads attached to the outer surface of the test specimen and to the reference specimen connecting the specimens in a Wheatstone bridge circuit for measuring the resistance of the test specimen relative to the reference specimen to indicate the extent of corrosion of the test specimen.

2. Apparatus as set forth in claim 1 characterized by electrically insulating couplings connecting the ends of the test specimen to the means for passing the fluid through the test specimen to electrically insulate the test specimen from said means.

3. Apparatus as set forth in claim 2 characterized by the insulating couplings being outside of the housing, and temperature control means within the housing adapted to adjust the temperature in the test specimen to the temperature at which knowledge of the rate of corrosion is desired.

4. Apparatus as set forth in claim 2 characterized by the Wheatstone bridge circuit being a phase sensitive circuit.

5. Apparatus as set forth in claim 2 including a temperature recorder constructed and arranged to indicate the rate of change of temperature of the fluid flowing through the test specimen.

6. Apparatus as set forth in claim 2 characterized by temperature control means in the means for passing the fluid through the test specimen adapted to maintain the fluid delivered to the test specimen at a substantially constant temperature.

7. Apparatus as set forth in claim 2 characterized by the thermal insulation being adapted to maintain the temperatures of the test specimen and reference specimen within 0.1°

F. of one another.

8. Apparatus as set forth in claim 2 characterized by the test specimen being curved and the reference specimen having substantially the same shape as the test specimen.

9. In apparatus for measuring the rate of corrosion of a test specimen by a flowing fluid wherein the resistance of a test specimen is periodically compared in an alternating current Wheatstone bridge circuit with the resistance of a reference specimen, the improvement comprising a tubular test specimen through which the fluid flows, a tubular reference specimen of the same diameter and composition as the test specimen adjacent the test specimen, means for flowing the fluid through the test specimen, electrical insulation between the test specimen and the reference specimen, and means for maintaining the temperatures of the test specimen and the reference specimen within 0.5°

F. of one another.

10. Apparatus for indicating the rate of corrosion of a metal by a flowing fluid comprising a tubular test specimen of the metal;

means for flowing the fluid through the test specimen;

means around the test specimen for adjusting the temperature of the fluid flowing through the test specimen;

a reference specimen of the metal adjacent to the test specimen;

electrical insulation separating the test specimen and the reference specimen;

a housing enclosing the test specimen, reference specimen and means for adjusting the temperature;

thermal insulation within the housing around the test specimen and the reference specimen adapted to maintain the temperature of the specimens within 1°

F. of one another;

an alternating current source connected to the test specimen and the reference specimen to pass a current therethrough; and

electrical leads attached to the outer surface of the test specimen and to the reference specimen connecting the specimens in a Wheatstone bridge circuit for measuring the resistance of the test specimen relative to the reference specimen to indicate the extent of corrosion of the test specimen.