Research Article Electrochemical Impedance and Modelling ... · Electrochemical Impedance and Modelling Studies of the Corrosion of Three Commercial Stainless Steels in Molten Carbonate

Research ArticleElectrochemical Impedance and Modelling Studies ofthe Corrosion of Three Commercial Stainless Steels inMolten Carbonate

C S Ni and L Y Lu

State Key Laboratory for Corrosion and Protection Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China

Correspondence should be addressed to C S Ni nichengsheggmailcom

Received 2 June 2014 Revised 22 October 2014 Accepted 23 October 2014 Published 6 November 2014

Academic Editor Flavio Deflorian

Copyright copy 2014 C S Ni and L Y LuThis 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

The corrosion induced by molten carbonates on the metallic structure materials is a problem constraining the life span of moltencarbonate fuel cell (MCFC) at elevated temperatures The reaction between the outgrowing oxide scale and lithium carbonate inthe electrolyte is generally a slow process and very important to the passivation behaviour of the underlying steel The corrosionbehaviour of three commercial alloys (P92 SS304 and SS310) with different Cr contents in molten (062Li 038K)

2CO3at 650∘C

was monitored by electrochemical impedance spectroscopy (EIS) for 120 hours to investigate the lithiation process With SEMimages and extensive XRD analysis of the oxides equivalent circuits were proposed to interpret the impedance data and explainthe corrosion behaviour of the three alloys at different stage with respect to lithiation process

1 Introduction

Cathode dissolution and metallic corrosion in contact withmolten carbonate are two crucial problems limiting the lifespan of a molten carbonate fuel cell (MCFC) The metallicstructurematerials subjected to corrosion are separator platesand the current collectors Aluminium-containing materialsare extremely corrosion resistant in molten carbonate [1ndash3] and can be used for wet-sealing area but they are tooelectrically resistive to be used for current collecting areasA balance between the corrosion resistance and oxide scaleresistivity for materials of bipolar plates at the workingtemperature of 650∘C should be struck in order to achieve along life span of 40000 hours with high productivity [4ndash6]Biedenkopf et al [4] reported that the electrical conductivitywas limited by the inner chromium-containing oxide ofa multilayered corrosion scale and chromium-rich alloyswith a Cr content higher than 20wt showed extremelyhigh ohmic resistance of the Cr-containing corrosion scale incontrast to the formation of highly conductive mixed spinellayers on steels with Cr content less than 20wt In additionSpiegel et al [7 8] studied the corrosion of iron-based alloyand high alloys in eutectic Li

2CO3-K2CO3melt and pointed

out that the chromium content of the alloy should not exceed12ndash15 wt to prevent the loss of chromium through theformation of dissolvable potassium chromate

The corrosion caused bymolten salt is an electrochemicalprocess in nature so electrochemical techniques can beapplied to study the mechanism [9ndash16] Electrochemicalimpedance spectroscopy (EIS) is a technique that has provento be effective in investigating reaction mechanisms andkinetics in hot corrosion induced by molten carbonate Theimpedance response of pureNi FeAl (Fe-244Al-012Bwt)CuAl (Cu-15Al wt) NiTi (Ni-10 15Ti wt) NiCo (Ni-50Cowt) and AISI 310 stainless steel (Fe-25Cr-20Niwt)after different immersion times in molten carbonate at 650∘Cwas monitored and corresponding models were proposed tospecify the corrosion mechanism [9ndash11 17 18] Electrochem-ical impedance was also used to assess the corrosion resis-tance of different chromium content alloys against moltencarbonate after a given immersion period [12 13] Frangini[14] compared the corrosion kinetics of 310S stainless steelin molten carbonates obtained with impedance spectra andlinear polarization and concluded that the presence of diffu-sion impedance terms and formation of resistive surface filmscoupled with lithiation process might result in unreliable

Hindawi Publishing CorporationInternational Journal of CorrosionVolume 2014 Article ID 721208 13 pageshttpdxdoiorg1011552014721208

2 International Journal of Corrosion

resistance values obtained with the linear polarization Zhuet al [15] found that the corrosion rates estimated fromthe two electrochemical techniques concurred only at theinitial period of immersion before the formation of protectivescales The significant perturbations of the current in Tafelpolarization on the scale bring error to the calculation ofcorrosion rate while EIS is a good tool in studying theproperties of scales by applying small perturbation (lt10mV)to the system

The lithiation process is one of the reasons for theelectrolyte loss during the operating time of anMCFC [19 20]andmore importantly this process will change the propertiesof the scales of stainless steel under thin film of moltencarbonate [21ndash24] The corrosion of stainless steel in thecathode compartment or the immersion corrosion will lastlonger times than thin-film corrosion so longer testingwouldbe required to study the whole processThe surroundingmeltin dip-melt test will provide sufficient lithium and potassiumto react with the oxide scale Unlike the general short-termor instant testing this report serves to study the corrosionprocess of three commercial alloys with different chromiumcontent for extended times by impedance techniques interms of monitoring the outgrowth of oxide scale and thelithiation process To be specific the corrosion process ofthree commercial stainless steels P92 SS304 and SS310when immersed fully in molten (062Li 038K)

2CO3at

650∘C was investigated using EIS technique This techniqueprovides a real-time monitoring process of the experimentwithout disturbing the thermodynamic system so manymeasurements can be taken at different times to establish thecorrosion mechanism

2 Experimental

The powers of anhydrous carbonates 62 Li2CO3and 38

K2CO3in mole fraction were weighed and mixed in an

alumina crucible which was then placed in a cylindricalfurnace to be baked at 350∘C for 24 h in order to purgethe residual moisture And then the furnace was heated to650∘C at a ramp of 3∘Cmin Flat rectangular specimens werecut from bulk alloys and ground to 800 emery paper Thecompositions of the three alloys were shown in Table 1

A two-electrode system was used for the impedancemeasurements where the working electrode was identicalto reference electrode and auxiliary electrode The referenceprobe is connected to the probe of auxiliary electrode Theimpedance measurement is assumed to be at OCV and theimpedance for each sample should be the final impedancedivided by a factor of two A detailed experimental setupcan be found in [2] Two specimens of the same stainlesssteel were imbedded in an alumina tube and sealed withhigh temperature cement after a Fe-Cr lead wire had beenspot-welded on the fringe of each specimen The workingsurface of each electrode was 10mm times 8mm For each alloythe electrochemicalmeasurements are reproduced twice withthe same materials and working conditions to confirm thevalidity of the modeling

Electrochemical-impedance measurements up to 120 hwere performed at open-circuit potential in air between 001

Table 1 The compositions of the three commercial stainless steels

Stainless steel Composition (wt)P92 Fe-90Cr-18W-05Mn-04Mo-011Si-02VSS304 Fe-193Cr-94Ni-20Mn-09SiSS310 Fe-264Cr-185Ni-14Mn

and 1 times 105Hz with a M398 impedance system composedof a Princeton applied research (PAR) 5210 lock-in amplifierand a PAR 263 potentiostat interfaced through an IEEE 488bus to a compatible computer A fast Fourier transform (FFT)technique was employed for frequencies from 001 to 113Hzto increase measurement speed and lower the degree ofperturbation to the cell The amplitude of input sine signalwas 10 mV A commercial software (ZSimpWin) developedby PAR was used to fit the impedance spectra using complexnonlinear least squares (CNLS) method

The corroded samples were examined by X-ray diffrac-tion (XRD) and scanning electron microscopy (SEM) cou-pled with an energy-dispersive X-ray (EDX) microanalysissystem The XRD patterns of the corrosion products at innerlayer were obtained by scrubbing off the surface product layerwith sand paper

3 Results

31 EIS Measurement The corresponding Bode phase plotsas shown in Figure 1 show two time constants during theinitial 48 hours but one time constant at high frequencyat 72 h and 120 h The characteristic frequency of the high-frequency loop is at 1000Hz through the whole process Theimpedance moduli begin to decrease after the disappearanceof time constant at frequency of 01 Hz in contrast to therelatively stable value during the first 48 hours

Over the whole corrosion process the Bode plots ofSS304 consist of only one time constant with a characteristicfrequency of 1000Hz and a line at low-frequency range asshown in Figure 2 It is noteworthy that the phase angle ofthe low frequency angle of the Bode plots decreases whenthe corrosion proceededThemoduli of the impedance at lowfrequency almost do not change with time

Figure 3 is the Bode plots of SS310 in molten carbonate atdifferent timesWhen the immersion time is prior to 12 hourstwo time constants one at 1000Hz and one at 05Hz can beidentified From 12 h onward to the end of the test a line atlow frequency in addition to the two time constants can befound in the impedance spectra

32 Scale Morphology and Phase Analysis Amultilayer scaleis formed on P92 after 120 h immersion in molten carbonateat 650∘C The thickness of the scale is 80 120583m and a darkerlayer in contact with the indented steel substrate as shown inFigure 4(a) An enlarged view of the inner layer (Figure 4(b))indicates that this layer is more porous than the out layerand some bright W or Mo particles are scattering in theoxide Parezanovic et al [25] found that Mo preferred tostay at the metal side in solid solution with spinel oxides

International Journal of Corrosion 3

0 5 10 15 20 250

5

10

15

10

20

30

40

001 101 10 100 1000 100001

10

0 5 10 15 20 250

5

Frequency (Hz)

10

15

10

20

30

001 101 10 100 1000 100001

10

Frequency (Hz)

minusZ

i(O

hmmiddotcm

2)

Zr (Ohmmiddotcm2)

Zr (Ohmmiddotcm2)

|Z|

(Ohm

middotcm2)

4 h8 h 24 h

24 h48 h

72 h

12 h 4 h8 h 24 h

12 h

120 h24 h48 h

72 h120 h

minusPh

ase (

deg)

minusPh

ase (

deg)

minusZ

i(O

hmmiddotcm

2)

|Z|

(Ohm

middotcm2)

