Measuring Corrosion and Corrosion Control (CC) on Water Pipe Materials Graham E.C. Bell, Ph.D., P.E. Water/Wastewater Forum Corrosion: Why Should I Be Concerned? Corrosion 2010/San Antonio CC in the Water Industry is Fundamentally Different from CC in Oil & Gas Pipe Materials, Coatings and Linings CIP, DIP, Steel, and Reinforced/Pre-stressed/tension Concrete Mortar and Concrete Coatings and Linings Push-on NOT Welded Joints Lack of Regulatory Requirement for Corrosion Control and Monitoring. Cathodic Protection is the last resort of a desperate water corrosion engineer. Corrosion Control tends to be more passive and buried with the asset. Ferrous Pipe Materials Steel Pipe AWWA C200 Dielectric Coating AWWA C203 AWWA C210 AWWA C214 AWWA C222 Ductile Iron Pipe AWWA C151 AWWA C105 1
Mortar/Concrete Encased Steel Mortar Coated Steel Pipe AWWA C200+C205 Concrete Pipe AWWA C300 AWWA C301 AWWA C302 AWWA C303 Focus on Corrosion Monitoring Oil & Gas Corrosion Monitoring Focuses on Adequacy of Cathodic Protection for Compliance. Water Industry focuses on asset preservation and capital conservation Measuring -850 is not sufficient in the Water Industry Regulatory Compliance monitoring is fundamentally different. NACE standards focus on measurement of pipe or structure to electrolyte potential measurements (SP-0169). Asset Preservation and Capital Conservation Requires measuring corrosion damage or corrosion rate. Fundamentally, we need to measure corrosion current (i corr ) or mils lost. 2
Use of CP with Ferrous Water Pipe Materials is Spotty More common on NEW large diameter steel transmission pipelines with dielectric coatings. Retrofitting of existing ferrous pipelines occurs when leak rates become unacceptable. CP of DIP is a controversial subject. Most DIP is installed with out protection Small percentage with polyethylene encasement (PE) Even smaller percentage installed with PE and CP or even just CP. Surrogates Methods for Measuring Corrosion Coupons Probes Electrical Resistance (ER) Electrochemical Techniques Linear Polarization Advanced Electrochemical Methods Principals of Operation for ER Probes Thin cross section of metal corrodes. As metal thins uniformly, resistance of the strip increases. Changes in resistance of strip record metal loss (corrosion damage) Slope of line is the corrosion rate. 3
WIRE LOOP ER PROBE SCHEMATIC PROBE INTERNAL C CORROSION ENVIRONMENT CHECK REFERENCE MEASURE F E D A AC DRIVE B B C = MEASURE C D = REFERENCE D E = CHECK Installation of ER Probes Field Tests Cathodic Protection and ER Probes in Soil works! SANTA MARGARITA PROBE TEST CORROSION LOSS 1.80 1.60 CONNECT C.S. TO PIPE CORROSION LOSS S (mils) 1.40 1.20 1.00 0.80 0.60 0.40 CARBON STEEL DUCTILE IRON 0.20 0.00 0 200 400 600 800 1000 1200 TIME (DAYS) 4
0 Continuing Field Tests CR on DIP Probe w/o CP similar to Bare Steel with CP SANTA MARGARITA PROBE TEST CORROSION RATE 7.0 6.0 CONNECT C.S. TO PIPE CORROSION RATE (MP PY) 5.0 4.0 3.0 2.0 1.0 CARBON STEEL DUCTILE IRON 0.0 0 200 400 600 800 1000 1200-1.0 TIME (DAYS) Mortar or Concrete Coated Steel Commonly used in water industry. High ph environment passivates and protects steel. Typical Pipe to Soil Potentials Bare, Coated or depassivated mortar coated steel 400 to -700 mv vs. CSE Passivated Steel in high ph environment 0 to -200 mv vs. CSE Mortar Coated Steel tells you when it is in trouble. Change in Mortar Encased Steel Potential with Time PRE-STRESSING WIRE ER PROBE TEST CK-3 READING (DIVISI IONS) 120.0 110.0 100.0 90.0 80.0 70.0 60.0 50.0 40.0 30.0 20.0 10.0 0.0-100.0-200.0-300.0-400.0-500.0-600.0-700.0-800.0 30 60 90 120 150 180 210 240 270 300 330 360 POTENTIAL VS. CS SE 390 420 450 480 510 540 570 600 630 660 690 720 750 780 810 840 870 TIME IN DAYS PROBE 1 CORROSION PROBE 2 CORROSION PROBE 1 POTENTIAL PROBE 2 POTENTIAL 5
