detection of t91 steel corrosion with a fe 3+ -enhanced...

Research ArticleDetection of T91 Steel Corrosion with a Fe3+-EnhancedFluorescence Probe

Tie Feng Xia Li Zhang Da Quan Zhang and Li Xin Gao

Department of Environmental Engineering Shanghai University of Electric Power Shanghai 200090 China

Correspondence should be addressed to Da Quan Zhang zhangdaquanshiepeducn

Received 6 July 2014 Accepted 12 September 2014

Academic Editor X Guo

Copyright copy 2015 Tie Feng Xia et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

We study a rhodamine-based fluorescent compound (FD2) as corrosion indicator for T91 steel in 3 NaCl solution FD2 has adesirable property of ldquoturn-onrdquo fluorescence emission via forming a complex with Fe3+ ions The varying of fluorescence intensityis linked to that of weight-loss of T91 steel Early attack onT91 steel was detected using fluorescencemicroscopyThis nondestructivemethod of initial corrosion detection can be used during maintenance before serious damage happens

1 Introduction

T91 alloy is widely used as tube material for heater orsuper-heater in the thermal power equipment because ofits excellent creep resistance Metal corrosion is one of themajor damage reasons influencing the structural integrity ofequipment Usually corrosion is a dissolving of metal causedby an electrochemical reaction involving the electron lossand ionization of metal For iron-based alloy corroding inwater solution the anodic reactions can be represented as

Fe 997888rarr Fe2+ + 2e (1)

Fe2+ +H2O 997888rarr Fe(OH)+ +H+ (2)

3Fe(OH)+ +H2O 997888rarr Fe

3O4+ 5H+ + 2e (3)

The cathodic reaction in a near neutral solution involvesreduction of the dissolved oxygen according to

O2+ 2H2O + 4e 997888rarr 4OHminus (4)

The cathodic reaction in the acidic solution is as follows

O2+ 4H+ + 4e 997888rarr 2H

2O (5)

2H+ + 2e 997888rarr H2uarr (6)

Metal loses electron at the anode and ionization leads tocorrosion dissolution At the cathode electrons are captured

and damage such as hydrogen embitterment can occurDetection of corrosion at its earliest stages is essential to avoidcritical engineering failures which will reduce maintenancecosts and improve the safety of the electric generating unitsSeveral nondestructive techniques are implemented to detectcorrosion including ultrasonic testing eddy current andelectrochemical approaches [1 2] Early corrosion detectionby fluorescent compounds receives scientific interests due totheir nondestructive and sensitive properties [3 4] Peoplebelieve that probes with a fluorescence enhancement signalare much more efficient for early corrosion detection [56] Studies have mainly employed either fluorescent dyeadded in the solution itself or nonfluorescent agents in thesolution that form fluorescers and emit fluorescence aftercorrosion electrochemical reaction at interfacesMost studieshave examined initiation of localized corrosion based on pHsensitive dyes for aluminium alloys [7 8] However so farthere are relatively few reports on the fluorescent detectionof general corrosion and pitting corrosion for iron and steel[9 10] As for steel substrates the ferric ion is well known asfluorescence quencher owing to its paramagnetic nature [11]

In this paper a rhodamine-based compound (FD2) isdesigned to detect T91 steel corrosion Figure 1 shows the pro-posed FD2-Fe3+ bonding structure Fluorescence enhancedmethod is established to check T91 steel corrosion Thepolarization curves are used to study the electrochemicalproperty of T91 steel with and without FD2 in 3NaClsolution

Hindawi Publishing CorporationJournal of ChemistryVolume 2015 Article ID 654802 6 pageshttpdxdoiorg1011552015654802

2 Journal of Chemistry

NH2

Ominus

CNN

H

H2N

C

C

C

N

Ominus

N

H

NH O N

H

Fe3+

HNO

HN

∙ ∙

∙ ∙

Figure 1 Chelation of FD2 via binding with Fe3+ ion

2 Experimental Section

21 Materials The used steel specimens were from T91 alloywith the following composition (wt) C 008ndash012 Si 020ndash050 Mn 030ndash060 Cr 9ndash12 Mo 0085ndash105 V 018ndash025119875 le 002 S le 001 Ni le 040 and Fe balance FD2was facilelysynthesized from rhodamine 6G and diethylenetriamineaccording to the procedure reported in [7] All other reagentswere of analytical grade and employed as received

