Research Article Corrosion Performance of Cu-Based Coins ...downloads.hindawi.com/journals/jchem/2016/9542942.pdf · Research Article Corrosion Performance of Cu-Based Coins in Artificial

Research ArticleCorrosion Performance of Cu-Based Coins in Artificial Sweat

J Porcayo-Calderon12 R A Rodriacuteguez-Diacuteaz3 E Porcayo-Palafox1

and L Martinez-Gomez24

1CIICAp Universidad Autonoma del Estado de Morelos Avenida Universidad 1001 62209 Cuernavaca MOR Mexico2Instituto de Ciencias Fısicas UniversidadNacional Autonoma deMexico AvenidaUniversidad sn 62210 CuernavacaMORMexico3Universidad Politecnica del Estado de Morelos Boulevard Cuauhnahuac 566 Col Lomas del Texcal 62574 Jiutepec MOR Mexico4Corrosion y Proteccion (CyP) Buffon 46 11590 Mexico City Mexico

Correspondence should be addressed to J Porcayo-Calderon jporcayocgmailcom

Received 8 July 2016 Revised 6 October 2016 Accepted 20 October 2016

Academic Editor Stefano Caporali

Copyright copy 2016 J Porcayo-Calderon et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

The performance of different Cu-based coins in artificial sweat was evaluated The electrochemical behavior of the coins wasdetermined by potentiodynamic polarization curves linear polarization resistance and electrochemical impedance spectroscopyRegardless of the chemical composition of the Cu-based coins they showed similar polarization curves particularly the observedsimilarity in the anodic zone suggests that the corrosion mechanism is the same in all cases The presence of Ni and Zn doesnot appreciably affect the corrosion resistance of Cu However the presence of both elements affects the corrosion resistanceof Cu Electrochemical impedance spectroscopy measurements showed the presence of three time constants with very similarcharacteristics again indicating that the main corrosion mechanism is the same in all cases Equivalent circuits confirmed that thecorrosion performance of the Ni-Zn-Cu coins depends on the ZnNi ratio such that decreasing this value decreases the corrosionresistance of the alloy In general nickel has a detrimental effect due to the formation of highly soluble Ni-based corrosion products

1 Introduction

Metallic corrosion originated by metal alloys in contactwith human body has been assessed and studied in variousresearches Frequently this problem is associated with thetarnishing of the metals as a consequence of the contact ofthe sweat generated by some parts of human body in contactwith pieces of metals or alloys such as coins jewels piercingand earrings The contact of metals with human sweat canproduce undesirable effects The problem of the metalliccorrosion resulting from the formation of corrosion productsor liberation of metallic ions originated by the palmar sweatis typical to a great number of industrial occupations [1]

Besides the tarnishing that occurs in metals whenexposed to artificial sweat another aspect concerning humanhealth which cannot be disregarded is the detrimental effectson human body that could induce the metal contact withhuman body Metallic objects in long periods of contactwith human skin may in fact produce a toxic effect usuallyattributed to the release of metal ions For example dermal

hypersensitivity to Ni or Ni-based alloys is typical In thiscase contact dermatitis is not originated by nickel itselfbut by the nickel salts which are formed as a result of thecontact of human sweat with a metallic object for examplea necklace ring or watch This phenomenon is developedsimultaneously with the corrosion of the object Once aperson acquired nickel allergy this illness lasts for life [2]The metallic corrosion induced by human sweat has beenknown since a century approximately Various researchershave stated that metals such as Mg Ni and stainless steelshave experienced pitting and crevice corrosion and hencemust be protected with appropriate passive layers for a betterperformance in service [3]

Human sweat is constituted of greatly variable quantitiesof primary electrolytes organic acids and carbohydratesionic constituents nitrogenous substances amino acids andvitamins and miscellaneous constituents Sweat is composedof 990ndash995 water and 05ndash10 solids The publishedliterature describing synthetic sweat formulations is diverseand includes many different compounds All of the published

Hindawi Publishing CorporationJournal of ChemistryVolume 2016 Article ID 9542942 11 pageshttpdxdoiorg10115520169542942

2 Journal of Chemistry

synthetic formulas differ in composition concentration andpH Although there have been few reports concerning theallergy induced by cooper recently this element has beenincreasingly recognized as an allergen Despite the fact thatCu shows allergenic potential lower than the other metalsthe allergy induced by this element has an undoubtfulclinical importance Corrosion studies of copper alloys inartificial sweat and in Ringer biological solution showed thatat low potentials a thin oxide layer was produced but atnobler potentials a thick chloride or oxychloride layer wasoriginated The composition and thickness of the surfacelayers depended on the stability of complexes of the metalions with the chloride ions and with the complexing agentspresent in the artificial sweat The corrosion products wereformed simultaneously with an increment of the dissolutionrate of zinc and nickel and this behavior augmented theallergen problem of nickel in contact with human skin [4ndash6]

Corrosion of the coins is a common phenomenon duringthe circulation process which shortens its service life andreduces its collectable value Coins come into contact withthe skin during the usage process and sweat left on thembecomes a major reason for their tarnishing [7] A lot ofthe current coins consist of a ring and an inner pill andthe bimetallic structure of these coins can be a problembecause of the metallic enrichment of both pill and ringsurfaces [5] Due to prolonged contact with human skin themetal dissolution is important because of potential allergicreactions [6]

Therefore the purpose of this study is to evaluate thecorrosion behavior of Cu-based coins in artificial sweat Theelectrochemical performance of the coins was determinedby potentiodynamic polarization curves linear polarizationresistance and electrochemical impedance spectroscopy

2 Experimental Procedure

A batch of 20 Cu-based coins from different countries wascorrosion tested by means of electrochemical techniquesHowever because in many cases the nominal chemicalcomposition reported does not correspond to the actualchemical composition [8] it was decided to determine theelemental chemical composition by EDS (Energy DispersiveSpectroscopy) techniqueTherefore for electrochemical testsonly the coins with the chemical composition reportedin Table 1 were selected In addition high-purity copper(9999wt) (Goodfellow) was evaluated for comparisonpurposes The coins consisted of binary ternary and qua-ternary alloy systems and for analysis purposes the alloysonlywill be referred to by the percentage of alloying elementsIn general Ni-Zn-Cu alloys are known as Alpaca GermanSilver Nickel Bronze or Nickel Silver and the Cu6Zn5Al1Snalloy is known as Nordic Gold

Coins were cut into rectangular form in order to be usedas electrode work They were spot-welded to a Cu wire andthen mounted in polyester resin In this state the coins wereabraded with emery paper down to 1200 SiC and once thesurface of the specimens was metallographically prepared

Table 1 Chemical composition of the Cu-based coins (wt)

Alloy Ni Zn Al Mn Sn CuCu lt001 lt001 lt001 lt001 lt001 999923Ni 230 mdash mdash mdash mdash Bal32Zn mdash 315 mdash mdash mdash Bal10Ni25Zn 97 255 mdash mdash mdash Bal13Ni17Zn 130 170 mdash mdash mdash Bal15Ni22Zn 145 220 mdash mdash mdash Bal8Ni27Zn 85 270 mdash mdash mdash Bal6Al2Ni 20 mdash 60 mdash mdash Bal13Zn6Mn4Ni 36 133 mdash 60 mdash Bal6Zn5Al1Sn mdash 60 55 mdash 12 Bal

Table 2 Chemical composition of artificial sweat (pH adjusted to47 by NaOH)

Compound Content [gL]NaCl 200NH4Cl 175Acetic acid 50Lactic acid 150

samples were washed with distilled water and then by ethanolin an ultrasonic bath for 10 minutes

Corrosive electrolyte used for the electrochemical essayswas a synthetic sweat solution which was prepared accordingto ISO 3160-2 standard [9] Table 2 shows the chemicalcomposition of the artificial sweat

Electrochemical tests were performed in a Gamry Inter-face 1000 Potentiostat controlled by a personal computerand the Framework data acquisition software version 703Experiments were performed in a three-electrode electro-chemical cell (working electrode saturated calomel electrode(SCE) as the reference electrode and a high-purity graphiterod as the auxiliary electrode) In order to obtain thepotentiodynamic polarization curves coins were polarizedfrom minus400mV to 800mV from 119864corr value at a scan rate of1mVs Frompotentiodynamic polarization curves the valuesof corrosion potential (119864corr) current density (119868corr) and Tafelslopes (ba bc) were determined Before starting the test thesystem was allowed to stabilize for a period of 05 hours Forthe purpose of obtaining the values of polarization resistance119877119901 the linear polarization resistance (LPR) was measuredwithin the interval ofplusmn20mV from119864corr valuewith a scan rateof 1mVs After determining 119877119901 value the corrosion currentdensity (119868corr) was calculated by applying the Stern-Gearyequation

