The Effect of Concentration of Lawsonia inermis as a ...downloads.hindawi.com/journals/apc/2017/8521623.pdf2 AdvancesinPhysicalChemistry Table1:Compositionofaluminiumalloy5083(AA5083)

Research ArticleThe Effect of Concentration of Lawsonia inermis asa Corrosion Inhibitor for Aluminum Alloy in Seawater

F Zulkifli1 Norarsquoaini Ali1 M Sukeri M Yusof2 Wan M Khairul2

Rafizah Rahamathullah2 M I N Isa2 and W B Wan Nik1

1School of Ocean Engineering Universiti Malaysia Terengganu 21030 Kuala Terengganu Terengganu Malaysia2School of Fundamental Science Universiti Malaysia Terengganu 21030 Kuala Terengganu Terengganu Malaysia

Correspondence should be addressed to W B Wan Nik niksaniumtedumy

Received 11 October 2016 Revised 2 January 2017 Accepted 23 January 2017 Published 16 February 2017

Academic Editor Claudio Fontanesi

Copyright copy 2017 F Zulkifli et alThis is an open access article distributed under theCreative CommonsAttribution License whichpermits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Lawsonia inermis also known as henna was studied as a corrosion inhibitor for aluminum alloy in seawater The inhibitorhas been characterized by optical study via Fourier transform infrared spectroscopy (FTIR) The FTIR proves the existence ofhydroxyl and carbonyl functional groups in Lawsonia inermis Aluminum alloy 5083 immersed in seawater in the absence andpresence of Lawsonia inermis was tested using electrochemistry method namely electrochemical impedance spectroscopy (EIS)and potentiodynamic polarization (PP) EIS and PP measurements suggest that the addition of Lawsonia inermis has caused theadsorption of inhibitor on the aluminum surface The adsorption behavior of the inhibitor follow Langmuir adsorption modelwhere the value of free energy of adsorption minusΔ119866 is less than 40 kJmol indicates that it is a physical adsorption Finally it wasinferred that Lawsonia inermis has a real potential to act as a corrosion inhibitor for aluminum alloy in seawater

1 Introduction

Recently eco-friendly and biodegradable commodities havecaused a shift towards the use of natural product insteadof using toxic materials [1] Furthermore natural productsderived from various flora and fauna are believed to be safedue to their nontoxic noncarcinogenic and biodegradablenature [2ndash4] Heavy metals such as lead (Pb) which areproduced from industry (painting charcoal burning andleaded gasoline) are known to be a threat to the marineenvironment [5] A previous research has employed Thymusvulgaris as a corrosion inhibitor for stainless steel in acidicsolution [6] The findings show that the inhibitor efficiencyincreases as the concentration increase A very similar findingwas obtained by the other researchers using various plantextracts such as Piper longum Griffonia simplicifolia albapendula and tobacco rob [7ndash10]

Lawsonia inermis (henna) could become one of thepotential natural materials for anticorrosion due to its appli-cation for more than 5000 years as hair and skin pigmentsdue to its excellent dye property [11 12] The presence of

2-hydroxy-14-naphthoquinone attributes to the importantactivities such as antioxidant anti-inflammatory anticancerand anticorrosion [13ndash15] Lawsonia inermis exhibits anexquisite inhibition effect towards corrosion [16ndash18] Polar-ization technique was used to characterize the aqueousextract of the henna leaves as a corrosion inhibitor of carbonsteel nickel and zinc in acidic neutral and alkaline solutionsreported elsewhere [19]

The mechanism of the organic inhibitor is usuallyan adsorption process The heteroatom in the inhibitorrsquosmolecule acts as an active site for the adsorption to take placeThe physical and chemical properties of inhibitor moleculeinfluence the adsorption process and this is related to theelectronic density of donor atoms and the possible stericeffects [20] Furthermore the nature of metal surface thechemical composition of the corrosive medium and temper-ature of the reaction and on the electrochemical potential atthe metalsolution interface also manipulate the adsorptionprocess [21] Nevertheless to the best of authorrsquos knowledgethe study of Lawsonia inermis as a corrosion inhibitor hasnever been employed to aluminum alloy in seawater

HindawiAdvances in Physical ChemistryVolume 2017 Article ID 8521623 12 pageshttpsdoiorg10115520178521623

2 Advances in Physical Chemistry

Table 1 Composition of aluminium alloy 5083 (AA5083)

Element Mg Mn Fe Si Zn Cr Ti Cu AlWeight percent wt 45 07 04 04 025 015 015 01 Remaining

In marine industry metals like aluminum alloy playtremendous roles in which they are used widely for ship-building chemical plant and offshore structure [22 23] Theincreasing sector demand for higher speed performances andcheap assembly technology has made aluminum alloy as oneof the best choices as a structural material for boats vesselsand components [24 25] The advantages of aluminum inmany ways have propelled it into one of the widely usedmetals in the marine industries

To better understand the inhibitive behavior of natu-ral products Lawsonia inermis as corrosion inhibitor wasinvestigated via electrochemical impedance spectroscopy andpotentiodynamic polarization Meanwhile the optical studywas conducted by using Fourier transform infrared (FTIR)and the quantum chemical calculationwas done to determinethe synergism behavior of the inhibitor

2 Experimental

21 Surface Preparation of Aluminum Alloy 5083 (AA5083)AA5083 with the dimension of 25mm times 25mm times 3mm waspolished by using emery paper with different grades (600900 and 1200) Then the samples were cleaned with acetoneand rinsed with distilled water dried in air and then storedin desiccators prior to use Table 1 shows the composition ofAA5083 [26]

22 Extraction of Lawsonia inermis (Henna) The fresh leavesof Lawsonia inermiswere dried at room temperature and thencrushed into powder form Lawsonia inermis powder wasmixed with ethanol and left for a week Then the mixturewas extracted by means of the rotary evaporator The residueleft in the flush was used directly by diluting it to 20 litersof seawater with respect to inhibitor concentration Seawaterwas collected at Universiti Malaysia Terengganu beachfrontThe composition of South China Sea seawater is shown inTable 2