Figure 1 Nyquist and Bode plots of P92 in molten carbonate at 650∘C in air Scattered points are measured data and lines are simulated data

and tungsten precipitates also situated on the matrix-scaleinterface in our case The EDX line plot along the scaleshows that no chromium-rich scale is formed in the wholerange and significant potassium can be detected in theporous scale close to the base metal Judging from the XRDresults in Figure 7(a) one can see that the outer layer wascomposed of LiFeO

2and K

2Fe2O4while the inner layer was

composed of FeO and FeCr2O4 At the eutectic composition

with x (Li2CO3) = 062 the production of LiFeO

2other

than K2Fe2O4at the scalemelt interface is attributed to

the lower stability of Li2CO3and higher Li activity even

though K2Fe2O4shows higher stability energy at 650∘C The

lithiation could happen with the transport of the Li ionthrough the LiFeO

2scale that combined with the incoming

Fe3+ ion to form new ternary oxides LiFeO2 However the

potassium is less likely to diffuse through the scale owingto its large ionic radius so the potassium containing oxidesare generally at the scalemelt interface as in K

2CrO4[11]

According to the phase diagramof Li-K-C-Fe [26] the porousK2Fe2O4can be a result of the direct penetration of the

viscous mixed carbonate into the metalscale interface andreact with newly formed Fe

2O3after the depletion of Li from

the melt in this area as is reported by Spiegel in the study ofcorrosion of metals underneath chlorides [27]

The scale on SS304 (Figure 5(a)) was 40 120583m thick andcontains three layers the 20120583m outermost layer and theinnermost layer are separated by a darker region in themiddle The outermost layer has even thickness in the wholerange and shows a clear boundary tithe the intermediate layerThe innermost layer has a rugged surface toward the metalside and is dispersed by bright particles The surface mor-phology of the scale on SS304 where the outermost layerspalled off is shown in Figure 8(a) The outermost layer iscomposed of compact crystals as shown in the enlarged viewin Figure 8(b) whose metallic elements judged from EDXare mostly Fe and slight Cr The surface morphology of


0 10 200

10

20

0102030405060

001 101 10 100 1000 10000

1

10

0 5 10 15 200

5

10

15

0

10

20

30

40

50

001 101 10 100 1000 10000

10

Frequency (Hz)

4 h8 h 24 h

12 h 4 h8 h 24 h

12 h

Frequency (Hz)

minusPh

ase (

deg)

minusPh

ase (

deg)

24 h48 h

72 h120 h

24 h48 h

72 h120 h

minusZ

i(O

hmmiddotcm

2)

minusZ

i(O

hmmiddotcm

2)

Zr (Ohmmiddotcm2)

Zr (Ohmmiddotcm2)

|Z|

(Ohm

middotcm2)

|Z|

(Ohm

middotcm2)

Figure 2 Nyquist and Bode plots of SS304 in molten carbonate at 650∘C in air Scattered points are measured data and lines are simulateddata

LiFeO2seems to be fairly dense but the cross-sectional image

indicates the existence of fissures throughout the scale Thecomposition of oxides on the top of intermediate layer was67 Cr-26 Fe-7 Ni in atomic percent Assisted by XRDpatterns in Figure 7(b) one can judge that the outer layer iscomposed of exclusively LiFeO

2 the intermediate layer mix-

ture is composed of LiFeO2and LiCrO

2and (Fe Ni)Cr

2O4

and Ni particles and the innermost layer is composed ofmainly (Fe Ni)Cr

2O4

A 10 120583m double-layered scale outgrows the 310 alloy sur-face after 120 h of corrosion as shown in Figure 6 The con-tinuous thin dark layer is surmounted by a bright layer con-taining bright particles on the surface and pore in themiddleA comparison between the XRD patterns (Figure 5(c)) of theinner layer and outer layer indicates that the outer layer wasLiFeO

2and the inner layer is LiCrO

2because the peaks of

LiFeO2stun much when the specimen is scrubbed with sand

paper to remove the top layer With EDX data the especiallybright particles on the surface containing 35 at Mn arethought to be Mn dissolved LiFeO

2[8]

33 Impedance Models The impedance spectra of P92 at theinitial stage showed clearly the features of a porous-scalecovered electrode Therefore the impedance model for thecorrosion of P92 at this stage may be described by circuitof Figure 9(a) where 119877

119890represents the electrolyte resistance

119862dl and 119862119891 represent the double-layer capacitance and oxidecapacitance respectively 119877ct and 119877119891 represent the charge-transfer resistance and oxide resistance respectively and 119860

119889

represents the diffusion-induced Warburg resistance Takinginto account the dispersion effect a constant phase angle


0 5 10 15 20 25 30 35 400

10

20

30

0102030405060

001 101 10 100 1000 100001

10

0 10 20 30 40 500

10

Frequency (Hz)

20

30

40

0102030405060

001 101 10 100 1000 100001

10

Frequency (Hz)

4 h8 h 24 h

12 h 4 h8 h 24 h

12 h

minusPh

ase (

deg)

minusPh

ase (

deg)

24 h48 h

72 h120 h

24 h48 h

72 h120 h

minusZ

i(O

hmmiddotcm

2)

minusZ

i(O

hmmiddotcm

2)

|Z|

(Ohm

middotcm2)

|Z|

(Ohm

middotcm2)

Zr (Ohmmiddotcm2)

Zr (Ohmmiddotcm2)


element (CPE) Q was used to describe the parameters 119862dland 119862

119891in the fitting procedure The impedance spectra at 72

and 120 h of P92 were fit for the diffusion-controlled reactionwhich could be simulated with the equivalent circuit inFigure 9(b) where 119885

119889was the diffusion-induced resistance

TheWarburg resistance 119885119889can be expressed by (1) Con-

sider

119885119889= 119860119889(119895120596)minus119899119889 (1)

where119860119889is the modulus of diffusion-induced resistance and

119899119889is the coefficient of diffusion impedance ranging between

0 and 1 related to the direction of the oxidants diffusionWhen 119899

119889is equal to 05 the diffusion direction of the oxidants

is parallel to their concentration gradient inmolten-salts andaccordingly the slope of the line at low frequency in Nyquist

plot is equal to 1 When 119899119889lt 05 the diffusion direction

of the oxidants deviates from their concentration gradient asituation denoted by ldquotangential diffusionrdquo and the slope ofthe line at low frequency in Nyquist plot is smaller than unityWhen n 05 lt 119899

119889lt 1 the diffusion process was impeded by

obstacles and the slope of the line at low frequency inNyquistplot is smaller than unity

According to the parameters in Table 2 the values of119877119891tend to increase and the values of 119877ct undulate with

time prior to the appearance of Warburg impedance atthe low frequency This may be resulted from the trade-inbetween the outgrowth of oxide layer which makes the oxidethicker and the dissolution process which compromises thecompactness of the scale The appearance of K

2Fe2O4causes

the abrupt appearance of the low-frequency loop and thesmall values of 119860

119889due to the porous nature of this oxide


100 120583m

(a)

Mo or W

20 120583m

FeO Fe3O4

K2Fe2O4

(b)

0 20 40 60 80

Fe

Cr

O K

(c)

Figure 4 SEMmorphology of P92 ((a) and (b)) after 120 h of corrosion in molten carbonate (b) is the enlarged figures in the rectangles for(a) (c) is the EDX composition profile across the line in (b)

Table 2 Results of the CNLS fit to EIS data of P92

Time 119877119890

Ω cm2119884dl

Ωminus1 Sminus119899dl cmminus2 119899dl

119877ctΩ cm2

119884119891

Ωminus1 Sminus119899dl cmminus2

119899119891

119877119891

Ω cm2119860119889

Ω S119899119889 cm2 119899119889

1205942

4 h 079 348 times 10minus2 049 354 020 044 11650 10 times 10minus3





72 h 088 850 times 10minus3 061 219 375 046 50 times 10minus4


and its damage on the integrity of scale The 119899119889value is less

than 05 indicating an infinite half-length diffusion affectedby tangential diffusion process Moreover the decline of 119877ctand 119860

119889suggest that the alloy suffered accelerated corrosion

The impedance spectra of SS304 at all test times showonlyone time constant close to the one at high-frequency part ofP92 and are consisted of one line at low frequency and a loopwhich can be simulated by equivalent circuit of Figure 9(b)This implies that the oxides on the surface may be permeable

to the molten carbonate In contrast to P92 the 119877ct of SS304increases persistently through the immersion test from 177to 317Ω cm2 as shown inTable 3The 119899

119889values for simulated

data of SS304 varied greatly from 073 to 047 meaning thediffusion process shifted from a finite diffusion length dueto the oxide growth to an infinite tangential diffusion Afterthe complete lithiation process of the Fe

2O3 the porous

LiFeO2scale is not able to inhibit the diffusion of charged

particles through the outer scale The 119877ct values undertook


100 120583m

(a)

20 120583m

(b)

0 20 40 60 80

Fe

Cr O

Ni

(c)

Figure 5 SEM morphology of SS304 ((a) and (b)) after 120 h of corrosion in molten carbonate (b) is the enlarged figures in the rectanglesfor (a) (c) is the EDX composition profile across the line in (b)

Table 3 Results of the CNLS fit to EIS data of SS304

Time 119877119890

Ω cm2119884dl


119877ctΩ cm2

119860119889

Ω S119899119889 cm2 119899119889

1205942








a prevalent increase and 119860119889remain fairly stable after the dip

from 4 to 8 h The steady increase of 119877ct could be a result ofconductive spinel blocking layers which does not contributeto a distinguishable 119877

119891but blocks the transport of ionic

particles between the metal and outer scaleThe impedance spectra before 12 h are showing two time

constants and a LiFeO2scale was formed so the equivalent

circuit of Figure 9(a) is applicable to this circumstance The

impedance spectra after 24 h own a line in the low-frequencyrange showing diffusion-controlled reaction because thelocalized failure of oxide scales and the circuit of Figure 9(c)can be used to fit the impedance data in this case Franginiand Loreti [14 16] used similar equivalent circuit to simulatethe impedance spectra of the corrosion of SS310 in moltencarbonate As can be seen from Table 4 the value of 119877ct ismuch larger than that of 119877

