CorroZone: Fundamentals of Cathodic Protection

Full courses here A whole-course recap of how the four sections fit together — from the electrochemistry of corrosion and cathodic protection, through measuring and judging whether protection is working, to how protection spreads across a real structure, and finally to designing a system that delivers it. Course wrap-up A whole-course recap of the four sections that build on each other: Section 1...

Full courses here A consolidating final lecture that pulls the twenty-seven preceding lectures into one framework — recapping the four sections, drawing out five cross-cutting principles, offering a six-step way to approach a real CP problem, and signposting the advanced topics and standards that come next. What you'll learn How the four course sections fit together — fundamental concepts, core CP...

Full courses here How to design a cathodic protection system as the inverse of assessment: a seven-step workflow that turns a protection requirement into a verified specification — current demand from the breakdown factor, choosing sacrificial versus ICCP, sizing anodes by Faraday's law, the Dwight-formula groundbed resistance and rectifier voltage budget, current distribution, and commissioning w...

Full courses here How the current drain test directly measures, on the real structure in its real environment, the current a cathodic protection system needs to reach the protection criterion — the equipment, the stepwise procedure, reading the polarisation curve, the ON-versus-instant-OFF distinction, and the uncertainties that justify a safety margin. What you'll learn What a current drain test...

Full courses here How organic coatings reduce cathodic protection current demand by shrinking the bare-metal area exposed to the electrolyte, why the coating breakdown factor f-c rises with age so CP must be designed for end-of-life, and how holidays concentrate current and drive disbondment, hydrogen evolution and shielding. What you'll learn Why organic coatings cut CP current demand so dramatic...

Full courses here The one number that can make or break an impressed-current design — the anode (groundbed) resistance. How current spreading sets it, the Dwight and Sunde formulas that quantify it, the factors that control it, and how it dictates the rectifier voltage and caps the current you can deliver. What you'll learn Explain anode (groundbed) resistance as a spreading resistance set by elec...

Full courses here Once you've chosen the anode metal, how much of it do you actually need? Building from Faraday's law to the working design equation — mass = I_p × T / (C_e × u_f) — with design life, electrochemical capacity, utilisation factor, coating breakdown, and three worked examples. What you'll learn Derive the anode-mass design equation, mass = Ip × T / (Ce × u_f), from Faraday's law lin...

Full courses here What an anode should be made of, and why it matters. A walk through the sacrificial alloys (zinc, magnesium, aluminium) and impressed-current materials (MMO, high-silicon cast iron, graphite, platinised titanium/niobium), the four electrochemical properties that compare them, and how to match a material to environment and system type. What you'll learn Describe how a sacrificial...

Full courses here The turning point of the course: where assessment ends and design begins. This Section 4 introduction reframes the same CP science from reading measurements backward to a diagnosis toward reasoning forward from a requirement to a system specification. What you'll learn Distinguish CP assessment (start from measurements, work backward to a diagnosis) from CP design (start from a r...

Full courses here Why a structure's potential keeps rising after you switch cathodic protection current off — and how to read that decay curve as a diagnostic of coating condition, interference, and how well protected you really are. What you'll learn Explain potential decay as the sequential relaxation of stored polarisation — double-layer discharge (ms to seconds), concentration-gradient relaxat...

Full courses here Stray current corrosion: damage driven by external DC currents that leave their intended circuit and flow through buried metal. Covers the entry (cathodic) and exit (anodic) zones, Faraday's-law metal loss, the worsening effect of coating holidays, the main sources, how to detect it, and how to mitigate it. What you'll learn Explain the mechanism: stray current follows the path o...

Full courses here Why engineers often place CP anodes far from the structure: remote placement is a geometric strategy for uniform current distribution that also helps current get around shielding. Covers the distance trade-off against circuit voltage, groundbed design and types, distributed anode systems, and how to verify performance. What you'll learn Explain why a close anode causes non-unifor...

Full courses here How cathodic-protection current leaves a potential-gradient footprint in the electrolyte, why that gradient is the physical origin of IR drop, and how it drives non-uniform protection. Covers E = rho*J, the gradient around hemispherical and cylindrical anodes, what a reference electrode actually samples, and the three controlling variables. What you'll learn Derive the potential...

Full courses here A short bridge into Section 3, which extends CP assessment from a single measurement point to the whole structure. It explains why current distribution is the master idea and previews the four lectures ahead: potential gradients, remotely placed anodes, stray current corrosion, and potential decay. What you'll learn Recall what Section 2 equipped you with: reading potentials corr...

Full courses here How the OFF potential measurement removes the IR-drop error from cathodic-protection readings. Covers why ON potentials overstate protection, what the instant-off represents electrochemically, how to capture it in the field, and how to use ON-versus-OFF data to assess protection. What you'll learn Explain why the ON potential overstates protection: it equals the true polarised po...

Full courses here A CP potential is more than a single meter reading — the revealing part is how it behaves the moment you switch the current on or off. This episode explains the potential transient: the capacitive double layer, the three switch-off regimes (IR elimination, double-layer discharge, chemical relaxation), why instant-off must be caught within milliseconds, and how transient shape dia...

Full courses here Going more negative isn't always safer. This episode covers overprotection — driving the structure potential below the safe protection window — its causes, the three principal damage mechanisms (coating disbondment, excessive hydrogen evolution, and hydrogen embrittlement), how to recognise it in the field with IR-drop-free measurements, and how to prevent it through potential co...

Full courses here Applying current isn't the goal — reaching a measurable, verified condition is. This episode lays out the three dominant CP protection criteria (the -850 mV vs CSE potential, the 100 mV polarisation shift, and the 100 mV depolarisation test for reinforced concrete), why IR drop must be removed via instant-off measurements, and how criteria are applied at commissioning and in rout...

Full courses here Where does a 'safe' cathodic protection potential actually come from? This episode works through the thermodynamics — Gibbs free energy, the Nernst equation and the Pourbaix diagram's immunity, passivation and active-corrosion regions — to show why CP works, where the minus 850 mV criterion comes from, and where the thermodynamic view falls short. What you'll learn Distinguish th...

Full courses here Cathodic protection isn't only an electrical intervention — it actively changes the chemistry at the protected surface. This episode unpacks the cathodic reactions (oxygen reduction and hydrogen evolution), the local pH rise and calcareous deposits they cause, and the resulting risks of cathodic disbondment and hydrogen damage. What you'll learn Identify the two dominant cathodic...

Full courses here Examines ohmic effects — IR drop — that sit underneath almost every CP potential measurement. Shows why the ON potential isn't the true polarised state, how the soil voltage gradient biases readings more negative, the four factors that control IR drop magnitude, and the practical rules and instant-off technique for honest assessment. What you'll learn Define IR drop as Ohm's law...

Full courses here Sets the scene for Section 2, the bridge between Section 1's electrochemical theory and CP engineering practice. Maps the six interrelated concepts that define real-world CP assessment: ohmic effects/IR drop, near-surface reactions, Pourbaix thermodynamics, protection criteria, overprotection, and potential transients with OFF-potential measurement. What you'll learn See how Sect...

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 pote...

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),...

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 elect...