23 Fourier Transform Infrared Analysis (FTIR) and Ultravio-let Visible Spectroscopy (UV-Vis) FTIR was carried out usingThermo Nicolet 380 FTIR Spectrometer The spectrometerwas used to identify the functional groups of Lawsoniainermis by observing at the vibrationalmotion of bonds in themolecule An infrared light was passing through the samplethat was placed on the germanium crystal The frequencywas ranging from 4000 to 675 cmminus1 with spectra resolutionof 4 cmminus1 following the work done as reported elsewhere[27]The FTIR data was recorded in the transmittance modeThe transmittance and reflectance of the infrared rays atdifferent frequencies were translated into an IR absorptionplot consisting of reverse peaks The spectral pattern wasanalyzed and matched according to IR absorption table toidentify the functional group contained in the Lawsonia

Table 2 Composition of seawater from South China Sea

Parameter ReadingpH 7492Temperature (∘C) 2946Conductivity (mScm) 5256Salinity (ppt) 3158Dissolved oxygen (mgL) 7086Turbidity (NTU) 005

O

O

HO

Figure 1 Molecular structure of Lawsonia inermis

inermis Figure 1 shows themolecule structure of lawsone thatis the central component in Lawsonia inermis [16 28]

AUV-Vismeasurementwas performed using an in-housebuilt cell which allowed the transmission of light throughthe cell UVVis spectroscopy (Lambda 265 Perkin Elmer)recorded the absorbance between 200ndash800 nm in transmis-sion mode where ethanol was used as the background

24 Electrochemical Impedance Spectroscopy (EIS) EIS wasused to study the impedance characteristic as well as capac-itance behavior of AA5083 in the presence and absenceof henna The EIS measurement was performed by usingalternating current (AC) signal of impedance measurementsby means of Autolab PGSTAT302N with respect to the opencircuit potential (OCP) All the potentials referred wererelative to saturated calomel electrode (SCE)The impedancemeasurements used a frequency range of 1 kHz down to10mHz The results were analyzed using the fit program ofNOVA 110

Open circuit potential (OCP) measurement was con-ducted to investigate the potential of electrode at varioustemperatures OCP was run for 1800 s while the limit 119889119881119889119905was set to 1120583VsThe average potential was taken as the OCPof the electrode

25 Potentiodynamic Polarization (PP) Potentiodynamicpolarization (PP) is the most common polarization methodused for measuring corrosion resistant The cell used was aconventional three electrodes with a platinum wire counterelectrode (CE) and AgAgCl as a reference electrode (RE)The working electrode (WE) is in the form of a square

Advances in Physical Chemistry 3

cut so that the flat surface would be the only surface inthe electrode The potentiodynamic current-potential curvesrecorded the data after the electrode potential was automat-ically changed from minus200mV to +200mV with the scanningrate of 10mVsminus1 The results were analyzed and fitted usingNOVA 110 program Corrosion current density (119894corr) wascalculated by using a validated Stern-Geary equation [29] asshown in (1) where 119887119886 is anodic Tafel slope 119887119888 is cathodic Tafelslope and 119877119901 is the polarization resistance

119894corr =119887119886 times 119887119888

2303119877119901 (119887119886 + 119887119888) (1)

26 Inhibition Efficiency (120578) Inhibition efficiency (120578) wascalculated based on the findings gained from EIS and PPmeasurements The calculated value of 120578 from EIS methodwas done by employing (2) where 119877ct(inhibitor) is the chargetransfer resistance in the presence of inhibitor while 119877ct is thecharge transfer resistance in the absence of inhibitor

120578 () =119877ct(inhibitor) minus 119877ct

119877ct(inhibitor)times 100 (2)

The value of 119894corr was used to determine the inhibitionefficiency of Lawsonia inermis based on

120578 () =119894corr minus 119894corr(inhibitor)

119894corrtimes 100 (3)

where 119894corr is the corrosion current density in the absence ofinhibitor and 119894corr(inhibitor) is the corrosion current density inthe presence of inhibitor

27 Adsorption Isotherm To understand the adsorptionmode of the corrosion resistance on the surface of AA5083the data obtained from the three different techniques weretested with several adsorption isotherms models includingLangmuir Frumkin and Temkin The surface coverage 120579was calculated by following equationwhere 120578 is the inhibitionefficiency

120579 =120578 ()100 ()

(4)

The plots of concentration (119862) versus concentrationsurfacecoverage (119862120579) were plotted to determine the thermody-namic parameter

3 Results and Discussion

31 Fourier Transform Infrared (FTIR) FTIR method deter-mines the type of vibrational band presence in Lawsoniainermis Lawsonia inermis is known to contain various con-stituents such as lawsone flavonoids gallic acid and tannin[30]

Infrared spectrum forLawsonia inermis reveals twomajorexpected frequency regions of the band of interest namelyhydroxyl (OH) and carbonyl (C=O) Lawsone (2-hydroxy14-naphthoquinone) is represented by the hydroxyl group A

Wavenumbers (cmminus1)

Tran

smitt

ance

(au

)

102

100

098

096

094

092

090

088

086

084

3960

3376912

29777

16334922362488

144835

17222061265137

1045281

862067

3630 3300 1650

877496

904496

6601320 9902970 2640 2310 1980

Figure 2 FTIR spectrum of Lawsonia inermis

broadband centered at 3376 cmminus1 in Figure 2 was attributedto the stretching vibration of the hydroxyl group which canbe found at the first lawsone aromatic ring [31 32]The broadabsorbance is due to the intramolecular hydrogen bondingbetween the OH group and adjacent oxygen atom Lawsoneand tannin which were represented by hydroxyl and carbonylfunctional group improved Lawsonia inermis performance aschelating agent [33]

Quinones usually exhibit its carbonyl band in the range of1655ndash1690 cmminus1 [34] The adsorption bands which appearedat 1722 and 1633 cmminus1 were attributed to 120572120573-unsaturatedcarbonyl band [35] The presence of hydroxyl or oxidationprocess at C=O results in lowering the frequency due tocharge transfer complexes of hydroquinone [36] Quinonescan bond potentially to metal ions in three different states (i)quinone (ii) its one electron reduced to form semiquinoneand (iii) catechol the two electrons reduced form [37]