119891 the formation of oxide separated



Time 119877119890

Ω cm2119884119891

Ωminus1 Sminus119899119891 cmminus2

119899119891

119877119891

Ω cm2119884dl


119877ctΩ cm2

119860119889

Ω S119899119889 cm2 119899119889

1205942

4 h 100 138 times 10minus1 063 285 002 087 8707 mdash 69 times 10minus4


12 h 101 248 times 10minus2 056 119 011 057 2588 4950 087 82 times 10minus4





Dissolved Mn

20 120583m

Figure 6 SEM morphology of SS310 after 120 h of corrosion inmolten carbonate

the base alloy from the molten salt and the charge transferprocess is inhibited by the transport of charged particlesthrough the oxide scale The formation of chromium scalecan be used to interpret the large 119877

119891in the first 8 hours

and the lithiation happened can cause the abrupt decreaseof resistance and appearance of Warburg impedance from 12hours on After the diffusion element appears its value variesgreatly with immersion time and so was the value of 119877ctindicating the alteration of growth and dissolution of scalesduring the corrosion process However the 119899

119889is always larger

than 05 suggesting that the diffusion process is influenced bythe outgrowth of scale and lithiation process that causes theinfinite diffusion [16] Unlike the 119899

119889values for SS304 which

decrease from 073 to 047 the values for SS310 are above 077and slightly decrease over the immersion times indicatingthat the lithiation of the scale of SS310 lasts longer times

34 Validation of the Modeling with a Replicate Becausethe growth of a corrosion layer is a nucleation and growthprocess the small differences in the surface compositioncan lead to different corrosion products and varied kineticsof surface passivation and the microstructure of the scale

Keijzer et al [28] reported the three distinct open-circuitpotential variations within the first 24-hour immersionwhich indicates that the corrosion of Cr-containing steelcan vary with small perturbation at the initial stage Theelectrochemical impedancemeasurementswith the 120 hoursfor the three alloys are repeated as is called replicate and themodeling parameters are represented in Figure 10 One cansee that the 119877ct values for the three alloys are different by thefirst 40 hours of immersion but they converge to each other atthe end of the immersion test Even though there is a 10 hoursof lag between the appearance of diffusion-related elementfor the two replicates of P92 and SS304 the modeling stillholds during the 120-hour measurement The 119860

119889value for

the three alloys varies with time but the difference betweenthe two measurements for the same alloys diminishes at theend of the immersion tests The abrupt decrease of 119860

119889of

P92 at 85 h could be an abrupt appellation of the protectivescale The 119899

119889values for P92 are smaller than 05 but those for

SS304 decrease from 07 at the beginning to less than 05 at120 hours After the complete lithiation of the external Fe

2O3

film the 119899119889values are going to be less than 05 At the very

beginning of appearance of 119885119889 the 119899

119889values for both SS310

samples are close to 09 but the replicate shows an 119899119889value

smaller than 05 after 60 hours in contrast to the 119899119889values

listed in Table 4 The low 119899119889value suggests that the diffusion

in the microfissures of lithiation process is negligible thiscould be a result of denser chromia film on the metalscalesurface as indicated by the larger 119877ct of this sample during 10to 40 h and larger 119860

119889value between 40 and 100 h It is also

possible that the 119899119889value of the SS310 will decrease to a value

below 05 in longer immersion than 120 hours as the replicatedoes at 48 hours

4 Discussion

The corrosion of stainless steel is very complex becauseof the large number of components comprising the steeland because it can form multiple corrosion layers withmixed compositions However the oxidation of the metallicelements of the alloys can be reduced to the cathodic andanodic reactions on the cathode side the solubility of oxygenmolecular in molten carbonate is rather small and thusbefore being reduced it will be reduced to form O

2

minus or O2

2minus

through reactions (2) and (3) respectively which then was


20 40 60 80

(5) FeO(6) Steel substrate

5

5 4444

66

3

5

4

4

44

4

4

12 22

NF616 scrubbed

1 223

2

21

2

2NF616

2120579

(1) 120572-LiFeO2(2) 120574-LiFeO2(3) K2Fe2O4

(4) FeCr2O4 or Fe3O4

(a)

20 40 60 80

35 44 4 44

4

4

3

3

3 3

SS304 scrubbed

4

3

4

4

3

3

25

2

15

1

3

32

31

23

SS304

SS304 scrubbed

5

5

2120579

(1) 120572-LiFeO2(2) 120574-LiFeO2

(5) Substrate

(3) LiCrO2

(4) (Ni Fe) Cr2O4

(b)

20 40 60 80

3

3

3

1 1

SS310 scrubbed

1

12

22

3

3

311

1

1

1SS310

2120579

(1) 120572-LiFeO2

(3) Substrate(2) LiCrO2

(c)

Figure 7 XRD patterns for corrosion products on P92 (a) SS304 (b) and SS310 (c) after 120 h of immersion in molten carbonate

reduced to oxygen ion by the electrons provided by the anodereaction as in reaction (4) or (5) [21 29]

3O2+ 2CO

3

2minus997888rarr 4O

2

minus+ 2CO

2uarr (2)

O2+ 2CO

3

2minus997888rarr 2O

2

2minus+ 2CO

2uarr (3)

O2

2minus+ 2eminus 997888rarr 2O2minus (4)

O2

minus+ 3eminus 997888rarr 2O2minus (5)

Which reaction prevails depends on the acidity of the meltand in our case reactions (2) and (4) are the dominantreaction routes of oxygen in molten carbonate [30 31]

On the anode the metallic element M will be oxidizedthrough the reaction

M + 119899eminus 997888rarr M119899+ (119899 is the number of electrons) (6)

The metallic ion combines with oxygen ion to form oxidewhich can react with Li

2CO3or K2CO3to produce ternary

oxideWhen the Fe-Cr alloys are immersed in the molten car-

bonate chromium oxidizes faster than iron and chromium

oxide dissolvesmuch faster than iron oxide into the carbonateunder cathode gas [28] Hence when the chromium oxidedissolves a layer of iron oxide remains on the metal surfaceand then it is lithiated to form lithium ferrite whose solu-bility is determined to be 78 weight ppm in molten (Li

062

K038

)CO3at 650∘C [32] Unfortunately it is too porous to

prevent the corrosion of underlying metallic element Thecorrosion process of the three alloys diverged from oneanother thanks to the difference in chromium content andtheir manner of reaction with carbonate The scale on thesurface of the alloy could possibly be a mixture LiFeO

2and

LiCrO2depending on the Cr content

The chromium content of P92 was so low that noinner chromium oxide layer though the outer LiFeO

2was

supposed to prevent the oxide from catastrophic reactionwith the molten carbonate As the fast diffusion of inwardoxygen ion and outward diffusionwere not curbed that no Fe-or Cr-dominant scale can be distinguished throughout thescale leaving slightly Fe- or Cr-enriched layers due to thedifference of diffusion speed of Fe and Cr ion the existenceof continuous porous oxide layer also concurred with the EISdata and proposedmodel Given enough time FeO FeCr

2O4


0

Fe

Fe

Fe

Fe

Fe

Fe

Cr

Cr

Cr

CrCr

CrO

O

Ni NiNiAl

Si

Si

2 4 6 8 10 12 14 16(keV)

0 2 4 6 8 10 12 14 16(keV)

(a)

(b)

200 120583m

10 120583m

Spectrum 2

Spectrum 1

Figure 8 Surface morphology and EDX of the corrosion products on SS304 after 120 h of immersion in molten carbonate at 650∘C (a) is theoverview of the region where the outermost layer was partly spalled off and (b) is the enlarged view of the outermost layer

Re dlC

ctR fC

fR

(a)

Re

Zd

dlC

ctR

(b)

Zd

Re

dlC

ctR

fC

fR

(c)

Figure 9 Equivalent circuits for the corrosion of the three stainless steels in molten carbonate at 650∘C

or Fe3O4were able to precipitate where the oxygen pressure

was low enough beneath the thick LiFeO2layer but they

are confined to a 2120583m region on the bulk-metal surfaceAccording to the cross section image the inner layer was evenmore porous than the outer layer so the scale is permeable tomolten carbonate and the corrosion process was now subjectto the diffusion of ions in molten carbonate Judging fromthe simulated parameters of 119877ct and 119860119889 at this stage thecorrosion process was expedited along with the thickeningof inner layer The K

2Fe2O4is highly porous and in the

formation process the CO2is produced through reaction (6)

to enhance the delamination of scale from the substrate

Fe2O3+ K2CO3= K2Fe2O4+ CO2uarr (7)

Because SS304 contained 193 wt Cr a chromium-richoxide layer (67 Cr-26 Fe-7 Ni in atomic percent) wasable to persist beneath the LiFeO

2layer as the thin cap on top

of the intermediate layer This impure chromium oxide layerwas able to impede to some extent the diffusion of the inward


0 20 40 60 80 100 120

04

06

08

2345

05

1015

Time (hours)

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(a)

04

06

08

0

20

400 20 40 60 80 100 120

0 20 40 60 80 100 120

0 20 40 60 80 100 120

060810

Time (hours)

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(b)

0 20 40 60 80 100 12004060810

0

20

40

0100200300

Time (hours)

0 20 40 60 80 100 120

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(c)

Figure 10 Comparison of the simulated parameters of the P92 (a) SS304 (b) and SS310 (c) between two repetitions in terms of 119877ct (square)119860119889(circle) and 119899

119889(circle) The filled data corresponding to those listed in tables and the open mark are the replicate

oxygen ion andoutwardmetallic ion as indicated by 119899119889gt 05

With extended time insufficient chromiumdiffused from thesubstrate side to support the growth of oxide and thus thechromium content decreased gradually inward after 120 h ofcorrosion The composite of (Ni Fe)Cr