22 Fluorescence Spectra The fluorescence emission of FD2in the presence of different metal ions was examined usinga Shimadzu RF-5301 fluorescence spectrophotometer Theexcitation wavelength is 510 nm The scan range was setfrom 520 nm to 640 nm for emission spectra FeCl

3 FeSO

4

Zn(NO3)2 BaCl

2 Al(NO

3)3 CuSO

4 Na2SiO4 and MnSO

4

were used as the sources of metal cations

23 Weight-Loss Tests Weight-loss test was carried out in athermostat water bath (30∘C) The suspended coupons withthe size of 40mm times 10mm times 05mm were abraded withemery paper (01 04 and 06) and washed and degreasedwith alcohol These coupons were then fully immersed inthe 250mL 3NaCl solution containing 01 120583M FD2 Afterdifferent immersion time the corrosion solution was sent forfluorescence analysis The coupons were rinsed with waterand erased with a plastic brush then dried with hot air andweighed to determine the weight loss

24 Optical and Fluorescence Images T91 steel specimenswere removed at different immersion time and rinsed withenough deionized water to get rid of the physically adsorbedFD2The specimenswere investigatedwith anOlympus SZX7Stereo FluorescenceMicroscope Amercury vapor lampwithexcitation between 460 and 550 nm in combination witha 515 nm filter was used The optical and the fluorescencemicroscopic examination were compared to determine thecorrosion detection effect

25 Electrochemical Measurements Electrochemical mea-surements were performed in a conventional three-electrodecell connected to a computer-controlled electrochemicalworkstation (Solartron 1287 Electrochemical Interface cou-pled with a 1260 ImpedanceGain-Phase Analyzer) Zplotand CorrWare software packages were used for the electro-chemical analysis The electrochemical cell was open to theair and the test solution was not stirred or deaerated T91working electrodes (WE) were sealed with epoxy resin sothat only the circular cross section (05 cm2) was exposedSaturated calomel electrode (SCE) was used as referenceelectrode the counter electrodewas a platinum electrode EISmeasurements were done at the open-circuit potential in thefrequency range from 002Hz to 100 kHz A sine wave with5mV amplitude was used to perturb the system Polarizationstudies were carried out at a scan rate of 05mVsminus1 Allpotentials were presented in mV (SCE)

3 Results and Discussion

31 Fluorescence Emissions of FD2 in Aqueous SolutionFD2 was a pale pink solid and its molecular structure wassupported by IR analysis The peak at 1583 cmminus1 is causedby ]CndashN and 120575NndashH The bands around 3473 cmminus1 can beassigned to ]NndashH Although FD2 is a derivative of rhodamine6G it is nearly colorless in 3NaCl solution suggestingthat the spirocyclic forms exist mainly Figure 2(a) showsthe fluorescence emission of 01 120583M FD2 in the presence ofdifferent amounts of Fe3+ ions in 3NaCl solution FD2presented no fluorescence signal without Fe3+ ions WhenFe3+ ions were introduced to the solution the characteristicfluorescence emission at 550 nm was observed Besidesthe fluorescence intensity improved significantly with theincrease of Fe3+ concentration During steel corrosion otheralloy elements may also dissolve into cations The fluores-cence enhancement effects of FD2 by other metal ions weregiven in Figure 2(b) Obviously other ions such as Ba2+Cu2+ Mn2+ Zn2+ and SiO

4

2minus were unable to arouse a

Journal of Chemistry 3

520 560 600 6400

100

200

300

400

500

600

500120583M Fe3+

400120583M Fe3+

Blank

Wavelength (nm)

Inte

nsity

(au

) 200120583M Fe3+

100 120583M Fe3+

50120583M Fe3+

25120583M Fe3+

125 120583M Fe3+

(a)

525 550 575 600 6250

100

200

300

400

500

Inte

nsity

(au

)

Wavelength (nm)

200120583M Fe3+200 120583M Al3+

200 120583M Fe2+

200 120583M Ba2+200 120583M Zn2+200 120583M Cu2+200 120583M Mn2+

(b)

Figure 2 Fluorescence spectra of FD2 (01120583M) in 3NaCl solution containing different concentrations of Fe3+ ions (a) and other metal ions(b)

0 100 200 300 400 500

0

100

200

300

400

500

600

Inte

nsity

(au

)

CFe3+ (120583M)

