corrosion measurement techniques in steel reinforced

Journal of ASTM International, Vol. 8, No. 5Paper ID JAI103283

Available online at www.astm.org

CopDowNati

A. Poursaee1

Corrosion Measurement Techniques in Steel ReinforcedConcrete

ABSTRACT: The main goal of this study was to evaluate different corrosion measurement techniques inorder to determine the most accurate methods for measuring the corrosion rate of steel bars in reinforcedsteel concrete. For this purpose, reinforced concrete specimens were cast and exposed to salt solution andthe corrosion activity of the bars was investigated by half-cell potential, potentiostatic linear polarizationresistance, galvanostatic pulse polarization, Electrochemical Impedance Spectroscopy, potentiodynamiccyclic polarization, and galvanodynamic polarization. The results obtained by the aforementioned methodswere then compared with the actual mass loss of the steel bars due to corrosion �gravimetry test� and itshows that techniques based on applying potential are more reliable measuring techniques compared tothose based on applying current.

KEYWORDS: corrosion, reinforced concrete, electrochemical techniques

Introduction

Low cost, readily available raw materials, and ease of forming at ambient temperatures make steel rein-forced concrete the most widely used structural material. Concrete provides corrosion resistance to thesteel reinforcement physically, by acting as a barrier and chemically, due to its high pH. However,reinforcing steel does corrode. The two most common causes of reinforcement corrosion are localizedbreakdown of the passive film on the steel by chloride ions and general breakdown of passivity due toneutralization of the concrete pore solution by reaction with atmospheric carbon dioxide.

Corrosion of reinforcing steel in concrete is a serious problem from the point of view of both safetyand economy.

In spite of using the same principles for determination of the corrosion rate, there are inconsistenciesbetween data obtained using different electrochemical measurements �1–5�. Therefore, it is essential tohave reliable measurement techniques to evaluate the corrosion condition of the steel bars in the reinforc-ing concrete. The aim of this project was to evaluate different corrosion measurement techniques in orderto recommend the most reliable method for the laboratory investigations. The test methods used in thisstudy were chosen based on their popularity and applications in the laboratory and field examinations.Advantages, disadvantages, and their applicability for laboratory measurements are investigated and ex-plained in this paper.

Materials and Methods

Ordinary Portland cement concrete and plain carbon steel bars, which are the most common combinationin reinforced concrete structures, were chosen. Table 1 shows the concrete mixture proportion used forpreparing the 1 m3 concrete. Five beams with one pre-weighted segmented 10 M rebar ��=10 mm� ineach were cast with the cover depth of 50 mm, as illustrated in Fig. 1. To separate and isolate the steelsegments, a small plastic spacer was used between each segment. Segments and plastic spacers weretapped and were connected together by a 6 mm threaded rod. For electrical connection, copper wires wereused and connected to each steel segment. To prevent extraneous effects, the ends of the bars and allconnections were coated with epoxy resin to define the exposed length of 200 mm for each bar. Theconcrete for each beam was cast in two parts: the concrete for one half was as given in Table 1 while that

Manuscript received July 21, 2010; accepted for publication April 4, 2011; published online May 2011.1
Ph.D., P.Eng., Assistant Professor, Dept. of Civil Engineering, Clemson Univ., Clemson, SC 29634, e-mail: [email protected]
Copyright © 2011 by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959.

yright by ASTM Int'l (all rights reserved); Thu Aug 25 15:36:10 EDT 2011nloaded/printed byonal Instiute of Technology Calicut pursuant to License Agreement. No further reproductions authorized.

2 JOURNAL OF ASTM INTERNATIONAL

CopDowNati

for the second half had the same mixture proportions but with 2.5 % Cl− by weight of cement added to themixing water as NaCl. Later in the process, a ponding well was installed on the Cl− contaminated part ofeach beam and that section was alternately exposed to two week periods with saturated sodium chloridesolution then two weeks without solution to accelerate the corrosion on that side.

Corrosion Evaluation Techniques

The corrosion condition of the rebars in the beams was evaluated for 2.5 years by �1� half-cell potential,�2� potentiostatic linear polarization resistance �LPR�, �3� galvanostatic pulse polarization, �4� Electro-chemical Impedance Spectroscopy �EIS�, �5� potentiodynamic cyclic polarization, and �6� galvanodynamicpolarization. Both EIS and cyclic polarization tests are time consuming experiments and based on theextent of the corrosion, more than one week may be required to perform each of these tests �6�. Therefore,these tests were performed less frequently compared to the other electrochemical measurements. Allmeasurements were performed during the second week of the wet period and in the laboratory conditionat a temperature of �23°C and relative humidity of �50 %.

When the bars were deemed to have corroded sufficiently to allow gravimetric measurements of themass loss due to corrosion, the specimens were autopsied and the extent and distribution of the corrosionwere recorded. These actual corroded surface areas were used to calculate the corrosion current density inall measurements. The bars were then weighed and a comparison of the mass loss determined by gravim-etry test, which is the most accurate corrosion measuring method, and that estimated by the cumulativevalues of icorr, was performed.

