Masters thesis of civil engineering an investigation into impressed current cathodic protection systems in australian wharves

An investigation into impressed current cathodic protection systems in Australian wharves A thesis submitted in fulfilment of the requirements for the degree of Master of Civil Engineering Peter Nicholls B.Eng, B.Biomed Sci School of Civil Environmental and Chemical Engineering College of Science Engineering and Health RMIT University January 2017 i Declaration I, Peter Nicholls, certify that except where due acknowledgement has been made, the work is that of the author alone; the work has not been submitted previously, in whole or in part, to qualify for any other academic award; the content of the thesis is the result of work which has been carried out since the official commencement date of the approved research program; any editorial work, paid or unpaid, carried out by a third party is acknowledged; and, ethics procedures and guidelines have been followed Peter Nicholls 4th of March 2017 ii Acknowledgement Firstly I would like to thank Dr David Law for his guidance and insight throughout my candidature David’s support both technically and logistically was critical to my completion I would also like to thank Associate-Professor Tom Molyneux and Dr Liam Ward for their help and advice To the two principal asset owners, the Port of Melbourne Corporation and the Port of Portland, who allowed RMIT access to their wharves for this study I would like to, extend my most genuine thanks Without this access to these sites this study would not have been possible I would like to extend particular thanks to Christine Crawshaw, Mark Kamphuis and Bruce Ackland I am certain that my constant requests for yet more information was taxing at times however their generosity and patience was ceaseless I would like to extend a special thanks to Graham and Marcus Eldridge of Eldridge Electrical for their assistance and time Time and time again their generosity made overwhelming tasks simple As this was a part time program, I would not have been able to complete this work without the ongoing support of my managers and supervisor at work, to whom I would like to extend my thanks and express my gratitude To Frederic Blin of AECOM for providing me with this opportunity, and supporting me during the early days of the project To Adam O’Dea and Jeff Pritchard of Freyssinet Australia for their ongoing support and understanding I was lucky enough to have the support and friendship of my fellow students Thank you to Shamir Bhuiyan for your help and guidance and to Amy Spark Eichenbaum for now helping me through both undergraduate and post graduate study Finally I would like to thank my family and friends for their support and understanding during my candidature In particular I would like to thank my partner for her patience iii Contents Declaration ii Acknowledgement iii Notation and Abbreviations Abstract Overview of Chapters Introduction 1.1 Basis of Corrosion 1.2 Thermodynamic Considerations of the Corrosion of Steel in Concrete 1.3 Kinetic Considerations of the Corrosion of Steel in Concrete 1.4 Corrosion of Steel in Concrete in Marine Environment – Chloride Induced Corrosion 12 1.5 Exposure Zones in Marine Structures 16 1.6 Monitoring Corrosion of Steel in Concrete 18 1.7 Impressed Current Cathodic Protection of Steel in Concrete 22 1.8 Monitoring the Effect of an ICCP System 26 1.9 Disruptive Technologies and Residual Protection 28 Methodology 30 Wharf Description and History 33 Wharf A Results 39 4.1 Transverse Beams Detailed Analysis of Operation to Date 39 4.2 Fender Blocks Detailed Analysis of Operation to Date 44 4.3 Transverse Beams Study Results 47 4.4 Fender Block’s Study Results 52 Wharf B Results 55 5.1 Wharf B Detailed Analysis of Operation to Date 55 5.2 Wharf B Study Results 58 Wharf A Discussion 62 6.1 Transverse Beams Discussion 62 6.2 Fender Blocks Discussion 71 Wharf B Discussion 75 Overall Discussion 80 Conclusion and Future Study 82 10 References 83 Appendix A 86 iv Appendix B 111 Appendix C 227 Appendix D 276 Table of Figures Figure Pourbaix diagram of Fe - H2O [11] Figure 