119868corr =119887a119887c

2303119877119901 (119887a + 119887c) (1)

Measurements of electrochemical impedance spectroscopy(EIS) were performed in the frequency range of 001Hzto 100000Hz with a perturbation of plusmn10mV In each testperformed a new working electrode was used The testswere performed in triplicate and the values reported are theaverage of the values obtained

Journal of Chemistry 3

Table 3 Electrochemical parameters of the Cu-based coins evaluated in artificial sweat at 37∘C

Alloy 119864corr(mV)

ba(mVDec)

bc(mVDec)

119868corr(mAcm2)

119877119901(Ohms-cm2)

ZnNiratio

Cu minus310 300 69 001110 2276 mdash23Ni minus285 207 67 000734 3085 mdash32Zn minus347 355 67 000854 2950 mdash10Ni25Zn minus332 334 72 000941 3298 2513Ni17Zn minus301 343 62 000810 3236 1315Ni22Zn minus323 230 58 000573 2900 1478Ni27Zn minus271 330 75 000406 4880 3376Al2Ni minus344 244 70 000624 4708 mdash13Zn6Mn4Ni minus346 333 68 000724 3350 3256Zn5Al1Sn minus360 195 61 000362 4152 mdash

00001 0001 001 01 1 10 100000001

Current density (mAcm2)

Cu23Ni32Zn

minus080

minus060

minus040

minus020

000

020

Pote

ntia

l (V

ver

sus E

CS)

Figure 1 Polarization curves for the Cu-based binary alloys inartificial sweat at 37∘C (dEdt = 10mVs)

3 Results and Discussion

31 Potentiodynamic Polarization Curves The polarizationcurves for Cu and binary alloys are displayed in Figure 1The polarization curves for pure copper and binary alloysexhibited similar active-passive behavior similar observa-tions have been reported by other authors [5] The additionof Ni and Zn to the copper generated a diminution ofthe corrosion rate however the Ni induces a shift of thecorrosion potential towards the noble side and the Znaddition conversely Also Cu and 32Zn alloy showed a moredefined passivation zone compared to 23Ni alloy and theyare passivated at lower overpotentials The potentiodynamicbehaviors of pure copper and the ternary alloys are presentedin Figure 2 The variation in the composition of the coinsinfluences the polarization and the passivation nature Theaddition of both Ni and Zn induces a decrease of corrosionrate however it seems that this decrease is dependent on theZnNi ratio Figure 3 shows the polarization curves for pure

000001 0001 001 01 1 10 10000001


Cu8Ni27Zn

13Nil7Zn15Ni22Zn2Ni6Al10Ni25Zn

minus080

minus060

minus040

minus020

000

020

Pote

ntia

l (V

ver

sus E

CS)

Figure 2 Polarization curves for the Cu-based ternary alloys inartificial sweat at 37∘C (dEdt = 10mVs)

Cu together with the quaternary alloysThe anodic branch ofCu and quaternary alloys exhibits an active-passive behaviorSimilarly to the polarization behavior of ternary alloys theaddition of the groups of triad elements Zn-Al-Sn and Zn-Mn-Ni to the pure Cu induced a diminution of its corrosionrate It is worth noticing that the quaternary Cu-Zn-Al-Snalloys exhibited the lowest corrosion rate

Table 3 shows the electrochemical parameters of theCu-based coins determined from polarization curves inthe region of plusmn250mV with respect to corrosion potentialImportantly all tested coins show a similar anodic-cathodicbehavior with possible significant variations at overpotentialsabove 0 volts The low value of the anodic slopes (60ndash70mV)suggests a process of active dissolution due to the formation ofsoluble species (CuCl2

minus) and on the other hand the presenceof the passive region is due to the Cu2O formation as otherauthors have suggested [5] The observed similarity in theanodic zone at potentials above 119864corr value (up to 300mV)suggests that themain corrosionmechanism is the same in all


Cu

00001 0001 001 01 1 10 100000001


6Zn5Al1Sn13Zn6Mn4Ni

minus080

minus060

minus040

minus020

000

020

Pote

ntia

l (V

ver

sus E

CS)

Figure 3 Polarization curves for the Cu-based quaternary alloys inartificial sweat at 37∘C (dEdt = 10mVs)

cases Regardless of the number of alloying elements variousstudies on copper-based alloys in artificial sweat confirm thisassertion [4ndash7 10 11] such that the main corrosion productdetected is the cuprous oxide (Cu2O) besides copper chloridehydroxide (Cu2(OH)3Cl) This confirms that the sodiumchloride (NaCl) present in the artificial sweat accelerates theanodic reaction process

32 Linear Polarization Resistance Curves The variation ofcorrosion rate in terms of 119868corr as a function of the immersiontime for pure copper together with the binary ternary andquaternary alloys exposed to artificial sweat is presented inFigure 4 119868corr values were obtained from the Stern-Gearyequation Tafel slopes (from polarization curves) and 119877119901values It can be seen that the alloy 15Ni22Zn displayedthe highest corrosion rate after the two hours of exposurewhile the 13Zn6Mn4Ni and 6Zn5Al1Sn exhibited the lowercorrosion rate in terms of 119868corr besides the fact that thecorrosion current density of these quaternary alloys remainedalmost constant during the 24 hours of immersion Alsothe corrosion rate of Cu tended to prevail more or lessconstantly during the whole exposure period Besides it isworth noticing that pure copper exhibited a lower corrosionrate than the binary and ternary alloys during the lapse oftime from around the 8th hour of exposure up to the end ofthe linear polarization test The fact that the corrosion rateof Cu remained more or less constant for 24 hours can becertainly related to the good stability of the Cu2O passivefilm formed onto copper surface It can be observed thatthe behavior of binary alloys was very similar to that ofcopper this may indicate that in long exposures the presenceof Ni and Zn does not appreciably affect the corrosionresistance of Cu However in the case of ternary alloys thepresence of both elements affects the corrosion resistance ofCu apparently at higher nickel content and the corrosionrate is increased Also corrosion rate of binary and ternary

13Ni17Zn23Ni15Ni22Zn32Zn

2Ni6Al8Ni27Zn13Zn6Mn4Ni10Ni25Zn6Zn5Al1Sn

Cu

0001

01

001

2 4 6 8 10 12 14 16 18 20 22 240Time [hours]

I cor

r[m

Ac

m2 ]

Figure 4 Change of 119868corr values with time for Cu-based coinsevaluated in artificial sweat at 37∘C

alloys increased while the exposure time had elapsed Thistrend could be ascribed to the detrimental effect induced inthe protective nature of the copper oxide formed on surfaceof materials Specifically the formation of NiO and ZnOcould have produced a reduction of the protective characterof the passive film formed on the surface of the alloys Inthis sense Milosev and Kosec [4] studied the nickel ionrelease associated with nickel allergy which was released bythe Cu18Ni20Zn alloy after an immersion period in artificialsweat solution for 30 days In this research the authorsreported that the surface layer of the alloy was constitutedpredominantly by Cu2O but the presence of NiO and ZnOalso was detected on the other hand they also found that theNi concentration into electrolyte is two times higher than thatof Cu and Zn while the concentrations of Cu and Zn weresimilar this being due to the formation of Ni-based corrosionproducts being highly solubleThis may also explain the poorperformance of the 2Ni6Al ternary alloy on one hand thepresence of nickel may form soluble corrosion products andon the other hand the formation of aluminumoxide provideslittle protection because of its low stability in halides-richelectrolytes [12 13]

33 EIS Measurements Impedance spectra for copper andbimetallic alloys after 24 hours of immersion in artificialsweat at 37∘C are shown in Figure 5 The analysis of theNyquist plot shows very similar characteristics for copperand bimetallic alloys namely the apparent presence of acapacitive semicircle and the formation of a ldquotailrdquo of scatteredpoints in the low frequency region where this scattering maycorrespond to processes of either diffusion or adsorption ofspecies Generally the information provided or interpretedfrom the analysis of the Nyquist plot is limited and can leadto erroneous conclusions this being mainly because it isimpossible to define the frequency range where the surface