The adsorption of Lawsonia inermis on the metal surfacegreatly depends on its functional groups Carbonyl (C=O)and hydroxyl (-OH) as the major Lawsonia inermis con-stituents improve henna as chelating agent [38 39] Theexistence of these compounds helps henna molecules tochelate on the surface of AA5083 and hence reduces thesurface exposure to the chloride attack where the similarresult has been demonstrated [33]

While C=C has a lower dipole it gives a less absorbanceintensity compared toC=OUsually this functional group canbe found at lower frequency that is less than 1600 cmminus1 Asseen in this IR spectra C=C was found as a weak band at1448 cmminus1 signifying aromatic C=C group [36]

TheUV-Vis spectra of Lawsonia inermis and itsmain con-stituent 2-hydroxy-14-naphthoquinone (HNQ) are depict-ed in Figure 3 A weak absorption band of Lawsonia inermisat 286 nm is due to the presence of benzene and quinone with120587-120587lowast electron transitionThe attachment of functional groupsuch as hydroxyl (OH) at the benzene ring causes a longerwavelength peak at 342 nm as shown by the HNQ Anotherweak absorption band at 416 nm is due to the 119899-120587lowast transitionsof carbonyl group in the quinone ring [40]


32 Electrochemical Impedance Spectroscopy (EIS) Electro-chemical impedance spectroscopy (EIS) was further con-ducted in order to investigate the impedance and capacitivebehavior at the metalsolution interface Figure 4(a) showsNyquist plots obtained from AC impedance measurementsof AA5083 at different doses of Lawsonia inermis The semi-circular shapes observed at all concentrations of Lawsoniainermis indicate that there are no changes in corrosionmechanism irrespective of the absence and presence ofinhibitor The size of the semicircle reflects the degree ofthe inhibitorrsquos impedance Larger semicircle visualizes higherimpedance that contributes to better inhibition performanceAs seen there are a few imperfect semicircles in the plotswhich are due to the inhomogeneity or surface roughnessof the electrode [41ndash44] and hence lead to the frequencydispersion which is typical for solid metal electrode [45]

Oxidation of aluminum by oxygen O2 is a fast reactionHence it is impossible to produce an oxide-free surface [46]The formation of the oxide layer on the aluminum surfacedue to the interfacial reaction and the adsorption of Lawsoniainermis on the aluminum surface are defined by the singlecapacitive loop as seen in the plotsThe loop is also associatedwith the charge transfer involved in the corrosion process aswell as double layer behavior All processes that is formationof oxide layer and adsorption of inhibitor on the metalsurface are represented by a single capacitive loop due to ofthe overlapping of these processes

Theoretically the dissolution of aluminum in seawaterstarts when there is a formation of Al+ at the metal-oxideinterface [47] The ions then migrate through oxide-solutioninterface and oxidized to Al3+ which is similar to the workby previous researcher [45]The presence of inhibitor promi-nently causes the complexation of the inhibitor with an oxidelayer at the aluminum surface The adsorption that occurs atthe interface (metal-oxide-hydroxide-inhibitor) leads to theformation of a complex compound [45 48] The chronologyof the mechanisms can be determined as follows

In the anodic half-cell reaction the dissolution of alu-minum takes place according to the following equation [49ndash51]

Alads 997888rarr Al3+ + 3119890minus (5)

Theoxygen reduction occurs at cathodic half-cell yieldingthe following equation

1

2O2 + 2H2O + 3eminus 997888rarr 3OHminus + 1

2H2 (6)

The overall equation is represented by the followingequation

Al3+ + 3OHminus 997888rarr Al (OH)3 sdot 3H2O (7)

In chloride containing solution like seawater the alu-minum anion undergoes hydrolysis

Al3+ +H2Olarrrarr H+ + Al (OH)2+ (8)

Aluminum hydroxide reacts with chloride

Al (OH)2+ + Clminus 997888rarr Al (OH)Cl+ (9)

0010203040506070809

1

200 250 300 350 400 450 500 550 600

Abso

rban

ce

Wavelength (nm)

Lawsonia inermisHNQ

418 nm

342nm

286 nm

Figure 3 UV-Vis spectrum of Lawsonia inermis and its mainconstituent

Table 3 EIS parameters of aluminum in the absence and presenceof Lawsonia inermis

Concentration (ppm) CPE (119865) 119877ct (Ω) CPE (119899) 120578 ()0 400119864 minus 04 11023 0998 mdash200 140119864 minus 04 52938 0998 79400 160119864 minus 04 96567 0998 89600 780119864 minus 05 143840 0996 92800 620119864 minus 05 96942 0997 891000 150119864 minus 04 57612 0998 81

It further reactswithwater consequently producing acidicconditions

Al (OH)Cl+ +H2Olarrrarr Al (OH)2 Cl +H+ (10)

The inhibitor acts by adsorbing on the metal surface bydisplacing the water molecules hence [4 47]

Org (sol) + 119909H2O 997888rarr Org (ads) 119909H2O (11)

Due to positively charge of the inhibitory complex therepulsion on H+ occurs and reduces the hydrogen evolutionprocess

The value of charge transfer resistance119877ct constant phaseelement CPE and inhibition efficiency 120578 is tabulated inTable 3119877ct is the valuewhich represents ameasure of electrontransfer across the surface and is inversely proportional to thecorrosion rate [52 53] The value of 119877ct is low in the absenceof inhibitor and upon addition of the inhibitor this valueincreases until 600 ppm Exceeding this dose causes the valueof 119877ct to decrease due to the electrostatic repulsion at themetal-inhibitor interface and the remaining inhibitors in thesystem have likely to form natural aggregate which resultedin the decrease of the inhibition efficiency Therefore theoptimumvalue of119877ct and inhibition efficiency (120578) at 600 ppmindicates that this is the best concentration of Lawsoniainermis in this system

In this study CPE is treated as a parallel combination ofa pure capacitor and a resistor being inversely proportional


to the angular frequency where 119877119904 is solution resistor and 119877ctis charge transfer resistance A greater depression in Nyquistsemicircle diagram is due to the electrode surface irregularitywhere the metal-solution interface acts as a capacitor withirregular surface The impedance of the CPE is expressed as[50 53 54]