3.Evans diagram showing anodic and cathodic reactions of steel[8] 10 Figure 4.Evans diagram showing active (a) and active – passive (b) behaviour of steel [15] 11 Figure 5.Steel potential versus chloride content in concrete [21] 14 Figure 6.Classification of marine zones 17 Figure Example of a three electrode system using potentiostatic control 20 Figure 8.Schematic of basic elements of an ICCP system 22 Figure Schematic of a) the transverse beam region arrangement and b) the fender block zone arrangement 34 Figure 10 Schematic showing the transverse beam zone arrangement 35 Figure 11 Schematic showing the elements of wharf B 37 Figure 12.Characteristic depolarisation curve noted in many beam elements 49 Figure 13.Potential versus time plot for fender block 13 52 Figure 13.Output dials of transformer rectifier at wharf B 56 Figure 15.Potential versus time plot of D29 60 Figure 16.Potential versus time plot of D29 60 Figure 17.Typical section of the potential versus time graph for reference D9 61 Figure 18.Potential versus time plot of beam 205 66 Figure 19.Illustration of sharp negative excursion, beam 199 zone one 70 Figure 20.Potential versus time graph for reference B41 76 Figure 21.Section of the potential versus time graph for reference B41 77 Table of Tables Table 1.Steel corrosion status as per corrosion current density and corrosion rate[16, 32] 21 Table 2.Summary of the historical current analysis for the transverse beams 40 Table 3.Historical current analysis for each transverse beam and zone 40 Table Summary of current density applied during operational life of transverse beams 42 Table 5.Historical current analysis for the fender blocks 44 Table 6.Showing the results of the historical current analysis for the fender blocks 45 Table 7.Summary of current density applied during operational life of fender blocks 46 Table 8.Results Wharf A - beams 50 Table 9.Resultswharf A – fender blocks 52 Table 10 Ratio of the steel surface area (m²) to concrete surface area (m²) 55 Table 11 Calculated current densities based on total current of 14A 56 Table 12.Results Wharf B 58 v Table 13.Historical charge data for beams which displayed residual protection 62 Table 14.Near passive beams 64 Table 15.Showing the beams classified by zone and passive or near passive status 64 Table 16.Average charge passed into beams based on activity and group status 65 Table 17 Difference between the final and instant off potentials for beams 67 Table 18.Fender blocks based on the charge per square metre of steel surface area injected 71 Table 19.Difference between the final and instant off potentials of the fender blocks 72 Table 20.Showing direction of maximal wind speed for the year February 2015 to January 2016 74 Table 21.Showing the difference between the native and final potential 77 Table 22 Distribution of elements types amounts the passive and near passive cohorts 79 vi Notation and Abbreviations Cathodic Protection Corrosion Current Impressed Current Cathodic Protection Iron North American Corrosion Association Sacrificial Cathodic Protection Water Junction Box Transformer Rectifier Unit Ordinary Portland Cement – CP - Ic – ICCP – Fe – NACE – SCP – H2O - JB - TRU - OPC Abstract Over the past forty years a significant number of corroding and at risk reinforced concrete structures have been successfully managed using Impressed Current Cathodic Protection (ICCP) ICCP systems are electrochemical treatments which are capable of arresting the corrosion of steel A recent study of ten structures in the UK showed steel reinforcement in bridges remained passive up to three years after ICCP was no longer applied Similar findings were reported in a study conducted in southern Australia These findings indicate that ICCP can provide a form of lasting residual protection Whilst the presence of residual protection has been established both the reasons for, and the mechanisms behind it and the duration for which it persists are currently unknown It is believed that the period of passivity is due to changes in the microenvironment of the concrete adjacent to the steel The most likely cause for this is prolonged