0 How to Monitor Mortar or Concrete Encased Steel Make the pipeline intentionally electrically continuous so you can monitor it. Install Test Stations and Use them Measure base line pipe to soil potentials Look for changes Don t collect, file and forget. Change in Mortar Encased Steel Potential Tells You the Pipe Is Not Happy! PRE-STRESSING WIRE ER PROBE TEST CK-3 READING (DIVISI IONS) 120.0 110.0 100.0 90.0 80.0 70.0 60.0 50.0 40.0 30.0 20.0 10.0 0.0-100.0-200.0-300.0-400.0-500.0-600.0-700.0-800.0 30 60 90 120 POTENTIAL VS. CS SE 150 180 210 240 270 300 330 360 390 420 450 480 510 540 570 600 630 660 690 720 750 780 810 840 870 TIME IN DAYS PROBE 1 CORROSION PROBE 2 CORROSION PROBE 1 POTENTIAL PROBE 2 POTENTIAL 6
0 Early EC-PCCP Section 1.5 m to 6.5 m diameter Pre-Stressing Wire ER Probe Pre-stressing wire used as probe In-situ pre-stressing can be wired as a probe Probe can be used as a proxy on mortar coated joints Need to provide mortar environment. Pre-Stressing Wire ER Probe Testing PRE-STRESSING WIRE ER PROBE TEST CK-3 READING (D IVISIONS) 120.0 110.0 100.0 90.0 80.0 70.00 60.0 50.0 40.0 30.0 20.0 10.0 0.0-100.0-200.0-300.0-400.0-500.0-600.0-700.0-800.0 30 60 90 POTENTIAL VS S. CSE 120 150 180 210 240 270 300 330 360 390 420 450 480 510 540 570 600 630 660 690 720 750 780 810 840 870 TIME IN DAYS PROBE 1 CORROSION PROBE 2 CORROSION PROBE 1 POTENTIAL PROBE 2 POTENTIAL 7
Linear Polarization Resistance (LPR) LPR is a measurement technique that provides a direct electrochemical measurement of corrosion rate in a conductive electrolyte (soil or water) The measurement is made from two small electrodes made from the material (metal or alloy) of interest. The determination of the corrosion rate is calculated from a series of electronic measurements The LPR Equivalent Circuit R P R P Electrode 1 R S Electrode 2 C dl C dl R P = Polarization Resistance R s = Solution Resistance C dl = Double Layer Capacitance The behavior of a metal in an electrolyte 8
DIP + OX DIP + No OX DIP + BS 16,000 LPR-Bare Carbon Steel -1000 ANCE (ohm-cm^2) POLARIZATION RESISTA 14,000-900 12,000-800 10,000-700 8,000-600 6,000-500 4,000-400 2,000-300 LPR Reference Potential 0-200 0 10 20 30 40 50 60 70 DAYS REFERENCE POTE ENTIAL (mv) 9
7,000 LPR DIP No OX -980 ANCE (ohm-cm^2) POLARIZATION RESISTA 6,000-960 5,000-940 4000 4,000-920 3,000-900 2,000-880 1,000-860 LPR Reference Potential 0-840 0 10 20 30 40 50 60 70 DAYS ENTIAL (mv) REFERENCE POTE LPR DIP + OX 25,000-1000 NCE (ohm-cm^2) POLARIZATION RESISTAN 20,000 15,000 10,000 5,000 LPR Reference Potential -960-920 -880-840 REFERENCE POTEN NTIAL (mv) 0-800 0 10 20 30 40 50 60 70 DAYS DIP + OX DIP + No OX DIP + BS 10
LPR on Coated Steel 350,000-970 CE (ohm-cm^2) POLARIZATION RESISTAN 300,000-950 250,000-930 200,000-910 150,000-890 100,000-870 50,000-850 LPR Reference Potential 0-830 0 5 10 15 20 25 30 35 40 45 DAYS TIAL (mv) REFERENCE POTENT EIS Coated 1010 EN Showing SCC 11
Other Possible Electrochemical Measurements Electrochemical Impedance Spectroscopy (EIS) Electrochemical Noise (EN) Etc., etc.,. The point is that we can measure and estimate corrosion rates on ferrous metals very well and relatively accurately using surrogates. Design and Long Term Current Requirements for Water Pipe Materials Conclusions Motivation for Corrosion Control is Different in Water and Wastewater than it is in Oil & Gas Asset Preservation requires measuring corrosion rates rather than assuring compliance. We can measure corrosion rates using surrogates. Data need to be turned into actionable information. If you are not going to do anything, remain ignorant. 12
Thank you for your time Questions? 13