CorroZone: Fundamentals of Cathodic Protection

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A plain-language audio walk through the fundamentals and design of cathodic protection — section by section, from CorroZone's Cathodic Protection course. From the core electrochemistry and CP concepts to current distribution, potential gradients and CP design principles. Free, no login. From CorroZone. Full courses here: https://corrozone.com/courses#udemy

  1. Episode 1

    Master the Fundamentals of Cathodic Protection — Course Introduction

    Full courses here A big-picture tour of the whole cathodic protection course — how its four sections build from the fundamentals, through core CP assessment concepts and current distribution, to design principles. What this course covers A comprehensive, end-to-end course on cathodic protection (CP), organised into four sections that build on each other. Section One, Fundamental Concepts, lays the groundwork — what CP is, free corrosion, how applying a current to a corroding surface changes things, how charge is transported through electrolytes, the two main types of CP systems, and how potentials are measured. Section Two, Core Cathodic Protection Concepts, covers practical assessment — ohmic effects, the electrochemical reactions and their effects, a thermodynamic perspective on why CP works, protection criteria, overprotection, potential transients, and OFF potential measurement. Section Three, Current Distribution and Potential Gradients, widens the lens to how current and potential spread through the environment — potential gradients around a structure, remotely placed anodes, stray current corrosion, and potential decay. Section Four, CP Design Principles, brings it together with the core design calculations — anode material selection, working out anode mass, anode resistance and groundbed considerations, the effect of organic coatings on current demand, and the current drain test. The arc runs from understanding CP, to assessing it, to seeing how it behaves across an environment, and finally to designing it. Who this is for Engineers, technicians, students, and professionals who want a practical and conceptually solid foundation in cathodic protection, so that by the end they can approach real CP assessment and design problems with confidence.

  2. Episode 2

    01 · Introduction to Section 1: Fundamental Concepts

    Full courses here Introduces Section 1 by placing cathodic protection among corrosion-control strategies, explaining why corrosion matters, contrasting the sacrificial anode and impressed current approaches, and mapping the four sections ahead. What you'll learn Explain what cathodic protection is and why it's effective at the electrochemical level Place cathodic protection among the broad corrosion-control strategies and understand why it's used alongside coatings Distinguish between sacrificial anode and impressed current (ICCP) systems and their key components Describe how electrolytes carry current and why their conductivity and geometry matter Identify the four sections of the course and how each builds on the previous one Who this is for Engineers, technicians, and students beginning their study of cathodic protection who want a solid foundation. No prior CP background is assumed — this lecture opens the course and lays the groundwork.

  3. Episode 3

    02 · What is cathodic protection?

    Full courses here Explains what cathodic protection is at the electrode level — shifting a metal's potential negative to suppress dissolution — and contrasts the two ways of doing it: self-powered sacrificial anodes and externally powered impressed current systems. What you'll learn Explain how a metal corrodes via a corrosion cell and settles at its mixed potential, E-corr Describe cathodic polarization — shifting the potential negative — as the core operating principle of CP, with a defined protective window Describe sacrificial anode CP and the common anode metals (zinc, magnesium, aluminium alloys) and where each suits Describe impressed current CP (ICCP), its inert anodes, and the four key system components Compare the advantages and limitations of the two methods and recognise typical applications across pipelines, offshore, tanks, and reinforced concrete Who this is for Engineers, technicians, and students working with cathodic protection who want a clear conceptual foundation. No prior CP background is assumed — this lecture defines CP from first principles.

  4. Episode 4

    03 · Free Corrosion

    Full courses here Examines free corrosion — the natural, unprotected state of a metal in an electrolyte — covering the simultaneous anodic and cathodic reactions, the corrosion potential and current density they settle at, and the environmental and material factors that govern the rate of attack. What you'll learn Describe the simultaneous anodic (metal dissolution) and cathodic (oxygen reduction or hydrogen evolution) reactions at free corrosion Explain mixed potential theory — how the surface settles at the corrosion potential E-corr where anodic and cathodic rates balance Identify the corrosion current density i-corr as the measure of metal-loss rate and how it appears on an Evans diagram Explain how dissolved oxygen, electrolyte resistivity, and pH shift E-corr and i-corr Explain how material factors — electrode potential, passivation tendency, and microstructure — shape the anodic response, and why the free corrosion baseline is essential for CP design Who this is for Engineers, technicians, and students working with cathodic protection. This lecture builds on the earlier introduction to CP and corrosion, establishing the unprotected baseline that every CP assessment and design starts from.