Cu23Ni32Zn

Cu23Ni32Zn

Cu23Ni32Zn

200 400 600 800 1000 16000 1200 1400Z (Ohm-cm2)

0

minus200

minus400

minus600

minus800

Z

(Ohm

-cm2)

minus1600

minus1400

minus1200

minus1000

1

10

100

1000

10000

01 1 10 100 1000 10000 100000001Frequency (Hz)

0

minus10

minus20

minus30

minus40

minus50

minus60

minus70

minus80

minus90

01 1 10 100 1000 10000 100000001Frequency (Hz)

Phas

e ang

le (∘

)

|Z|

(ohm

-cm

2 )

Figure 5 Nyquist and Bode plots for the Cu-based binary alloys in artificial sweat at 37∘C after 24 hours Points are the experimental dataand the continuous lines are the fitting data

phenomena are occurring [13ndash15] It is therefore importantto perform a complete analysis of impedance spectra thatis taking into account the Bode plots Furthermore analysisof the Bode plot is simpler because the dispersion of theexperimental data is minimized and the analysis can beperformed by frequency range In particular the phaseangle-frequency relationship clearly indicates howmany timeconstants exist in the system under analysis and this isimpossible to observe from the analysis of the Nyquist plotespecially in the high frequency region Bode diagrams can beanalyzed for frequency ranges regions of high intermediateand low frequency [13ndash17] In the high frequency region (1 kndash100 kHz) Bode plot shows a horizontal line (high frequencyplateau) with the phase angle approaching 0∘This fingerprintis the characteristic response of the electrolytic resistance(solution resistance119877119904) In the intermediate frequency region(1000 to 10Hz) the capacitive behavior of the passive oxideand its dielectric properties can be observed In general

the spectra display a linear slope in log |119885| as log (119891)decreases and the maximum phase angle is reached andfinally in the low frequency region (119891 lt 10Hz) is possibleto detect a horizontal line (low frequency plateau with thephase angle approaching 0∘) for charge-transfer processes ora deviation from the behavior described for other relaxationprocesses (mass transfer adsoption etc) taking place at thefilm-electrolyte interface or into the pores of the surfacefilm The basic elements that could be observed from Bodediagrams are resistors R (high and low frequencies plateaus)in which |119885| = 119877 and the phase angle is approaching0∘ capacitors C in which log |119885| is a straight line witha minus1 slope and the phase angle is approaching 90∘ andelements associated with diffusion in which log |119885| has aminus05 slope and the phase angle is approaching 45∘ Thismode of interpretation of the impedance spectra is veryuseful in order to define reliably the equivalent circuits of thesystem


Based on this Bode plot it can be observed again thatthe behavior of copper and bimetallic alloys is very similarHowever from the phase angle-frequency relationship onecan deduce the presence of three time constants (threemaximums of phase angle) One of them is at the high-intermediate frequency region (phase angle approaching 0∘and formation of the plateau at higher frequencies than10000Hz) with a maximum phase angle of 53ndash58∘ at 300ndash400Hz This indicates that the time constant for the threematerials has very similar characteristics andmay correspondto the presence of a viscous film ontomaterial surface [13 14]and this may be associated with the formation of hydrides ormetallic oxyhydrides as has been previously reported [4 57 11] The second time constant is observed in the region ofintermediate-low frequency where for the bimetallic alloysthemaximumphase angle is located approximately 10Hz andfor copper around 2Hz in addition the phase angle is less inthe case of copper (45∘) compared to those of the bimetallicalloys (above 50∘) and on the other hand the slope of the log|Z|-f relationship is smaller for the case of copper and similarin the case of the bimetallic alloys These features indicatesusceptibility to corrosion of materials in artificial sweat thatis phase angle values smaller than 90∘ and slopes smaller thanminus1 and it means that the protective layer is not an effectiveinsulating barrier and is permeable to ions from solution [18]Finally in the low frequency region the third time constantis observed 119891 lt 01Hz however the phase angle does nottend to zero degrees and the plateau region is not developedThis behavior can be associated with mass transfer processes(diffusion) due to the presence of the viscous film defined bythe first time constant [13 19]

Liang et al [7] have shown that the main corrosionproducts developed on a Cu30Zn alloy immersed in artificialsweat are copper chloride hydroxide (Cu2(OH)3Cl) andcuprous oxide (Cu2O) Then it is possible that Zn-basedcorrosion products are completely soluble in the electrolyteSimilar observations have been reported for Cu-based alloysevaluated in artificial sweat further indicating that copperchloride hydroxide (Cu2(OH)3Cl) is almost insoluble incontrast to CuCl2sdot2H2O which is very soluble [5] Moreoverapparently the presence of nickel into alloy does not signif-icantly improve its corrosion resistance because Ni-basedcorrosion products formed are soluble in the electrolyte [11]It has been reported that the amount of dissolved Ni is twicethat of dissolved Cu and however the amount of dissolvedZn is similar to that of dissolved Cu [4]

Figure 6 shows the impedance spectra for copper andternary alloys in the Nyquist and Bode format after 24 hoursof immersion in artificial sweat at 37∘C Analysis of the plotsshows similar characteristics in all spectra and the maindifferences are the diameter of the capacitive semicircles andthe magnitude of the impedance module at low frequencyregion this is apparently a function of alloy compositionFurthermore from the phase angle-frequency relationshipthe presence of three time constants is also observedThe timeconstant observed in high-intermediate frequency regionshows important differences that is the maximum phaseangle of the ternary alloys is smaller than that observed forcopper This may indicate that the addition of Zn and Ni

influences the corrosion resistance of the alloy and this isa function of the ZnNi ratio added The interpretation ofthe three time constants has the same meaning described forthose of the bimetallic alloys It has also been shown that themain corrosion products formed onto Cu-base ternary alloysare copper chloride hydroxide (Cu2(OH)3Cl) and cuprousoxide (Cu2O) [4 5 7 11] The presence of both Zn- andNi-based corrosion products is rarely detected because theircorrosion products are soluble in the electrolyte and thepresence of chloride ions breaks down the passivation layerin Cu-Zn-Ni alloys the concentration of dissolved Ni isthe highest one [11] Therefore it might be expected thatincreasing the concentration of nickel in the ternary alloyincreases its corrosion rate Cu- Zn- and Ni-based solublecorrosion products are formed according to [5]

Zn + (OH)adsminus larrrarr ZnO +H+ + eminus (2)

Zn + 4Cladminus larrrarr ZnCl4minus + 2eminus (3)

Ni (H2O)ad larrrarr Ni (OH)ad +Haq+ + eminus (4)

Ni (H2O)ad + Clminus larrrarr Ni (ClOH)adminus +H+ + eminus (5)

Ni (OH)ad +H+ + eminus larrrarr Niaq2+ + (H2O)ad + eminus larrrarr Ni (OH)2 (6)

Cu + 2Clminus larrrarr CuCl2minus + eminus (7)

On the other hand corrosion performance of the 2Ni6Alalloy was better than that of both 13Ni15Zn and 15Ni22Znalloys This best performance can be associated with theformation of Al+ ions (metaloxide interface) and theirmigration (oxidesolution interface) to be oxidized to Al3+according to the following [13 20]

Al +H2Olarrrarr AlOHads +H+ + e (8)

AlOHads 997888rarr Al (OH)+ + e (9)

Al (OH)+ + 5H2O +H+ larrrarr Al3+ + 6H2O + e (10)

However Al-based corrosion products are soluble in theelectrolyte and on the other hand in the presence of halidesthe Al2O3 is frequently subjected to breakdown [12 13]

Figure 7 shows the impedance spectra for copper andquaternary alloys in Nyquist and Bode format after 24 hoursof immersion in artificial sweat at 37∘C Again it is observedthat the impedance spectra are very similar to those observedfor copper and alloys both binary and ternary In this case it isobserved that the diameter of the capacitive semicircle as themagnitude of the impedance module at low frequency regionof the ternary alloys is greater than those observed for copperIn addition from the phase angle-frequency relationship thepresence of three time constants with identical features isalso observed The corrosion resistance of these alloys wasgreater than the others previously described Although the13Zn6Mn4Ni alloy contains a high percentage of Zn and anappreciable amount of Ni its performance was better thanthat of copper This may be due to the presence of Mn sinceit is known that the addition of this element increases thepitting corrosion resistance in chloride-rich electrolytes [21]