Figure 3 Correlations analysis of fluorescence intensity of 01120583MFD2 with Fe3+ ions concentration

distinct fluorescence response while Al3+ and Fe2+ ions havetiny fluorescence response compared with Fe3+ ions Thedistinct discrimination between Fe3+ and other ions providedan opportunity for FD2 to detect Fe3+ in aqueous systemcontaining some coexisting ions showing that FD2 has a verypractical corrosion detection effect

The relationship between fluorescence intensity and Fe3+concentration was presented in Figure 3 It is indicated thatthe enhanced extents of the fluorescence were in goodproportion to the Fe3+ concentrations from 30120583Mto 250 120583MIt shows FD2 can be used to monitor the concentration ofFe3+ in the neutral water solution to some extent

The effect of pH on the fluorescence intensity of FD2 inthe water solution is shown in Figure 4

From Figure 4 we can see that the fluorescence intensityof FD2 increased gradually with the decrease of pH valuesFluorescence emission of FD2 increased sharply in the

0 1 2 3 4 5 6 7 80

100

200

300

400

500In

tens

ity (a

u)

pH

01 120583M FD201 120583M FD2 + 200120583M Fe3+

Figure 4 Effect of pH on the fluorescence intensity of 01 120583M FD2in water solution without (a) and with 200 120583M Fe3+ ions

presence of 200120583M Fe3+ ions Fluorescence intensity hasthe similar variation tendency with the change of pH valuesfor FD2 with and without Fe3+ ions This shows FD2 has areorganization of Fe3+ ions in a wide pH range

32 FD2 as a Corrosion Indicator for T91 Steel In order toexamine the correlation between fluorescence emission andT91 steel corrosion the weight-loss of T91 steel in 3NaClsolution was tested The fluorescence spectra of the testsolution were determined at the same time The relationshipbetween weight-loss (Δ119882) and fluorescence intensities (119868

119865) is

shown in Figure 5 It is clear the values of Δ119882 and 119868119865follow

similar variation trends


0 2 4 6 8 10 12 14 16 18

50

100

150

200

0

5

10

15

20

Inte

nsity

(au

)

T (h)

IF

ΔW

ΔW

(mg)

Figure 5 Variation ofweight-loss (Δ119882) and fluorescence intensities(119868119865) for T91 steels in 3NaCl solution

After T91 steel specimens were immersed in 3NaClsolution and Fe3+ ions from corrosion dissolution lead toenhance the fluorescence emission of FD2 The fluorescenceintensity varies periodically with the weight-loss of T91steel specimens More weight-loss of steel has the higherconcentration of the dissolved Fe3+ ions is and the strongerfluorescence emission exists Thus FD2 can be used for cor-rosion detection of T91 steel in aqueous solution Howeveras shown in Figure 3 the quantitative determination for Fe3+ions by FD2 during corrosion process still needs furtherstudy

Figure 6 displays the optical and fluorescence imagesobserved in 3NaCl solution during the weight-loss test Atfirst no significant corrosion was observed by the opticalmicroscope after 2 h immersion Meanwhile a few brightred spots appear from the fluorescence image The red spotswere due to the formation of the FD2-Fe3+ complexesWith prolonging immersion time some corrosion spots wereobserved from the optical images Red bright spots increaseand become larger from the fluorescence images FD2 reportsthe onset of corrosion by red bright areas Clearly theresponse for corrosion was more visible for the fluorescenceimages than that for the optical images It shows that FD2 actsas an initial corrosion indicator This is critical to the timelymaintenance of metal equipment before too much damageoccurs

33 Inhibition of FD2 on Steel Corrosion A suitable corrosionindicator should not have any corrosive effect on the metalconcerned Figure 7 shows the impedance spectra of T91steel in 3NaCl solution after 1 h immersion with andwithout FD2 A capacitive loop was observed for the T91steel electrode suggesting that the corrosion of T91 steelis controlled by the charge transfer process The equivalentcircuit employed to analyze the impedance plots is inserted inFigure 7 In the circuits 119877

119904stands for the solution resistance

119877ct the charge-transfer resistance and 119862dl the double layercapacitance The impedance parameters are given in Table 1From Table 1 we can see that the presence of FD2 gives a

larger 119877ct value showing that FD2 has no corrosion effect forT91 steel

Figure 8 is the polarization curves of T91 steel in 3NaClsolution after 1 h immersionThe polarization parameters areshown in Table 2 It is obvious that the anodic corrosionprocess of T91 steel was suppressed by FD2 The presenceof FD2 shifts the corrosion potential in a positive directionand decreases the corrosion current density significantlyThus FD2 can be used as a corrosion indicator without anycorrosion damage risks

