PolRes Talk for NACE 2009

Leaders in Corrosion Control Technology

Theory and Applications of the Measurement of Corrosion Rate with Polarization Resistance

Dr. Pete PetersonGamry Instruments

www.gamry.com


Agenda

1. Introduction

2. Some Electrochemical Fundamentals

3. Some Electrochemical Corrosion Theory

4. The Polarization Resistance Experiment

5. What Can Go Wrong in Polarization Resistance?

6. Some Examples of Polarization Resistance Applications


Assumptions• You have a serious interest in corrosion measurement.• You would like to know more about electrochemical corrosion

measurement.• You are skeptical.

Goal• Explain electrochemical corrosion measurement in simple

terms and demystify the jargon that electrochemists have carefully developed over the years to create the impression that these techniques are very, very difficult.


Two Different Views of Electrochemical Corrosion Measurements

• Electrochemical corrosion measurements are easy because most of the techniques are standardized and are centered about Eoc.

• Electrochemical corrosion measurements are difficult because the Working Electrode is actively reacting!


Why Are Electrochemical Techniques Used for Corrosion Measurement?

• Corrosion is an electrochemical (redox*) process involving electron transfer.Fe Fe2+ + 2e–

*redox = reduction-oxidation

• A broad range of electrochemical techniques have been developed specifically for corrosion measurement.

• Electrochemical techniques are fast.

• Electrochemical techniques are sensitive.

• Can be used in the lab or in the field.

• In 2008, electrochemical techniques are well-accepted by the corrosion community. Well…most of the corrosion community!


Electrochemical Techniques are Fast!

• Corrosion is an inherently slow process. A typical corrosion rate is 10 milli-inches per year (mpy) or 0.254 millimeters per year (mmpy) or 254 microns per year.

• The “best” corrosion tests are weight loss measurements after exposure. However, they are very slow (weeks, months, or years).

• Why are they fast? Because electrochemical instruments polarize the sample to accelerate the corrosion process and make the measurement in minutes or hours.


Electrochemical Techniques Are Sensitive!

• Electrochemical techniques can measure very low corrosion rates.

• A sample with a low corrosion rate will exhibit a low current during the electrochemical experiment. Corrosion scientists often use “rate” and “current” interchangeably.

• Electrochemical instruments can be designed to measure low currents very accurately. A 1 cm2 iron sample with a corrosion rate of 1 mpy (milli-inch per year) will exhibit a current in the range of 2-5 μA, which can be measured very accurately by a modern potentiostat.

• 4 milli-inches corresponds roughly to the diameter of a human hair.


Electrochemistry and the Corrosion Scientist• Corrosion measurement is THE best example of applied

electrochemistry.• Corrosion scientists have developed a number of

electrochemical techniques for corrosion studies.• DC Techniques such as Polarization Resistance, Tafel Plots, and

Cyclic Polarization are used strictly for corrosion measurement.• Electrochemical Impedance Spectroscopy (AC Impedance) is a

powerful and popular tool for corrosion scientists.• Electrochemical Noise is used exclusively for corrosion studies.• There are a number of societies and publications to serve the

corrosion community, e.g., NACE International, The Electrochemical Society, International Society of Electrochemistry, the International Corrosion Congress, LatinCorr, and the European Federation of Corrosion (EUROCORR).

• Short Courses in Electrochemical Corrosion Measurement are taught each summer at Pennsylvania State University and North Dakota State University.


Before we continue, a brief word about the fundamentals of electrochemistry.


A Review of Electrochemistry!

Electrochemistry – The study of chemical reactions accompanied by the exchange of electrons. Electron-transfer is always a factor in electrochemistry. Chemistry is sometimes a factor in electrochemistry.

O = Oxidized Species Red = Reduced Species

Oxidation: Loss of electrons Fe Fe2+ + 2 e-

Reduction: Gain of electrons 2H+ + 2e- H2

Ox + ne- RedThe Oxidized species accepts an electron to form the Reduced species.

Remember that LEO says GER!


Redox Reactions (Half-Reactions) in Corrosion

Oxidation: The Metal Being TestedFe Fe2+ + 2e–

Reduction: Usually Some Solution SpeciesHydrogen ion: 2H+ + 2e– H2Water: 2H2O + 2e– H2 + 2OH–

Oxygen: O2 + 2H2O + 2e– 4OH– (neutral/alkaline)O2 + 4H+ + 4e– H2 + 2OH– (acid)

• Oxidation is always accompanied by Reduction in both the Real World and the electrochemical experiment.