operation of the ICCP system changing the chemistry of the concrete however at this time this is yet to be conclusively shown This study examined the phenomenon of residual protection by suspending the operation of established ICCP systems in two wharves located in southern Victoria and monitoring the effect on the passivity of the steel via electrochemical testing The results of the study confirm that the steel in selected elements within these structures remained passive once the ICCP system was interrupted The primary factor in determining which elements remained passive, and the duration of passivity was the amount of charge injected into the element over the life of the ICCP system The environment surrounding the element was also observed to influence the residual protection The study also highlighted that the currently accepted criterion for absolute passivity cannot reliably be applied to the tidal zone Overview of Chapters Chapter Introduction A brief description of the current state of knowledge field highlighting the main drivers for the study and potential outcomes Finally identifying the core aims and detailing the research questions 1.1 Basis of Corrosion A discussion of the underlying chemical reactions behind and conditions required for corrosion 1.2 Thermodynamic Considerations of the Corrosion of Steel in Concrete A discussion of the thermodynamic driving forces behind corrosion and how it is affected by environmental factors 1.3 Kinetic Considerations of the Corrosion of Steel in Concrete A discussion of the kinetics of corrosion and how interaction with the environment defines the overall corrosion rate 1.4 Corrosion of Steel in Concrete in Marine Environment – Chloride Induced Corrosion An introduction into the effects of chloride on the reaction kinetics and an exploration of the mechanisms behind these effects 1.5 Exposure Zones in Marine Structures A discussion of the different exposure zones which are present in marine infrastructure and of how these different levels of exposure affect the corrosion reactions 1.6 Monitoring Corrosion of Steel in Concrete A description of the industry standard testing and inspection techniques used to monitor and assess the corrosion of steel in concrete 1.7 Impressed Current Cathodic Protection of Steel in Concrete An introduction to the technique of impressed current cathodic protection, its underlying principles and constituent elements 1.8 Monitoring the Effect of an ICCP System A description of the currently accepted methods for monitoring an ICCP system 1.9 Disruptive Technologies and Residual Protection A discussion of alternate electrochemical protection techniques and the phenomena of residual protection Chapter Methodology An explanation of the methodology employed including; how sites were selected, the method of monitoring the system during the study and how the results were examined Chapter Wharf Description and History A brief structural and operational history of the two wharves and their ICCP systems Chapter Wharf A Results 4.1 Transverse Beams Detailed Analysis of Operation to Date A presentation of the calculated steel densities and total charge passed to the Transverse Beams during the operation of the ICCP system at the time of the study’s commencement 4.2 Fender Blocks Detailed Analysis of Operation to Date A presentation of the calculated steel densities and total charge passed to the Fender Blocks during the operation of the ICCP system at the time of the study’s commencement 4.3 Transverse Beams Study Results A presentation of the study results including the transverse beam’s protection status and passivity status 4.4 Fender Block’s Study Results A presentation of the study results including the fender block’s protection status and passivity status Chapter Wharf B Results 5.1 Wharf B Detailed Analysis of Operation to Date A presentation of the calculated steel densities at the time the study’s commenced 5.2 Wharf B Study Results A presentation of the study results including the elements protection status and passivity status Chapter Wharf A Discussion 6.1 Transverse Beams Discussion An exploration of the results