Cu8Ni27Zn10Ni25Zn

13Ni17Zn15Ni22Zn2Ni6Al

Cu8Ni27Zn10Ni25Zn


Cu8Ni27Zn10Ni25Zn


0

minus200

minus400

minus600

minus800

minus1000

minus1200

minus1400

minus1600Z

(Ohm

-cm2)

1200 1400600 800 1000200 400 16000Z (Ohm-cm2)

1

10

100

1000

10000

01 1 10 100 1000 10000 100000001Frequency (Hz)

0

minus10

minus20

minus30

minus40

minus50

minus60

minus70

minus80

minus90

01 1 10 100 1000 10000 100000001Frequency (Hz)

|Z|

(ohm

-cm

2 )

Phas

e ang

le (∘

)

Figure 6 Nyquist and Bode plots for the Cu-based ternary alloys in artificial sweat at 37∘C after 24 hours Points are the experimental dataand the continuous lines are the fitting data

On the other hand 6Zn5Al1Sn alloy showed similar behaviorto that of 13Zn6Mn4Ni alloy and this may indicate thatthe aluminum addition enhances the corrosion performanceof the alloy contrary to that observed with the addition ofnickel

Based on that discussed above it is possible to establishthat the equivalent circuit shown in Figure 8 is suitable formodeling the electrochemical behavior of the Cu-based coinstested in artificial sweat at 37∘C Because in the impedancespectra (Figures 5ndash7) a nonideal frequency response wasevident a constant phase element (CPE) was used in theequivalent circuit Typically a CPE is used to compensatefor surface irregularities such as roughness or nonuniformdistribution of charge transfer Its impedance value is afunction of the frequency and the phase is independent of thefrequency

119885CPE =1

119876 (119895120596)119899 (11)

119876 is a proportional factor which combines properties relatedto the surface and electroactive species and it is independentof the frequency 119895 is imaginary number (radicminus1) 120596 is theangular frequency (120596 = 2120587119891) 119891 being the frequencyand 119899 is related to the slope of the log |119885| versus log119891 plot If 119899 is equal to 1 the CPE is an ideal capacitorwhere 119876 is equal to the capacitance however if 05 lt119899 lt 1 then the CPE describes a distribution of dielectricrelaxation times in frequency space and if 119899 = 05 thenthe CPE represents a Warburg impedance with diffusionalcharacter

As discussed previously the impedance spectra indicatethe presence of three time constants The first time constantrepresents the surface layer (rich in copper chloride hydrox-ide andor metallic hydroxides) through which the metalions diffuse the second time constant represents the charge-transfer process of the metal dissolution or the oxide dissolu-tion and the third one represents the diffusional effects due tothe presence of the surface layer From equivalent circuit 119876119891


Cu13Zn6Mn4Ni6Zn5Al1Sn



500 1000 1500 2000 25000Z (Ohm-cm2)

0

minus500

minus1000

minus1500

minus2000

minus2500Z

(Ohm

-cm2)

1

10

100

1000

10000

01 1 10 100 1000 10000 100000001Frequency (Hz)

0

minus10

minus20

minus30

minus40

minus50

minus60

minus70

minus80

minus90

01 1 10 100 1000 10000 100000001Frequency (Hz)

|Z|

(ohm

-cm

2 )

Phas

e ang

le (∘

)

Figure 7 Nyquist and Bode plots for the Cu-based quaternary alloys in artificial sweat at 37∘C after 24 hours Points are the experimentaldata and the continuous lines are the fitting data

Cu-based alloy

Surface oxides

Electrolyte

Surface layer

(copper chloride hydroxide

metallic hydroxides)

Rs

RfQf

W

Qdl

Rct

Figure 8 Equivalent circuit for Cu-based coins evaluated inartificial sweat at 37∘C

represents the CPE of the surface layer 119877119891 is the resistanceof the surface layer 119876dl represents the CPE of the doublelayer capacitor 119877ct is the resistance to the charge transfer

and 119882 is the element for the finite length Warburg (FLW)diffusion

119885119882 =119877119882 lowast tanh ([radicminus1 lowast 119879 lowast 120596]119875)

(radicminus1 lowast 119879 lowast 120596)119875 (12)

where 119879 = 1198712119863 119871 is the effective diffusion thickness 119863is the effective diffusion coefficient and 119875 = 05 Theimpedance spectra were modeled with the Zview softwareThe evolution of the main fitting parameters obtained ispresented in Figures 9 and 10

Figure 9 shows the variation of 119877ct and 119877119891 for Cu-basedcoins evaluated in artificial sweat at 37∘C From 119877ct plot itcan be seen that both alloys 13Ni17Zn and 15Ni22Zn showedthe lowest corrosion resistance and the corrosion resistanceof the quaternary alloys (13Zn6Mn4Ni and 6Zn5Al1Sn) wasgreater On the other hand 119877119891 values observed are lowerwith respect to those of 119877ct This is consistent because 119877119891


0 4 8 12 16 20 24Time (hours)

Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1SnCu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn

10

100

1000

2 4 6 8 10 12 14 16 18 20 22 240Time (hours)

100

1000

10000

Rf

[Ω-c

m2]

Rct

[Ω-c

m2 ]

Figure 9 119877ct and 119877119891 variation against time for Cu-based coins evaluated in artificial sweat at 37∘C

Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn

000001

00001

0001

248 12 16 2040Time (hours)

000001

00001

0001

2 4 6 8 10 12 14 16 18 20 22 240Time (hours)

Cf

[Fcm

minus2 ]

Cdl

[Fcm

minus2 ]

Figure 10 119862dl and 119862119891 variation against time for Cu-based coins evaluated in artificial sweat at 37∘C

represents the resistance of the surface layer through whichthe metal ions diffuse

Figure 10 shows plots of the capacitance (119862dl and 119862119891)versus time for Cu-based coins evaluated in artificial sweatat 37∘C Capacitance values were obtained from 119876 valuesaccording to the following equation

119862119894 = (119876119894119877(1minus119899119894)119894 )1119899119894 (13)

Values of 119862119891 are slightly lower than those of 119862dl For Cuand bimetallic alloys 119862dl values tend to decrease and at thesame time their 119862119891 values tend to increase For the others

alloys both values of119862dl and119862119891 remain almost constantThisbehavior indicates a more active corrosion process both forCu and for the bimetallic alloys

Figure 11 shows the variation of 119868corr values versus timefor the Cu-based coins evaluated in artificial sweat at 37∘C119868corr values were calculated from 119877ct values obtained duringthe modeling process of the impedance spectra using thesame procedure as that employed from LPR values It can beobserved that both the performance ranking and 119868corr valuesare similar to those observed from LPR measurements (Fig-ure 4) This indicates that the proposed equivalent circuit is


Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn

0001

001

01

2 4 6 8 10 12 14 16 18 20 22 240Time [hours]

I cor

r[m

Ac

m2 ]

Figure 11 119868corr variation against time for Cu-based coins evaluatedin artificial sweat at 37∘C (119868corr values from 119877ct values of EISmeasurements)

suitable to simulate the impedance spectra and is compatiblewith the surface processes described above

Binary alloys have a similar behavior to that observed forcopper Apparently the corrosion resistance of the ternaryalloys (mainly the Ni-Zn-Cu ones) depends on the ZnNiratio such that decreasing this value decreases the corrosionresistance of the alloy Although the Zn is the the most elec-tronegative element its presence does not cause a detrimentaleffect as that observed by the presence of Ni this could bedue to the high solubility of the Ni-based corrosion productsAgain it is observed that the 13Zn6Mn4Ni quaternary alloyshowed the best performance It appears that the presenceof Mn improved its corrosion performance regardless ofwhether the ZnNi ratio was similar to that of the 8Ni27Znalloy In the case of the 2Ni6Al ternary and 6Zn5Al1Snquaternary alloys both have a similar aluminum contenthowever their corrosion performance was different again itappears that high corrosion rate of the ternary alloy was dueto its Ni content These observations indicate that nickel hasa detrimental effect because it increases the corrosion rate ofCu-based coins and this is due to the formation of solubleNi-based corrosion products which cause defect points in theprotective layer Also this may increase the risk to the healthof people allergic to Ni