What is Potential?Potential or Voltage (E, sometimes V):

– Unit: Volt– The Potential is the driving force for the redox reaction. – The potential is related to the thermodynamics of the

system:ΔG = -n F ΔE (negative ΔG is spontaneous)

– Potential is always measured versus a Reference Electrode.– A positive voltage is oxidative and a negative voltage is

reductive.– 0 Volts is not nothing! Redox reactions happen at 0 volts

that do not happen at +1 volt.

Remember: There is no correlation between the thermodynamics of the chemical system and the kinetics (rate) of the reaction.


What is Current?Current (i):

– Unit: Ampere– Electron flow is the result of a redox reaction.– Current measures the rate of the reaction (electrons

per second).– Zero current is nothing, i.e., if the current is zero, no

redox reactions are occurring (that’s not quite true in corrosion!).

– Anodic (oxidation) and cathodic (reduction) currents have different polarity (signs).

– Current may be expressed as current or current density.

– Don’t worry about which way the current flows.


A Simple Description of Potential and Current as a Flowing Water Circuit


Range of Potential and Current that is Encountered in Corrosion

Experiments• 95% of electrochemical corrosion experiments take

place within ± 2 volts vs. SCE.

• Current can vary from hundreds of milliamps to femtoamps (10-15 amps). That’s 12-13 orders of magnitude! Modern potentiostats are capable of auto-ranging the current over 7-11 decades of current, which makes your life relatively easy.


Electrochemical TechniquesElectrochemistry is simple in principal…there are only three variables:

potential (E), current (i), and time.

“Active Experiments”: Apply an excitation, measure a response. Make something happen!

• Potentiostatic: Control E, Measure i, Plot E vs. i or i vs. t• Galvanostatic: Control i, Measure E, Plot i vs. E or E vs. t

“Passive Experiments”: Observe the experiment electrochemically.• Potentiometric: Measure E at i=0 (for example, a pH Meter) • Zero Resistance Ammeter (ZRA): Measure i between two connected

electrodes. Examples: galvanic corrosion and electrochemical noise.

• Active experiments give faster results, but risk changing the sample.

• Polarization Resistance is an active experiment.


Controlled Potential (Potentiostatic) Experiments are Most Commonly Used in the

Corrosion Lab• In most electrochemical corrosion experiments, the potential is

controlled. Because of the relationship between the potential and the thermodynamics of the system, controlled potential experiments are more informative than controlled current experiments.

• The (three-electrode) Potentiostat is the electronic instrument that controls the potential between the Working Electrode (your sample!) and the Reference Electrode while it measures the current between the Working Electrode and the Counter Electrode.

• Why three electrodes? A three-electrode Potentiostat allows potential control and current measurement at the Working Electrode with no “interference” from other electrochemical events in the cell.

• To perform an electrochemical measurement, we change the potential in some systematic way and measure the current response. The applied potential will allow a redox reaction to occur and the current will be indicative of the rate (kinetics) of the reaction.


An Electrochemical Corrosion Measurement System

• A Corrosion Measurement System consists of a potentiostat, software, a computer, and a cell.

• Analog (non-computerized) systems are not

recommended for corrosion experiments.

• The corroding sample is placed in a Electrochemical Cell and connected to the Potentiostat.

• Prices range from $5000 to $40,000.


The Potentiostat

• The Potentiostat is the electronic instrument that controls potential or current, and measures current or potential, respectively.

• A Potentiostat is complicated! Build it yourself at your peril!

• The performance (accuracy, precision, stability, and bandwidth) of a potentiostat are affected by the electrical characteristics of the Working Electrode, which are unknown to the manufacturer.


• Working Electrode: Corrosion sample being studied.

• Reference Electrode: Saturated Calomel (SCE) or Silver-Silver Chloride (Ag/AgCl). Others are available (Cu/CuSO4).

• Counter Electrode: Should be conductive and inert (Graphite or Platinum).

• Note: Notice that we do NOT use the terms “anode” or “cathode”. Why?

• Solution may be stirred and deaerated to remove O2.

• Temperature control is encouraged! Rates of chemical reactions are very temperature dependent!

