Measure Corrosion by Electrochemical Impedance Spectroscopy

Name: Measure Corrosion by Electrochemical Impedance Spectroscopy
Rating: 4.7 (16 reviews)

A practical approach to using electrochemical impedance spectroscopy, or EIS, for corrosion measurement and analysis.

Created byCorroZone Ltd.

Last updated 12/2024

English

What you'll learn

Understand EIS and how it can be used to study corrosion.
Understand processes contributing to EIS response, including polarization resistance, double layer capacitance, and electrolyte resistance.
Understand resistive and capacitive contributions to the EIS response of corroding surfaces.
Learn how to combine impedances in series and parallel.
Learn to measure EIS spectra and understand how corrosion processes affect EIS response shape.
Understand the impact of surface conditions and measurement settings on EIS results.
Learn to select suitable signal amplitude, potential, and frequency, and understand measurement effects on accuracy and time.
Construct and interpret equivalent circuit models for EIS spectra.
Recognize responses of individual circuit components and identify key spectral features.
Learn to fit EIS data using circuit models and extract meaningful insights.

Course content

4 sections • 46 lectures • 3h 57m total length

Introduction to Section 12:09
Explore the basics of electrochemical impedance spectroscopy, including anodic and cathodic reactions, polarization resistance, corrosion current, and the roles of capacitance and electrolyte resistance in impedance measurements.
What is electrochemical impedance spectroscopy (EIS)?4:31
Discover how electrochemical impedance spectroscopy enables non-destructive study of corrosion by applying a sinusoidal potential and interpreting impedance spectra to reveal oxide layers, coating water uptake, and corrosion processes.
Understanding the corroding surface9:33
Examine how anodic and cathodic currents balance at the corrosion potential and how a three-electrode setup with a potentiostat probes current, potential, and polarization effects.
Resistive response of a simple corroding surface and Stern-Geary equation5:23
Measure the polarization resistance near the corrosion potential to estimate the corrosion current using the stern gear coefficient, with ba and bc from the tafel coefficients, enabling non-destructive corrosion-rate assessment.
Double layer capacitance3:21
Describe how a metal in electrolyte forms an electrical double layer that acts as a capacitor, with double layer capacitance contributing alongside polarization resistance to the impedance response.
Electrolyte resistance3:43
Examine how electrolyte resistance arises from ion movement and how electrode spacing and potentiostat compensation affect impedance measurements in ac electrochemical impedance spectroscopy.
Alternating current (AC) signals2:29
Learn how electrochemical impedance spectroscopy uses a potentiostat in corrosion studies, applying a sinusoidal potential of a given amplitude and frequency around the corrosion potential to measure impedance across frequencies.
Understanding the concept of impedance8:23
Define impedance as a complex quantity that generalizes resistance for alternating current, linking voltage and current through phasors with magnitude and phase, including a capacitor example.
Connecting impedances in series and in parallel7:13
Understand how series and parallel impedance combine in resistor-capacitor circuits, and compute total impedance, noting frequency effects on polarization resistance, double layer capacitance, and electrolyte resistance.
Section 1 Summary2:52
Explore how corrosion is an electrochemical process with anodic and cathodic reactions, polarization resistance translating to corrosion current and rate, plus capacitive and resistive surface responses and impedance concepts.
Section 1 Quiz