gathered for the transverse beams and how these results relate to residual protection and the corrosion process occurring at the steel surface 6.2 Fender Blocks Discussion An exploration of the results gathered for the fender blocks and how these results relate to residual protection and the corrosion process occurring at the steel surface B22 0 20 40 60 80 100 120 140 160 180 140 160 180 140 160 180 Potential (mV) -100 -200 -300 -400 -500 -600 Time Elasped (5 second intervals) B22 D21 0 20 40 60 80 100 120 Potential (mV) -100 -200 -300 -400 -500 Time Elasped (5 second intervals) D21 D20 -50 20 40 60 80 100 120 Potential (mV) -100 -150 -200 -250 -300 -350 -400 Time Elasped (5 second intervals) D20 269 B20 0 20 40 60 80 100 120 140 160 180 140 160 180 Potential (mV) -50 -100 -150 -200 -250 Potential (mV) -300 Time Elasped (5 second intervals) B20 -185 -190 -195 -200 -205 -210 -215 -220 -225 -230 -235 FB18 20 40 60 80 100 120 Time Elasped (5 second intervals) FB18 D16 0 20 40 60 80 100 120 140 160 Potential (mV) -100 -200 -300 -400 -500 -600 Time Elasped (5 second intervals) D16 270 180 B16 Potential (mV) -50 20 40 60 80 100 120 140 160 180 140 160 180 140 160 180 -100 -150 -200 -250 -300 -350 Time Elasped (5 second intervals) B16 D15 0 -50 20 40 60 80 100 120 Potential (mV) -100 -150 -200 -250 -300 -350 -400 Time Elasped (5 second intervals) D15 D14 0 20 40 60 80 100 120 Potential (mV) -100 -200 -300 -400 -500 Time Elasped (5 second intervals) D14 271 B13 50 Potential (mV) 0 20 40 60 80 100 120 140 160 180 140 160 180 140 160 180 -50 -100 -150 Time Elasped (5 second intervals) B13 B12 0 20 40 60 80 100 120 Potential (mV) -50 -100 -150 -200 -250 Time Elasped (5 second intervals) B12 D11 Potential (mV) -50 20 40 60 80 100 120 -100 -150 -200 -250 -300 -350 Time Elasped (5 second intervals) D11 272 B11 Potential (mV) -50 20 40 60 80 100 120 140 160 140 160 140 160 180 -100 -150 -200 -250 -300 -350 Time Elasped (5 second intervals) B11 D9 -50 20 40 60 80 100 120 180 Potential (mV) -100 -150 -200 -250 -300 -350 -400 Time Elasped (5 second intervals) D9 B9 -184 -185 20 40 60 80 100 120 Potential (mV) -186 -187 -188 -189 -190 -191 -192 Time Elasped (5 second intervals) B9 273 180 D7 500 Potential (mV) 400 300 200 100 0 20 40 60 -100 80 100 120 140 160 180 140 160 180 140 160 180 Time Elasped (5 second intervals) D7 BW6 500 Potential (mV) 400 300 200 100 0 20 40 -100 60 80 100 120 Time Elasped (5 second intervals) BW6 FB5 350 300 Potential (mV) 250 200 150 100 50 -50 20 40 60 80 100 120 Time Elasped (5 second intervals) FB5 274 B5 -50 20 40 60 80 100 120 140 160 180 140 160 180 140 160 180 Potential (mV) -100 -150 -200 -250 -300 -350 -400 Time Elasped (5 second intervals) B5 D3 0 20 40 60 80 100 120 Potential (mV) -100 -200 -300 -400 -500 D3 Time Elasped (5 second intervals) B2 -50 20 40 60 80 100 120 Potential (mV) -100 -150 -200 -250 -300 -350 -400 -450 Time Elasped (5 second intervals) B2 275 Appendix D Wind Direction Data Wharf A Date 01-02-15 02-02-15 03-02-15 04-02-15 05-02-15 06-02-15 07-02-15 08-02-15 09-02-15 10-02-15 11-02-15 12-02-15 13-02-15 14-02-15 15-02-15 16-02-15 17-02-15 18-02-15 19-02-15 20-02-15 21-02-15 22-02-15 23-02-15 24-02-15 25-02-15 26-02-15 27-02-15 28-02-15 01-03-15 02-03-15 03-03-15 04-03-15 05-03-15 06-03-15 07-03-15 08-03-15 09-03-15 10-03-15 11-03-15 12-03-15 13-03-15 14-03-15 15-03-15 16-03-15 17-03-15 Direction of maximum wind gust SSW SSW S SSW SSW SSE N S SSW SSW SSW SSW W S NNE SSE SSW SSW SSW SSW NW N SSW SSE SE SSW SSW W SSW SSW S S SW SSW NNW S SSW SSW S S SSW NNW SSW NNW N 276 Date 18-03-15 19-03-15 20-03-15 21-03-15 22-03-15 23-03-15 24-03-15 25-03-15 26-03-15 27-03-15 28-03-15 29-03-15 30-03-15 31-03-15 01-04-15 02-04-15 03-04-15 04-04-15 05-04-15 06-04-15 07-04-15 08-04-15 09-04-15 10-04-15 11-04-15 12-04-15 13-04-15 14-04-15 15-04-15 16-04-15 17-04-15 18-04-15 19-04-15 20-04-15 21-04-15 22-04-15 23-04-15 24-04-15 25-04-15 26-04-15 27-04-15 28-04-15 29-04-15 30-04-15 01-05-15 02-05-15 03-05-15 04-05-15 05-05-15 Direction of maximum wind gust WSW N SSE SE N N SSW S NNW SSW WSW SSW S SSW N S SSE SW SSW SSE SSW SSW SSE SSW S SSW S NNE N W N S S SSE SSE SSE