119885CPE =1

1198840 (119895120596)119899 (12)

where1198840 is themagnitude of the CPE 119895 is the imaginary unit120596 is the angular frequency (120596 = 2120587119891 where 119891 is the ACfrequency) and 119899 is the CPE exponent (phase shift)

The value of CPE in this study was in the opposite trendcompared to the value of 119877ct The decrease of CPE was due tothe decrease in the local dielectric constant andor an increasein the electrical double layer This phenomenon shows thatthe inhibitorworks by the adsorption process where thewatermolecule on the metal surface is replaced by the inhibitor

Two assumptions were made in order to determine thevalue of CPE in which the first assumption is CPE is due tothe surface distribution across an interface Physically thismodel implies that the interface varies in impedance withinthe plane of interface and would be the case if the oxide filmwas uniformacross the surfaceThe second assumption is thatthe film varies through its thickness and the film impedanceand is modeled as a series of R-C-R circuits as shown inFigure 5 [55]

The Bode plot represents a wide range of frequencydata which can be plotted in one graph In the Bode plotslog |119885| and phase angle (∘) are plotted against log119891 (Hz)A Bode phase in Figure 4(b) shows phase angle plots foraluminum alloy in seawater In the absence of inhibitor thephase angle falls nearly at 0∘ in the high frequency regionThis is a characteristic response to resistive behavior Thepresence of Lawsonia inermis has caused the phase angleto fall at higher degree compared to uninhibited sampleThe presence of Lawsonia inermis has remarkably alteredthe system to act more likely a capacitive behavior At theintermediate frequency the phase angle of 0 ppm (774∘)200 ppm (743∘) 400 ppm (74∘) 600 ppm (727∘) 800 ppm(723∘) and 1000 ppm (679∘) can be observed A high degreeof phase angle in this intermediate frequency region indicatesthe capacitive behavior of the system An ideal capacitivebehavior will show a minus90∘ phase angle The deviation of fromthe ideal capacitor (minus90∘) arises due to the nonideal behaviorof the capacitor represented by the control phase element inthe circuit (Figure 4)

For a log |119885| versus log119891 plots as depicted in Figure 4(c)the uninhibited system tends to approach zero which repre-sented the resistive behavior at high frequency All the inhib-ited systems show a minus1 slope which lies from high frequencyto intermediate frequency The magnitude of log |119885| wasfound to be the lowest at uninhibited systemwhile the highestmagnitude of log |119885| was found at 600 ppm which indi-cates that this is the optimum concentration of inhibitor to beusedThe capacitive behavior is represented by the liner rela-tionship between the log |119885| and log119891 It is evidence that theaddition of Lawsonia inermis has changed the characteristicof the system from resistive behavior to capacitive behavior

Open circuit potential (OCP) is measured to determinethe potential stability of aluminum alloy (5083) in the pres-ence and absence of Lawsonia inermis as shown in Figure 6To this point there is no electrical interruption and the netpotential measured on electrode is the noble potential [56]The absence of Lawsonia inermis has caused the electrodeto be in the most negative potential region It is prominentfor the electrode to undergo general corrosion in this regioncompared to the electrode which has more positive potential[57] Apparently after the addition of Lawsonia inermis thepotential moves towards more positive region The electrodebecomes less active due to the decreased rate of metaldissolution [58]

33 Potentiodynamic Polarization (PP) Potentiodynamicpolarization study was conducted to distinguish the effectof the inhibitor on the anodic dissolution of AA5083 andcathodic oxygen reduction correspondingly Table 4 revealspolarization parameters of AA5083 in the presence andabsence of Lawsonia inermis Lawsonia inermis was assumedto act as an anodic inhibitor due to its noticable changes inanodic Tafel branch 119887119886 value The adsorption of Lawsoniainermis on AA5083 surface restrained the corrosion processby merely blocking the reaction site of the metal surface andconsequently reducing the value of 119887119886 [59 60]

A graphical data as depicted in Figure 7 shows a promi-nent shifting in cathodic Tafel branch 119887119888 to a lower valueof corrosion current density The mechanism of the oxygenreduction occurs at the cathodic region which afterwardcauses the shifting of 119887119888 [45 61] It is well known that thechanges in 119887119888 justify the modification in the cathodic reactionmechanism Hence the second assumption was made thatLawsonia inermis act as cathodic inhibitor

A breakdown potential 119864119887 was prominently seen for thealuminum samples inhibited at 800 ppm and 1000 ppm 119864119887is a potential at which the anodic polarization curve shows amarked increase in current density leading to the breakdownof the passive film and pit initiation For both concentrations119864119887 is an indicator as a breakdown of the inhibition filmwhichcauses a further reduction in inhibition efficiency

34 Adsorption Isotherm Adsorption isotherm study wasconducted to investigate the interaction between the metaland inhibitor as well as the equilibriumof the adsorptionTheprocess of adsorption occurs when liquid or gas accumulateson the surface of a solid or liquid forming a molecular oratomic film In general adsorption isotherm can be dividedinto two categories First category occurs when themoleculesadsorb but their chemical originality remains unchanged Inthis state the adsorption bond between inhibitor moleculeand surface is fairly weak The molecules may exchange theirpeer molecules from solution In contrast the adsorptionbond may be very strong due to charge transfer reaction andresult in the formation of new species

Organic inhibitor adsorption is generally a substitutionprocess of water molecules on the metal surface by inhibitormolecule There are a few models available for the fittingpurposes but the Langmuir adsorption model was found tofit well with the experimental data The plot of Langmuir


0

1000

2000

3000

4000

5000

6000

7000

8000

0 1000 2000 3000 4000 5000 6000 7000 8000

1000 ppm

800 ppm

600 ppm

400 ppm

200 ppm

0 ppm

Z998400 (Ωmiddotcm2)

minusZ998400998400

(Ωmiddotcm

2)

(a)

0

10

20

30

40

50

60

70

80

90

01 1 10 100 1000

1000 ppm

800 ppm

600 ppm

400 ppm

200 ppm

0 ppm

logf (Hz)