4 Conclusions

The corrosion performance of Cu-based coins in artifi-cial sweat was studied by potentiodynamic polarizationcurves linear polarization resistance and electrochemicalimpedance spectroscopy The main results showed that thepolarization curves of pure copper and Cu-based coins aresimilar suggesting that the main corrosion mechanism isthe same regardless of the number of alloying elements

It was found that the impedance spectra are very similaragain regardless of the number of alloying elements howeverthe main differences were the diameter of the capacitivesemicircles and the magnitude of the impedance moduleat low frequency region Impedance spectra indicated thepresence of three time constants where the first one rep-resents a surface layer (rich in copper chloride hydroxideandor metallic hydroxides) through which the metal ionsdiffuse the second one represents the charge-transfer process(metal dissolution or the oxide dissolution) and the thirdone represents the diffusional effects due to the presenceof the surface layer The agreement of the obtained resultsof modeling of the impedance spectra with those of thelinear polarization resistance measurements indicates thatthe proposed equivalent circuit is compatible with the surfaceprocesses described In general binary alloys have a similarperformance as copper however corrosion resistance ofternary alloys depends on the ZnNi ratio and by increasingthe Ni content increases the corrosion rate Ni causes adetrimental effect due to the high solubility of the Ni-based corrosion products Quaternary alloys showed thebest performance results showed that the Mn enhanced thecorrosion performance and that the Al addition does notcause a negative effect as that observed by the Ni addition

Competing Interests

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

Acknowledgments

Financial support from Consejo Interinstitucional de Cien-cia y Tecnologıa (CONACYT Mexico) (Projects 196205159898 and 159913) is gratefully acknowledged The authorsacknowledge the support of I S Arizmendi-Carbajal andE Y Bautista-Flores (Universidad Politecnica del Estado deMorelos)

References

[1] R J Rathish S Rajendran J L Christy et al ldquoCorrosionbehaviour of metals in artificial sweatrdquo The Open CorrosionJournal vol 3 no 1 pp 38ndash44 2010

[2] I Rezic L Curkovic and M Ujevic ldquoStudy of microstructureand corrosion kinetic of steel guitar strings in artificial sweatsolutionrdquo Materials and Corrosion vol 61 no 6 pp 524ndash5292010

[3] Y W Song D Y Shan and E H Han ldquoCorrosion behaviorsof electroless plating Ni-P coatings deposited on magnesiumalloys in artificial sweat solutionrdquo Electrochimica Acta vol 53no 4 pp 2009ndash2015 2007

[4] I Milosev and T Kosec ldquoMetal ion release and surface com-position of the Cu-18Ni-20Zn nickel-silver during 30 daysimmersion in artificial sweatrdquo Applied Surface Science vol 254no 2 pp 644ndash652 2007

[5] I Milosev and T Kosec ldquoStudy of Cu-18Ni-20Zn Nickel Silverand other Cu-based alloys in artificial sweat and physiological


solutionrdquo Electrochimica Acta vol 52 no 24 pp 6799ndash68102007

[6] N Fredj J S Kolar D M Prichard and T D Burleigh ldquoStudyof relative color stability and corrosion resistance of commercialcopper alloys exposed to hand contact and synthetic handsweatrdquo Corrosion Science vol 76 pp 415ndash423 2013

[7] C-H Liang S-SWang N-B Huang and PWang ldquoCorrosionbehavior of brass coinage in synthetic sweat solutionrdquo Transac-tions of Nonferrous Metals Society of China vol 25 no 2 pp654ndash660 2015

[8] M L Mendoza-Lopez J J Perez-Bueno and M E Rodrıguez-Garcıa ldquoCharacterizations of silver alloys used inmodernMex-ican coinsrdquoMaterials Characterization vol 60 no 9 pp 1041ndash1048 2009

[9] ISO ldquoWatch-cases and accessories gold alloy coveringmdashpart2 determination of fineness thickness corrosion resistanceand adhesionrdquo ISO 3160-22003 International Organization forStandardization (ISO) Geneva Switzerland 2003

[10] D J Horton H Ha L L Foster H J Bindig and J R ScullyldquoTarnishing and Cu ion release in selected copper-base alloysimplications towards antimicrobial functionalityrdquo Electrochim-ica Acta vol 169 pp 351ndash366 2015

[11] S Colin E Beche R Berjoan H Jolibois and A ChambaudetldquoAn XPS and AES study of the free corrosion of Cu- Ni- andZn-based alloys in synthetic sweatrdquo Corrosion Science vol 41no 6 pp 1051ndash1065 1999

[12] M G Mahjani M Sabzali M Jafarian and J Neshati ldquoAninvestigation of the effects of inorganic inhibitors on thecorrosion rate of aluminum alloy using electrochemical noisemeasurements and electrochemical impedance spectroscopyrdquoAnti-Corrosion Methods and Materials vol 55 no 4 pp 208ndash216 2008

[13] J Porcayo-Calderon R A Rodriguez-Diaz E Porcayo-PalafoxJ Colin A Molina-Ocampo and L Martinez-Gomez ldquoEffectof Cu addition on the electrochemical corrosion performanceof Ni3Al in 10 M H2SO4rdquo Advances in Materials Science andEngineering vol 2015 Article ID 209286 18 pages 2015

[14] S Godavarthi J Porcayo-Calderon E Vazquez-Velez MCasales-Diaz D M Ortega-Toledo and L Martinez-GomezldquoInfluence of the chemical composition in the electrochemicalresponse of permanent magnetsrdquo Journal of Spectroscopy vol2015 Article ID 356027 16 pages 2015

[15] J Porcayo-Calderon I Regla E Vazquez-Velez et al ldquoEffect ofthe unsaturation of the hydrocarbon chain of fatty-amides onthe CO2-corrosion of carbon steel using EIS and real-timecorrosion measurementrdquo Journal of Spectroscopy vol 2015Article ID 184140 10 pages 2015

[16] J E G Gonzalez and J C Mirza-Rosca ldquoStudy of the corrosionbehavior of titanium and some of its alloys for biomedicaland dental implant applicationsrdquo Journal of ElectroanalyticalChemistry vol 471 no 2 pp 109ndash115 1999

[17] S Tamilselvi V Raman and N Rajendran ldquoCorrosionbehaviour of Ti-6Al-7Nb and Ti-6Al-4V ELI alloys in the sim-ulated body fluid solution by electrochemical impedance spec-troscopyrdquo Electrochimica Acta vol 52 no 3 pp 839ndash846 2006

[18] F Matemadombo and T Nyokong ldquoCharacterization of self-assembled monolayers of iron and cobalt octaalkylthiosubsti-tuted phthalocyanines and their use in nitrite electrocatalyticoxidationrdquo Electrochimica Acta vol 52 no 24 pp 6856ndash68642007

[19] J Porcayo-Calderon L M Martınez De La Escalera J Cantoand M Casales-Diaz ldquoImidazoline derivatives based on coffee

oil as CO2 corrosion inhibitorrdquo International Journal of Electro-chemical Science vol 10 no 4 pp 3160ndash3176 2015

[20] J Porcayo-Calderon L M Martınez de la Escalera J Canto MCasales-Diaz and V M Salinas-Bravo ldquoEffect of the temper-ature on the CO2-corrosion of Ni3Alrdquo International Journal ofElectrochemical Science vol 10 no 4 pp 3136ndash3151 2015

[21] G Rondelli B Vicentini and A Cigada ldquoInfluence of nitrogenand manganese on localized Corrosion behaviour of stainlesssteels in chloride environmentsrdquo Materials and Corrosion vol46 no 11 pp 628ndash632 1995

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy


Carbohydrate Chemistry

International Journal of


Journal of

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


synthetic formulas differ in composition concentration andpH Although there have been few reports concerning theallergy induced by cooper recently this element has beenincreasingly recognized as an allergen Despite the fact thatCu shows allergenic potential lower than the other metalsthe allergy induced by this element has an undoubtfulclinical importance Corrosion studies of copper alloys inartificial sweat and in Ringer biological solution showed thatat low potentials a thin oxide layer was produced but atnobler potentials a thick chloride or oxychloride layer wasoriginated The composition and thickness of the surfacelayers depended on the stability of complexes of the metalions with the chloride ions and with the complexing agentspresent in the artificial sweat The corrosion products wereformed simultaneously with an increment of the dissolutionrate of zinc and nickel and this behavior augmented theallergen problem of nickel in contact with human skin [4ndash6]