It was believed that the pitting corrosion of steel in halide-containing solution involves the following steps

Fe 997888rarr Fe2+ + 2e (7)

Fe2+ + 2Clminus 997888rarr FeCl2

(8)

FeCl2+ 2H2O 997888rarr Fe(OH)

2+ 2Clminus + 2H+ (9)

4Fe2+ +O2997888rarr 4Fe3+ + 2O2minus (10)

Fe3+ + 3H2O 997888rarr Fe(OH)

3+ 3H+ (11)

Fe(OH)3997888rarr 120574-FeOOH +H

2O (12)

2120574-FeOOHlarrrarr Fe2O3+H2O (13)

The initiation of pitting attacks by the aggressive Clminus ionscould be attributed to competitive adsorption between Clminusions and oxygenated species (OHminus and H

2O dipoles) at the

active sites on oxide covered layer [12] The adsorbed Clminusions can penetrate through the passive layer especially at itspoint defects and flaws with the assistance of a high electricfield across the passive film to reach the base metal surfaceand accelerate the local anodic dissolution [13] FD2 and theanodic dissolved Fe3+ ions have the following reaction

2FD + Fe3+ 997888rarr FD sdot sdot sdot Fe3+ sdot sdot sdot FD (14)

The formation of the complex on the film surface acts asbarrier layers to diffusion of Clminus anions from attackingthe passive film The complex of FD-Fe3+-FD moves Ecorrtowards more positive potential and retards the anodicdissolution reaction effectively It is reported that the iron-inhibitor complex formed on steel surface can be detected byfluorescence spectral analysis [14] In the present study Fe3+ions produced from localized corrosion on T91 steel surfaceare monitored in-situ by FD2 whose fluorescence intensityhas Fe3+-enhanced features The dissolution of the FD-Fe3+-FD complex also leads to the improvement of the fluorescenceemission in 3NaCl solution

4 Conclusions

The ldquoturn-onrdquo fluorescence emission via chelation betweenFD2 and Fe3+ ions can be used for corrosion detection ofT91 steel in 3NaCl solution The fluorescence intensity inthe test solution also varies periodically with the weight lossof T91 steel The initiation of localized corrosion can beindicated by the bright red fluorescence spots on T91 steel


Pitting PittingPitting

2h 4h 8h 16h

(a)

PittingPitting Pitting

Pitting

2h 4h 8h 16h

(b)

Figure 6 Optical images (a) and fluorescence images (b) observed at different immersion times during weight-loss test

0 1000 2000 3000 40000

Equivalent circuit

Blank FD2

minus1000

minus2000

minus3000Cdl

RS

Rct

Z998400 (Ω cm2)

Z998400998400

(Ωcm

2)

Figure 7 Nyquist plots of T91 steel in 3NaCl solutionwithout andwith 01 120583M FD2

Table 1 Electrochemical parameters for T91 steel in 3 NaClsolution

Concentration 119877119904(Ωsdotcm2) Cdi (10

minus5 Fcmminus2) 119877ct (Ωsdotcm2)

Blank 8876 1366 267101 120583M FD2 6764 1297 3470

surface FD2 provides a useful tool for early nondestructioncorrosion detection of T91 steel based on its Fe3+-amplifiedfluorescence property

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Blank FD2

minus08 minus07 minus06 minus05 minus04 minus03 minus02 minus01

minus8

minus7

minus6

minus5

minus4

minus3

E (V)

Log(i(A

cmminus2))

Figure 8 Polarization curves of T91 steel in 3NaCl solutionwithout and with 01120583M FD2


Concentration 119864corr (V) 119868corr (120583Acmminus2)

Blank minus0498 5713FD2 minus0483 1897

Acknowledgments

The authors are grateful to supports from Shanghai SampTCommittee Project (11JC1404400) and from ShanghaiEnergy-Saving Center of Heat-Exchange-System


References

[1] Y Tan ldquoExperimental methods designed for measuring corro-sion in highly resistive and inhomogeneous mediardquo CorrosionScience vol 53 no 4 pp 1145ndash1155 2011

