Cathodic protection system using impressed current and galvanic action

• US 20060108235A1
• Filed: 11/26/2004
• Published: 05/25/2006
• Est. Priority Date: 11/23/2004
• Status: Active Grant

• Current Assignee: Vector Corrosion Technologies Incorporated (Vector Corrosion Technologies)
• Original Assignee: Vector Corrosion Technologies Incorporated (Vector Corrosion Technologies)
• Inventors: Whitmore, David, Ball, John Christopher
• Granted Patent: US 7,264,708 B2
• Time in Patent Office: Days
• US Class Current: 205/724
• CPC Class Codes: C23F 13/06 Constructional parts, or assemblies of cathodic-protection apparatus
• CPC Class Codes: C23F 13/22 Monitoring arrangements therefor
• CPC Class Codes: C23F 2201/02 Concrete, e.g. reinforced
• CPC Class Codes: C23F 2213/21 combining at least two types of anodic or cathodic protection
• CPC Class Codes: Y10S 241/605 Hay unbaler

Abstract

Cathodic protection of steel in a building or other concrete or similar structure is provided by locating an anode in a suitable location adjacent to the steel and providing an impressed current from a power supply to the anode. The anode is formed from a material which is more electro-negative than the steel so that in the event that the power supply falls below the galvanic potential therebetween, current flows under galvanic action to replace the impressed current. A diode in the circuit prevents flow of current across the power supply but allows the galvanic current when the power supply fails open circuit. An additional diode can be provided in the event the power supply fails closed circuit to prevent reverse current flow.

Claims

1. A method for cathodic protection comprising:

providing steel material;

providing a covering material such that at least a part of the steel material is at least partly covered by the covering material;

providing at least one anode member which is formed of a material which is more electro-negative than the steel material such that galvanic action will generate an electric potential difference therebetween tending to cause a flow of ions;

arranging the anode member at least partly in contact with the covering material for communication of ions therebetween;

providing a first connection between the at least one anode member and the steel material so that the galvanic potential difference between the anode member and the steel material generated by the galvanic action causes ions to flow through the covering material tending to inhibit corrosion of the steel material while causing corrosion of the anode member;

providing a second connection between the at least one anode member and the steel material including a DC power supply having a supply potential difference greater than the galvanic potential difference between the anode member and the steel material generated by the galvanic action such that the supply potential difference causes ions to flow through the covering material tending to inhibit corrosion of the steel material;

the first and second connections being arranged to prevent communication of current through the first connection across the power supply such that when the DC power supply potential difference exceeds the galvanic potential difference current flows through the second connection;

the first and second connections being arranged to allow communication of current through the first connection such that when the supply potential difference falls below the galvanic potential difference current flows through the first connection;

whereby ions are caused by the power supply to flow to provide cathodic protection to the steel material for as long as the power supply is active and, when the power supply is inactive, ions are caused to continue to flow by the galvanic action to continue to provide cathodic protection to the steel material.

2. The method according to claim 1 wherein the power supply is a battery.

3. The method according to claim 2 wherein the battery has a potential of the order of or greater than 1.5V.

4. The method according to claim 1 wherein there is provided a diode in the first connection to prevent communication of current through the first connection across the power supply.

5. The method according to claim 1 wherein the first connection bridges output terminals of the power supply.

6. The method according to claim 1 wherein there is provided a diode in second connection to prevent flow of current in a reverse direction.

7. The method according to claim 2 wherein the battery is not replaced when expired such that when the battery expires the protection is wholly provided by the galvanic action.

8. The method according to claim 2 wherein the covering material comprises a structural material of a building and wherein the battery is buried in the structural material of the building.

9. The method according to claim 8 wherein the structural material forms a wall and wherein the battery is buried in a cavity in the wall.

10. The method according to claim 8 wherein the covering material comprises a structural material of a building and wherein there is provided a plurality of batteries at plurality of respective locations on the building.

11. The method according to claim 8 wherein the building includes a plurality of steel elements of the building and wherein there is provided a separate battery for each element.

12. A method for cathodic protection comprising:

providing steel material;

providing a covering material such that at least a part of the steel material is at least partly covered by the covering material;

providing at least one anode member;

arranging the anode member at least partly in contact with the covering material for communication of ions therebetween;

providing a connection between the at least one anode member and the steel material including a DC power supply having a supply potential difference between the anode member and the steel material such that the supply potential difference causes current to flow in the connection in a direction to cause ions to flow through the covering material tending to inhibit corrosion of the steel material;

and providing a diode in connection to prevent flow of current in a reverse direction.

13. The method according to claim 12 wherein the power supply is a battery.

14. The method according to claim 13 wherein the battery has a potential greater than 1.5V.

15. The method according to claim 12 wherein the covering material comprises a structural material of a building and wherein the power supply comprises a battery which is buried in the structural material of the building.

16. The method according to claim 15 wherein the structural material forms a wall and wherein the battery is buried in a cavity in the wall.

17. The method according to claim 15 wherein the covering material comprises a structural material of a building and wherein there is provided a plurality of batteries at plurality of respective locations on the building.

18. The method according to claim 15 wherein the building includes a plurality of steel elements each forming a lintel of the building and wherein there is provided a separate battery for each lintel.