The PARSTAT® 22632 potentiostat was used to perform all electrochemical experiments except thegalvanostatic pulse technique. To perform the tests with the PARSTAT, a 100�200 mm stainless steelplate with the hole at its center ��=15 mm� was placed on the concrete surface, on top of each segment.Saturate Calomel Electrode �SCE� was used as the reference electrode and was placed in the hole. Figure2�a� schematically shows the test setup for all measurements using potentiosat/galvanostat. Sponge wasused to improve the contact between the counter and the reference electrodes and the surface of theconcrete. The GalvaPulse™ was used for galvanostatic pulse technique with guard ring.

Half-Cell Potential Technique—The half-cell potential technique is the most widely used technique ofcorrosion measurement of the steel rebars in concrete. It was introduced in the 1970s by Richard F.Stratfull in North America �7,8�. In 1980, the test was approved as a standard, as ASTM C876-09,

2Certain commercial products are identified in this paper to specify the materials used and procedures employed. In no case does such identifi-

TABLE 1—Concrete mixture proportion for making 1 m3 concrete.

Component

Type 10 Portland, kg 355

Sand, kg 770

Stone 20 mm, kg 1070

Water, L 160

Eucon MRC air entrainment 40 mL/100 kg cement

W/CM 0.43

FIG. 1—Schematic drawing of a beam with segments steel bar.

cation imply endorsement by the author, nor does it indicate that the products are necessarily the best available for the purpose.


POURSAEE ON CORROSION MEASUREMENT TECHNIQUES 3

CopDowNati

“Standard Test Method for Half-Cell Potentials of Uncoated Reinforcing Steel in Concrete” �9�. Thistechnique is based on measuring the electrochemical potential of the steel rebar with respect to a standardreference electrode placed on the surface of the concrete and can provide an indication of the corrosionrisk of the steel. Figure 2�b� schematically shows the test setup for half-cell potential measurement. Asponge is used to improve contact between the reference electrode and the surface of the concrete. Thesuggested reference electrode by ASTM is a copper/copper sulfate electrode �CSE�. The recommendedguidelines for interpretation of the half-cell potential results according to ASTM are given in Table 2. Itshould be noted that the probability of corrosion and not the actual corrosion rate can be determined bythis technique. In this study, the half-cell potential values of the segmented steel bars were measuredversus CSE, starting 24 h after casting, using an HP model 34401A high impedance digital multimeter.

Potentiostatic Linear Polarization Resistance—In the potentiostatic LPR technique, a constant poten-tial signal is applied for a certain period of time, which is determined by the time for the current to reachsteady state in the form of a square wave between the working electrode �steel bar in concrete� and thereference electrode; and the response current ��I in Fig. 3� is measured. By using Eq 1, the RP andStern–Geary equation �Eq 2� �10� corrosion current can be calculated

FIG. 2—Schematic drawing of the setup used for (a) corrosion rate measurements and (b) half-cellpotential measurement.

TABLE 2—Probability of corrosion according to half-cell potential reading [9].

Half-Cell Potential Reading Versus Cu/CuSO4 Corrosion Activity

More positive than �200 mV 90 % probability of no corrosion

Between �200 and �350 mV An increase probability of corrosion

More negative than �350 mV 90 % probability of corrosion



CopDowNati

Rp =�E

�I�1�

Icorr =B

Rp�2�

B is the Stern–Geary constant. The value of B is empirically determined and has been measured as 0.026V for active and 0.052 V for passive corrosion of plain carbon steel in concrete �11,12�.

The corrosion current density, icorr, can then be calculated by dividing the corrosion current �Icorr� bythe surface area of the polarized area �A� as follows:

icorr =B

RpA�3�

The relationship between Icorr and mass loss or reacted �m� in an electrochemical reaction is given byFaraday’s law

m =Icorr � t � a

n � F�4�

where:m=mass �g�,t=time �s�,a=atomic weight �g/mol�,n=number of equivalents exchanged, andF=Faraday’s constant �96 500 coulomb/equivalent�.In this study, �20 mV was used as the applied potential.It should be mentioned that the polarization measurements in concrete include an ohmic potential drop

through the concrete cover. This ohmic potential drop always occurs between the working electrode andthe capillary tip of the reference electrode, which affects the detected potential by the reference electrode,and consequently, usually causes underestimation of the corrosion current density. Therefore, it is impor-tant to consider the concrete resistance in all the calculations. The concrete resistance �shown in Fig. 4�was measured using the galvanostatic pulse method by applying 100 �A for 60 s; and the effect of ohmicresistance on the applied potential was compensated in all calculations. Measurements were started fourweeks after casting.

