Cathodic protection evaluation.

Details

• Creators:
  Tinnea, John S. ; Tinnea, Ryan J. ; Andrade, Carmen
• Corporate Creators:
  Tinnea & Associates, LLC
• Subject/TRT Terms:
  • Reinforced concrete bridges
  • Corrosion tests
  • Sensors
  • Electrodes
  • Cathodic protection
  • Evaluation
  • Reinforcing bars
  • Testing equipment
• Resource Type:
  Tech Report
• Geographical Coverage:
  Oregon
• Corporate Publisher:
  Oregon. Dept. of Transportation
• Abstract:
  This research investigates the effectiveness of a new corrosion rate test instrument in making field evaluations of the corrosion condition of ; several conventionally reinforced concrete coastal bridges. The instrument is the Gecor 9 Corrosion Rate Meter and comes with several sensors. ; This device is able to perform several techniques to evaluate the corrosion activity of steel reinforcement under diverse conditions. The Gecor’s ; Sensor A is equipped with three reference electrodes (RE), 1 counter electrode (CE), and 1 guard electrode (GE). Sensor A was used to measure ; the rebar corrosion current, icorr, using a DC galvanostatic pulse with modulated applied current confinement. This procedure was used to obtain ; baseline data for 21 zones of an impressed current cathodic protection (ICCP) system recently installed on the Conde McCullough Bridge in ; Coos Bay. That same procedure was also used to evaluate the reinforcement corrosion activity at two failed ICCP zones at the Yaquina Bay ; Bridge. Both of those ICCP systems utilized thermally sprayed zinc as distributed anodes. Sensor A is also able to perform an AC-based test to ; qualitatively evaluate the effectiveness of cathodic protection (CP) systems without the need to interrupt the applied CP current. That test ; protocol was applied to the same 21 ICCP zones at the Coos Bay Bridge and to six test location of the Lint Creek Bridge that has a galvanic ; anode CP (GACP) system installed to control rebar corrosion. Gecor Sensor B is equipped with one RE and one CE and is used to concurrently ; measure a rebar’s corrosion potential, Ecorr, and the resistivity of the surrounding concrete. Firmware in the Gecor 9 uses the observed corrosion ; potential and concrete resistivity to state the corrosion risk for the steel at the location tested. In general, the Gecor 9 performed very well. ; However, although it is a sophisticated instrument, it is able to produce data that is clearly questionable. Fortunately, since the Gecor has the ; ability to perform several markedly different types of tests, inconsistencies are generally obvious and a suspicious reading can be re-tested. ; Measurement errors were less a problem on the Yaquina Bay and Lint Creek Bridges because rebar could be clearly located before testing. At ; Coos Bay, the presence of a new zinc coating interfered with being able to identify rebar locations prior to removing the zinc on the concrete ; surface. At locations where reference electrodes were present and in areas of rebar structure bonds, a reasonable estimation of the rebar location ; could be made prior to removal of the zinc anode over an area of 8-9 inches in diameter to allow testing with the Gecor. Generally speaking, the ; Gecor 9 was able to make reasonable evaluations of cathodically protected rebar without having to interrupt the CP system. In terms of CP ; operation, this research demonstrated that: 1) the GACP system at Lint Creek is working well and protecting the embedded rebar; 2) All 12 ; locations tested in the two failed CP zones at Yaquina Bay reflect passive behavior of the embedded rebar even after the CP current had been ; interrupted for a number of years; Although the Gecor performance at Coos Bay was not as consistent as observed at the other bridges, it ; appears for future application, if rebars at test locations were located prior to applying the zinc coating, the test could be conducted with the ; sensor in proper alignment with the embedded steel, and that would significantly improve the performance of the instrument.
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• Format:
  PDF
• Alternate URL:
  http://ntl.bts.gov/lib/54000/54000/54082/CP_Evaluation_Appendices.pdf
• Funding:
  PSK28885
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/28120/dot_28120_DS1.pdf
• File Type:
  [PDF - 4.98 MB]
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha256:aac9d1bd11af692bca8a1c478606536e43c8321bb836d90ab4ad8c4d5b4e5580