Corrosion of the coins is a common phenomenon duringthe circulation process which shortens its service life andreduces its collectable value Coins come into contact withthe skin during the usage process and sweat left on thembecomes a major reason for their tarnishing [7] A lot ofthe current coins consist of a ring and an inner pill andthe bimetallic structure of these coins can be a problembecause of the metallic enrichment of both pill and ringsurfaces [5] Due to prolonged contact with human skin themetal dissolution is important because of potential allergicreactions [6]

Therefore the purpose of this study is to evaluate thecorrosion behavior of Cu-based coins in artificial sweat Theelectrochemical performance of the coins was determinedby potentiodynamic polarization curves linear polarizationresistance and electrochemical impedance spectroscopy

2 Experimental Procedure

A batch of 20 Cu-based coins from different countries wascorrosion tested by means of electrochemical techniquesHowever because in many cases the nominal chemicalcomposition reported does not correspond to the actualchemical composition [8] it was decided to determine theelemental chemical composition by EDS (Energy DispersiveSpectroscopy) techniqueTherefore for electrochemical testsonly the coins with the chemical composition reportedin Table 1 were selected In addition high-purity copper(9999wt) (Goodfellow) was evaluated for comparisonpurposes The coins consisted of binary ternary and qua-ternary alloy systems and for analysis purposes the alloysonlywill be referred to by the percentage of alloying elementsIn general Ni-Zn-Cu alloys are known as Alpaca GermanSilver Nickel Bronze or Nickel Silver and the Cu6Zn5Al1Snalloy is known as Nordic Gold

Coins were cut into rectangular form in order to be usedas electrode work They were spot-welded to a Cu wire andthen mounted in polyester resin In this state the coins wereabraded with emery paper down to 1200 SiC and once thesurface of the specimens was metallographically prepared

Table 1 Chemical composition of the Cu-based coins (wt)

Alloy Ni Zn Al Mn Sn CuCu lt001 lt001 lt001 lt001 lt001 999923Ni 230 mdash mdash mdash mdash Bal32Zn mdash 315 mdash mdash mdash Bal10Ni25Zn 97 255 mdash mdash mdash Bal13Ni17Zn 130 170 mdash mdash mdash Bal15Ni22Zn 145 220 mdash mdash mdash Bal8Ni27Zn 85 270 mdash mdash mdash Bal6Al2Ni 20 mdash 60 mdash mdash Bal13Zn6Mn4Ni 36 133 mdash 60 mdash Bal6Zn5Al1Sn mdash 60 55 mdash 12 Bal

Table 2 Chemical composition of artificial sweat (pH adjusted to47 by NaOH)

Compound Content [gL]NaCl 200NH4Cl 175Acetic acid 50Lactic acid 150

samples were washed with distilled water and then by ethanolin an ultrasonic bath for 10 minutes

Corrosive electrolyte used for the electrochemical essayswas a synthetic sweat solution which was prepared accordingto ISO 3160-2 standard [9] Table 2 shows the chemicalcomposition of the artificial sweat

Electrochemical tests were performed in a Gamry Inter-face 1000 Potentiostat controlled by a personal computerand the Framework data acquisition software version 703Experiments were performed in a three-electrode electro-chemical cell (working electrode saturated calomel electrode(SCE) as the reference electrode and a high-purity graphiterod as the auxiliary electrode) In order to obtain thepotentiodynamic polarization curves coins were polarizedfrom minus400mV to 800mV from 119864corr value at a scan rate of1mVs Frompotentiodynamic polarization curves the valuesof corrosion potential (119864corr) current density (119868corr) and Tafelslopes (ba bc) were determined Before starting the test thesystem was allowed to stabilize for a period of 05 hours Forthe purpose of obtaining the values of polarization resistance119877119901 the linear polarization resistance (LPR) was measuredwithin the interval ofplusmn20mV from119864corr valuewith a scan rateof 1mVs After determining 119877119901 value the corrosion currentdensity (119868corr) was calculated by applying the Stern-Gearyequation

119868corr =119887a119887c

2303119877119901 (119887a + 119887c) (1)

Measurements of electrochemical impedance spectroscopy(EIS) were performed in the frequency range of 001Hzto 100000Hz with a perturbation of plusmn10mV In each testperformed a new working electrode was used The testswere performed in triplicate and the values reported are theaverage of the values obtained




ba(mVDec)

bc(mVDec)

119868corr(mAcm2)

119877119901(Ohms-cm2)

ZnNiratio


00001 0001 001 01 1 10 100000001


Cu23Ni32Zn

minus080

minus060

minus040

minus020

000

020

Pote

ntia

l (V

ver

sus E

CS)




000001 0001 001 01 1 10 10000001


Cu8Ni27Zn


minus080

minus060

minus040

minus020

000

020

Pote

ntia

l (V

ver

sus E

CS)






Cu

00001 0001 001 01 1 10 100000001


6Zn5Al1Sn13Zn6Mn4Ni

minus080

minus060

minus040

minus020

000

020

Pote

ntia

l (V

ver

sus E

CS)






Cu

0001

01

001

2 4 6 8 10 12 14 16 18 20 22 240Time [hours]

I cor

r[m

Ac

m2 ]





Cu23Ni32Zn

Cu23Ni32Zn

Cu23Ni32Zn

200 400 600 800 1000 16000 1200 1400Z (Ohm-cm2)

0

minus200

minus400

minus600

minus800

Z

(Ohm

-cm2)

minus1600

minus1400

minus1200

minus1000

1

10

100

1000

10000

01 1 10 100 1000 10000 100000001Frequency (Hz)

0

minus10

minus20

minus30

minus40

minus50

minus60

minus70

minus80

minus90

01 1 10 100 1000 10000 100000001Frequency (Hz)

Phas

e ang

le (∘

)

|Z|

(ohm

-cm

2 )






















Cu8Ni27Zn10Ni25Zn


Cu8Ni27Zn10Ni25Zn


Cu8Ni27Zn10Ni25Zn


0

minus200

minus400

minus600

minus800

minus1000

minus1200

minus1400

minus1600Z

(Ohm

-cm2)

1200 1400600 800 1000200 400 16000Z (Ohm-cm2)

1

10

100

1000

10000

01 1 10 100 1000 10000 100000001Frequency (Hz)

0

minus10

minus20

minus30

minus40

minus50

minus60

minus70

minus80

minus90

01 1 10 100 1000 10000 100000001Frequency (Hz)

|Z|

(ohm

-cm

2 )

Phas

e ang

le (∘

)




119885CPE =1

119876 (119895120596)119899 (11)







500 1000 1500 2000 25000Z (Ohm-cm2)

0

minus500

minus1000

minus1500

minus2000

minus2500Z

(Ohm

-cm2)

1

10

100

1000

10000

01 1 10 100 1000 10000 100000001Frequency (Hz)

0

minus10

minus20

minus30

minus40

minus50

minus60

minus70

minus80

minus90

01 1 10 100 1000 10000 100000001Frequency (Hz)

|Z|

(ohm

-cm

2 )

Phas

e ang

le (∘

)


Cu-based alloy

Surface oxides

Electrolyte

Surface layer



Rs

RfQf

W

Qdl

Rct









0 4 8 12 16 20 24Time (hours)

Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1SnCu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn

10

100

1000

2 4 6 8 10 12 14 16 18 20 22 240Time (hours)

100

1000

10000

Rf

[Ω-c

m2]

Rct

[Ω-c

m2 ]


Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn

000001

00001

0001

248 12 16 2040Time (hours)

000001

00001

0001

2 4 6 8 10 12 14 16 18 20 22 240Time (hours)

Cf

[Fcm

minus2 ]

Cdl

[Fcm

minus2 ]




119862119894 = (119876119894119877(1minus119899119894)119894 )1119899119894 (13)





Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn

0001

001

01

2 4 6 8 10 12 14 16 18 20 22 240Time [hours]

I cor

r[m

Ac

m2 ]




4 Conclusions



Competing Interests


Acknowledgments


References


































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of




ba(mVDec)

bc(mVDec)

119868corr(mAcm2)

119877119901(Ohms-cm2)

ZnNiratio


00001 0001 001 01 1 10 100000001


Cu23Ni32Zn

minus080

minus060

minus040

minus020

000

020

Pote

ntia

l (V

ver

sus E

CS)