Galvanostatic Pulse Method—The galvanostatic pulse technique was introduced for field applicationin 1988 �13�. This method is a rapid non-destructive polarization technique. In this method, a short-timeanodic current pulse is applied galvanostatically between a counter electrode placed on the concretesurface and the rebar. The applied current is usually in the range of 10–100 �A and the typical pulseduration is between 5 and 30 s. The reinforcement is anodically polarized and the resulting change of the

FIG. 3—Concrete resistance values of the beams.

electrochemical potential of the reinforcement is measured with a reference electrode, which is usually inyright by ASTM Int'l (all rights reserved); Thu Aug 25 15:36:10 EDT 2011nloaded/printed byonal Instiute of Technology Calicut pursuant to License Agreement. No further reproductions authorized.


CopDowNati

the center of the counter electrode and recorded as a function of polarization time �14,15�. A typicalpotential response for a corroding reinforcement is shown in Fig. 5. The polarization resistance �RP� canbe determined by this technique and the corrosion current Icorr can then be calculated from the Stern–Gearyequation.

The major sources of error when measuring the corrosion rate of steel in concrete are the uncertaintyof the area of the steel bar affected by the electrical signal from the counter electrode and the non-uniformcurrent distribution on the steel rebar, and this has been studied by many researchers �16–22�. One of theapproaches to overcome the aforementioned difficulties is using a second electrode to confine the polarizedarea, and this is employed by most commercially available instruments for field measurements. In thisapproach, the extra electrode, a “guard ring” �usually ring-shaped� is used to confine the signal appliedfrom the counter electrode to a known length at the working electrode �steel bar�. A secondary current isapplied between the guard ring and the rebar while the rebar is polarized by the counter electrode�2,18,23–25�. The objective is for the current applied from the guard ring to repel the lines of current fromthe central counter electrode and confine them to an area of the structure located approximately under the

FIG. 4—Applied potential and current response during LPR measurement.

FIG. 5—Schematic illustration of galvanostatic pulse results.yright by ASTM Int'l (all rights reserved); Thu Aug 25 15:36:10 EDT 2011nloaded/printed byonal Instiute of Technology Calicut pursuant to License Agreement. No further reproductions authorized.


CopDowNati

counter electrode �Fig. 6�. In this study, the GalvaPulse™ system, developed by FORCE Technology inDenmark, was used. The electrode assembly has an Ag/AgCl reference electrode at the center with a zinccounter electrode and a zinc guard ring, as illustrated in Fig. 6. The instrument consists of a handheldcomputer that generates a small galvanostatic pulse, controls the pulse duration, and processes the data.The applied current was chosen as 25 �A for 60 s during the experimental period. Measurements werestarted 24 h after casting

Electrochemical Impedance Spectroscopy—The popularity of the EIS method for reinforced concretehas increased remarkably in recent years. Analysis of the system response can provide information aboutthe double-layer capacitance, interface, structure, reactions that are taking place, corrosion rate, and elec-trolyte �environment� resistance �26–28�.

EIS studies the system response �the impedance of a system� to the application of a small amplitudealternating potential �usually 20 mV� signal at different frequencies.

The most common expression of the data obtained by EIS is in a Bode plot and a Nyquist plot. ANyquist plot is the plot of the imaginary impedance component �Z�� against the real impedance component�Z�� at each excitation frequency. The Bode plot format examines the absolute impedance, �Z�, as calcu-lated and the phase shift, �, of the impedance, each as a function of frequency. In this study, the Nyquistplots were used to measure the values of polarization resistance and concrete resistance. Figure 7 shows anillustration of a Nyquist plot

Potentiodynamic Cyclic Polarization—The cyclic potentiodynamic polarization technique is a rela-tively non-destructive measurement that can provide information about the corrosion rate, corrosion po-tential, and susceptibility to pitting corrosion of the metal. The technique is built on the idea that predic-tions of the behavior of a metal in an environment can be made by forcing the material from its steadystate condition and monitoring how it responds to the force as the force is removed at a constant rate andthe system is reversed to its steady state condition.

The cyclic polarization curve of one of the steel segments in a chloride free section is shown in Fig.8. Applied potential is the force and is raised at a continuous, often slow, rate by using potentiostat. Thisrate is called the polarization scan rate and is an experimental parameter. It is very important to choose themost appropriate scan rate, specifically in the complicated system such as reinforced concrete; otherwise,the result does not reflect the actual corrosion behavior. The appropriate scan rate was determined beforeeach experiment, using the method described in Ref 29. For all of the experiments, the scan started at�100 mV below half-cell potential, increased to +500 mV, and decreased to �500 mV versus SCE.

Galvanodynamic Polarization—Galvanodynamic polarization refers to a technique in which currentthat is continuously varied at a selected rate is applied to an electrode �rebar� in an electrolyte �concretepore solution�. The galvanodynamic method plots the variation in potential versus the controlled current.

FIG. 6—Schematic plan of the instrument using guarding to limit the polarized area while performing thecorrosion measurement.