Phas

e ang

le (∘

)

(b)

1

10

100

1000

10000

01 1 10 100 1000

1000 ppm

800 ppm

600 ppm

400 ppm

200 ppm

0 ppm

logf (Hz)

logZ

(Ωcm

2)

(c)

Figure 4 (a) Nyquist plots (b) phase angle versus log119891 plots and (c) log119885 versus log119891 plots of AA5083 in the absence and presence ofinhibitor

Table 4 Nyquist parameters for aluminum alloy in the absence and presence of Lawsonia inermis

Concentration (ppm) 119887119886 (Vdec) 119887119888 (Vdec) 119864corr (V) 119894corr (Acm2) Corr rate (mmyear) 120578 ()

0 027 026 minus072 171119864 minus 05 110 mdash200 009 012 minus073 356119864 minus 06 032 79400 007 007 minus074 192119864 minus 06 028 89600 007 012 minus076 112119864 minus 06 009 93800 012 019 minus073 180119864 minus 06 040 891000 013 019 minus074 323119864 minus 06 018 81


CPE

Rct

Rs

Figure 5 The Randles CPE circuit which is equivalent for thisimpedance spectrum

minus07

minus08

minus09

minus10

minus11

600 ppm800 ppm

1000 ppm

400 ppm

200 ppm

0 ppm

0 50 100 150

Time (s)

Pote

ntia

l (V

)

Figure 6 OCP of AA5083 in the presence and absence of Lawsoniainermis

adsorptionmodel is shown in Figure 8 where the value of 120579 isequal to 120578100 The general form of the Langmuir adsorptionmodel is [62]

119902119890 = 119902max119870119871119862119890

1 + 119870119871119862119890 (13)

where 119902119890 is the amount of adsorbate adsorbed on the adsorb-ent at equilibrium (mol gminus1) 119902max is themaximumadsorptioncapacity corresponding to a complete monolayer coverage onthe adsorbent surface (mol gminus1)119870119871 is the Langmuir constant(dm3molminus1) and 119888119890 is the concentration of adsorbate atequilibrium (mol dmminus3) The values of 119902max and 119870119871 can beevaluated from the slope and the intercept of the linear formof the Langmuir equation

119888119890119902119890=

1

119902max119870119871+

119888119890119902max

(14)

The free energy change Δ119866 of adsorption is given byΔ119866 = minus119877119879 ln119870 where 119877 is the universal gas constant(8314 Jmolminus1 Kminus1) 119879 is the temperature (K) and 119870 is theequilibrium constant

Free energy of adsorption Δ119866 values is tabulated inTable 5 The negative value indicates that the adsorption onthe metal surface is spontaneous Δ119866 values around minus20 kJmol or lower are consistent with the electrostatic interactionbetween charged molecule and charged metal surface knownas physisorption If the value is higher the chemisorptionswill occur where the coordinate type of metal bond will be

Table 5 The calculated values of 119870119871 and minusΔ119866 gained from twoexperimental methods (EIS and PP)

119870119871 dm3molminus1 minusΔ119866 kJmol

PP EIS PP EIS3275 3247 9 9

formed by the charge sharing or transfer from organic mole-cules to the metal surface The negative value of Δ119866 suggeststhat the physisorption of inhibitor on the metal surface is aspontaneous process and the adsorbed layer was stable [63]

The adsorption of Lawsonia inermis is favored by the pre-sence of lone pair electrons of O atom Lawsonia inermismolecules were adsorbed on the aluminum surface due toelectrostatic forces [64ndash66] Adsorption of this inhibitor hasdisplaced the water molecules available on the metal surfaceThe interaction between the organic molecules and the metalsurfaces is obtained from various adsorption isotherm mod-els Assuming that the inhibition was due to the adsorption120578 was considered as surface coverage on the molecule [67]

The presence of electrons donating group in the inhibitorand delocalized aromatic ring may provide electrostaticadsorptionThe higher inhibition efficiency may also suggestthe formation of inhibitor surface complex that offers barrierprotection The positively charged surface complex preventsthe approach of H+ ion by electrostatic repulsion

Figure 9(a) represents a metal-solution interface foruninhibited system The charge transfer resistance 119877ct is acorresponding value between the metal and the OHP (outerHelmholtz plane) Without the inhibitor the ionic layer isdense with the cation which migrates from the bulk solutionand accumulates near the OHP due to the polarity of watermolecules Hence the value of CPE is high at this stateFigure 9(b) shows that the protonation of Lawsonia inermishas caused the protonated inhibitor to electrostatically adsorbonto themetal surface through its hydrogen ionsThe adsorp-tion of this ion consequently reduces the value of CPE due tothe reduction of thin ionic layer at the OHP and at the sametime increases the value of 119877ct as well

Lawsonia inermis can be categorized as a cooperativeadsorbent due to its ion adsorption on metaloxidesurfaceimpurities such as chloride ion For cooperative adsorptionthe protonated lawsone can electrostatically adsorb onto thechloride-covered surface through its hydrogen ion as shownin Figure 10 As previously discussed quinone reduces its oneelectron to form semiquinone while the available hydrogenions adsorb electrostatically with chloride ion on the alumi-num surface

35Morphology Study via Scanning ElectronMicroscope Fig-ure 11 shows the SEMmicrograph of AA5083 at 600 ppm con-centration of Lawsonia inermis An adsorbed white flake canbe seen on the metal surface and densely distributed on themetal surface The adsorption of Lawsonia inermis reducedthe free space onmetal surface and hence the chloride cannotattack the metal surface The display figure shows no cracksand pits at this concentration The employment of Lawsonia


10E minus 03

10E minus 04

10E minus 05

10E minus 06

10E minus 07

10E minus 08

minus095 minus085 minus075 minus065 minus055 minus045

Potential (V versus SCE)

logi

(120583A

cm

2)

1000 ppm

800 ppm

600 ppm

400 ppm

200 ppm

0 ppm

Eb

Figure 7 Tafel plot of aluminum alloy in the absence and presence of Lawsonia inermis

0

200

400

600

800

1000

1200

1400

0 200 400 600 800 1000 1200

EISPP

C120579

C (ppm)