000001 0001 001 01 1 10 10000001


Cu8Ni27Zn


minus080

minus060

minus040

minus020

000

020

Pote

ntia

l (V

ver

sus E

CS)






Cu

00001 0001 001 01 1 10 100000001


6Zn5Al1Sn13Zn6Mn4Ni

minus080

minus060

minus040

minus020

000

020

Pote

ntia

l (V

ver

sus E

CS)






Cu

0001

01

001

2 4 6 8 10 12 14 16 18 20 22 240Time [hours]

I cor

r[m

Ac

m2 ]





Cu23Ni32Zn

Cu23Ni32Zn

Cu23Ni32Zn

200 400 600 800 1000 16000 1200 1400Z (Ohm-cm2)

0

minus200

minus400

minus600

minus800

Z

(Ohm

-cm2)

minus1600

minus1400

minus1200

minus1000

1

10

100

1000

10000

01 1 10 100 1000 10000 100000001Frequency (Hz)

0

minus10

minus20

minus30

minus40

minus50

minus60

minus70

minus80

minus90

01 1 10 100 1000 10000 100000001Frequency (Hz)

Phas

e ang

le (∘

)

|Z|

(ohm

-cm

2 )






















Cu8Ni27Zn10Ni25Zn


Cu8Ni27Zn10Ni25Zn


Cu8Ni27Zn10Ni25Zn


0

minus200

minus400

minus600

minus800

minus1000

minus1200

minus1400

minus1600Z

(Ohm

-cm2)

1200 1400600 800 1000200 400 16000Z (Ohm-cm2)

1

10

100

1000

10000

01 1 10 100 1000 10000 100000001Frequency (Hz)

0

minus10

minus20

minus30

minus40

minus50

minus60

minus70

minus80

minus90

01 1 10 100 1000 10000 100000001Frequency (Hz)

|Z|

(ohm

-cm

2 )

Phas

e ang

le (∘

)




119885CPE =1

119876 (119895120596)119899 (11)







500 1000 1500 2000 25000Z (Ohm-cm2)

0

minus500

minus1000

minus1500

minus2000

minus2500Z

(Ohm

-cm2)

1

10

100

1000

10000

01 1 10 100 1000 10000 100000001Frequency (Hz)

0

minus10

minus20

minus30

minus40

minus50

minus60

minus70

minus80

minus90

01 1 10 100 1000 10000 100000001Frequency (Hz)

|Z|

(ohm

-cm

2 )

Phas

e ang

le (∘

)


Cu-based alloy

Surface oxides

Electrolyte

Surface layer



Rs

RfQf

W

Qdl

Rct









0 4 8 12 16 20 24Time (hours)

Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1SnCu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn

10

100

1000

2 4 6 8 10 12 14 16 18 20 22 240Time (hours)

100

1000

10000

Rf

[Ω-c

m2]

Rct

[Ω-c

m2 ]


Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn

000001

00001

0001

248 12 16 2040Time (hours)

000001

00001

0001

2 4 6 8 10 12 14 16 18 20 22 240Time (hours)

Cf

[Fcm

minus2 ]

Cdl

[Fcm

minus2 ]




119862119894 = (119876119894119877(1minus119899119894)119894 )1119899119894 (13)





Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn

0001

001

01

2 4 6 8 10 12 14 16 18 20 22 240Time [hours]

I cor

r[m

Ac

m2 ]




4 Conclusions



Competing Interests


Acknowledgments


References


































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


Cu

00001 0001 001 01 1 10 100000001


6Zn5Al1Sn13Zn6Mn4Ni

minus080

minus060

minus040

minus020

000

020

Pote

ntia

l (V

ver

sus E

CS)






Cu

0001

01

001

2 4 6 8 10 12 14 16 18 20 22 240Time [hours]

I cor

r[m

Ac

m2 ]





Cu23Ni32Zn

Cu23Ni32Zn

Cu23Ni32Zn

200 400 600 800 1000 16000 1200 1400Z (Ohm-cm2)

0

minus200

minus400

minus600

minus800

Z

(Ohm

-cm2)

minus1600

minus1400

minus1200

minus1000

1

10

100

1000

10000

01 1 10 100 1000 10000 100000001Frequency (Hz)

0

minus10

minus20

minus30

minus40

minus50

minus60

minus70

minus80

minus90

01 1 10 100 1000 10000 100000001Frequency (Hz)

Phas

e ang

le (∘

)

|Z|

(ohm

-cm

2 )






















Cu8Ni27Zn10Ni25Zn


Cu8Ni27Zn10Ni25Zn


Cu8Ni27Zn10Ni25Zn


0

minus200

minus400

minus600

minus800

minus1000

minus1200

minus1400

minus1600Z

(Ohm

-cm2)

1200 1400600 800 1000200 400 16000Z (Ohm-cm2)

1

10

100

1000

10000

01 1 10 100 1000 10000 100000001Frequency (Hz)

0

minus10

minus20

minus30

minus40

minus50

minus60

minus70

minus80

minus90

01 1 10 100 1000 10000 100000001Frequency (Hz)

|Z|

(ohm

-cm

2 )

Phas

e ang

le (∘

)




119885CPE =1

119876 (119895120596)119899 (11)







500 1000 1500 2000 25000Z (Ohm-cm2)

0

minus500

minus1000

minus1500

minus2000

minus2500Z

(Ohm

-cm2)

1

10

100

1000

10000

01 1 10 100 1000 10000 100000001Frequency (Hz)

0

minus10

minus20

minus30

minus40

minus50

minus60

minus70

minus80

minus90

01 1 10 100 1000 10000 100000001Frequency (Hz)

|Z|

(ohm

-cm

2 )

Phas

e ang

le (∘

)


Cu-based alloy

Surface oxides

Electrolyte

Surface layer



Rs

RfQf

W

Qdl

Rct









0 4 8 12 16 20 24Time (hours)

Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1SnCu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn

10

100

1000

2 4 6 8 10 12 14 16 18 20 22 240Time (hours)

100

1000

10000

Rf

[Ω-c

m2]

Rct

[Ω-c

m2 ]


Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn

000001

00001

0001

248 12 16 2040Time (hours)

000001

00001

0001

2 4 6 8 10 12 14 16 18 20 22 240Time (hours)

Cf

[Fcm

minus2 ]

Cdl

[Fcm

minus2 ]




119862119894 = (119876119894119877(1minus119899119894)119894 )1119899119894 (13)





Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn

0001

001

01

2 4 6 8 10 12 14 16 18 20 22 240Time [hours]

I cor

r[m

Ac

m2 ]




4 Conclusions



Competing Interests


Acknowledgments


References


































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


Cu23Ni32Zn

Cu23Ni32Zn

Cu23Ni32Zn

200 400 600 800 1000 16000 1200 1400Z (Ohm-cm2)

0

minus200

minus400

minus600

minus800

Z

(Ohm

-cm2)

minus1600

minus1400

minus1200

minus1000

1

10

100

1000

10000

01 1 10 100 1000 10000 100000001Frequency (Hz)

0

minus10

minus20

minus30

minus40

minus50

minus60

minus70

minus80

minus90

01 1 10 100 1000 10000 100000001Frequency (Hz)

Phas

e ang

le (∘

)

|Z|

(ohm

-cm

2 )






















Cu8Ni27Zn10Ni25Zn


Cu8Ni27Zn10Ni25Zn


Cu8Ni27Zn10Ni25Zn


0

minus200

minus400

minus600

minus800

minus1000

minus1200

minus1400

minus1600Z

(Ohm

-cm2)

1200 1400600 800 1000200 400 16000Z (Ohm-cm2)

1

10

100

1000

10000

01 1 10 100 1000 10000 100000001Frequency (Hz)

0

minus10

minus20

minus30

minus40

minus50

minus60

minus70

minus80

minus90

01 1 10 100 1000 10000 100000001Frequency (Hz)

|Z|

(ohm

-cm

2 )

Phas

e ang

le (∘

)




119885CPE =1

119876 (119895120596)119899 (11)







500 1000 1500 2000 25000Z (Ohm-cm2)

0

minus500

minus1000

minus1500

minus2000

minus2500Z

(Ohm

-cm2)

1

10

100

1000

10000

01 1 10 100 1000 10000 100000001Frequency (Hz)

0

minus10

minus20

minus30

minus40

minus50

minus60

minus70

minus80

minus90

01 1 10 100 1000 10000 100000001Frequency (Hz)

|Z|

(ohm

-cm

2 )

