DESIGN OF CATHODIC PROTECTION USING BEM Anode: 0.6lb ..... 52 4.3.2. Sacrificial Anode: 1lb ........

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  • DESIGN OF CATHODIC PROTECTION USING BEM FOR COMPONENTS

    OF THE PILOT OCEAN ENERGY SYSTEM

    by

    Nicolas Gantiva

    A Thesis Submitted to the Faculty of

    The College of Engineering and Computer Science

    In Partial Fulfillment of the Requirements for the Degree of

    Master of Science

    Florida Atlantic University

    Boca Raton, Florida

    August 2010

  • ii

  • iii

    ACKNOWLEDGEMENTS

    The author wishes to express his most heartfelt thanks to his family for their constant

    support and encouragement in the pursuit of this year-and-a-half-long enterprise. It played a key

    role in enduring this experience being far from home. The author is also immensely grateful to

    both the US and UK technical support staff from the BEASY Software company for all their help

    and patience. To the Center for Ocean Energy Technology thanks for having established the

    project and providing the funds for this thesis to materialize. To the advisory committee for being

    part of this endeavor and for their words of advice, many thanks. Finally, a special thanks to

    thesis advisor Dr. Francisco Presuel-Moreno, without whom none of this could have been

    possible.

  • iv

    ABSTRACT

    Author: Nicolas Gantiva

    Title: Design of Cathodic Protection Using BEM for Components of the Pilot Ocean Energy System.

    Institution: Florida Atlantic University

    Thesis Advisor: Dr. Francisco Presuel-Moreno

    Degree: Master of Science

    Year: 2010

    The Center for Ocean Energy Technology at Florida Atlantic University is developing an

    ocean energy turbine system to investigate the feasibility of harnessing Floridas Gulf Stream

    current kinetic energy and transforming it into a usable form. The turbine system has components

    which are prone to marine corrosion given the materials they are made of and to the harsh

    environment they will be exposed to. This study assumes a two-part system composed of a

    coating system acting as a barrier and sacrificial anode cathodic protection which polarizes the

    metal structures to a potential value where corrosion is significantly reduced. Several

    configurations (varying in anode quantity, size and location) were considered in order to

    cathodically protect the structures with various coating qualities (poor, good and excellent). These

    cases were modeled and simulated via Boundary Element Method software and analyzed so as

    to assess the most appropriate design.

  • DEDICATION

    This manuscript and all the work associated to it are entirely dedicated to my family,

    particularly to my father, Diego, my constant role model in integrity and exceptional

    professionalism. I only wish I can follow in your footsteps. To the love of my life, this work and

    the effort I poured into it represents my commitment of returning by your side as I had promised.

  • v

    DESIGN OF CATHODIC PROTECTION USING BEM FOR COMPONENTS OF THE PILOT OCEAN ENERGY SYSTEM

    List of Tables ............................................................................................................................. ix

    List of Figures ............................................................................................................................. x

    Nomenclature ........................................................................................................................... xiii

    1. Introduction ......................................................................................................................... 1

    1.1. Ocean Energy Project...................................................................................................... 2

    1.2. Purpose Statement.......................................................................................................... 3

    1.3. Structure Characteristics.................................................................................................. 4

    1.3.1. Base Material............................................................................................................... 5

    1.3.2. Coatings ...................................................................................................................... 5

    1.4. Concept of Operation....................................................................................................... 8

    1.4.1. Environment and Location ........................................................................................... 8

    1.5. Preliminary Suggestions ................................................................................................ .. 9

    2. Background....................................................................................................................... 10

    2.1. Corrosion ...................................................................................................................... 10

    2.1.1. Corrosion Theory ....................................................................................................... 12

    2.1.1.1. Polarization............................................................................................................ 13

    2.2. Cathodic Protection ....................................................................................................... 18

    2.2.1. Graphical Representation of Cathodic Protection ....................................................... 20

    2.2.2. Impressed Current ..................................................................................................... 22

    2.2.3. Sacrificial Anode (Galvanic) ....................................................................................... 22

    2.3. Coated vs. Uncoated Structures .................................................................................... 25

    2.4. Stationary vs. Moving Structures.................................................................................... 27

    2.5. Location Corrosion by Seawater ................................................................................. 28

    2.6. BEM to Model CP.......................................................................................................... 30

    2.6.1. BEM Mathematics...................................................................................................... 31

    2.6.2. Beasy Software ......................................................................................................... 36

  • vi

    3. Previous Work................................................................................................................... 38

    3.1. The Structures and Their Simpler Models ...................................................................... 38

    3.2. General Boundary Conditions ........................................................................................ 44

    4. Exact Geometry Creation ................................................................................................ .. 45

    4.1. Monitoring and Telemetry Buoy ..................................................................................... 45

    4.2. A-Frame........................................................................................................................ 48

    4.3. Anodes.......................................................................................................................... 51

    4.3.1. Sacrificial Anode: 0.6lb .............................................................................................. 52

    4.3.2. Sacrificial Anode: 1lb ................................................................................................ . 52

    4.3.3. Sacrificial Anode: 2lb ................................................................................................ . 53

    5. Polarization Data............................................................................................................... 55

    5.1. Carbon Steel ................................................................................................................. 55

    5.2. Stainless Steel............................................................................................................... 56

    5.3. Zinc............................................................................................................................... 57

    6. Simulation Results............................................................................................................. 59

    6.1. MTB Lead Hull Buoy................................................................................................ ... 60

    6.1.1. Two-Anode Configuration .......................................................................................... 61

    6.1.1.1. Bare Steel.............................................................................................................. 61

    6.1.1.2. Coating Efficiency: 80% ......................................................................................... 65

    6.1.1.3. Coating Efficiency: 90% ......................................................................................... 68

    6.1.1.4. Coating Efficiency: 98% ......................................................................................... 70

    6.1.2. Four-Anode Configutation.......................................................................................... 73

    6.1.2.1. Bare............................................................................