This is a relatively fast method to obtain the value of RP, and consequently, the corrosion rate. In thisyright by ASTM Int'l (all rights reserved); Thu Aug 25 15:36:10 EDT 2011nloaded/printed byonal Instiute of Technology Calicut pursuant to License Agreement. No further reproductions authorized.


CopDowNati

experiment, an applied current was raced continuously between �100 and +100 �A at the rate of10 �A /s and the resultant potential was monitored. The value of RP is the slope of the potential versuscurrent curve at i=0 A. Where there is hysteresis, the slope of the line between the maximum values ofthe current �positive and negative� is taken as RP, as shown in Fig. 9. Measurements were started onemonth after casting.

FIG. 7—Nyquist plot of one of the segments in chloride contaminated section.

FIG. 8—Cyclic polarization curve of one of the segments in chloride free section.yright by ASTM Int'l (all rights reserved); Thu Aug 25 15:36:10 EDT 2011nloaded/printed byonal Instiute of Technology Calicut pursuant to License Agreement. No further reproductions authorized.


CopDowNati

Gravimetry—To evaluate and determine the most accurate electrochemical corrosion measurementtechnique, all beams were autopsied and each segment was weighed and the amount of mass loss wasdetermined. To perform the test, the corrosion products were removed using the Clark solution �1000 mlHCl with specific gravity=1.19+20 g antimony trioxide �Sb2O3�+50 g stannous chloride �SnCl2��, ac-cording to the ASTM G1-90 �30� standard procedure. This solution is effective in cleaning corrosionproducts at room temperature. The steel segments were immersed in Clark solution until the corrosionproducts were entirely removed. The time is based on the extent of the corroded area and could be moreor less than 30 min. Due to the toxic nature of the Clark solution, the cleaning procedure must be carriedout under a fume hood with safety glasses and gloves.

Using the area under the corrosion current density versus time curves, the cumulative mass loss wascalculated and compared to the actual mass loss obtained by the gravimetry method.

Results and Discussions

Figures 10 shows the half-cell potential values measured versus CSE for the chloride free and chloridecontaminated sections of all beams. The dash lines indicate the ASTM C876-09 guidelines �Table 2� forinterpretation of the data. As can be seen, in the chloride contaminated concrete, the segments show thepotential to be more negative than �350 mV versus CSE, indicating that there is a 90 % probability ofactive corrosion according to ASTM C876-09. The half-cell potential values of the steel segments in thechloride free section of the beams are more positive than �350 mV versus CSE, which is in uncertaintyregion based on the ASTM C876-09 recommendation. The potential values were fluctuated considerably atthe beginning of the test �about 4 months� but became more constant after this time, implying that the steelbars were in a more stable state. As mentioned before, the beams were broken at different times and afterthat time, there are no points for that broken beam in Fig. 10.

Figures 11–13 show the corrosion current densities of the segments, measured by potentiostatic LPR,galvanostatic pulse technique �with GalvaPulse-guard on�, and galvanodynamic LPR, respectively. Itshould be noted that the scale of the Y axis in Fig. 11 is different from that in Figs. 12 and 13.

As can be seen in Figs. 11–13, at the beginning of the measurement �about 4 months�, the corrosion

FIG. 9—Schematic of a galvanodynamic polarization curve.

current densities were higher than what was expected in a high alkaline environment when the steel isyright by ASTM Int'l (all rights reserved); Thu Aug 25 15:36:10 EDT 2011nloaded/printed byonal Instiute of Technology Calicut pursuant to License Agreement. No further reproductions authorized.


CopDowNati

expected to be in its passive state. As abovementioned, the half-cell potential values were also fluctuatingduring that period of time. This can be attributed to the fact that the measured Rp represents the currentexchange of the redox process �Fe2+↔Fe3+� in the passive layer �31–34�. At potentials more positive than�200 mV versus CSE, two processes act together at the metal/concrete interface: The corrosion process�Fe→Fe2++2e−� and the phase transformation in the oxide layer according to the following process:

3Fe3O4 ↔ 4�-Fe2O3 + Fe3+ + 3e− �5�

As the value of the corrosion potential becomes more positive, more Fe3+ presents in the oxide layer andconsequently, the redox process contribution in whole process is more extended �32�. Therefore, due to the

FIG. 10—Half-cell potential values of the segmented bars.

FIG. 11—Corrosion current density of the segmented bars, measured by the potentiostatic LPR technique.yright by ASTM Int'l (all rights reserved); Thu Aug 25 15:36:10 EDT 2011nloaded/printed byonal Instiute of Technology Calicut pursuant to License Agreement. No further reproductions authorized.


CopDowNati

redox process, the measured corrosion current densities at the beginning of passivation of steel do notrepresent the actual steel dissolution. It should be noted that this process cannot be noticed clearly whenthe steel is showing active corrosion. It seems that in active corrosion, the redox process is masked by afaradaic �corrosion of steel bar� process �34�.