Linear (PP) R2 = 09842

Linear (EIS) R2 = 09862

Figure 8 Langmuir adsorption model from two experimental methods (EIS and PP) at 30 days of immersion

inermis as corrosion inhibitor was seen to be successful dueto this behavior

While in the absence of Lawsonia inermis the surface ofAA5083 shows cracks pits and heterogenous layers as canbe seen in Figure 12 The black spot around the cracks wasbelieved to be the redeposition of copper (Cu) due to theintermetallic reaction with the metal matrix

4 Conclusion

Lawsonia inermis is a possible green material to be devel-oped as corrosion inhibitor for aluminum alloy in marine

environment This is due to the existing of heteroatomslike oxygen and hydrogen which become active centres foradsorption process Via electrochemical method the inhi-bitor was found to enhance the charge transfer resistance119877ct as the concentration increases The capacitive behaviorof the inhibitor decreases correspondingly to the increasingof concentration signifying that the inhibitor alters the die-lectric constant of the layer 119864corr value shifted towards thecathodic region and the difference of 119864corr in the absenceand presence of inhibitor is 34mV suggesting that Lawsoniainermis is a mixed type inhibitor The corrosion currentdensity value 119868corr decreases upon the addition of inhibitor


+

+

+

+

+

+

eminus

eminus

eminus

eminus

eminus

eminus

eminus

eminus

OHP

Met

al

Solu

tion

(a)

++

+

+

OHP

H+

H+

Met

al

Solu

tion

(b)

Figure 9 A schematic presentation of (a) metal-solution interface and (b) metal-inhibitor-solution interface

Metal surface Metal surface

Clminus ClminusH2O H2O

(Org)

(Org)

H+

H+

Figure 10 The adsorption mechanism of Lawsonia inermis onAA5083

Figure 11 SEM micrograph of AA5083 at 600 ppm

suggesting that the adsorption of the inhibitor has reducedthe current passing through the system and at the same timethe inhibitor demonstrates the semiconductor behavior bylimiting the current flow through the system

The adsorption isotherm calculation shows that theinhibitor is well fitted to the Langmuir adsorption modelwhile the value of free energy Δ119866 is less than minus20 kJmolindicating that the inhibitor performs an electrostatic adsorp-tion which is considered as physical adsorption All charac-terizations show that at 600 ppm the inhibitor is excellentlyinhibiting the corrosion process and the highest inhibitionefficiency is gained at this concentrationTherefore 600 ppm

Figure 12 SEM micrograph of AA5083 in the absence of Lawsoniainermis

of Lawsonia inermis is the best concentration to be used ascorrosion inhibitor for aluminum alloy in seawater

Competing Interests

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

Acknowledgments

The authors would like to express their deepest gratitude forthe scholarship provided by Ministry of Education Malaysia(MyPhD) Fundamental Research Grant Scheme (VOT 59210and VOT 59283) Look East Policy Grant (VOT 53168) andMiss Suria Hani Binti Ibrahim (English Learning Centre) forEnglish language proofread

References

[1] S Ananth P Vivek T Arumanayagam and P MurugakoothanldquoNatural dye extract of lawsonia inermis seed as photo sen-sitizer for titanium dioxide based dye sensitized solar cellsrdquoSpectrochimica Acta Part A Molecular and Biomolecular Spec-troscopy vol 128 pp 420ndash426 2014


[2] S Ali T Hussain and R Nawaz ldquoOptimization of alkalineextraction of natural dye from Henna leaves and its dyeing oncotton by exhaust methodrdquo Journal of Cleaner Production vol17 no 1 pp 61ndash66 2009

[3] F Suedile F Robert C Roos and M Lebrini ldquoCorrosioninhibition of zinc by Mansoa alliacea plant extract in sodiumchloride media extraction characterization and electrochemi-cal studiesrdquo Electrochimica Acta vol 133 pp 631ndash638 2014

[4] D Prabhu and P Rao ldquoCoriandrum sativum Lmdasha novel greeninhibitor for the corrosion inhibition of aluminium in 10 Mphosphoric acid solutionrdquo Journal of Environmental ChemicalEngineering vol 1 no 4 pp 676ndash683 2013

[5] M Chen J-M Lee I S Nurhati A D Switzer and E A BoyleldquoIsotopic record of lead in Singapore Straits during the last 50years spatial and temporal variationsrdquo Marine Chemistry vol168 pp 49ndash59 2015

[6] A Ehsani M Mahjani M Hosseini R Safari R Moshrefi andH M Shiri ldquoEvaluation of Thymus vulgaris plant extract as aneco-friendly corrosion inhibitor for stainless steel 304 in acidicsolution by means of electrochemical impedance spectroscopyelectrochemical noise analysis and density functional theoryrdquoJournal of Colloid and Interface Science vol 490 pp 444ndash4512017

[7] A Singh I Ahamad andMAQuraishi ldquoPiper longum extractas green corrosion inhibitor for aluminium in NaOH solutionrdquoArabian Journal of Chemistry vol 9 no 2 pp S1584ndashS15892012

[8] E Ituen O Akaranta A James and S Sun ldquoGreen and sustain-able local biomaterials for oilfield chemicals Griffonia simpli-cifolia extract as steel corrosion inhibitor in hydrochloric acidrdquoSustainable Materials and Technologies vol 11 pp 12ndash18 2017

[9] M Jokar T S Farahani and B Ramezanzadeh ldquoElectrochem-ical and surface characterizations of morus alba pendula leavesextract (MAPLE) as a green corrosion inhibitor for steel in 1MHClrdquo Journal of the Taiwan Institute of Chemical Engineers vol63 pp 436ndash452 2016

[10] HWangM Gao Y Guo Y Yang and R Hu ldquoA natural extractof tobacco rob as scale and corrosion inhibitor in artificialseawaterrdquo Desalination vol 398 pp 198ndash207 2016

[11] D Kirkland and D Marzin ldquoAn assessment of the genotoxicityof 2-hydroxy-14-naphthoquinone the natural dye ingredient ofHennardquo Mutation ResearchmdashGenetic Toxicology and Environ-mental Mutagenesis vol 537 no 2 pp 183ndash199 2003