The 3-Electrode Electrochemical Cell


Three Electrode CellWorking Electrode: The corrosion sampleReference Electrode: Saturated Calomel or Silver-Silver ChlorideCounter Electrode: Graphite or PlatinumThe Potentiostat controls the potential between the Working-Reference and measures the current between the Working-Counter electrodes.The area of the sample being tested should be known. The cell may include stirrers and/or temperature control. The Working Electrode may rotate!There are many types of electrochemical cells.

An Example of an Electrochemical Cell


Controlling the Temperature during a Corrosion Rate Measurement is Important!

• Rule of Thumb: Increasing the temperature 10° C doubles the rate of a chemical reaction.

• Mild Steel in 1 M HCl + 2x10-2 M BTA1

– Rp@ 40° C = 250 Ω-cm2

– Rp@ 50° C = 110 Ω-cm2

– Rp@ 60° C = 49.6 Ω-cm2

1 BTA = Benzotriazole

A. Popova, “Temperature Effect on Mild Steel Corrosion in Acid Media in Presence of Azoles”, Corrosion Science, 49, 2144 (2007).


Controlling the Temperature in the Cell• Reference Electrode• Working Electrode• Counter Electrode

• Water Jacket for temperature Control with a Water Bath


I. The Open Circuit Potential• The Open Circuit Potential, EOC, is the potential difference

between the metal Working Electrode and the Reference Electrode when immersed in the electrolyte.

• EOC is a mixed potential whose value is determined by the potentials of the two or more half-reactions of the electrochemical system, not by the potentiostat!

• EOC is where corrosion occurs in service. It’s very, very, very important!

• EOC is the starting point for virtually all electrochemical corrosion experiments. A stable EOC is taken to indicate that the corroding system has reach a “steady state” and the experiment may begin. This may require minutes to days.

.


II. The Open Circuit Potential

• No measurable current is flowing at Eoc.

• An applied voltage that is positive of EOC will accelerate an oxidation (corrosion) reaction. An applied voltage that is negative of EOC will accelerate a reduction reaction. This makes life somewhat easy.

• The terms “EOC” and “Ecorr” (corrosion potential) are often used interchangeably.

• The value of the EOC is not particularly useful as a predictive tool.


Controlled Potential (Potentiostatic) Experiments

• The Potentiostat controls the potential between the Working Electrode and the Reference Electrode while it measures the current between the Working Electrode and the Counter Electrode.

• To run an experiment, change the potential in some systematic way and measure the current response. The applied potential will allow a redox reaction to occur.


Applying the Voltage in a Controlled Potential Experiment

Computerized potentiostats generate a potential waveform that is described by the “Scan Rate”:

Scan Rate (mV/sec) = Step Height/Step TimeThe Scan Rate is an important experimental parameter in the

electrochemical corrosion experiment and it’s always slow, e.g., 0.166 mV/sec!

Time

Pote

ntia

l, V

Step Height, mV

Step Time, sec


We now return you to your normally scheduled presentation.


Electrochemical Corrosion Applications

• Quantitative Corrosion Rate Measurements (for uniform corrosion only)

• Qualitative Indication of Passivation Tendencies

• Qualitative Pitting and Crevice Corrosion Studies

• Galvanic Corrosion

• Intergranular Corrosion (Sensitization)

• Stress Corrosion Cracking (the sample is under load during the test)

• Evaluation of Organic Coatings with EIS


Quantitative Corrosion Rate Measurements• Polarization Resistance and Tafel Plots are experiments designed

to measure the rate of uniform corrosion in units of penetration (mmpy or mpy).

• Designed to measure the corrosion current, ICORR, from which we can calculate the corrosion rate.

• Unlike weight loss, electrochemical techniques provide a “snapshot” of the corrosion rate.

• Should be performed when the system has reached “steady state”, indicated by a stable EOC.

• Note: “Linear Polarization Resistance (LPR)” is not a correct term, but we use it anyway. The correct term is “Polarization Resistance”. (See CORROSION, November 2005.)


Corrosion Current, Icorr

• At EOC, imeas = 0, but we know that corrosion is occurring.Fe Fe2+ + 2 e-

2H+ + 2e- H2

Fe + 2H+ Fe2+ + H2

• We need to somehow measure the current due to the anodic or cathodic half-reaction. This current is called the Corrosion Current, ICORR.

• The goal of the Polarization Resistance experiment is to determine the Corrosion Current.

• From the Corrosion Current, we can calculate corrosion rate.