2O4 LiCrO

2 LiFeO

2

and Ni-rich metallic particle that replaced the chromium-rich layer undermined the blocking effect of the chromium-rich oxide layer and thus Warburg impedance appeared at48 h Previous investigations of the corrosion of Fe-basedalloys with similar content of Ni and Cr in molten carbonate[8] revealed that the formation of LiFeO

2was controlled

by outward diffusion of Fe ion and the formation of (NiFe)2CrO4by inward diffusion or transport of oxygen ion

which explained the wavy interface between the matrix andspinel oxide In the spots where the diffusion path of oxygenion were blocked by heterogeneous inclusions like nickel

particles or LiCrO2aggregations the matrix underwent

slower oxidation as shown in Figure 5(b) The blocking effectof the spinels causes the unbalanced diffusion path and theresultant indented scale structure

Therewas sufficient chromium in SS310 to form abundantchromium oxides which precipitated immediately after theformation of outer LiFeO

2layer and the alloy suffered a resul-

tant localized fast corrosion From 12 h onward a continuouschromium oxide that is LiCrO

2 layer was formed that the

diffusion of the ions was blocked by the continuous innerlayer so an infinite diffusion reaction can be seen from thesimulated parameters Takeuchi et al [17] reported that whenthe chromium content is up to 25wt in Fe-Cr alloy thecomposite of LiCrO

2and LiFeO

2tended to disappear Ahn

et al [33] reported that the decrease in the corrosion rate ofSS310 is much greater than that on SS316 at the initial stage


of the corrosion process thanks to the higher Cr contentin SS310 At extended immersion times the formation ofK2CrO4is possible and contributes to the Cr loss from the

inner scale thoughwe did not observe this in our study Fromour study we found that the significantly thinner scale onSS310 after 120 h compared with that on SS304 is very likelydue to purer LiCrO

2layer which could be a result of dense

chromia layer at the initial stage

5 Conclusion

EIS has been applied to monitor the corrosion of threestainless steels in molten carbonate at 650∘C for extendedtimes Proper equivalent circuits were proposed to explainthe corrosion mechanism by analyzing the impedance datain combination with laminated XRD pattern andmicroscopyimages Due to the high chromium content SS310 was theonly alloy that formed compact pure LiCrO

2which prevents

the diffusion of Fe ion and oxygen species Although achromium layer appeared to prevent the transport of materi-als at the beginning the blocking layer which contained largeamount of LiFeO

2 disintegrated afterwards and a spinel layer

was formed in the matrix side for SS304 With insufficientchromium P92was not able to fromany chromium-rich layerthroughout the whole test A double-layer scale formed onthe surface an outer layer containing LiFeO

2andK

2FeO2and

a porous inner layer containing FeO and Fe3O4FeCr

2O4

Conflict of Interests

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

Acknowledgment

This work was supported by the National Natural ScienceFoundation of China under Contracts nos 51371183 and50971129

References

[1] M Palm ldquoFe-Al materials for structural applications at hightemperatures current research at MPIErdquo International Journalof Materials Research vol 100 no 3 pp 277ndash287 2009

[2] C SNi L Y Lu C L Zeng andYNiu ldquoEvaluation of corrosionresistance of aluminium coating with and without annealingagainst molten carbonate using electrochemical impedancespectroscopyrdquo Journal of Power Sources vol 261 pp 162ndash1692014

[3] S Freni S Cavallaro M Aquino D Ravida and N GiordanoldquoLifetime-limiting factors for a molten carbonate fuel cellrdquoInternational Journal of Hydrogen Energy vol 19 no 4 pp 337ndash341 1994

[4] P BiedenkopfMM Bischoff andTWochner ldquoCorrosion phe-nomena of alloys and electrode materials in Molten carbonatefuel cellsrdquoMaterials and Corrosion vol 51 pp 287ndash302 2000

[5] A C Schoeler T D Kaun I Bloom M Lanagan and MKrumpelt ldquoCorrosion behavior and interfacial resistivity ofbipolar platematerials undermolten carbonate fuel cell cathode

conditionsrdquo Journal of the Electrochemical Society vol 147 no 3pp 916ndash921 2000

[6] C Yuh R Johnsen M Farooque and H Maru ldquoStatus ofcarbonate fuel cell materialsrdquo Journal of Power Sources vol 56no 1 pp 1ndash10 1995

[7] M Spiegel P Biedenkopf and H J Grabke ldquoCorrosion of ironbase alloys and high alloy steels in the Li

2CO3-K2CO3eutectic

mixturerdquo Corrosion Science vol 39 no 7 pp 1193ndash1210 1997[8] P Biedenkopf M Spiegel and H J Grabke ldquoHigh temperature

corrosion of low and high alloy steels under molten carbonatefuel cell conditionsrdquoMaterials and Corrosion vol 48 no 8 pp477ndash488 1997

[9] Z Chaoliu G Pingyi and W Weitao ldquoElectrochemical impe-dance of two-phase Ni-Ti alloys during corrosion in eutectic(062Li 038K)

2CO3at 650 ∘Crdquo Electrochimica Acta vol 49 no

14 pp 2271ndash2277 2004[10] C L Zeng W Wang and W T Wu ldquoElectrochemical-impe-

dance study of the corrosion of Ni and FeAl intermetallic alloyin molten (062Li 038K)

2CO3at 650 ∘Crdquo Oxidation of Metals

vol 53 no 3 pp 289ndash302 2000[11] F J Perez M P Hierro D Duday C Gomez M Romero

and L Daza ldquoHot-corrosion studies of separator plates of AISI-310 stainless steels in molten-carbonate fuel cellsrdquo Oxidation ofMetals vol 53 no 3 pp 375ndash398 2000

[12] B Young Yang and K Young Kim ldquoThe oxidation behavior ofNi-50Co alloy electrode in molten Li+K carbonate eutecticrdquoElectrochimica Acta vol 44 no 13 pp 2227ndash2234 1999

[13] S A Salih A N El-Masri and A M Baraka ldquoCorrosionbehaviour of some stainless steel alloys in molten alkali carbon-ates (I)rdquo Journal of Materials Science vol 36 no 10 pp 2547ndash2555 2001

[14] S Frangini ldquoTesting procedure to obtain reliable potentiody-namic polarization curves on type 310S stainless steel in alkalicarbonate meltsrdquo Materials and Corrosion vol 57 no 4 pp330ndash337 2006

[15] B Zhu G Lindbergh and D Simonsson ldquoComparison of elec-trochemical and surface characterisationmethods for investiga-tion of corrosion of bipolar plate materials in molten carbonatefuel cell Part I Electrochemical studyrdquo Corrosion Science vol41 no 8 pp 1497ndash1513 1999

[16] S Frangini and S Loreti ldquoThe role of temperature on thecorrosion and passivation of type 310S stainless steel in eutectic(Li + K) carbonate meltrdquo Journal of Power Sources vol 160 no2 pp 800ndash804 2006

[17] K Takeuchi A Nishijima K Ui N Koura and C-K LoongldquoCorrosion behavior of Fe-Cr alloys in Li

2CO3-K2CO3molten

carbonaterdquo Journal of the Electrochemical Society vol 152 no 9pp B364ndashB368 2005

[18] C L Zeng P Y Guo and W T Wu ldquoElectrochemicalimpedance spectra for the corrosion of two-phase Cu-15Al alloyin eutectic (Li K)

2CO3at 650 ∘C in airrdquoElectrochimicaActa vol

49 no 9-10 pp 1445ndash1450 2004[19] S Frangini ldquoCorrosion of metallic stack components in molten

carbonates critical issues and recent findingsrdquo Journal of PowerSources vol 182 no 2 pp 462ndash468 2008

[20] J Youn B Ryu M Shin et al ldquoEffect of CO2partial pressure

on the cathode lithiation in molten carbonate fuel cellsrdquoInternational Journal of Hydrogen Energy vol 37 no 24 pp19289ndash19294 2012

[21] T Nishina I Uchida and J R Selman ldquoGas electrode reactionsin molten carbonate media Part V Electrochemical analysis


of the oxygen reduction mechanism at a fully immersed goldelectroderdquo Journal of the Electrochemical Society vol 141 no 5pp 1191ndash1198 1994

[22] K-I Ota K Toda S Mitsushima and N Kamiya ldquoAcceleratedcorrosion of stainless steels with the presence ofmolten carbon-ates below 923Krdquo Bulletin of the Chemical Society of Japan vol75 no 4 pp 877ndash881 2002

[23] C S Ni L Y Lu C L Zeng and Y Niu ldquoElectrochemicalimpedance studies of the initial-stage corrosion of 310S stainlesssteel beneath thin film ofmolten (062Li038K)

2CO3at 650∘ Crdquo

Corrosion Science vol 53 no 3 pp 1018ndash1024 2011[24] S Mitsushima Y Nishimura N Kamiya and K-I Ota ldquoCor-

rosion model for iron in the presence of molten carbonaterdquoJournal of the Electrochemical Society vol 151 no 6 pp A825ndashA830 2004

[25] I Parezanovic E Strauch and M Spiegel ldquoDevelopment ofspinel forming alloys with improved electronic conductivity forMCFC applicationsrdquo Journal of Power Sources vol 135 no 1-2pp 52ndash61 2004

[26] H Yakakawa N Sakai T Kawada M Dokiya and K-I OtaldquoChemical potential diagrams for Fe-Cr-Li-K-C-O systemthermodynamic analysis on reaction profiles between alloysand alkali carbonaterdquo Journal of the Electrochemical Society vol140 no 12 pp 3565ndash3577 1993

[27] M Spiegel ldquoSalt melt induced corrosion of metallic materials inwaste incineration plantsrdquoMaterials and Corrosion vol 50 no7 pp 373ndash393 1999

[28] M Keijzer G Lindbergh K Hemmes P J J M van der PutJ Schoonman and J H W de Wit ldquoCorrosion of 304 stainlesssteel in molten-carbonate fuel cellsrdquo Journal of the Electrochem-ical Society vol 146 no 7 pp 2508ndash2516 1999