Phas

e ang

le (∘

)


Cu-based alloy

Surface oxides

Electrolyte

Surface layer



Rs

RfQf

W

Qdl

Rct









0 4 8 12 16 20 24Time (hours)

Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1SnCu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn

10

100

1000

2 4 6 8 10 12 14 16 18 20 22 240Time (hours)

100

1000

10000

Rf

[Ω-c

m2]

Rct

[Ω-c

m2 ]


Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn

000001

00001

0001

248 12 16 2040Time (hours)

000001

00001

0001

2 4 6 8 10 12 14 16 18 20 22 240Time (hours)

Cf

[Fcm

minus2 ]

Cdl

[Fcm

minus2 ]




119862119894 = (119876119894119877(1minus119899119894)119894 )1119899119894 (13)





Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn

0001

001

01

2 4 6 8 10 12 14 16 18 20 22 240Time [hours]

I cor

r[m

Ac

m2 ]




4 Conclusions



Competing Interests


Acknowledgments


References


































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of



















Cu8Ni27Zn10Ni25Zn


Cu8Ni27Zn10Ni25Zn


Cu8Ni27Zn10Ni25Zn


0

minus200

minus400

minus600

minus800

minus1000

minus1200

minus1400

minus1600Z

(Ohm

-cm2)

1200 1400600 800 1000200 400 16000Z (Ohm-cm2)

1

10

100

1000

10000

01 1 10 100 1000 10000 100000001Frequency (Hz)

0

minus10

minus20

minus30

minus40

minus50

minus60

minus70

minus80

minus90

01 1 10 100 1000 10000 100000001Frequency (Hz)

|Z|

(ohm

-cm

2 )

Phas

e ang

le (∘

)




119885CPE =1

119876 (119895120596)119899 (11)







500 1000 1500 2000 25000Z (Ohm-cm2)

0

minus500

minus1000

minus1500

minus2000

minus2500Z

(Ohm

-cm2)

1

10

100

1000

10000

01 1 10 100 1000 10000 100000001Frequency (Hz)

0

minus10

minus20

minus30

minus40

minus50

minus60

minus70

minus80

minus90

01 1 10 100 1000 10000 100000001Frequency (Hz)

|Z|

(ohm

-cm

2 )

Phas

e ang

le (∘

)


Cu-based alloy

Surface oxides

Electrolyte

Surface layer



Rs

RfQf

W

Qdl

Rct









0 4 8 12 16 20 24Time (hours)

Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1SnCu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn

10

100

1000

2 4 6 8 10 12 14 16 18 20 22 240Time (hours)

100

1000

10000

Rf

[Ω-c

m2]

Rct

[Ω-c

m2 ]


Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn

000001

00001

0001

248 12 16 2040Time (hours)

000001

00001

0001

2 4 6 8 10 12 14 16 18 20 22 240Time (hours)

Cf

[Fcm

minus2 ]

Cdl

[Fcm

minus2 ]




119862119894 = (119876119894119877(1minus119899119894)119894 )1119899119894 (13)





Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn

0001

001

01

2 4 6 8 10 12 14 16 18 20 22 240Time [hours]

I cor

r[m

Ac

m2 ]




4 Conclusions



Competing Interests


Acknowledgments


References


































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


Cu8Ni27Zn10Ni25Zn


Cu8Ni27Zn10Ni25Zn


Cu8Ni27Zn10Ni25Zn


0

minus200

minus400

minus600

minus800

minus1000

minus1200

minus1400

minus1600Z

(Ohm

-cm2)

1200 1400600 800 1000200 400 16000Z (Ohm-cm2)

1

10

100

1000

10000

01 1 10 100 1000 10000 100000001Frequency (Hz)

0

minus10

minus20

minus30

minus40

minus50

minus60

minus70

minus80

minus90

01 1 10 100 1000 10000 100000001Frequency (Hz)

|Z|

(ohm

-cm

2 )

Phas

e ang

le (∘

)




119885CPE =1

119876 (119895120596)119899 (11)







500 1000 1500 2000 25000Z (Ohm-cm2)

0

minus500

minus1000

minus1500

minus2000

minus2500Z

(Ohm

-cm2)

1

10

100

1000

10000

01 1 10 100 1000 10000 100000001Frequency (Hz)

0

minus10

minus20

minus30

minus40

minus50

minus60

minus70

minus80

minus90

01 1 10 100 1000 10000 100000001Frequency (Hz)

|Z|

(ohm

-cm

2 )

Phas

e ang

le (∘

)


Cu-based alloy

Surface oxides

Electrolyte

Surface layer



Rs

RfQf

W

Qdl

Rct









0 4 8 12 16 20 24Time (hours)

Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1SnCu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn

10

100

1000

2 4 6 8 10 12 14 16 18 20 22 240Time (hours)

100

1000

10000

Rf

[Ω-c

m2]

Rct

[Ω-c

m2 ]


Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn

000001

00001

0001

248 12 16 2040Time (hours)

000001

00001

0001

2 4 6 8 10 12 14 16 18 20 22 240Time (hours)

Cf

[Fcm

minus2 ]

Cdl

[Fcm

minus2 ]




119862119894 = (119876119894119877(1minus119899119894)119894 )1119899119894 (13)





Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn

0001

001

01

2 4 6 8 10 12 14 16 18 20 22 240Time [hours]

I cor

r[m

Ac

m2 ]




4 Conclusions



Competing Interests


Acknowledgments


References


































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of





500 1000 1500 2000 25000Z (Ohm-cm2)

0

minus500

minus1000

minus1500

minus2000

minus2500Z

(Ohm

-cm2)

1

10

100

1000

10000

01 1 10 100 1000 10000 100000001Frequency (Hz)

0

minus10

minus20

minus30

minus40

minus50

minus60

minus70

minus80

minus90

01 1 10 100 1000 10000 100000001Frequency (Hz)

|Z|

(ohm

-cm

2 )

Phas

e ang

le (∘

)


Cu-based alloy

Surface oxides

Electrolyte

Surface layer



Rs

RfQf

W

Qdl

Rct









0 4 8 12 16 20 24Time (hours)

Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1SnCu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn

10

100

1000

2 4 6 8 10 12 14 16 18 20 22 240Time (hours)

100

1000

10000

Rf

[Ω-c

m2]

Rct

[Ω-c

m2 ]


Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn

000001

00001

0001

248 12 16 2040Time (hours)

000001

00001

0001

2 4 6 8 10 12 14 16 18 20 22 240Time (hours)

Cf

[Fcm

minus2 ]

Cdl

[Fcm

minus2 ]




119862119894 = (119876119894119877(1minus119899119894)119894 )1119899119894 (13)





Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn

0001

001

01

2 4 6 8 10 12 14 16 18 20 22 240Time [hours]

I cor

r[m

Ac

m2 ]




4 Conclusions



Competing Interests


Acknowledgments


References


































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


0 4 8 12 16 20 24Time (hours)

Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1SnCu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn

10

100

1000

2 4 6 8 10 12 14 16 18 20 22 240Time (hours)

100

1000

10000

Rf

[Ω-c

m2]

Rct

[Ω-c

m2 ]


Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn

000001

00001

0001

248 12 16 2040Time (hours)

000001

00001

0001

2 4 6 8 10 12 14 16 18 20 22 240Time (hours)

Cf

[Fcm

minus2 ]

Cdl

[Fcm

minus2 ]




119862119894 = (119876119894119877(1minus119899119894)119894 )1119899119894 (13)





Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn

0001

001

01

2 4 6 8 10 12 14 16 18 20 22 240Time [hours]

I cor

r[m

Ac

m2 ]




4 Conclusions



Competing Interests


Acknowledgments


References


































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


Cu

23Ni

32Zn

8Ni27Zn

10Ni25Zn

13Ni17Zn

15Ni22Zn

2Ni6Al

13Zn6Mn4Ni

6Zn5Al1Sn

0001

001

01

2 4 6 8 10 12 14 16 18 20 22 240Time [hours]

I cor

r[m

Ac

m2 ]




4 Conclusions



Competing Interests


Acknowledgments


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










Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

Documents

Research Article Corrosion Performance of Cu-Based Coins ...downloads.hindawi.com/journals/jchem/2016/9542942.pdf · Research Article Corrosion Performance of Cu-Based Coins in Artificial