• Don’t forget the electrode area! iCORR is usually current (A) and ICORR is usually current density (A/cm2).


Precision of Electrochemical Corrosion Rate Measurements

• Corrosion is a messy business!-Dr. Jerry FrankelThe Ohio State University

• Corrosion is a surface process involving a large number of variables that are difficult to understand and/or control.

• A Relative Standard Deviation of 15% is Excellent!

• A minimum of 3 replicates is recommended for corrosion measurements. (“Increase Your Confidence in Corrosion Test Data”, Steve Tait, MATERIALS PERFORMANCE, March 2001)

Error as a Function of Sample Size


Comments on the Precision of Electrochemical Corrosion Measurements

• Electrochemical instrumentation is very accurate (<0.5% error)

• High purity Fe polished to a mirror finish gives great results!

• When corrosion occurs, anodic and cathodic reactions are occurring simultaneously on the surface of the sample

• The surface of a metal sample is not homogeneous. In fact, it may be very heterogeneous.

• The anodic and cathodic sites may “turn on” or “turn off” and move around as the local environment changes

• Electrolyte impurities can also affect the results

• The corrosion environment is very dynamic and the result is…poor precision


Corrosion is a messy business, but…it always involves electrochemistry

Sometimes electrochemical techniques work great…and sometimes they work…not so great.

Electrochemical corrosion measurement techniques always provide some information on the corrosion process.

To avoid misinterpretation, it’s important to be able to recognize non-ideal behavior.

Important: Use as many electrochemical (or other) tools (LPR, Tafel Plots, EIS, etc.) as possible to characterize a corrosion process.


Electrochemical Corrosion Measurements are based on good solid science developed over many

years.

So we’ll touch very briefly on the theoretical aspects of electrochemical corrosion

measurement.


Mixed Potential TheoryThe principal of charge conservation requires that there must be a

least one reduction and oneoxidation in an electrochemical reaction.

• 2H+ + 2e- H2

• Zn Zn2+ + 2e-

• The anodic current equals the cathodic current at icorr.

• Both reactions must occur on the same surface, so their potentials must change to a common value, which is Ecorr (same as EOC).

• This is an example of a “mixed potential system” and Ecorr is called a “mixed potential”.

“Principles and Prevention of Corrosion”, Jones

Note: The X axis may sometimes be labeled “APPLIED CURRENT DENSITY”. Don’t let this confuse you!


Butler-Volmer EquationThe Butler-Volmer Equation is a general electrochemical

equation that describes the relationship between the potential and the current (kinetics) in a mixed potential system.

I = Ia + Ic = ICORR(e(2.3(E-Eoc)/a) – e(-2.3(E-Eoc)/c))

Where: I = cell current (A)ICORR = corrosion current (A) E = applied potential (V)Eoc = corrosion potential (V)a = anodic Tafel constant (V/decade)c = cathodic Tafel constant (V/decade)

Rate of anodic reaction

Rate of cathodic reaction


Graphical Representation of the Butler-Volmer Relationship between Potential and Current in a Mixed Potential System

J. Scully & R. Kelly, ASM Handbook, Volume 13A,

2003

M + 2H+ M2+ + H2

An experiment like this is called a “Tafel Plot” and is relatively common in today’s corrosion laboratory.

Experimental data from the corrosion measurement system.


Butler-Volmer EquationThe Butler-Volmer Equation only holds if:

• The rate is charge-transfer controlled (aka, activation-controlled, electron-transfer controlled). Complicating factors are:– Passivity– Diffusion-controlled (concentration polarization)– Adsorption

• Only one reduction and one oxidation reaction are occurring (first order)– Alloys can be complicated

• If the Butler-Volmer equation doesn’t hold, then the electrochemical response will not be “classic” and must be interpreted in terms of the chemistry of the system.


Stern-Geary Equation and Polarization Resistance

• The purpose of the Polarization Resistance experiment is to determine the Polarization Resistance (Rp).

• The Stern-Geary Equation describes the relationship between the Polarization Resistance (Rp) and the Corrosion Current (iCORR).

• RP = E/i = ßaßc/2.3 iCORR (ßa + ßc)

• The Stern-Geary Equation is derived from the Butler-Volmer Equation via a series expansion in which ΔE /βa,c is assumed to be less than 0.1.

• Therefore, in Polarization Resistance the applied potential should be within ±5-10 mV of Eoc.

• The plot of potential vs. current is approximately linear in this region.