[2] X Sun G Jiang P L Bond T Wells and J Keller ldquoA rapidnon-destructive methodology to monitor activity of sulfide-induced corrosion of concrete based onH

2S uptake raterdquoWater

Research vol 59 pp 229ndash238 2014[3] D Q Zhang P-H Liu L X Gao H G Joo and K Y Lee

ldquoPhotosensitive self-assembled membrane of cysteine againstcopper corrosionrdquo Materials Letters vol 65 no 11 pp 1636ndash1638 2011

[4] M Buchler T Watari and W H Smyrl ldquoInvestigation of theinitiation of localized corrosion on aluminum alloys by usingfluorescence microscopyrdquo Corrosion Science vol 42 no 9 pp1661ndash1668 2000

[5] T H Nguyen T Venugopala S Chen et al ldquoFluorescencebased fibre optic pH sensor for the pH 10ndash13 range suitablefor corrosion monitoring in concrete structuresrdquo Sensors andActuators B Chemical vol 191 pp 498ndash507 2014

[6] F Faraldi G J Tserevelakis G Filippidis G M Ingo CRiccucci and C Fotakis ldquoMulti photon excitation fluorescenceimaging microscopy for the precise characterization of corro-sion layers in silver-based artifactsrdquoApplied Physics AMaterialsScience and Processing vol 111 no 1 pp 177ndash181 2013

[7] M Buchler J Kerimo F Guillaume and W H Smyrl ldquoFluo-rescence and near-field scanning optical microscopy for inves-tigating initiation of localized corrosion of Al 2024rdquo Journal ofthe Electrochemical Society vol 147 no 10 pp 3691ndash3699 2000

[8] M P Sibi and Z Zong ldquoDetermination of corrosion onaluminum alloy under protective coatings using fluorescentprobesrdquo Progress in Organic Coatings vol 47 no 1 pp 8ndash152003

[9] A Augustyniak and W Ming ldquoEarly detection of aluminumcorrosion via ldquoturn-onrdquo fluorescence in smart coatingsrdquoProgressin Organic Coatings vol 71 no 4 pp 406ndash412 2011

[10] X Liu H Spikes and J S S Wong ldquoIn situ pH responsivefluorescent probing of localized iron corrosionrdquo CorrosionScience vol 87 pp 118ndash126 2014

[11] J Mao Q He and W Liu ldquoAn rhodamine-based fluorescenceprobe for iron(III) ion determination in aqueous solutionrdquoTalanta vol 80 no 5 pp 2093ndash2098 2010

[12] A I Munoz J G Anton J L Guinon and V P HerranzldquoInhibition effect of chromate on the passivation and pittingcorrosion of a duplex stainless steel in LiBr solutions usingelectrochemical techniquesrdquo Corrosion Science vol 49 no 8pp 3200ndash3225 2007

[13] M A Deyab and S S Abd El-Rehim ldquoInhibitory effect oftungstate molybdate and nitrite ions on the carbon steel pittingcorrosion in alkaline formation water containing Clminus ionrdquoElectrochimica Acta vol 53 no 4 pp 1754ndash1760 2007

[14] S S S Abuthahir A J A Nasser and S Rajendran ldquoInhibitionof mild steel corrosion by 1-(8-hydroxyquinolin-2-ylmethyl)ureardquo European Chemical Bulletin vol 3 pp 40ndash45 2013

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Chemistry


Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of


Chromatography Research International


Applied ChemistryJournal of



Theoretical ChemistryJournal of


Journal of

Spectroscopy

Analytical ChemistryInternational Journal of


Journal of


Quantum Chemistry


Organic Chemistry International

ElectrochemistryInternational Journal of



CatalystsJournal of


NH2

Ominus

CNN

H

H2N

C

C

C

N

Ominus

N

H

NH O N

H

Fe3+

HNO

HN

∙ ∙

∙ ∙

Figure 1 Chelation of FD2 via binding with Fe3+ ion

2 Experimental Section

21 Materials The used steel specimens were from T91 alloywith the following composition (wt) C 008ndash012 Si 020ndash050 Mn 030ndash060 Cr 9ndash12 Mo 0085ndash105 V 018ndash025119875 le 002 S le 001 Ni le 040 and Fe balance FD2was facilelysynthesized from rhodamine 6G and diethylenetriamineaccording to the procedure reported in [7] All other reagentswere of analytical grade and employed as received