SSE NW S SSW W SSE SSW SE NE N SW N NNW 277 Date 06-05-15 07-05-15 08-05-15 09-05-15 10-05-15 11-05-15 12-05-15 13-05-15 14-05-15 15-05-15 16-05-15 17-05-15 18-05-15 19-05-15 20-05-15 21-05-15 22-05-15 23-05-15 24-05-15 25-05-15 26-05-15 27-05-15 28-05-15 29-05-15 30-05-15 31-05-15 01-06-15 02-06-15 03-06-15 04-06-15 05-06-15 06-06-15 07-06-15 08-06-15 09-06-15 10-06-15 11-06-15 12-06-15 13-06-15 14-06-15 15-06-15 16-06-15 17-06-15 18-06-15 19-06-15 20-06-15 21-06-15 22-06-15 23-06-15 Direction of maximum wind gust NNW WNW NW N W NW NW WSW SSW S SSW NNW N N N S SSW SSW NNW NNE N N N NW NNW S SSW SSW NNE N N N N NNW WNW SSW NNE NNE NNE ESE N SSE SE SSW SSW NNE N N 278 Date 24-06-15 25-06-15 26-06-15 27-06-15 28-06-15 29-06-15 30-06-15 01-07-15 02-07-15 03-07-15 04-07-15 05-07-15 06-07-15 07-07-15 08-07-15 09-07-15 10-07-15 11-07-15 12-07-15 13-07-15 14-07-15 15-07-15 16-07-15 17-07-15 18-07-15 19-07-15 20-07-15 21-07-15 22-07-15 23-07-15 24-07-15 25-07-15 26-07-15 27-07-15 28-07-15 29-07-15 30-07-15 31-07-15 01-08-15 02-08-15 03-08-15 04-08-15 05-08-15 06-08-15 07-08-15 08-08-15 09-08-15 10-08-15 11-08-15 Direction of maximum wind gust N W N N NNE S SSW NNW SW N NNW N N N NW N NNW N SSW SSW N SSE SE S SSW SSW N NNW N N N N NNW NW NW N NNW N N NW W W SSW SSW W SSW N NNW N 279 Date 12-08-15 13-08-15 14-08-15 15-08-15 16-08-15 17-08-15 18-08-15 19-08-15 20-08-15 21-08-15 22-08-15 23-08-15 24-08-15 25-08-15 26-08-15 27-08-15 28-08-15 29-08-15 30-08-15 31-08-15 01-09-15 02-09-15 03-09-15 04-09-15 05-09-15 06-09-15 07-09-15 08-09-15 09-09-15 10-09-15 11-09-15 12-09-15 13-09-15 14-09-15 15-09-15 16-09-15 17-09-15 18-09-15 19-09-15 20-09-15 21-09-15 22-09-15 23-09-15 24-09-15 25-09-15 26-09-15 27-09-15 28-09-15 29-09-15 Direction of maximum wind gust N SSW WNW S N WSW WSW SSW N N N SSW SSE SE ESE SSW SSW SSW SSW S NNE NNE SSW SSW SSW N NNW SSW SSW SSW NNW N NNW N WNW SSW SSE SSW N N N S SSE SSW SSE S SSE SSW NW 280 Date 30-09-15 01-10-15 02-10-15 03-10-15 04-10-15 05-10-15 06-10-15 07-10-15 08-10-15 09-10-15 10-10-15 11-10-15 12-10-15 13-10-15 14-10-15 15-10-15 16-10-15 17-10-15 18-10-15 19-10-15 20-10-15 21-10-15 22-10-15 23-10-15 24-10-15 25-10-15 26-10-15 27-10-15 28-10-15 29-10-15 30-10-15 31-10-15 01-11-15 02-11-15 03-11-15 04-11-15 05-11-15 06-11-15 07-11-15 08-11-15 09-11-15 10-11-15 11-11-15 12-11-15 13-11-15 14-11-15 15-11-15 16-11-15 17-11-15 Direction of maximum wind gust SSW SSW N N N N NNW SSW SSW N N SSW S S N N S S SSW SSW NNE SSW SSW SSW S NNW SSW SE N SSE SSE NNW N SSW SSW SSE N SSW SSW SSW N S SSW S S SSE SSW SSW NNW 281 Date 18-11-15 19-11-15 20-11-15 21-11-15 22-11-15 23-11-15 24-11-15 25-11-15 26-11-15 27-11-15 28-11-15 29-11-15 30-11-15 01-12-15 02-12-15 03-12-15 04-12-15 05-12-15 06-12-15 07-12-15 08-12-15 09-12-15 10-12-15 11-12-15 12-12-15 13-12-15 14-12-15 15-12-15 16-12-15 17-12-15 18-12-15 19-12-15 20-12-15 21-12-15 22-12-15 23-12-15 24-12-15 25-12-15 26-12-15 27-12-15 28-12-15 29-12-15 30-12-15 31-12-15 01-01-16 02-01-16 03-01-16 04-01-16 05-01-16 Direction of maximum wind gust N SSW NNE SSW S S NNW NW SSW WSW S SSW NW SSW S SSW SSW S SSE WSW NNW SSE SSE SW SSE SSW SW SSW SSW NNW N N S SW SSW SSW SE N SSW S S SSW SSE N SSW ESE SE SSE NNE 282 Date 06-01-16 07-01-16 08-01-16 09-01-16 10-01-16 11-01-16 12-01-16 13-01-16 14-01-16 15-01-16 16-01-16 17-01-16 18-01-16 19-01-16 20-01-16 21-01-16 22-01-16 23-01-16 24-01-16 25-01-16 26-01-16 27-01-16 28-01-16 29-01-16 30-01-16 Direction of maximum wind gust SSW SSW SSW S SW NW SSW WSW SSW S S N NNW SSW SW SSW SSW S SSW SSW SE N N S S 283 ... the significant advantages of being easier to install and possessing an aesthetically pleasing finish However the life and current distribution of these anode systems can be below that of the more... Corrosion of Steel in Concrete in Marine Environment – Chloride Induced Corrosion An introduction into the effects of chloride on the reaction kinetics and an exploration of the mechanisms behind these... Current Cathodic Protection of Steel in Concrete An introduction to the technique of impressed current cathodic protection, its underlying principles and constituent elements 1.8 Monitoring the