That concludes the theoretical portion of this presentation…


The Polarization Resistance Experiment


Experimental Procedure for Polarization Resistance

1. Measure EOC and allow to stabilize.

2. Apply initial E that is 10 mV negative of EOC.

3. Scan at a slow scan rate (~0.125 mV/s) to a final E that is 10 mV positive of EOC.

4. Measure current, plot E (Y-axis) versus I (X-axis)

5. Measure slope, which has units of resistance (E/i = R).

6. Convert Rp to icorr

7. Convert icorr to Corrosion Rate.




Setting Up of a Polarization Resistance Experiment with Computer-Controlled

Instrumentation


Calculation of ICORR from RP

Stern-Geary Equation

RP = E/i = ßaßc/2.3 iCORR (ßa + ßc)WhereRP = Slope at the origin of the Polarization Resistance Plot

in ohms or ohms-cm2

iCORR = Corrosion Current, Amperes

ßa, ßc = Tafel Constants from a Tafel Curve, volts/decade of current.

Note: The area of the electrode must be taken into account somewhere!


I. Calculation of Corrosion Rate from ICORR

Faraday’s Law

Q = nFm/A = it

Q = coulombs (A-s/eq), n = number of electrons, F = the Faraday (96,487 coulombs), m = mass (g), A = atomic weight, i = current (A), t = time (s).

Since Equivalent Weight (EW) = A/n,m = it(EW)/F

Corrosion Rate (g/s) = m/t = i(EW)/F


II. Calculation of Corrosion Rate from ICORR

From the engineering standpoint, it is convenient to express Corrosion Rate in units of penetration, mpy (milli-inches per year), mmpy (mm per year), or microns per year.

Divide both sides of the equation Corrosion Rate (g/s) = m/t = i(EW)/F

by electrode area and density,Corrosion Rate (cm/s) = i(EW)/FdA

i/A = current density (I). After conversion of cm to inches or mm, and seconds to years,

Corrosion Rate (mpy) = 0.13 Icorr (EW)/dCorrosion Rate (mmpy) = 0.00327 Icorr(EW)/d



First, the Good News…Polarization Resistance Works Very Nicely for the Measurement of

Corrosion Rates• Very fast (< 5 minutes). Scanning 20 mV at 0.1 mV/sec requires 200

seconds.

• In general, plots exhibit good linearity, so data interpretation is easy.

• Potential remains close to EOC, so it is essentially a non-destructive technique and can be used for continuous monitoring for inhibitor evaluation.

• Described in ASTM G 59.


And Now, the Bad News…What Can Go Wrong with Polarization Resistance?

• You need to know the Tafel Constant(s).

• EOC may be unstable.

• Use of a Scan Rate that is too fast (Step Height too high or Sampling Period too short).

• Complications from alloys containing several electroactive metals (reduction or oxidation of more than one electroactive species).

• Uncompensated solution resistance.


The Trouble with Tafel ConstantsFor best results in Polarization Resistance, the Tafel Constants are needed

in the Stern-Geary equation.

• It can be very difficult to experimentally determine the Tafel Constants with a reasonable level of confidence.

a is not expected to equal c.

a varies from 0.06 to 0.12 V/decade. c varies from 0.06 to infinity (diffusion control). (Jones)

• Because of the form of the Stern-Geary equation, ICORR is not hyper-sensitive to the Tafel values. Using 0.1 V/decade as a and c results in a maximum error of a factor of 2. (Jones)

• For “corrosion monitoring”, Tafel Constants are not required. Simply observe changes in Rp.


To Determine the Tafel Constants, Run a Tafel Plot

1. Measure EOC and allow to stabilize.

2. Apply initial E that is 250 mV negative of EOC.

3. Scan at a slow scan rate (0.125 mV/s) to a final E that is 250 mV positive of EOC.

4. Measure current, plot E (Y-axis) versus log I (X-axis).


Tafel Curve Analysis



Examine the Tafel Region


Measurement of Tafel Constants

• Insufficient linear region is a major problem.

• The cathodic Tafel Plot is likely to be reasonably linear.

• The anodic Tafel Plot is not likely to be reasonably linear.

• Remember, if all else fails, use 0.1 for the Tafel Constants and your results will be pretty good!

• If you’re just looking for a change in the corrosion rate, Tafel Constants are not required. Simply observe changes in Rp.