22 Fluorescence Spectra The fluorescence emission of FD2in the presence of different metal ions was examined usinga Shimadzu RF-5301 fluorescence spectrophotometer Theexcitation wavelength is 510 nm The scan range was setfrom 520 nm to 640 nm for emission spectra FeCl

3 FeSO

4

Zn(NO3)2 BaCl

2 Al(NO

3)3 CuSO

4 Na2SiO4 and MnSO

4

were used as the sources of metal cations

23 Weight-Loss Tests Weight-loss test was carried out in athermostat water bath (30∘C) The suspended coupons withthe size of 40mm times 10mm times 05mm were abraded withemery paper (01 04 and 06) and washed and degreasedwith alcohol These coupons were then fully immersed inthe 250mL 3NaCl solution containing 01 120583M FD2 Afterdifferent immersion time the corrosion solution was sent forfluorescence analysis The coupons were rinsed with waterand erased with a plastic brush then dried with hot air andweighed to determine the weight loss

24 Optical and Fluorescence Images T91 steel specimenswere removed at different immersion time and rinsed withenough deionized water to get rid of the physically adsorbedFD2The specimenswere investigatedwith anOlympus SZX7Stereo FluorescenceMicroscope Amercury vapor lampwithexcitation between 460 and 550 nm in combination witha 515 nm filter was used The optical and the fluorescencemicroscopic examination were compared to determine thecorrosion detection effect

25 Electrochemical Measurements Electrochemical mea-surements were performed in a conventional three-electrodecell connected to a computer-controlled electrochemicalworkstation (Solartron 1287 Electrochemical Interface cou-pled with a 1260 ImpedanceGain-Phase Analyzer) Zplotand CorrWare software packages were used for the electro-chemical analysis The electrochemical cell was open to theair and the test solution was not stirred or deaerated T91working electrodes (WE) were sealed with epoxy resin sothat only the circular cross section (05 cm2) was exposedSaturated calomel electrode (SCE) was used as referenceelectrode the counter electrodewas a platinum electrode EISmeasurements were done at the open-circuit potential in thefrequency range from 002Hz to 100 kHz A sine wave with5mV amplitude was used to perturb the system Polarizationstudies were carried out at a scan rate of 05mVsminus1 Allpotentials were presented in mV (SCE)

3 Results and Discussion

31 Fluorescence Emissions of FD2 in Aqueous SolutionFD2 was a pale pink solid and its molecular structure wassupported by IR analysis The peak at 1583 cmminus1 is causedby ]CndashN and 120575NndashH The bands around 3473 cmminus1 can beassigned to ]NndashH Although FD2 is a derivative of rhodamine6G it is nearly colorless in 3NaCl solution suggestingthat the spirocyclic forms exist mainly Figure 2(a) showsthe fluorescence emission of 01 120583M FD2 in the presence ofdifferent amounts of Fe3+ ions in 3NaCl solution FD2presented no fluorescence signal without Fe3+ ions WhenFe3+ ions were introduced to the solution the characteristicfluorescence emission at 550 nm was observed Besidesthe fluorescence intensity improved significantly with theincrease of Fe3+ concentration During steel corrosion otheralloy elements may also dissolve into cations The fluores-cence enhancement effects of FD2 by other metal ions weregiven in Figure 2(b) Obviously other ions such as Ba2+Cu2+ Mn2+ Zn2+ and SiO

4

2minus were unable to arouse a


520 560 600 6400

100

200

300

400

500

600

500120583M Fe3+

400120583M Fe3+

Blank

Wavelength (nm)

Inte

nsity

(au

) 200120583M Fe3+

100 120583M Fe3+

50120583M Fe3+

25120583M Fe3+

125 120583M Fe3+

(a)

525 550 575 600 6250

100

200

300

400

500

Inte

nsity

(au

)

Wavelength (nm)

200120583M Fe3+200 120583M Al3+

200 120583M Fe2+

200 120583M Ba2+200 120583M Zn2+200 120583M Cu2+200 120583M Mn2+

(b)


0 100 200 300 400 500

0

100

200

300

400

500

600

Inte

nsity

(au

)

CFe3+ (120583M)






0 1 2 3 4 5 6 7 80

100

200

300

400

500In

tens

ity (a

u)

pH

01 120583M FD201 120583M FD2 + 200120583M Fe3+




119865) is




0 2 4 6 8 10 12 14 16 18

50

100

150

200

0

5

10

15

20

Inte

nsity

(au

)