[29] S Frangini and S Scaccia ldquoThe role of foreign cations inenhancing the oxygen solubility properties of alkali moltencarbonate systems Brief survey of existing data and newresearch resultsrdquo International Journal of Hydrogen Energy vol39 pp 12266ndash12272 2014

[30] J G Gonzalez-Rodriguez M Cuellar-Hernandez M Gonza-lez-Castaneda V M Salinas-Bravo J Porcayo-Calderon andG Rosas ldquoEffect of heat treatment and chemical compositionon the corrosion behavior of FeAl intermetallics inmolten (Li +K) carbonaterdquo Journal of Power Sources vol 172 no 2 pp 799ndash804 2007

[31] F J Perez D Duday M P Hierro et al ldquoHot corrosion study ofcoated separator plates of molten carbonate fuel cells by slurryaluminidesrdquo Surface and Coatings Technology vol 161 no 2-3pp 293ndash301 2002

[32] H S Hsu J H DeVan and M Howell ldquoSolubilities of LiFeO2

and (LiK)2CrO4in Molten Alkali carbonates at 650∘Crdquo Journal

of the Electrochemical Society vol 34 no 9 pp 2146ndash2150 1987[33] S Ahn K Oh M Kim et al ldquoElectrochemical analysis on the

growth of oxide formed on stainless steels in molten carbonateat 650 ∘Crdquo International Journal of Hydrogen Energy vol 39 no23 pp 12291ndash12299 2014

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


resistance values obtained with the linear polarization Zhuet al [15] found that the corrosion rates estimated fromthe two electrochemical techniques concurred only at theinitial period of immersion before the formation of protectivescales The significant perturbations of the current in Tafelpolarization on the scale bring error to the calculation ofcorrosion rate while EIS is a good tool in studying theproperties of scales by applying small perturbation (lt10mV)to the system

The lithiation process is one of the reasons for theelectrolyte loss during the operating time of anMCFC [19 20]andmore importantly this process will change the propertiesof the scales of stainless steel under thin film of moltencarbonate [21ndash24] The corrosion of stainless steel in thecathode compartment or the immersion corrosion will lastlonger times than thin-film corrosion so longer testingwouldbe required to study the whole processThe surroundingmeltin dip-melt test will provide sufficient lithium and potassiumto react with the oxide scale Unlike the general short-termor instant testing this report serves to study the corrosionprocess of three commercial alloys with different chromiumcontent for extended times by impedance techniques interms of monitoring the outgrowth of oxide scale and thelithiation process To be specific the corrosion process ofthree commercial stainless steels P92 SS304 and SS310when immersed fully in molten (062Li 038K)

2CO3at

650∘C was investigated using EIS technique This techniqueprovides a real-time monitoring process of the experimentwithout disturbing the thermodynamic system so manymeasurements can be taken at different times to establish thecorrosion mechanism

2 Experimental

The powers of anhydrous carbonates 62 Li2CO3and 38

K2CO3in mole fraction were weighed and mixed in an

alumina crucible which was then placed in a cylindricalfurnace to be baked at 350∘C for 24 h in order to purgethe residual moisture And then the furnace was heated to650∘C at a ramp of 3∘Cmin Flat rectangular specimens werecut from bulk alloys and ground to 800 emery paper Thecompositions of the three alloys were shown in Table 1

A two-electrode system was used for the impedancemeasurements where the working electrode was identicalto reference electrode and auxiliary electrode The referenceprobe is connected to the probe of auxiliary electrode Theimpedance measurement is assumed to be at OCV and theimpedance for each sample should be the final impedancedivided by a factor of two A detailed experimental setupcan be found in [2] Two specimens of the same stainlesssteel were imbedded in an alumina tube and sealed withhigh temperature cement after a Fe-Cr lead wire had beenspot-welded on the fringe of each specimen The workingsurface of each electrode was 10mm times 8mm For each alloythe electrochemicalmeasurements are reproduced twice withthe same materials and working conditions to confirm thevalidity of the modeling

Electrochemical-impedance measurements up to 120 hwere performed at open-circuit potential in air between 001

Table 1 The compositions of the three commercial stainless steels

Stainless steel Composition (wt)P92 Fe-90Cr-18W-05Mn-04Mo-011Si-02VSS304 Fe-193Cr-94Ni-20Mn-09SiSS310 Fe-264Cr-185Ni-14Mn

and 1 times 105Hz with a M398 impedance system composedof a Princeton applied research (PAR) 5210 lock-in amplifierand a PAR 263 potentiostat interfaced through an IEEE 488bus to a compatible computer A fast Fourier transform (FFT)technique was employed for frequencies from 001 to 113Hzto increase measurement speed and lower the degree ofperturbation to the cell The amplitude of input sine signalwas 10 mV A commercial software (ZSimpWin) developedby PAR was used to fit the impedance spectra using complexnonlinear least squares (CNLS) method

The corroded samples were examined by X-ray diffrac-tion (XRD) and scanning electron microscopy (SEM) cou-pled with an energy-dispersive X-ray (EDX) microanalysissystem The XRD patterns of the corrosion products at innerlayer were obtained by scrubbing off the surface product layerwith sand paper

3 Results

31 EIS Measurement The corresponding Bode phase plotsas shown in Figure 1 show two time constants during theinitial 48 hours but one time constant at high frequencyat 72 h and 120 h The characteristic frequency of the high-frequency loop is at 1000Hz through the whole process Theimpedance moduli begin to decrease after the disappearanceof time constant at frequency of 01 Hz in contrast to therelatively stable value during the first 48 hours

Over the whole corrosion process the Bode plots ofSS304 consist of only one time constant with a characteristicfrequency of 1000Hz and a line at low-frequency range asshown in Figure 2 It is noteworthy that the phase angle ofthe low frequency angle of the Bode plots decreases whenthe corrosion proceededThemoduli of the impedance at lowfrequency almost do not change with time

Figure 3 is the Bode plots of SS310 in molten carbonate atdifferent timesWhen the immersion time is prior to 12 hourstwo time constants one at 1000Hz and one at 05Hz can beidentified From 12 h onward to the end of the test a line atlow frequency in addition to the two time constants can befound in the impedance spectra

32 Scale Morphology and Phase Analysis Amultilayer scaleis formed on P92 after 120 h immersion in molten carbonateat 650∘C The thickness of the scale is 80 120583m and a darkerlayer in contact with the indented steel substrate as shown inFigure 4(a) An enlarged view of the inner layer (Figure 4(b))indicates that this layer is more porous than the out layerand some bright W or Mo particles are scattering in theoxide Parezanovic et al [25] found that Mo preferred tostay at the metal side in solid solution with spinel oxides


0 5 10 15 20 250

5

10

15

10

20

30

40

001 101 10 100 1000 100001

10

0 5 10 15 20 250

5

Frequency (Hz)

10

15

10

20

30

001 101 10 100 1000 100001

10

Frequency (Hz)

minusZ

i(O

hmmiddotcm

2)

Zr (Ohmmiddotcm2)

Zr (Ohmmiddotcm2)

|Z|

(Ohm

middotcm2)

4 h8 h 24 h

24 h48 h

72 h

12 h 4 h8 h 24 h

12 h

120 h24 h48 h

72 h120 h

minusPh

ase (

deg)

minusPh

ase (

deg)

minusZ

i(O

hmmiddotcm

2)

|Z|

(Ohm

middotcm2)



2and K




2other








2CrO4[11]







0 10 200

10

20

0102030405060

001 101 10 100 1000 10000

1

10

0 5 10 15 200

5

10

15

0

10

20

30

40

50

001 101 10 100 1000 10000

10

Frequency (Hz)

4 h8 h 24 h

12 h 4 h8 h 24 h

12 h

Frequency (Hz)

minusPh

ase (

deg)

minusPh

ase (

deg)

24 h48 h

72 h120 h

24 h48 h

72 h120 h

minusZ

i(O

hmmiddotcm

2)

minusZ

i(O

hmmiddotcm

2)

Zr (Ohmmiddotcm2)

Zr (Ohmmiddotcm2)

|Z|

(Ohm

middotcm2)

|Z|

(Ohm

middotcm2)






2and (Fe Ni)Cr

2O4


2O4






2[8]




119889



0 5 10 15 20 25 30 35 400

10

20

30

0102030405060

001 101 10 100 1000 100001

10

0 10 20 30 40 500

10

Frequency (Hz)

20

30

40

0102030405060

001 101 10 100 1000 100001

10

Frequency (Hz)

4 h8 h 24 h

12 h 4 h8 h 24 h

12 h

minusPh

ase (

deg)

minusPh

ase (

deg)

24 h48 h

72 h120 h

24 h48 h

72 h120 h

minusZ

i(O

hmmiddotcm

2)

minusZ

i(O

hmmiddotcm

2)

|Z|

(Ohm

middotcm2)

|Z|

(Ohm

middotcm2)

Zr (Ohmmiddotcm2)

Zr (Ohmmiddotcm2)







sider

119885119889= 119860119889(119895120596)minus119899119889 (1)












2Fe2O4causes




100 120583m

(a)

Mo or W

20 120583m

FeO Fe3O4

K2Fe2O4

(b)

0 20 40 60 80

Fe

Cr

O K

(c)



Time 119877119890

Ω cm2119884dl


119877ctΩ cm2

119884119891


119899119891

119877119891

Ω cm2119860119889

Ω S119899119889 cm2 119899119889

1205942















2O3 the porous




100 120583m

(a)

20 120583m

(b)

0 20 40 60 80

Fe

Cr O

Ni

(c)