Introduction to Section 22:04
Explore how polarisation resistance, double layer capacitance, and solution resistance shape the impedance spectrum, and how frequency, surface coatings, defects, and active area influence measurements.
Measuring the EIS spectrum10:03
Apply a sinusoidal potential across a corroding surface and sweep frequency to measure current, constructing an impedance spectrum with modulus and phase and Nyquist representation, noting polarization and electrolyte resistance.
Interactive App: Simulate EIS signal0:36
Explore electrochemical impedance spectroscopy with an app that simulates and visualizes a circuit: solution resistance in series with polarization resistance in parallel with a double-layer capacitor, in frequency and time.
Effects of polarization resistance, double layer capacitance, and electrolyte6:06
Explore how polarization resistance, electrolyte resistance, and double layer capacitance shape the impedance spectrum and Nyquist plots, and how these factors influence phase peaks and corrosion behavior.
Interactive App: Simulate EIS spectrum0:26
Explore how a series solution resistance and a parallel double layer capacitance with polarization resistance shape an electrochemical impedance spectrum, adjustable with sliders and displayed on plots.
Interactive App: Simulate EIS spectrum (multi-curve)0:25
Explore an interactive app to simulate EIS spectra, overlaying new curves on prior ones to visualize how parameter changes affect multiple impedance spectra.
Impact of frequency range on resolvable parameters5:49
Explore how the measurement frequency range affects which corrosion parameters you can resolve, such as polarization resistance, electrolyte resistance, and capacitance, with guidance on low and high frequency trade-offs.
Impact of surface layers on EIS response14:13
Examine how a surface layer like oxide or paint modifies the EIS response, introducing a layer resistance, charge transfer resistance, and double layer capacitance.
Interactive App: Effect of parameters on EIS for surface with layer0:54
Explore a multi-branch impedance model of a surface with a layer, with electrolyte resistance in series with layer resistances and capacitances; adjust five sliders to view spectrum effects.
Effect of area and relative area on EIS spectra11:57
Understand how electrode area and the relative area of two surface regions govern the impedance in EIS, including area normalization and parallel combination of local impedances.
EIS response of a surface supporting a coating with defects8:09
Explore how electrochemical impedance spectroscopy captures a surface with coating and defects in parallel, revealing two time constants and defect detectability depending on gamma.
Interactive App: Effect of relative area of regions with different behaviour.0:46
Explore how adjusting the gamma slider to vary the area ratio between a protective-layer region and a bare metal region changes the overall impedance response of the electrode.
Interactive App: Effect of relative area of regions (multi curve)0:24
Visualize the impact of gamma changes by overlaying new spectra with previously calculated spectra on the same graph, enabling multi-curve comparison in electrochemical impedance spectroscopy.
Section 2 Summary1:22
Learn how an AIS spectrum is measured and how polarisation resistance, solution resistance, and capacitance shape it. See how measurement frequency, surface coatings, defects, and specimen area influence impedance interpretation.
Section 2 Quiz

Introduction to Section 31:56
Explore factors shaping the accuracy of electrochemical impedance spectroscopy, including choosing the corrosion potential, amplitude for linear response, and frequency range, plus how measurement time and noise affect data.
Measuring EIS at the corrosion potential4:13
Perform electrochemical impedance spectroscopy at the corrosion potential using a two-step measurement with a sinusoidal wave, ensuring zero volt versus corrosion potential settings and avoiding zero volt versus reference errors.
Influence of signal amplitude on the EIS measurement11:40
Use about five millivolts as the starting amplitude for EIS near the corrosion potential, ensuring a linear response and considering kinetics and Tafel coefficients.
Interactive App: Current response near corrosion potential0:23
Explore how the current responds near the corrosion potential using an interactive app, visualize behavior across potential ranges, and assess linearity of the response.
Impact of measurement frequency range on measurement time12:40
Explore how impedance spectroscopy uses a frequency sweep, choosing start and end frequencies, points per decade, and cycles to balance data quality with measurement time and noise.
Interactive App: Impact of parameters on measurement time0:26
Explore how impedance spectroscopy parameters like the minimum frequency and points per decade determine the total measurement time in this interactive app.
Charge passed during EIS measurements6:22
Evaluate how low-frequency impedance measurements can cause anodic oxidation and use Faraday's law to estimate the charge passed; adjust amplitude or frequency to minimize perturbation while preserving a good spectrum.
Interactive App: Thickness of oxidised material0:42
Explore an interactive app that models the current response of a corroding surface under a potential waveform, using Faraday's law and anodic charge to estimate oxidized material and assess risk.
Requirement of stationarity and noise-related issues9:18
Recognize non-stationarity in corroding surfaces causes current fluctuations during electrochemical impedance spectroscopy. Wait for quasi steady state when possible and verify with the Kramers-Kronig relation to assess noise across frequencies.
Section 3 Summary1:51
Explore factors affecting AIS measurement quality: corrosion-potential measurements at zero volts, appropriate amplitude for linear response to avoid surface damage, a frequency trade-off with time, and stationarity checks via kramers-kronig.
Section 3 Quiz