The corrosion current densities, measured by the potentiostatic LPR technique �Fig. 11�, show that allsegments in chloride contaminated sections were actively corroding while the segments in chloride freeconcrete were not actively corroded and their corrosion current density stayed in the passive range �35�.

Measurements carried out by the GalvaPulse™ �Fig. 12� show at least two times higher values than

FIG. 12—Corrosion current density of the segmented bars, measured by the GalvaPulse™, with the guardring on.

FIG. 13—Corrosion current density of the segmented bars, measured by the galvanodynamic polarization
technique.yright by ASTM Int'l (all rights reserved); Thu Aug 25 15:36:10 EDT 2011nloaded/printed byonal Instiute of Technology Calicut pursuant to License Agreement. No further reproductions authorized.


CopDowNati

values obtained by the potentiostatic LPR for similar segments. It should be noted that in all measure-ments, the guard ring in GalvaPulse™ was used and therefore this difference could be due to a highercurrent applied by the GalvaPulse™ �3�. In addition, current densities measured by the GalvaPulse™ showmore fluctuations and distinguishing the corrosion densities in chloride contaminated and chloride freesections is difficult. These behaviors could be attributed to the fact that applying the appropriate current byGalvaPulse™ to stay in the linear region of the potential versus current curve is a difficult task, while in thepotentiostatic LPR, the applied potential is constant and certainly is in the linearity range. Difficulties withthe galvanostatic pulse technique with the guard ring are explained by the author and his colleague inprevious studies �3�.

Comparison between Figs. 11 and 13 shows that the galvanodynamic LPR compared to the potentio-static LPR generally shows higher values. This could be due to the fact that applying 100 �A to the steelbar polarized it between 50 and 100 mV, depending on the condition of the surface of the rebar, which isbeyond the linear region of the potential versus current curve. However, compared to the galvanostaticpulse technique, the results of the galvanodynamic LPR show less fluctuations and differentiating thecorrosion densities of the segments in chloride free and chloride contaminated concrete is easier. There-fore, galvanodynamic LPR can be used as a rapid method to distinguish between actively corroded barsand the areas with less corrosion activities. This test is relatively fast and can be performed in thelaboratory as well as field measurements. It should be noted that the frequency of measurements performedby this technique was less than the potentiostatic LPR and the galvanostatic pulse technique.

As mentioned before, the corrosion current densities of some of the segmented bars were also mea-sured by cyclic polarization and electrochemical impedance techniques at different times, which are shownin Table 3. It is clear that the values of the corrosion current densities measured by the potentiostatic LPR,cyclic polarization, and EIS are close together and are lower than those measured by the other twotechniques.

To obtain the actual mass loss, the concrete beams were autopsied at different times, and then, byusing the area under the corrosion current density versus time curves obtained by different techniques, thecumulative mass loss was calculated and compared to the actual mass loss. Figure 14 shows one of thesegments in chloride contaminated concrete after the autopsy and cleaning the corrosion products from itssurface. The actual mass loss during the period of the test for each beam is given in Table 4. In Fig. 15, thecomparison between different techniques and the actual mass loss are shown. It is clear that the mass lossdetermined using the potentiostatic LPR technique is very close to the actual mass loss and both galvano-static pulse and galvanodynamic LPR techniques overestimate the mass loss.

TABLE 3—Corrosion current density of some of the segmented bars measured with potentiostatic LPR, galvanostatic pulse, galvano-dynamic LPR, cyclic polarization, and EIS.

WeeksAfterCasting

Corrosion Current Density �A·m−2�

PotentiostaticLPR

GalvanostaticPulse

GalvanodynamicLPR

CyclicPolarization EIS

Steel segments in chloride free concrete

23 0.0005 0.0049 0.0012 0.0001 0.0003

24 0.0039 0.0093 0.0124 0.0040 0.0051

54 0.0004 0.0030 0.0018 0.0003 0.0001

62 0.0028 0.0053 0.0083 0.0015 0.0033

87 0.0005 0.0049 0.0019 0.0004 0.0003

116 0.0004 0.0052 0.0009 0.0004 0.0002

119 0.0007 0.0059 0.0025 0.0005 0.0003

Steel segment in chloride contaminated concrete

17 0.015 0.015 0.048 0.013 0.017

25 0.018 0.029 0.042 0.017 0.012

52 0.014 0.005 0.039 0.020 0.012

69 0.011 0.016 0.039 0.014 0.010

84 0.011 0.003 0.044 0.010 0.013

118 0.011 0.008 0.044 0.015 0.012

120 0.015 0.050 0.051 0.020 0.014

Results from all measuring techniques confirm that potentiostatic LPR, cyclic polarization, and EISyright by ASTM Int'l (all rights reserved); Thu Aug 25 15:36:10 EDT 2011nloaded/printed byonal Instiute of Technology Calicut pursuant to License Agreement. No further reproductions authorized.