T (h)

IF

ΔW

ΔW

(mg)










Fe 997888rarr Fe2+ + 2e (7)


(8)


2+ 2Clminus + 2H+ (9)



3+ 3H+ (11)


2O (12)



2O dipoles) at the




4 Conclusions




2h 4h 8h 16h

(a)


Pitting

2h 4h 8h 16h

(b)


0 1000 2000 3000 40000

Equivalent circuit

Blank FD2

minus1000

minus2000

minus3000Cdl

RS

Rct

Z998400 (Ω cm2)

Z998400998400

(Ωcm

2)





Blank 8876 1366 267101 120583M FD2 6764 1297 3470




Blank FD2


minus8

minus7

minus6

minus5

minus4

minus3

E (V)

Log(i(A

cmminus2))





Acknowledgments



References


























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


520 560 600 6400

100

200

300

400

500

600

500120583M Fe3+

400120583M Fe3+

Blank

Wavelength (nm)

Inte

nsity

(au

) 200120583M Fe3+

100 120583M Fe3+

50120583M Fe3+

25120583M Fe3+

125 120583M Fe3+

(a)

525 550 575 600 6250

100

200

300

400

500

Inte

nsity

(au

)

Wavelength (nm)

200120583M Fe3+200 120583M Al3+

200 120583M Fe2+

200 120583M Ba2+200 120583M Zn2+200 120583M Cu2+200 120583M Mn2+

(b)


0 100 200 300 400 500

0

100

200

300

400

500

600

Inte

nsity

(au

)

CFe3+ (120583M)






0 1 2 3 4 5 6 7 80

100

200

300

400

500In

tens

ity (a

u)

pH

01 120583M FD201 120583M FD2 + 200120583M Fe3+




119865) is




0 2 4 6 8 10 12 14 16 18

50

100

150

200

0

5

10

15

20

Inte

nsity

(au

)

T (h)

IF

ΔW

ΔW

(mg)










Fe 997888rarr Fe2+ + 2e (7)


(8)


2+ 2Clminus + 2H+ (9)



3+ 3H+ (11)


2O (12)



2O dipoles) at the




4 Conclusions




2h 4h 8h 16h

(a)


Pitting

2h 4h 8h 16h

(b)


0 1000 2000 3000 40000

Equivalent circuit

Blank FD2

minus1000

minus2000

minus3000Cdl

RS

Rct

Z998400 (Ω cm2)

Z998400998400

(Ωcm

2)





Blank 8876 1366 267101 120583M FD2 6764 1297 3470




Blank FD2


minus8

minus7

minus6

minus5

minus4

minus3

E (V)

Log(i(A

cmminus2))





Acknowledgments



References


























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


0 2 4 6 8 10 12 14 16 18

50

100

150

200

0

5

10

15

20

Inte

nsity

(au

)

T (h)

IF

ΔW

ΔW

(mg)










Fe 997888rarr Fe2+ + 2e (7)


(8)


2+ 2Clminus + 2H+ (9)



3+ 3H+ (11)


2O (12)



2O dipoles) at the




4 Conclusions




2h 4h 8h 16h

(a)


Pitting

2h 4h 8h 16h

(b)


0 1000 2000 3000 40000

Equivalent circuit

Blank FD2

minus1000

minus2000

minus3000Cdl

RS

Rct

Z998400 (Ω cm2)

Z998400998400

(Ωcm

2)





Blank 8876 1366 267101 120583M FD2 6764 1297 3470




Blank FD2


minus8

minus7

minus6

minus5

minus4

minus3

E (V)

Log(i(A

cmminus2))





Acknowledgments



References


























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of



2h 4h 8h 16h

(a)


Pitting

2h 4h 8h 16h

(b)


0 1000 2000 3000 40000

Equivalent circuit

Blank FD2

minus1000

minus2000

minus3000Cdl

RS

Rct

Z998400 (Ω cm2)

Z998400998400

(Ωcm

2)





Blank 8876 1366 267101 120583M FD2 6764 1297 3470




Blank FD2


minus8

minus7

minus6

minus5

minus4

minus3

E (V)

Log(i(A

cmminus2))





Acknowledgments



References


























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


References


























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of










Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

detection of t91 steel corrosion with a fe 3+ -enhanced...

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