[12] K N Jallad and C Espada-Jallad ldquoLead exposure from the useof Lawsonia inermis (Henna) in temporary paint-on-tattooingand hair dyingrdquo Science of the Total Environment vol 397 no1-3 pp 244ndash250 2008

[13] S Salunke-Gawali L Kathawate Y Shinde V G Puranik andT Weyhermuller ldquoSingle crystal X-ray structure of Lawsoneanion evidence for coordination of alkalimetal ions and forma-tion of naphthosemiquinone radical in basic mediardquo Journal ofMolecular Structure vol 1010 pp 38ndash45 2012

[14] E C Jeyaseelan S Jenothiny M K Pathmanathan and JP Jeyadevan ldquoAntibacterial activity of sequentially extractedorganic solvent extracts of fruits flowers and leaves of Lawsoniainermis L from Jaffnardquo Asian Pacific Journal of Tropical Bio-medicine vol 2 no 10 pp 798ndash802 2012

[15] I Abulyazid E M E Mahdy and R M Ahmed ldquoBiochemicalstudy for the effect of henna (Lawsonia inermis) on Escherichiacolirdquo Arabian Journal of Chemistry vol 6 no 3 pp 265ndash2732013

[16] S Rajendran M Agasta R Bama Devi B Shyamala Devi KRajam and J Jayasundari ldquoCorrosion inhibition by an aqueousextract of Henna leaves (Lawsonia inermis L)rdquo Zastita Mater-ijala vol 50 pp 77ndash84 2009

[17] A Ostovari S M Hoseinieh M Peikari S R Shadizadehand S J Hashemi ldquoCorrosion inhibition of mild steel in 1M HCl solution by henna extract a comparative study of theinhibition by henna and its constituents (Lawsone Gallic acid120572-d-Glucose and Tannic acid)rdquo Corrosion Science vol 51 no 9pp 1935ndash1949 2009

[18] A Motalebi M Nasr-Esfahani R Ali and M PourriahildquoImprovement of corrosion performance of 316L stainless steelvia PVTMShenna thin filmrdquo Progress in Natural ScienceMaterials International vol 22 no 5 pp 392ndash400 2012

[19] J Buchweishaija ldquoPhytochemicals as green corrosion inhibitorsin various corrosive media a reviewrdquo Tanzania Journal ofScience vol 35 pp 77ndash92 2009

[20] K F Khaled and N Hackerman ldquoInvestigation of the inhibitiveeffect of ortho-substituted anilines on corrosion of iron in 1 MHCl solutionsrdquo Electrochimica Acta vol 48 no 19 pp 2715ndash2723 2003

[21] B Liu H Xi Z Li and Q Xia ldquoAdsorption and corro-sion-inhibiting effect of 2-(2-[2-(4-Pyridylcarbonyl) hydra-zono]methylphenoxy)acetic acid on mild steel surface in sea-waterrdquo Applied Surface Science vol 258 no 17 pp 6679ndash66872012

[22] Z Hu LWan S Lu P Zhu and SWu ldquoResearch on themicro-structure fatigue and corrosion behavior of permanent moldand die cast aluminum alloyrdquoMaterials and Design vol 55 pp353ndash360 2014

[23] H-C Jiang L-Y Ye X-M Zhang G Gu P Zhang and Y-L Wu ldquoIntermetallic phase evolution of 5059 aluminum alloyduring homogenizationrdquo Transactions of Nonferrous MetalsSociety of China vol 23 no 12 pp 3553ndash3560 2013

[24] S Ferraris and L M Volpone ldquoAluminum alloys in third mil-lennium shipbuilding Materials technologies perspectivesrdquo inProceedings of the 5th International Forum on Aluminum Shipspp 1ndash10 Tokyo Japan 2005

[25] S Benson J Downes and R S Dow ldquoLoad shortening charac-teristics of marine grade aluminium alloy plates in longitudinalcompressionrdquoThin-Walled Structures vol 70 pp 19ndash32 2013

[26] M Ashjari A Mostafapour Asl and S Rouhi ldquoxperimentalinvestigation on the effect of process environment on themech-anical properties of AA5083Al2O3 nanocomposite fabricatedvia friction stir processingrdquo Materials Science and EngineeringA vol 645 pp 40ndash46 2015

[27] A S Samsudin W M Khairul and M I N Isa ldquoCharacteriza-tion on the potential of carboxy methylcellulose for applicationas proton conducting biopolymer electrolytesrdquo Journal of Non-Crystalline Solids vol 358 no 8 pp 1104ndash1112 2012

[28] S Elavarasan and M Gopalakrishnan ldquoSynthesis structuralanalysis theoretical studies of some lawsone derivativesrdquo Spec-trochimica Acta Part A Molecular and Biomolecular Spec-troscopy vol 133 pp 1ndash6 2014

[29] A Poursaee ldquoPotentiostatic transient technique a simpleapproach to estimate the corrosion current density and Stern-Geary constant of reinforcing steel in concreterdquo Cement andConcrete Research vol 40 no 9 pp 1451ndash1458 2010

[30] A Y El-Etre M Abdallah and Z E El-Tantawy ldquoCorrosioninhibition of some metals using lawsonia extractrdquo CorrosionScience vol 47 no 2 pp 385ndash395 2005


[31] Y Takeda and M O Fatope ldquoNew phenolic glucosides fromLawsonia inermisrdquo Journal of Natural Products vol 51 no 4pp 725ndash729 1988

[32] N Uddin B S Siddiqui S Begum et al ldquoBioactive flavonoidsfrom the leaves of Lawsonia alba (Henna)rdquo PhytochemistryLetters vol 4 no 4 pp 454ndash458 2011

[33] K E Jasim S Al-Dallal and A M Hassan ldquoHenna (Lawsoniainermis L) dye-sensitized nanocrystalline titania solar cellrdquoJournal of Nanotechnology vol 2012 Article ID 167128 6 pages2012

[34] T L Brown ldquoThe infrared carbonyl absorption in some p-quinones and related substancesrdquo Spectrochimica Acta vol 18no 4 pp 1065ndash1071 1962