CopDowNati

techniques can estimate the most accurate mass loss during the corrosion process. In addition, measure-ments performed using these techniques show less fluctuations. Since all measurements were carried out inthe laboratory condition, the effect of the environment on corrosion measurements was minimized. There-fore, it can be concluded that techniques based on applying potential are more reliable than methods thatare based on applying current. In spite of the fact that techniques based on applying current are fast, theyusually overestimate the actual corrosion rate of the reinforcing steel bars. This could be due to difficultiesin maintaining the potential in the linear region and, consequently, not using accurate data in the Stern–Geary equation �Eq 2� to obtain the corrosion current. This is more significant if the equipment with theguard ring is used.

One of the variables in corrosion measurement could be the material and the geometry being used forthe counter electrode. Therefore in this study, different counter electrodes, as summarized in Table 5, werealso tested. The size of all the rings was chosen to match the size of the counter electrodes used in theGalvaPulse™. The potentiostatic LPR technique was used in this experiment. The measurements werecarried out on the steel segments in the chloride contaminated section. The standard deviation between thecorrosion current densities obtained by different counter electrodes was about 0.001 A·m−2, which indi-cates that there is no significant difference between different materials, size, and different shapes. It shouldbe noted that this conclusion could only be valid for the corrosion measurements of steel in concrete andthe results might be different in different solutions due to the exchange current density of the oxygen orhydrogen on different materials. Generally, the counter electrode should be made of materials that are inertto the electrolyte and they should have a high exchange current density.

Conclusion

• Although variations in the half-cell potential values of all beams were observed, in most cases whenthe steel bars were corroding actively, the half-cell potential values were more negative than �350mV versus CSE, which is in agreement with the ASTM C876-09 recommendations. However, itshould be noted that all the experiments were carried out in the laboratory condition and the resultsmight be different in field measurements.

• Gravimetry test shows that techniques based on applying potential �potentiostatic LPR, cyclicpolarization, and EIS� are more reliable measuring techniques compared to those based on applyingcurrent �galvanostatic LPR and galvanodynamic polarization�. The results obtained from techniquesbased on applying potential show less variation for all specimens. However, due to the required

TABLE 4—Mass loss and date of autopsy for all beams.

BeamDate of Autopsy

�Weeks After Casting�

Mass Loss �g�

Chloride Free Sections Chloride Contaminated Sections

1 2 3 4

1 61 0.04 0.09 0.45 0.44

2 80 0.1 0.04 0.7 0.64

3 87 0.05 0.08 0.46 0.5

4 120 0.26 0.05 0.26 0.5

5 120 0.39 0.1 0.85 0.71

FIG. 14—One of the steel segments after cleaning the corrosion products, removed from the chloridecontaminated section of one of the concrete beams.



CopDowNati

time for both cyclic polarization and EIS, potentiostatic LPR seems a reasonable technique to beused in the investigations. Nevertheless, it is recommended to confirm the results every couple oftests with cyclic polarization and EIS, as well.

• The galvanodynamic LPR is a relatively fast measurement method; however, the measured corro-sion current density values are higher than those values measured by the techniques based onapplying potential. This is a good technique for comparison purpose, but it is not recommended forprediction and modeling the remaining service life of the structure.

Acknowledgments

The writer gratefully acknowledges the support of the Ministry of Transportation of Ontario for this projectand Professor Carolyn Hansson for her extensive contributions in this study.

TABLE 5—Material, shape, and the size of the counter electrodes, used to determine the effect ofcounter electrode on the measurements.

Material Shape Size

Stainless steel Plate �rectangular� 100�180 mmStainless steel Ring ID=30 mm, OD=60 mmGalvanized steel Ring ID=30 mm, OD=60 mmGalvaPulse™ measuring unit-zinc Ring ID=30 mm, OD=60 mm

FIG. 15—Comparison of mass loss determined by gravimetry and (a) potentiostatic LPR, (b) galvanostaticLPR, and (c) galvanodynamic LPR techniques, in chloride free and chloride contaminated concrete.Values are in grams.



CopDowNati

References

�1� Weiermair, R., Hansson, C. M., Seabrook, P. T., and Tullmin, M., “Corrosion Measurements on SteelEmbedded in High Performance Concrete Exposed to a Marine Environment,” Third CANMET/ACIInternational Conference on Concrete in Marine Environment, New Brunswick, Canada, 1996,American Concrete Institute, St. Andrews by the Sea, NB, Canada.

�2� Gepraegs, O. K. and Hansson, C. M., “A Comparative Evaluation of Three Commercial Instrumentsfor Field Measurements of Reinforcing Steel Corrosion Rates,” Electrochemical Techniques forEvaluating Corrosion Performance and Estimating Service-Life of Reinforced Concrete, ASTM In-ternational, West Conshohocken, PA, 2004.