Time 119877119890

Ω cm2119884dl


119877ctΩ cm2

119860119889

Ω S119899119889 cm2 119899119889

1205942


















Time 119877119890

Ω cm2119884119891


119899119891

119877119891

Ω cm2119884dl


119877ctΩ cm2

119860119889

Ω S119899119889 cm2 119899119889

1205942








Dissolved Mn

20 120583m











119889value for


119889of




2O3











4 Discussion


2

minus or O2

2minus



20 40 60 80


5

5 4444

66

3

5

4

4

44

4

4

12 22

NF616 scrubbed

1 223

2

21

2

2NF616

2120579

(1) 120572-LiFeO2(2) 120574-LiFeO2(3) K2Fe2O4


(a)

20 40 60 80

35 44 4 44

4

4

3

3

3 3

SS304 scrubbed

4

3

4

4

3

3

25

2

15

1

3

32

31

23

SS304

SS304 scrubbed

5

5

2120579

(1) 120572-LiFeO2(2) 120574-LiFeO2

(5) Substrate

(3) LiCrO2

(4) (Ni Fe) Cr2O4

(b)

20 40 60 80

3

3

3

1 1

SS310 scrubbed

1

12

22

3

3

311

1

1

1SS310

2120579

(1) 120572-LiFeO2


(c)



3O2+ 2CO

3

2minus997888rarr 4O

2

minus+ 2CO

2uarr (2)

O2+ 2CO

3

2minus997888rarr 2O

2

2minus+ 2CO

2uarr (3)

O2


O2










062

K038



2and



2was


2O4


0

Fe

Fe

Fe

Fe

Fe

Fe

Cr

Cr

Cr

CrCr

CrO

O

Ni NiNiAl

Si

Si

2 4 6 8 10 12 14 16(keV)

0 2 4 6 8 10 12 14 16(keV)

(a)

(b)

200 120583m

10 120583m

Spectrum 2

Spectrum 1


Re dlC

ctR fC

fR

(a)

Re

Zd

dlC

ctR

(b)

Zd

Re

dlC

ctR

fC

fR

(c)













0 20 40 60 80 100 120

04

06

08

2345

05

1015

Time (hours)

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(a)

04

06

08

0

20

400 20 40 60 80 100 120

0 20 40 60 80 100 120

0 20 40 60 80 100 120

060810

Time (hours)

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(b)

0 20 40 60 80 100 12004060810

0

20

40

0100200300

Time (hours)

0 20 40 60 80 100 120

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(c)





2O4 LiCrO

2 LiFeO

2


2was controlled










2and LiFeO








5 Conclusion


2which prevents




2andK

2FeO2and


2O4



Acknowledgment


References









2CO3-K2CO3eutectic
















2CO3-K2CO3molten


































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0 5 10 15 20 250

5

10

15

10

20

30

40

001 101 10 100 1000 100001

10

0 5 10 15 20 250

5

Frequency (Hz)

10

15

10

20

30

001 101 10 100 1000 100001

10

Frequency (Hz)

minusZ

i(O

hmmiddotcm

2)

Zr (Ohmmiddotcm2)

Zr (Ohmmiddotcm2)

|Z|

(Ohm

middotcm2)

4 h8 h 24 h

24 h48 h

72 h

12 h 4 h8 h 24 h

12 h

120 h24 h48 h

72 h120 h

minusPh

ase (

deg)

minusPh

ase (

deg)

minusZ

i(O

hmmiddotcm

2)

|Z|

(Ohm

middotcm2)



2and K




2other








2CrO4[11]







0 10 200

10

20

0102030405060

001 101 10 100 1000 10000

1

10

0 5 10 15 200

5

10

15

0

10

20

30

40

50

001 101 10 100 1000 10000

10

Frequency (Hz)

4 h8 h 24 h

12 h 4 h8 h 24 h

12 h

Frequency (Hz)

minusPh

ase (

deg)

minusPh

ase (

deg)

24 h48 h

72 h120 h

24 h48 h

72 h120 h

minusZ

i(O

hmmiddotcm

2)

minusZ

i(O

hmmiddotcm

2)

Zr (Ohmmiddotcm2)

Zr (Ohmmiddotcm2)

|Z|

(Ohm

middotcm2)

|Z|

(Ohm

middotcm2)






2and (Fe Ni)Cr

2O4


2O4






2[8]




119889



0 5 10 15 20 25 30 35 400

10

20

30

0102030405060

001 101 10 100 1000 100001

10

0 10 20 30 40 500

10

Frequency (Hz)

20

30

40

0102030405060

001 101 10 100 1000 100001

10

Frequency (Hz)

4 h8 h 24 h

12 h 4 h8 h 24 h

12 h

minusPh

ase (

deg)

minusPh

ase (

deg)

24 h48 h

72 h120 h

24 h48 h

72 h120 h

minusZ

i(O

hmmiddotcm

2)

minusZ

i(O

hmmiddotcm

2)

|Z|

(Ohm

middotcm2)

|Z|

(Ohm

middotcm2)

Zr (Ohmmiddotcm2)

Zr (Ohmmiddotcm2)







sider

119885119889= 119860119889(119895120596)minus119899119889 (1)












2Fe2O4causes




100 120583m

(a)

Mo or W

20 120583m

FeO Fe3O4

K2Fe2O4

(b)

0 20 40 60 80

Fe

Cr

O K

(c)



Time 119877119890

Ω cm2119884dl


119877ctΩ cm2

119884119891


119899119891

119877119891

Ω cm2119860119889

Ω S119899119889 cm2 119899119889

1205942















2O3 the porous




100 120583m

(a)

20 120583m

(b)

0 20 40 60 80

Fe

Cr O

Ni

(c)



Time 119877119890

Ω cm2119884dl


119877ctΩ cm2

119860119889

Ω S119899119889 cm2 119899119889

1205942


















Time 119877119890

Ω cm2119884119891


119899119891

119877119891

Ω cm2119884dl


119877ctΩ cm2

119860119889

Ω S119899119889 cm2 119899119889

1205942








Dissolved Mn

20 120583m











119889value for


119889of




2O3











4 Discussion


2

minus or O2

2minus



20 40 60 80


5

5 4444

66

3

5

4

4

44

4

4

12 22

NF616 scrubbed

1 223

2

21

2

2NF616

2120579

(1) 120572-LiFeO2(2) 120574-LiFeO2(3) K2Fe2O4


(a)

20 40 60 80

35 44 4 44

4

4

3

3

3 3

SS304 scrubbed

4

3

4

4

3

3

25

2

15

1

3

32

31

23

SS304

SS304 scrubbed

5

5

2120579

(1) 120572-LiFeO2(2) 120574-LiFeO2

(5) Substrate

(3) LiCrO2

(4) (Ni Fe) Cr2O4

(b)

20 40 60 80

3

3

3

1 1

SS310 scrubbed

1

12

22

3

3

311

1

1

1SS310

2120579

(1) 120572-LiFeO2


(c)



3O2+ 2CO

3

2minus997888rarr 4O

2

minus+ 2CO

2uarr (2)

O2+ 2CO

3

2minus997888rarr 2O

2

2minus+ 2CO

2uarr (3)

O2


O2










062

K038



2and



2was


2O4


0

Fe

Fe

Fe

Fe

Fe

Fe

Cr

Cr

Cr

CrCr

CrO

O

Ni NiNiAl

Si

Si

2 4 6 8 10 12 14 16(keV)

0 2 4 6 8 10 12 14 16(keV)

(a)

(b)

200 120583m

10 120583m

Spectrum 2

Spectrum 1


Re dlC

ctR fC

fR

(a)

Re

Zd

dlC

ctR

(b)

Zd

Re

dlC

ctR

fC

fR

(c)













0 20 40 60 80 100 120

04

06

08

2345

05

1015

Time (hours)

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(a)

04

06

08

0

20

400 20 40 60 80 100 120

0 20 40 60 80 100 120

0 20 40 60 80 100 120

060810

Time (hours)

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(b)

0 20 40 60 80 100 12004060810

0

20

40

0100200300

Time (hours)

0 20 40 60 80 100 120

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(c)





2O4 LiCrO

2 LiFeO

2


2was controlled










2and LiFeO








5 Conclusion


2which prevents




2andK

2FeO2and


2O4



Acknowledgment


References









2CO3-K2CO3eutectic
















2CO3-K2CO3molten


































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0 10 200

10

20

0102030405060

001 101 10 100 1000 10000

1

10

0 5 10 15 200

5

10

15

0

10

20

30

40

50

001 101 10 100 1000 10000

10

Frequency (Hz)

4 h8 h 24 h

12 h 4 h8 h 24 h

12 h

Frequency (Hz)

minusPh

ase (

deg)

minusPh

ase (

deg)

24 h48 h

72 h120 h

24 h48 h

72 h120 h

minusZ

i(O

hmmiddotcm

2)

minusZ

i(O

hmmiddotcm

2)

Zr (Ohmmiddotcm2)

Zr (Ohmmiddotcm2)

|Z|

(Ohm

middotcm2)

|Z|

(Ohm

middotcm2)






2and (Fe Ni)Cr

2O4


2O4






2[8]




119889



0 5 10 15 20 25 30 35 400

10

20

30

0102030405060

001 101 10 100 1000 100001

10

0 10 20 30 40 500

10

Frequency (Hz)

20

30

40

0102030405060

001 101 10 100 1000 100001

10

Frequency (Hz)

4 h8 h 24 h

12 h 4 h8 h 24 h

12 h

minusPh

ase (

deg)

minusPh

ase (

deg)

24 h48 h

72 h120 h

24 h48 h

72 h120 h

minusZ

i(O

hmmiddotcm

2)

minusZ

i(O

hmmiddotcm

2)

|Z|

(Ohm

middotcm2)

|Z|

(Ohm

middotcm2)

Zr (Ohmmiddotcm2)

Zr (Ohmmiddotcm2)







sider

119885119889= 119860119889(119895120596)minus119899119889 (1)












2Fe2O4causes




100 120583m

(a)

Mo or W

20 120583m

FeO Fe3O4

K2Fe2O4

(b)

0 20 40 60 80

Fe

Cr

O K

(c)



Time 119877119890

Ω cm2119884dl


119877ctΩ cm2

119884119891


119899119891

119877119891

Ω cm2119860119889

Ω S119899119889 cm2 119899119889

1205942















2O3 the porous




100 120583m

(a)