  5. Episode 5

    04 · Effect of Applying a Current to a Corroding Surface

    Full courses here Traces what happens when external current is applied to a corroding surface — how the anodic and cathodic rates rebalance, how cathodic polarisation shifts the potential negative, and how this yields three practical states: underprotection, adequate protection, and overprotection. What you'll learn Explain how applying external current raises the cathodic rate and shifts the potential negative to a new balance (E-on), defining cathodic polarisation Use the Evans diagram and the net-current relationship to relate applied current, potential shift, and residual anodic current Explain why the amount of polarisation per unit current depends on reaction kinetics (Tafel slopes and exchange current densities) Distinguish underprotection, adequate protection, and overprotection — including the hazards of overprotection such as hydrogen evolution and coating disbondment Estimate residual corrosion and current demand using the Tafel relationship, and recognise the real-world complications of geometry, IR drop, time effects, and changing environments Who this is for Engineers, technicians, and students working with cathodic protection. This lecture builds directly on the previous lecture's free corrosion baseline, applying current to that starting state to show the electrochemical story behind CP.

  6. Episode 6

    05 · Transport of Electrical Charge in Electrolytes

    Full courses here Follows the cathodic protection current the rest of the way around the loop — through the electrolyte. Covers how charge moves ionically through soil, seawater and concrete pore water, how conductivity and resistivity shape current distribution, and why the resulting IR drop and potential gradients drive voltage demand and distort measurements. What you'll learn Distinguish electronic conduction in metal from ionic conduction in the electrolyte, where cations and anions carry the current between anode and structure Use conductivity (sigma) and resistivity (rho) to gauge how readily an electrolyte carries current, and compute bulk resistance as R = rho L over A Recognise the wide resistivity range across seawater, freshwater, soil and concrete, and how temperature shifts it, so you size a system for the worst case Explain spreading (anode-to-earth) resistance — R = rho over 2 pi r — and why most of the resistive drop concentrates near the anode, shaping groundbed design Account for the IR drop in the voltage budget and for the potential gradients that cause IR measurement error, interference and stray-current effects Who this is for Engineers, technicians and students working with cathodic protection who want to understand the electrolyte as an active circuit element rather than just the medium the structure sits in. Builds on earlier lectures that treated CP as electrochemistry at the metal surface.

  7. Episode 7

    06 · Cathodic Protection Systems

    Full courses here Turns the principle of cathodic protection into hardware, comparing the two main industrial system types — sacrificial (galvanic) anode systems and impressed current systems. Covers their shared four elements, components, strengths and limitations, and how to choose between them. What you'll learn Identify the four elements every CP system shares — protected structure (cathode), anode, electrolyte and metallic continuity — and how they form a circuit Explain how a sacrificial anode system uses the galvanic potential difference of zinc, magnesium or aluminium alloys to deliver self-regulating protection with no external power Explain how an impressed current system uses a transformer-rectifier and long-lived inert anodes (e.g. MMO-coated titanium) to force adjustable, high-capacity current Weigh the strengths and limitations of each type, including consumption, adjustability, high-resistivity capability and stray-current interference risk Apply selection factors — electrolyte resistivity, current demand, power availability, design life and maintenance access — to choose between the two systems Who this is for Engineers, technicians and students moving from CP electrochemistry to the engineering of real systems in soil, seawater and concrete. Builds on the earlier lectures that established how cathodic current shifts a metal's potential to suppress corrosion.

  8. Episode 8

    07 · Measuring Potentials

    Full courses here Explains where the single voltmeter number behind every CP decision actually comes from. Covers why a measured potential is always a difference against a reference electrode, the main reference electrode types and their conversions, how to set up a field measurement, and the error sources — above all IR drop — that contaminate readings. What you'll learn Understand that a CP potential is always a potential difference — structure potential minus reference potential — so both terms must be controlled Select and maintain the right reference electrode: copper/copper sulfate (CSE) for buried steel, silver/silver chloride offshore, with SCE and zinc as alternatives Convert measured potentials between reference scales via their known offsets versus SHE, and always record the reference type with every reading Set up a sound field measurement with a high-impedance voltmeter and the reference electrode placed close to the structure surface Recognise IR drop as the dominant error that makes ON potentials appear more negative than the true polarised potential, plus reference drift, poor connections and stray currents Who this is for Engineers, technicians and students who assess, commission or monitor CP systems and rely on field potential readings. Builds on earlier electrochemistry lectures, with the precise protection criteria and IR-correction techniques developed in later lectures.

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A plain-language audio walk through the fundamentals and design of cathodic protection — section by section, from CorroZone's Cathodic Protection course. From the core electrochemistry and CP concepts to current distribution, potential gradients and CP design principles. Free, no login. From CorroZone. Full courses here: https://corrozone.com/courses#udemy

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