�3� Poursaee, A. and Hansson, C. M., “Galvanostatic Pulse Technique with the Current ConfinementGuard Ring: The Laboratory and Finite Element Analysis,” Corros. Sci., Vol. 50�10�, 2008, pp.2739–2746.

�4� Andrade, C. and Alonso, C., “On-Site Measurements of Corrosion Rate of Reinforcements,” Constr.Build. Mater., Vol. 15, 2001, pp. 141–145.

�5� Soleymani, H. R. and Ismail, M. E., “Comparing Corrosion Measurement Methods to Assess theCorrosion Activity of Laboratory OPC and HPC Concrete Specimens,” Cem. Concr. Res., Vol. 34,2004, pp. 2037–2044.

�6� Poursaee, A. and Hansson, C. M., “Potential Pitfalls in Assessing Chloride-Induced Corrosion ofSteel in Concrete,” Cem. Concr. Res., Vol. 39�5�, 2009, pp. 391–400.

�7� Spellman, D. L. and Stratfull, R. F., “Laboratory Corrosion Test of Steel in Concrete,” Report No.M&R 635116-3, California Division of Highways, State of California, Sacramento, CA, 1968.

�8� Stratfull, R. F., “Half-Cell Potential and the Corrosion of Steel in Concrete,” Report No. CA-HY-MR-5116-7-72-42, California Division of Highways, State of California, Sacramento, CA, 1972.

�9� ASTM C876-09, 2009, “Standard Test Method for Half-Cell Potentials of Uncoated ReinforcingSteel in Concrete,” Annual Book of ASTM Standards, Vol. 3.02, ASTM International, West Consho-hocken, PA, pp. 446–451.

�10� Stern, M. and Geary, A. L., “Electrochemical Polarisation: I. A Theoretical Analysis of the Shape ofPolarisation Curves,” J. Electrochem. Soc., Vol. 104�1�, 1957, pp. 56–63.

�11� Andrade, C. and González, J. A., “Quantitative Measurements of Corrosion Rate of ReinforcingSteels Embedded in Concrete Using Polarization Resistance Measurements,” Werkst. Korros., Vol.29, 1978, pp. 515–519.

�12� Andrade, C., Marcias, A., Feliu, S., Escudero, M. L., and Gonzalez, J. A., “Quantitative Measure-ment of the Corrosion Rate Using a Small Counter Electrode in the Boundary of Passive andCorroded Zones of a Long Concrete Beam,” Corrosion Rates of Steel in Concrete, ASTM STP 1065,N. S. Berke, V. Chaker, and D. Whiting, Eds., ASTM International, West Conshohocken, PA, 1990.

�13� Newton, C. J. and Sykes, J. M., “A Galvanostatic Pulse Technique for Investigation of Steel Corro-sion in Concrete,” Corros. Sci., Vol. 28�11�, 1988, pp. 1051–1074.

�14� Klinghoffer, O., “In Situ Monitoring of the Reinforcement Corrosion by Means of ElectrochemicalMethods,” Nord. Concr. Res., Vol. 16, 1995, pp. 1–13.

�15� Elsener, B., Klinghoffer, O., Frolund, T., Rislund, E., Schiegg, Y., and Böhni, H., “Assessment ofReinforcement Corrosion by Means of Galvanostatic Pulse Technique,” Repair of Concrete Struc-tures, A. Blankvoll, Ed., Svolvær, Norway, 1997, pp. 391–400.

�16� Wojtas, H., “Determination of Corrosion Rate of Reinforcement with a Modulated Guard RingElectrode; Analysis of Errors Due to Lateral Current Distribution,” Corros. Sci. Vol. 46, 2004, pp.1621–1632.

�17� Nygaard, P. V., Geiker, M. R., Møller, P., Sørensen, H. E., and Klinghoffer, O., Effect of Guard RingArrangements on the Current Confinement and Polarisation of Steel in Concrete-Experiments andModeling, Eurocorr, Lisbon, Portugal, 2005.

�18� Feliu, S. and Gonzalez, J. A., “Determining Polarization Resistance in Reinforced Concrete Slabs,”Corros. Sci., Vol. 29�1�, 1989, pp. 105–113.

�19� Feliu, S., Gonzalez, J. A., and Andrade, C., “Multiple-Electrode Method for Estimating the Polar-ization Resistance in Large Structures,” J. Appl. Electrochem., Vol. 26, 1996, pp. 305–309.