• Note: A Tafel Plot can be used to measure Icorr and corrosion rate, but nonlinearity is also a problem for this application!


If EOC is Unstable, Using Galvanostatic Control Can Help

• A stable EOC indicates that the system has reached “steady state”.

• Despite my drifting EOC, I still need a Corrosion Rate! An LPR measurement with a drifting EOC will cause a current to flow that violates the Stern-Geary relationship.

• In “non-stationary” systems, i.e., systems in which the EOC drifts, galvanostatic control (control and scan the current while measuring the potential) can give more reliable results.

• Some work is usually required to determine the appropriate value of the applied current. Do NOT allow the potential to exceed ±10 mV!

F. Huet et al, “Polarization Resistance Measurements: Potentiostatically or Galvanostatically?”, CORROSION, 65, 136(2009).


Equivalent Weight of an Alloy

• The Equivalent Weight of an alloy is the reciprocal of the total number of equivalents of all alloying elements (Jones)

• EWalloy = 1/ Neq

• Neq = Σ fi/(ai/ni) = Σ (fin/a)f = mass fraction of element i, a = atomic weight, n = # of electrons

• Example: 304 SS is 19% Cr, 9.25% Ni, and 71.75% Fe. Equivalent weight = 25.12

• Question: do all elements in the alloy corrode at the same rate?


Scan Rates in Polarization Resistance

• If the Scan Rate is too high, errors can result due to the capacitance of the Working Electrode. The corrosion rate is usually overestimated.

• The solution? Scan rates are always slow, e.g., 0.125 mV/sec.

• EIS can be used to measure the appropriate scan rate for any system

Scan Rate = E f

• At these scan rates, an experiment may take a long time. But that’s why you have a computer-controlled instrument.


As With Any Experiment, There Can Be Measurement Problems

• If there’s a measurement problem, it’s either:

– The instrument

– The cell/electrodes

– The chemistry

– The local electronic environment




A Few Examples of Real-World Applications of Polarization Resistance




Evaluation of Corrosion Inhibitors• This is probably the single most popular application of electrochemical

corrosion measurements.

• Make Polarization Resistance measurements as a function of time. Dose the inhibitor and observe the change in corrosion rate.

• This measurement can be automated at a very reasonable cost.



Corrosion of Rebar in Concrete

• Corrosion of reinforcing rods in concrete continue to be a concern in coastal areas and in colder climates where road salts are used.

• LPR and EIS are used to monitor corrosion rate.

• Concrete is a reasonably good electrolyte!

• Photos courtesy of Dr. Andres Torres-Acosta, Instituto Mexicano del Transporte



• Experiments are run:– With electrolyte “ponded”

on the top of the concrete sample, and

– In a controlled humidity chamber with no “ponded” electrolyte



• Identical rebar used for working and counter electrode.

• Titanium rod used for reference electrode.

• Be careful! Rebar in concrete has a very high capacitance (200 microF/cm2).





References for Electrochemical Corrosion Testing

• Principles and Prevention of Corrosion, Denny A. Jones, Prentice-Hall, Upper Saddle River, NJ 07458 (1996). ISBN 0-13-359993-0.An excellent textbook covering all types of corrosion and corrosion testing.

• DC Electrochemical Test Methods, N. Thompson and J. Payer, NACE International, 1998, ISBN 1-877914-63-0.A very good tutorial that is highly recommended. Buy it while you’re in Atlanta.

• “Polarization Resistance Method for Determination of Instantaneous Corrosion Rates”, J. R. Scully, CORROSION, 56, 19-218 (2000).An excellent review of Polarization Resistance.

• Methods for Determining Aqueous Corrosion Reaction Rates, J. Scully and R. Kelly, ASM Handbook, Volume 13A, 2003.Addresses many electrochemical and other methods to measure the rate of corrosion.

• Electrochemical Techniques in Corrosion Engineering, 1986, NACE International36 papers. Covers the basics of the various electrochemical techniques and a wide variety of papers on the application of these techniques. Includes impedance spectroscopy.

• Corrosion Testing and Evaluation, STP 1000, Edited by R. Baboian and S. W. Dean., ASTM, 1989, ISBN 0-8031-1406-0.30 papers covering electrochemical and non-electrochemical corrosion testing.


Theory and Applications of the Measurement of Corrosion Rate with Polarization Resistance

Dr. Pete PetersonGamry Instruments

www.gamry.com

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PolRes Talk for NACE 2009