20 120583m

(b)

0 20 40 60 80

Fe

Cr O

Ni

(c)



Time 119877119890

Ω cm2119884dl


119877ctΩ cm2

119860119889

Ω S119899119889 cm2 119899119889

1205942


















Time 119877119890

Ω cm2119884119891


119899119891

119877119891

Ω cm2119884dl


119877ctΩ cm2

119860119889

Ω S119899119889 cm2 119899119889

1205942








Dissolved Mn

20 120583m











119889value for


119889of




2O3











4 Discussion


2

minus or O2

2minus



20 40 60 80


5

5 4444

66

3

5

4

4

44

4

4

12 22

NF616 scrubbed

1 223

2

21

2

2NF616

2120579

(1) 120572-LiFeO2(2) 120574-LiFeO2(3) K2Fe2O4


(a)

20 40 60 80

35 44 4 44

4

4

3

3

3 3

SS304 scrubbed

4

3

4

4

3

3

25

2

15

1

3

32

31

23

SS304

SS304 scrubbed

5

5

2120579

(1) 120572-LiFeO2(2) 120574-LiFeO2

(5) Substrate

(3) LiCrO2

(4) (Ni Fe) Cr2O4

(b)

20 40 60 80

3

3

3

1 1

SS310 scrubbed

1

12

22

3

3

311

1

1

1SS310

2120579

(1) 120572-LiFeO2


(c)



3O2+ 2CO

3

2minus997888rarr 4O

2

minus+ 2CO

2uarr (2)

O2+ 2CO

3

2minus997888rarr 2O

2

2minus+ 2CO

2uarr (3)

O2


O2










062

K038



2and



2was


2O4


0

Fe

Fe

Fe

Fe

Fe

Fe

Cr

Cr

Cr

CrCr

CrO

O

Ni NiNiAl

Si

Si

2 4 6 8 10 12 14 16(keV)

0 2 4 6 8 10 12 14 16(keV)

(a)

(b)

200 120583m

10 120583m

Spectrum 2

Spectrum 1


Re dlC

ctR fC

fR

(a)

Re

Zd

dlC

ctR

(b)

Zd

Re

dlC

ctR

fC

fR

(c)













0 20 40 60 80 100 120

04

06

08

2345

05

1015

Time (hours)

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(a)

04

06

08

0

20

400 20 40 60 80 100 120

0 20 40 60 80 100 120

0 20 40 60 80 100 120

060810

Time (hours)

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(b)

0 20 40 60 80 100 12004060810

0

20

40

0100200300

Time (hours)

0 20 40 60 80 100 120

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(c)





2O4 LiCrO

2 LiFeO

2


2was controlled










2and LiFeO








5 Conclusion


2which prevents




2andK

2FeO2and


2O4



Acknowledgment


References









2CO3-K2CO3eutectic
















2CO3-K2CO3molten


































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0 5 10 15 20 25 30 35 400

10

20

30

0102030405060

001 101 10 100 1000 100001

10

0 10 20 30 40 500

10

Frequency (Hz)

20

30

40

0102030405060

001 101 10 100 1000 100001

10

Frequency (Hz)

4 h8 h 24 h

12 h 4 h8 h 24 h

12 h

minusPh

ase (

deg)

minusPh

ase (

deg)

24 h48 h

72 h120 h

24 h48 h

72 h120 h

minusZ

i(O

hmmiddotcm

2)

minusZ

i(O

hmmiddotcm

2)

|Z|

(Ohm

middotcm2)

|Z|

(Ohm

middotcm2)

Zr (Ohmmiddotcm2)

Zr (Ohmmiddotcm2)







sider

119885119889= 119860119889(119895120596)minus119899119889 (1)












2Fe2O4causes




100 120583m

(a)

Mo or W

20 120583m

FeO Fe3O4

K2Fe2O4

(b)

0 20 40 60 80

Fe

Cr

O K

(c)



Time 119877119890

Ω cm2119884dl


119877ctΩ cm2

119884119891


119899119891

119877119891

Ω cm2119860119889

Ω S119899119889 cm2 119899119889

1205942















2O3 the porous




100 120583m

(a)

20 120583m

(b)

0 20 40 60 80

Fe

Cr O

Ni

(c)



Time 119877119890

Ω cm2119884dl


119877ctΩ cm2

119860119889

Ω S119899119889 cm2 119899119889

1205942


















Time 119877119890

Ω cm2119884119891


119899119891

119877119891

Ω cm2119884dl


119877ctΩ cm2

119860119889

Ω S119899119889 cm2 119899119889

1205942








Dissolved Mn

20 120583m











119889value for


119889of




2O3











4 Discussion


2

minus or O2

2minus



20 40 60 80


5

5 4444

66

3

5

4

4

44

4

4

12 22

NF616 scrubbed

1 223

2

21

2

2NF616

2120579

(1) 120572-LiFeO2(2) 120574-LiFeO2(3) K2Fe2O4


(a)

20 40 60 80

35 44 4 44

4

4

3

3

3 3

SS304 scrubbed

4

3

4

4

3

3

25

2

15

1

3

32

31

23

SS304

SS304 scrubbed

5

5

2120579

(1) 120572-LiFeO2(2) 120574-LiFeO2

(5) Substrate

(3) LiCrO2

(4) (Ni Fe) Cr2O4

(b)

20 40 60 80

3

3

3

1 1

SS310 scrubbed

1

12

22

3

3

311

1

1

1SS310

2120579

(1) 120572-LiFeO2


(c)



3O2+ 2CO

3

2minus997888rarr 4O

2

minus+ 2CO

2uarr (2)

O2+ 2CO

3

2minus997888rarr 2O

2

2minus+ 2CO

2uarr (3)

O2


O2










062

K038



2and



2was


2O4


0

Fe

Fe

Fe

Fe

Fe

Fe

Cr

Cr

Cr

CrCr

CrO

O

Ni NiNiAl

Si

Si

2 4 6 8 10 12 14 16(keV)

0 2 4 6 8 10 12 14 16(keV)

(a)

(b)

200 120583m

10 120583m

Spectrum 2

Spectrum 1


Re dlC

ctR fC

fR

(a)

Re

Zd

dlC

ctR

(b)

Zd

Re

dlC

ctR

fC

fR

(c)













0 20 40 60 80 100 120

04

06

08

2345

05

1015

Time (hours)

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(a)

04

06

08

0

20

400 20 40 60 80 100 120

0 20 40 60 80 100 120

0 20 40 60 80 100 120

060810

Time (hours)

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(b)

0 20 40 60 80 100 12004060810

0

20

40

0100200300

Time (hours)

0 20 40 60 80 100 120

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(c)





2O4 LiCrO

2 LiFeO

2


2was controlled










2and LiFeO








5 Conclusion


2which prevents




2andK

2FeO2and


2O4



Acknowledgment


References









2CO3-K2CO3eutectic
















2CO3-K2CO3molten


































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




100 120583m

(a)

Mo or W

20 120583m

FeO Fe3O4

K2Fe2O4

(b)

0 20 40 60 80

Fe

Cr

O K

(c)



Time 119877119890

Ω cm2119884dl


119877ctΩ cm2

119884119891


119899119891

119877119891

Ω cm2119860119889

Ω S119899119889 cm2 119899119889

1205942















2O3 the porous




100 120583m

(a)

20 120583m

(b)

0 20 40 60 80

Fe

Cr O

Ni

(c)



Time 119877119890

Ω cm2119884dl


119877ctΩ cm2

119860119889

Ω S119899119889 cm2 119899119889

1205942


















Time 119877119890

Ω cm2119884119891


119899119891

119877119891

Ω cm2119884dl


119877ctΩ cm2

119860119889

Ω S119899119889 cm2 119899119889

1205942








Dissolved Mn

20 120583m











119889value for


119889of




2O3











4 Discussion


2

minus or O2

2minus



20 40 60 80


5

5 4444

66

3

5

4

4

44

4

4

12 22

NF616 scrubbed

1 223

2

21

2

2NF616

2120579

(1) 120572-LiFeO2(2) 120574-LiFeO2(3) K2Fe2O4


(a)

20 40 60 80

35 44 4 44

4

4

3

3

3 3

SS304 scrubbed

4

3

4

4

3

3

25

2

15

1

3

32

31

23

SS304

SS304 scrubbed

5

5

2120579

(1) 120572-LiFeO2(2) 120574-LiFeO2

(5) Substrate

(3) LiCrO2

(4) (Ni Fe) Cr2O4

(b)

20 40 60 80

3

3

3

1 1

SS310 scrubbed

1

12

22

3

3

311

1

1

1SS310

2120579

(1) 120572-LiFeO2


(c)



3O2+ 2CO

3

2minus997888rarr 4O

2

minus+ 2CO

2uarr (2)

O2+ 2CO

3

2minus997888rarr 2O

2

2minus+ 2CO

2uarr (3)

O2


O2










062

K038



2and



2was


2O4


0

Fe

Fe

Fe

Fe

Fe

Fe

Cr

Cr

Cr

CrCr

CrO

O

Ni NiNiAl

Si

Si

2 4 6 8 10 12 14 16(keV)

0 2 4 6 8 10 12 14 16(keV)

(a)

(b)

200 120583m

10 120583m

Spectrum 2

Spectrum 1


Re dlC

ctR fC

fR

(a)

Re

Zd

dlC

ctR

(b)

Zd

Re

dlC

ctR

fC

fR

(c)













0 20 40 60 80 100 120

04

06

08

2345

05

1015

Time (hours)

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(a)

04

06

08

0

20

400 20 40 60 80 100 120

0 20 40 60 80 100 120

0 20 40 60 80 100 120

060810

Time (hours)

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(b)

0 20 40 60 80 100 12004060810

0

20

40

0100200300

Time (hours)

0 20 40 60 80 100 120

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(c)





