An Overview of Research Conducted for the EPCRC on Assessing the Performance of Coating & Cathodic Protection Mike YJ Tan, Institute for Frontier Materials and School of Engineering, Deakin University
Major Research Projects New findings on anodic transient effects on CP: New concepts of critical duration and amplitude of anodic transients Ying Huo and Mike Tan Industry advisors: Alan Bryson,
Brian Martin, Bruce Ackland and Geoff Cope Pipeline corrosion problems could be caused by anodic transients 1000mV 450mV Urban area
Rural area The pipeline industry needs to know exactly how big' these anodic transients (either in magnitude or length or frequency) need to be to cause a major pipeline corrosion problem. These are unanswered questions
Reference: AS2832.1 (Cathodic protection of metals: Pipes and cables). Main Findings There is a critical anodic transient duration that implies the allowable safe duration for single anodic transients on the
cathodically protected buried steel. Typical critical anodic transient durations for steel exposed to a constant anodic transient amplitude of 1000mV under CP of -950mVvs.CSE, were found to be approximately 9 minutes in 1000.cm resistivity sandy soil.
Snapshot of data showing critical duration of anodic transients Snapshot of data showing critical amplitude of anodic transients Explaining the critical anodic transient duration
24 hour CP State 1 General corrosion zone 4 3
2 Anodic transient Passive layer State 2
pH reducing 1 Passive layer break down State 3
New findings on cathodic shielding (CP current shielding by coatings) Mauricio (Max) Latino, Bob Varela and Mike Tan Industry advisors: Alan Bryson, Bruce Ackland, Geoff Cope, Brian Martin, Jan Lim Key findings
A high local pH has been confirmed to be a key to prevent corrosion under disbonded coatings. Most of commercial coatings shielded CP, however some thin epoxy coatings allow CP current permeation, affecting local pH under disbonded coatings. Coatings aging, disbondment dimension,
gap size and soil saturation status have been found to affect corrosion under disbonded coatings. Research issues on cathodic shielding and corrosion under disbonded coatings General
findings HDD Pipelines - Coating Integrity and CP Efficiency Ying Huo and Mike Tan Industry advisors: Alan Bryson, Brian Martin, Bruce Ackland and Geoff Cope
Horizontal directional drilling (HDD) pipelines and coating damages Obstacles Pull HDD pipeline
Sharp rock Coating defects HDD Pipelines quantifying coating integrity
and CP efficiency Laboratory sand box simulation of HDD pipelines in order to evaluate the performance of existing testing methods for Currently there are technical difficulties in accurately detecting coating defects, and to develop better methods for assessing HDD pipe coating
damage and(e.g. CP more accurate determination of coating defects efficiency,
andand asdistributions). a consequence the integrity and numbers, sizes durability of HDD pipes could not be assured. Findings and results
Both the on potential swing method and off potential method have shown significant uncertainties in measuring coating damage areas. A new EIS method has been developed based on the fact that capacitance values correlate better with coating damaged areas and it is nondestructive. A new local measurement method has been proposed and has shown to be able to detect
coating defect locations. Cathodic current density (mA/cm2) Off potential method: defect size 1 cm x 1 cm 3 cm x 3 cm
10 cm x 10 cm Defect area (cm2) Cathodic current density (mA/cm2) On potential swing method: defect size
1 cm x 1 cm 3 cm x 3 cm 10 cm x 10 cm Defect area (cm2) EIS method: Capacitance of defects Capacitance (F)
Size of defect (cm2) Neutralized defect capacitance A new local EIS measurement method 2.5cm x 44cm 171cm 215cm
2.5x44 No defect Trying to apply local EIS on HDD pipeline in the field
Corrosion monitoring probes and IT platform development Facundo Varela, Ke Wang, Indivarie Ubhayaratne, Mike YJ. Tan Industry advisors: Alan Bryson; Bruce Ackland; Brian Martin; Geoff Cope; Alireza Kouklan; Nick Doblo; Mark Dragar; Eric Jas
Pipeline condition monitoring probes & software A sample probe installation Sample results Sample findings
At the gas pipeline CP potentials, metal losses were low for all locations. At less negative CP potentials, metal losses were significantly higher . At the coating disbondment, soil moisture level, dry/wet weather, and air gaps at coating disbondment have found to affect corrosion significantly. They
appear to be more important than the level of CP applied. These field tests valid probe characteristics such as, The probes perform in-situ corrosion monitoring without CP interruption. The probes monitor corrosion without
the need of an accurate knowledge of the CP potential applied or the chemistry of the soil environment. The probes allow to inexpensively insitu evaluate corrosion rates, with higher sensitivity than current methods. Analysis, modelling and display of corrosion monitoring data
Acknowledgements This work was funded by the Energy Pipelines CRC, supported through the Australian Governments Cooperative Research Centres Program. The funding and in-kind support from the APGA RSC is gratefully acknowledged Industry Advisers, in particular Alan Bryson,
Geoff Callar, Brian Martin, Bruce Ackland, Geoff Cope, Alireza Kouklan; Craig Bonar, Mark Dragar and Huw Dent for their advice and comments on our research proposal and on this work.