Introduction to Section 42:04
Learn to interpret electrochemical impedance spectroscopy data by fitting spectra with equivalent circuits including resistors, capacitors, constant phase elements, inductors, and Warburg elements.
How fitting works12:56
Learn how to fit an impedance spectrum to an equivalent circuit to extract surface process parameters using error functions, addressing simple to complex circuits and avoiding local minima.
Interactive App: Fitting process and error surface0:35
Explore how fitting works by manually fitting the impedance spectrum of a parallel resistor and capacitor, visualizing the impedance response and the error surface in 3d.
Characteristic responses of individual equivalent circuit components8:45
Explore the key equivalent circuit elements used in corrosion impedance spectroscopy, including resistors, capacitors, constant phase elements, inductors, and Warburgs, and how they shape impedance spectra.
Interactive App: Individual components impedance0:28
Explore how individual components affect impedance in electrochemical impedance spectroscopy by inputting parameters for resistors, capacitors, constant phase elements, inductors, and Warburg elements, with overlapping Bode and Nyquist plots.
Key features in EIS spectra13:44
Identify how resistor, capacitor, constant phase element, inductor, and Warburg short shape EIS spectra. Learn to interpret Nyquist and Bode plots to model corrosion with diffusion and inductive effects.
Interactive App: Response of circuit containing a CPE0:27
Interact with a circuit of two resistors and a constant phase element to study impedance. Adjust the CPE exponent, visualize the impedance response, and learn how it alters overall impedance.
Interactive App: Response of circuit containing CPE and Warburg short.0:21
Explore how a circuit with a cpp and a Warburg short element responds in impedance spectra, visualizing how Warburg sigma and L parameters and other circuit parameters shift the impedance.
Constructing an equivalent circuit model16:28
Design an equivalent circuit to fit impedance data from aluminum alloy 2024 D3 in 3.5% sodium chloride. Represent oxide, diffusion by Warburg, and a cpp double-layer with two resistances.
Practical example of fitting EIS data16:36
Showcases a software-based practical example of fitting EIS data for a corroding aluminium alloy, emphasizing initial parameter estimation and stepwise refinement to obtain realistic fits.
Interactive App: Fitting Example0:43
Upload AIS electrochemical impedance data in CSV, practice finding good initial values by adjusting the equivalent circuit with sliders, then run the fit to estimate parameters.
Section 4 Summary1:57
Fit electrochemical impedance data with equivalent circuits (resistors, capacitors, constant phase elements, inductors, and Warburg elements), interpreting depressed semicircles and Warburg tails for physically meaningful fits on corroding surfaces.
Section 4 Quiz

Requirements

Basic understanding of corrosion processes (anodic and cathodic reactions, corrosion current)
Basic understanding of corrosion electrochemistry
Basic understanding of electrical concepts such as voltage, current and resistance

Description

Note: This course is also available on this platform in Spanish language ( Espectroscopía de impedancia electroquímica para corrosión ) and Italian language ( Spettroscopia di Impedenza Elettrochimica per la Corrosione )

In this course, we will take a practical approach to understanding and using electrochemical impedance spectroscopy (EIS) for corrosion measurement and analysis. We will begin by covering the basics of EIS, discussing essential concepts like impedance, alternating current signals, and corrosion surface phenomena, all aimed at making EIS accessible and straightforward for everyone, and we will finish with a practical example of fitting a complex EIS spectrum.

In Section 1, we will learn about the fundamentals of corrosion and impedance in electrochemical systems, building the foundation for understanding how and why EIS is applied to corrosion studies. In Section 2 we will look at how the processes occurring on the surface impact on the EIS responses, considering key factors like polarization resistance, double layer capacitance, and the impact of surface coatings on the EIS response.

In Section 3, we will focus on practical considerations for measuring EIS spectra. We will discuss critical topics such as the selection of signal amplitude, the measurement frequency range, and the importance of stationarity to obtain reliable results. Finally, in Section 4, we will learn how to interpret EIS spectra using equivalent circuit models, exploring characteristic responses and fitting techniques to extract valuable information from the data.

By the end of the course, we will have the knowledge and skills needed to confidently measure, model, and interpret EIS data for effective corrosion analysis.

Who this course is for:

Professionals working on corrosion and corrosion testing seeking practical skills to efficiently use EIS for corrosion testing and analysis.
Researchers working on corrosion-related matters looking to gain a deeper understanding of EIS to enhance their corrosion studies and data interpretation skills.
Students approaching the issue of corrosion testing via EIS aiming to build a foundational understanding of EIS to confidently measure, analyze, and interpret corrosion data.

Measure Corrosion by Electrochemical Impedance Spectroscopy

What you'll learn

Explore related topics

Course content

Basics of Corrosion and Impedance in Electrochemical Systems10 lectures • 50min

Surface processes and EIS responses14 lectures • 1hr 3min

Practical considerations for the measurement of EIS spectra10 lectures • 50min

Interpreting EIS spectra using equivalent circuit models and fitting12 lectures • 1hr 15min

Requirements

Description

Who this course is for: