Methods for controlling and monitoring the degree of cathodic protection for metal structures and buried pipelines using coupled multielectrode sensors

A cathodic protection system for protecting a metal structure (65) within an electrolyte (70), comprising:

• a multielectrode non-liquid-containing probe (15) having an insulator and a plurality of individual metal electrodes (10) including at least a first electrode, a second electrode, and a third electrode, with a first electrode current associated with the first electrode, a second electrode current associated with the second electrode and different than the first electrode current, and a third electrode current associated with the third electrode and different than the second electrode current, wherein the multielectrode non-liquid-containing probe (15) is at least partially located within the electrolyte (70), and the first electrode comprises a first electrode material, the second electrode comprises a second electrode material different than the first electrode material, and the third electrode comprises a third electrode material different than the first electrode material;
• a multielectrode CP instrument (31) having a multi-channel ammeter (35) in electrical communication with the plurality of individual metal electrodes (10) of the multielectrode non-liquid-containing probe (15) via a probe cable (20);
• an anode (80) at least partially located within the electrolyte (70);
• and
• a CP rectifier (75) in electrical communication with the multielectrode CP instrument (31), the metal structure (65), and the anode (80), wherein the CP rectifier (75) generates and controls a CP current flow through the metal structure (65) and the plurality of individual metal electrodes (10) of the multielectrode non-liquid-containing probe (15);
• wherein:
• the multi-channel ammeter (35) receives and monitors the first electrode current, the second electrode current, and the third electrode current, and the multielectrode CP instrument (31) identifies an initial most anodic electrode from the first electrode, the second electrode, and the third electrode, and an associated initial most anodic current (Iamax) from the first electrode current, the second electrode current, and the third electrode current;
• the multielectrode CP instrument (31) controls the CP rectifier (75) to generate and control the CP current to achieve a zero value of the initial most anodic current (Iamax) from the initial most anodic electrode, and then:
• the multielectrode CP instrument (31) monitors the first electrode current, the second electrode current, and the third electrode current, and the multielectrode CP instrument (31) identifies a controlled current (Iamax) associated with an initially positive-current electrode selected from the first electrode, the second electrode, and the third electrode current, that is now a controlled negative-current electrode selected from the first electrode, the second electrode, and the third electrode based upon which of the first electrode current, the second electrode current, and the third electrode current is negative but closest to zero, and determines a cathodic protection effectiveness margin (CPEM), defined as a percentage ratio of the controlled current (Iamax) to a maximum allowable CP current (ICP limit);
• and
• the multielectrode CP instrument (31) controls the CP rectifier (75) to adjust and maintain the CP current to (a) maintain the controlled current (Iamax) at no greater than zero, and (b) maintain the cathodic protection effectiveness margin (CPEM) between zero and 100%.

A cathodic protection system for protecting a metal structure (65) within an electrolyte (70), comprising:

• a multielectrode non-liquid-containing probe (15) having an insulator and a plurality of individual metal electrodes (10) including at least a first electrode, a second electrode, and a third electrode, with a first electrode current associated with the first electrode, a second electrode current associated with the second electrode, and a third electrode current associated with the third electrode, wherein the multielectrode non-liquid-containing probe (15) is at least partially located within the electrolyte (70), and the first electrode comprises a first electrode material, and the second electrode comprises a second electrode material different than the first electrode material, and at least one of the first electrode material and the second material is the same as a material of the metal structure (65);
• a multielectrode CP instrument (31) having a multi-channel ammeter (35) in electrical communication with the plurality of individual metal electrodes (10) of the multielectrode non-liquid-containing probe (15) via a probe cable (20);
• an anode (80) at least partially located within the electrolyte (70);
• and
• a CP rectifier (75) in electrical communication with the multielectrode CP instrument (31), the metal structure (65), and the anode (80), wherein the CP rectifier (75) generates and controls a CP current flow through the metal structure (65) and the plurality of individual metal electrodes (10) of the multielectrode non-liquid-containing probe (15);
• wherein:
• the multi-channel ammeter (35) (15) receives and monitors the first electrode current, the second electrode current, and the third electrode current, and the multielectrode CP instrument (31) identifies an initial most anodic electrode from the first electrode, the second electrode, and the third electrode, and an associated initial most anodic current (Iamax) from the first electrode current, the second electrode current, and the third electrode current;
• the multielectrode CP instrument (31) controls the CP rectifier (75) to generate and control the CP current to achieve a zero value of the initial most anodic current (1ªmax from the initial most anodic electrode, and then:
• the multielectrode CP instrument (31) monitors the first electrode current, the second electrode current, and the third electrode current, and the multielectrode CP instrument (31) identifies a controlled current (Iamax) associated with an initially positive-current electrode selected from the first electrode, the second electrode, and the third electrode current, that is now a controlled negative-current electrode selected from the first electrode, the second electrode, and the third electrode based upon which of the first electrode current, the second electrode current, and the third electrode current is negative but closest to zero, and determines a cathodic protection effectiveness margin (CPEM), defined as a percentage ratio of the controlled current (Iamax) to a maximum allowable CP current (ICP limit);
• the multielectrode CP instrument (31) controls the CP rectifier (75) to adjust and maintain the CP current to (a) maintain the controlled current (Iamax) at no greater than zero, and (b) maintain the cathodic protection effectiveness margin (CPEM) at zero % or greater;
• after the start of monitoring the controlled current (1ªmax), the multielectrode CP instrument (31) monitors the first electrode current, the second electrode current, and the third electrode current, and the multielectrode CP instrument (31) identifies a post-CP most cathodic current (Icmax) associated with a post-CP most cathodic electrode, and controls the CP rectifier (75) to adjust and maintain the CP current to maintain the cathodic protection effectiveness margin (CPEM) to less than an excessive CPEM;
• and
• the multielectrode CP instrument (31) monitors the post-CP most cathodic current (Ic max) and determines a second cathodic protection effectiveness margin (CPEMc), defined as a percentage ratio of the post-CP most cathodic current (I max) to a maximum allowable CP current (ICP limit), and the multielectrode CP instrument (31) controls the CP rectifier (75) to adjust and maintain the CP current to keep the second cathodic protection effectiveness margin (CPEMc) between zero and 100%.