2O4 LiCrO

2 LiFeO

2


2was controlled










2and LiFeO








5 Conclusion


2which prevents




2andK

2FeO2and


2O4



Acknowledgment


References









2CO3-K2CO3eutectic
















2CO3-K2CO3molten


































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




100 120583m

(a)

20 120583m

(b)

0 20 40 60 80

Fe

Cr O

Ni

(c)



Time 119877119890

Ω cm2119884dl


119877ctΩ cm2

119860119889

Ω S119899119889 cm2 119899119889

1205942


















Time 119877119890

Ω cm2119884119891


119899119891

119877119891

Ω cm2119884dl


119877ctΩ cm2

119860119889

Ω S119899119889 cm2 119899119889

1205942








Dissolved Mn

20 120583m











119889value for


119889of




2O3











4 Discussion


2

minus or O2

2minus



20 40 60 80


5

5 4444

66

3

5

4

4

44

4

4

12 22

NF616 scrubbed

1 223

2

21

2

2NF616

2120579

(1) 120572-LiFeO2(2) 120574-LiFeO2(3) K2Fe2O4


(a)

20 40 60 80

35 44 4 44

4

4

3

3

3 3

SS304 scrubbed

4

3

4

4

3

3

25

2

15

1

3

32

31

23

SS304

SS304 scrubbed

5

5

2120579

(1) 120572-LiFeO2(2) 120574-LiFeO2

(5) Substrate

(3) LiCrO2

(4) (Ni Fe) Cr2O4

(b)

20 40 60 80

3

3

3

1 1

SS310 scrubbed

1

12

22

3

3

311

1

1

1SS310

2120579

(1) 120572-LiFeO2


(c)



3O2+ 2CO

3

2minus997888rarr 4O

2

minus+ 2CO

2uarr (2)

O2+ 2CO

3

2minus997888rarr 2O

2

2minus+ 2CO

2uarr (3)

O2


O2










062

K038



2and



2was


2O4


0

Fe

Fe

Fe

Fe

Fe

Fe

Cr

Cr

Cr

CrCr

CrO

O

Ni NiNiAl

Si

Si

2 4 6 8 10 12 14 16(keV)

0 2 4 6 8 10 12 14 16(keV)

(a)

(b)

200 120583m

10 120583m

Spectrum 2

Spectrum 1


Re dlC

ctR fC

fR

(a)

Re

Zd

dlC

ctR

(b)

Zd

Re

dlC

ctR

fC

fR

(c)













0 20 40 60 80 100 120

04

06

08

2345

05

1015

Time (hours)

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(a)

04

06

08

0

20

400 20 40 60 80 100 120

0 20 40 60 80 100 120

0 20 40 60 80 100 120

060810

Time (hours)

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(b)

0 20 40 60 80 100 12004060810

0

20

40

0100200300

Time (hours)

0 20 40 60 80 100 120

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(c)





2O4 LiCrO

2 LiFeO

2


2was controlled










2and LiFeO








5 Conclusion


2which prevents




2andK

2FeO2and


2O4



Acknowledgment


References









2CO3-K2CO3eutectic
















2CO3-K2CO3molten


































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





Time 119877119890

Ω cm2119884119891


119899119891

119877119891

Ω cm2119884dl


119877ctΩ cm2

119860119889

Ω S119899119889 cm2 119899119889

1205942








Dissolved Mn

20 120583m











119889value for


119889of




2O3











4 Discussion


2

minus or O2

2minus



20 40 60 80


5

5 4444

66

3

5

4

4

44

4

4

12 22

NF616 scrubbed

1 223

2

21

2

2NF616

2120579

(1) 120572-LiFeO2(2) 120574-LiFeO2(3) K2Fe2O4


(a)

20 40 60 80

35 44 4 44

4

4

3

3

3 3

SS304 scrubbed

4

3

4

4

3

3

25

2

15

1

3

32

31

23

SS304

SS304 scrubbed

5

5

2120579

(1) 120572-LiFeO2(2) 120574-LiFeO2

(5) Substrate

(3) LiCrO2

(4) (Ni Fe) Cr2O4

(b)

20 40 60 80

3

3

3

1 1

SS310 scrubbed

1

12

22

3

3

311

1

1

1SS310

2120579

(1) 120572-LiFeO2


(c)



3O2+ 2CO

3

2minus997888rarr 4O

2

minus+ 2CO

2uarr (2)

O2+ 2CO

3

2minus997888rarr 2O

2

2minus+ 2CO

2uarr (3)

O2


O2










062

K038



2and



2was


2O4


0

Fe

Fe

Fe

Fe

Fe

Fe

Cr

Cr

Cr

CrCr

CrO

O

Ni NiNiAl

Si

Si

2 4 6 8 10 12 14 16(keV)

0 2 4 6 8 10 12 14 16(keV)

(a)

(b)

200 120583m

10 120583m

Spectrum 2

Spectrum 1


Re dlC

ctR fC

fR

(a)

Re

Zd

dlC

ctR

(b)

Zd

Re

dlC

ctR

fC

fR

(c)













0 20 40 60 80 100 120

04

06

08

2345

05

1015

Time (hours)

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(a)

04

06

08

0

20

400 20 40 60 80 100 120

0 20 40 60 80 100 120

0 20 40 60 80 100 120

060810

Time (hours)

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(b)

0 20 40 60 80 100 12004060810

0

20

40

0100200300

Time (hours)

0 20 40 60 80 100 120

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(c)





2O4 LiCrO

2 LiFeO

2


2was controlled










2and LiFeO








5 Conclusion


2which prevents




2andK

2FeO2and


2O4



Acknowledgment


References









2CO3-K2CO3eutectic
















2CO3-K2CO3molten


































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




20 40 60 80


5

5 4444

66

3

5

4

4

44

4

4

12 22

NF616 scrubbed

1 223

2

21

2

2NF616

2120579

(1) 120572-LiFeO2(2) 120574-LiFeO2(3) K2Fe2O4


(a)

20 40 60 80

35 44 4 44

4

4

3

3

3 3

SS304 scrubbed

4

3

4

4

3

3

25

2

15

1

3

32

31

23

SS304

SS304 scrubbed

5

5

2120579

(1) 120572-LiFeO2(2) 120574-LiFeO2

(5) Substrate

(3) LiCrO2

(4) (Ni Fe) Cr2O4

(b)

20 40 60 80

3

3

3

1 1

SS310 scrubbed

1

12

22

3

3

311

1

1

1SS310

2120579

(1) 120572-LiFeO2


(c)



3O2+ 2CO

3

2minus997888rarr 4O

2

minus+ 2CO

2uarr (2)

O2+ 2CO

3

2minus997888rarr 2O

2

2minus+ 2CO

2uarr (3)

O2


O2










062

K038



2and



2was


2O4


0

Fe

Fe

Fe

Fe

Fe

Fe

Cr

Cr

Cr

CrCr

CrO

O

Ni NiNiAl

Si

Si

2 4 6 8 10 12 14 16(keV)

0 2 4 6 8 10 12 14 16(keV)

(a)

(b)

200 120583m

10 120583m

Spectrum 2

Spectrum 1


Re dlC

ctR fC

fR

(a)

Re

Zd

dlC

ctR

(b)

Zd

Re

dlC

ctR

fC

fR

(c)













0 20 40 60 80 100 120

04

06

08

2345

05

1015

Time (hours)

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(a)

04

06

08

0

20

400 20 40 60 80 100 120

0 20 40 60 80 100 120

0 20 40 60 80 100 120

060810

Time (hours)

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(b)

0 20 40 60 80 100 12004060810

0

20

40

0100200300

Time (hours)

0 20 40 60 80 100 120

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(c)





2O4 LiCrO

2 LiFeO

2


2was controlled










2and LiFeO








5 Conclusion


2which prevents




2andK

2FeO2and


2O4



Acknowledgment


References









2CO3-K2CO3eutectic
















2CO3-K2CO3molten


































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0

Fe

Fe

Fe

Fe

Fe

Fe

Cr

Cr

Cr

CrCr

CrO

O

Ni NiNiAl

Si

Si

2 4 6 8 10 12 14 16(keV)

0 2 4 6 8 10 12 14 16(keV)

(a)

(b)

200 120583m

10 120583m

Spectrum 2

Spectrum 1


Re dlC

ctR fC

fR

(a)

Re

Zd

dlC

ctR

(b)

Zd

Re

dlC

ctR

fC

fR

(c)













0 20 40 60 80 100 120

04

06

08

2345

05

1015

Time (hours)

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(a)

04

06

08

0

20

400 20 40 60 80 100 120

0 20 40 60 80 100 120

0 20 40 60 80 100 120

060810

Time (hours)

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(b)

0 20 40 60 80 100 12004060810

0

20

40

0100200300

Time (hours)

0 20 40 60 80 100 120

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(c)





2O4 LiCrO

2 LiFeO

2


2was controlled










2and LiFeO








5 Conclusion


2which prevents




2andK

2FeO2and


2O4



Acknowledgment


References









2CO3-K2CO3eutectic
















2CO3-K2CO3molten


































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0 20 40 60 80 100 120

04

06

08

2345

05

1015

Time (hours)

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(a)

04

06

08

0

20

400 20 40 60 80 100 120

0 20 40 60 80 100 120

0 20 40 60 80 100 120

060810

Time (hours)

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(b)

0 20 40 60 80 100 12004060810

0

20

40

0100200300

Time (hours)

0 20 40 60 80 100 120

Rct

(Ωcm

2)

Ad

(ΩSn

cm2)

nd

(c)





2O4 LiCrO

2 LiFeO

2


2was controlled










2and LiFeO








5 Conclusion


2which prevents




2andK

2FeO2and


2O4



Acknowledgment


References









2CO3-K2CO3eutectic
















2CO3-K2CO3molten


































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials








5 Conclusion


2which prevents




2andK

2FeO2and


2O4



Acknowledgment


References









2CO3-K2CO3eutectic
















2CO3-K2CO3molten


































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



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