�20� Videm, K. and Mydal, R., “Electrochemical Behavior of Steel in Concrete and Evaluation of theyright by ASTM Int'l (all rights reserved); Thu Aug 25 15:36:10 EDT 2011nloaded/printed byonal Instiute of Technology Calicut pursuant to License Agreement. No further reproductions authorized.

http://dx.doi.org/10.1016/j.corsci.2008.07.017

http://dx.doi.org/10.1016/S0950-0618(00)00063-5

http://dx.doi.org/10.1016/S0950-0618(00)00063-5

http://dx.doi.org/10.1016/j.cemconres.2004.03.008

http://dx.doi.org/10.1016/j.cemconres.2009.01.015

http://dx.doi.org/10.1149/1.2428496

http://dx.doi.org/10.1002/maco.19780290804

http://dx.doi.org/10.1016/0010-938X(88)90101-1


http://dx.doi.org/10.1016/0010-938X(89)90083-8

http://dx.doi.org/10.1007/BF00242100


CopDowNati

Corrosion Rate,” Corros., Vol. 53�9�, 1997, pp. 734–742.�21� Feliu, S., Gonzalez, J. A., Miranda, J. M., and Feliu, V., “Possibilities and Problems of In Situ

Techniques for Measuring Steel Corrosion Rates in Large Reinforced Concrete Structures,” Corros.Sci., Vol. 47, 2005, pp. 217–238.

�22� Poursaee, A., 2010, Electrochemical Measurements of the Condition of Steel in Concrete, VDMVerlag Dr. Müller 256, Saarbrucken, Germany.

�23� Feliu, S., Gonzalez, J. A., Feliu, S., Jr., and Andrade, C., “Confinement of the Electrochemical Signalfor In-Situ Measurement of Polarization Resistance in Reinforced Concrete,” ACI Mater. J., Vol.87�5�, 1990, pp. 457–460.

�24� Kranc, S. C. and Sagues, A. A., “Polarization Current Distribution and Electrochemical ImpedanceResponse of Reinforced Concrete when Using Guard Ring,” Electrochim. Acta, Vol. 38�14�, 1993,pp. 2055–2061.

�25� Feliu, S., Gonzales, J. A., Andrade, C., and Feliu, V., “On-Site Determination of the PolarizationResistance in a Reinforced Concrete Beam,” Corros., Vol. 43�10�, 1987, pp. 761–767.

�26� Lasia, A., “Electrochemical Impedance Spectroscopy and its Applications,” Modern Aspects of Elec-trochemistry, B. E. Conway, J. Bockris, and R. E. White, Eds., Kluwer Academic/Plenum Publishers,New York, 1999, pp. 143–248.

�27� Jones, D. A., Principles and Prevention of Corrosion, Macmillan Publishing Company, New York,1992.

�28� Silverman, D. C., “Simple Models/Practical Answers Using the Electrochemical Impedance Tech-nique,” Corrosion Testing and Evaluation, R. Baboian and W. Dean, Eds., ASTM International, WestConshohocken, PA, 1990.

�29� Poursaee, A., “Determining the Appropriate Scan Rate to Perform Cyclic Polarization Test on theSteel Bars in Concrete,” Electrochim. Acta, Vol. 55�3�, 2010, pp. 1200–1206.

�30� ASTM G1-90, 1999, “Standard Practice for Preparing, Cleaning, and Evaluating Corrosion TestSpecimens,” Annual Book of ASTM Standards, Vol. 3.02, ASTM International, West Conshohocken,PA, pp. 1–8.

�31� Andrade, C., Merino, P., Novoa, X. R., Perez, M. C., and Solar, L., “Passivation of Reinforcing Steelin Concrete,” Mater. Sci. Forum, Vols. 192–194, 1995, pp. 861–898.

�32� Alonso, C., Andrade, C., Izquierdo, M., Novoa, X. R., and Perez, M. C., “Effect of Protective OxideScales in the Macrogalvanic Behaviour of Concrete Reinforcements,” Corros. Sci., Vol. 40�8�, 1998,pp. 1379–1389.

�33� Andrade, C., Keddam, M., No’voa, X. R., Perez, M. C., Rangel, C. M., and Takenouti, H., “Elec-trochemical Behaviour of Steel Rebars in Concrete: Influence of Environmental Factors and CementChemistry,” Electrochim. Acta, Vol. 46, 2001, pp. 3905–3912.

�34� Andrade, C. and Alonso, C., “Test Methods for On-Site Corrosion Rate Measurement of SteelReinforcement in Concrete by Means of the Polarisation Resistance Method,” Mater. Struct., Vol. 37,2004, pp. 623–643.

�35� Hansson, C. M., “Comments on Electrochemical Measurements of the Rate of Corrosion of Steel inConcrete,” Cem. Concr. Res., Vol. 14, 1984, pp. 574–584.


http://dx.doi.org/10.5006/1.3290308



http://dx.doi.org/10.1016/0013-4686(93)80340-6

http://dx.doi.org/10.1016/j.electacta.2009.10.004

http://dx.doi.org/10.1016/S0010-938X(98)00040-7

http://dx.doi.org/10.1016/S0013-4686(01)00678-8

http://dx.doi.org/10.1007/BF02483292

http://dx.doi.org/10.1016/0008-8846(84)90135-2

corrosion measurement techniques in steel reinforced

Documents