[35] B R Mikhaeil F A Badria G T Maatooq andMM A AmerldquoAntioxidant and immunomodulatory constituents of hennaleavesrdquo Zeitschrift fur Naturforschung - Section C Journal of Bio-sciences vol 59 no 7-8 pp 468ndash476 2004

[36] M Slifkin ldquoInfrared spectra of some organic charge-transfercomplexesrdquo SpectrochimicaActa Part AMolecular Spectroscopyvol 29 no 5 pp 835ndash838 1973

[37] S Oramas-Royo C Torrejon I Cuadrado et al ldquoSynthesis andcytotoxic activity of metallic complexes of lawsonerdquo Bioorganicand Medicinal Chemistry vol 21 no 9 pp 2471ndash2477 2013

[38] A E Musa and G A Gasmelseed ldquoCharacterization of Law-sonia inermis (henna) as vegetable tanning materialrdquo Journal ofForest Products amp Industries vol 1 no 2 pp 35ndash40 2012

[39] W B W Nik F Zulkifli O Sulaiman K B Samo and RRosliza ldquoStudy of Henna (Lawsonia inermis) as natural corro-sion inhibitor for aluminum alloy in seawaterrdquo IOP ConferenceSeries Materials Science and Engineering vol 36 no 1 ArticleID 012043 2012

[40] A Fernandez A George and V K Remadevi ldquoSynthesis cha-racterization antioxidant DNA cleavage and cytotoxic studiesof amino derivatives of lawsonerdquo International Journal of Phy-topharmacy vol 1 pp 36ndash41 2013

[41] L Li X Zhang J Lei J He S Zhang and F Pan ldquoAdsorptionand corrosion inhibition of Osmanthus fragran leaves extracton carbon steelrdquo Corrosion Science vol 63 pp 82ndash90 2012

[42] X-H Li S-D Deng and H Fu ldquoInhibition by Jasminumnudiflorum Lindl leaves extract of the corrosion of cold rolledsteel in hydrochloric acid solutionrdquo Journal of Applied Electro-chemistry vol 40 no 9 pp 1641ndash1649 2010

[43] N D Nam A Somers M Mathesh et al ldquoThe behaviour ofpraseodymium 4-hydroxycinnamate as an inhibitor for carbondioxide corrosion and oxygen corrosion of steel in NaClsolutionsrdquo Corrosion Science vol 80 pp 128ndash138 2014

[44] A R Hosein Zadeh I Danaee and M H Maddahy ldquoThermo-dynamic and adsorption behaviour of medicinal nitramine as acorrosion inhibitor for AISI steel alloy in HCl solutionrdquo Journalof Materials Science and Technology vol 29 no 9 pp 884ndash8922013

[45] X Li and SDeng ldquoInhibition effect ofDendrocalamus brandisiileaves extract on aluminum in HCl H3PO4 solutionsrdquo Corro-sion Science vol 65 pp 299ndash308 2012

[46] G T Burstein and R J Cinderey ldquoThe potential of freshlygenerated metal surfaces determined from the guillotinedelectrode-a new techniquerdquoCorrosion Science vol 32 no 11 pp1195ndash1211 1991

[47] L Johansson ldquoSynergistic effects of air pollutants on the atmos-pheric corrosion of metals and calcareous stonesrdquo MarineChemistry vol 30 pp 113ndash122 1990

[48] M Metikos-Hukovic R Babic and Z Grubac ldquoCorrosion pro-tection of aluminium in acidic chloride solutions with nontoxicinhibitorsrdquo Journal of Applied Electrochemistry vol 28 no 4 pp433ndash439 1998

[49] A Singh Y Lin W Liu et al ldquoPlant derived cationic dye as aneffective corrosion inhibitor for 7075 aluminum alloy in 35NaCl solutionrdquo Journal of Industrial and Engineering Chemistryvol 20 no 6 pp 4276ndash4285 2014

[50] S Khireche D Boughrara A Kadri L Hamadou and NBenbrahim ldquoCorrosion mechanism of Al Al-Zn and Al-Zn-Snalloys in 3wt NaCl solutionrdquo Corrosion Science vol 87 pp504ndash516 2014

[51] R E Melchers ldquoBi-modal trend in the long-term corrosion ofaluminium alloysrdquo Corrosion Science vol 82 pp 239ndash247 2014

[52] A M Abdel-Gaber B A Abd-El-Nabey I M Sidahmed A MEl-Zayady and M Saadawy ldquoInhibitive action of some plantextracts on the corrosion of steel in acidic mediardquo CorrosionScience vol 48 no 9 pp 2765ndash2779 2006

[53] M H Hussin and M J Kassim ldquoThe corrosion inhibition andadsorption behavior of Uncaria gambir extract on mild steel in1 M HClrdquo Materials Chemistry and Physics vol 125 no 3 pp461ndash468 2011

[54] A K Satapathy G Gunasekaran S C Sahoo K Amit and PV Rodrigues ldquoCorrosion inhibition by Justicia gendarussa plantextract in hydrochloric acid solutionrdquoCorrosion Science vol 51no 12 pp 2848ndash2856 2009

[55] R E Clegg ldquoMeasurements of the interface between 5083 alu-minium and liquid mercury using impedance spectroscopyrdquoCorrosion Science vol 52 no 12 pp 4028ndash4034 2010

[56] M Shabani-Nooshabadi and M S Ghandchi ldquoSantolinachamaecyparissus extract as a natural source inhibitor for 304stainless steel corrosion in 35 NaClrdquo Journal of Industrial andEngineering Chemistry vol 31 pp 231ndash237 2015

[57] G Ruhi O P Modi and S K Dhawan ldquoChitosan-polypyrrole-SiO2 composite coatings with advanced anticorrosive proper-tiesrdquo Synthetic Metals vol 200 pp 24ndash39 2015

[58] S M Abd El Haleem S Abd El Wanees E E Abd El Aal andA Farouk ldquoFactors affecting the corrosion behaviour of alu-minium in acid solutions I Nitrogen andor sulphur-contain-ing organic compounds as corrosion inhibitors for Al in HClsolutionsrdquo Corrosion Science vol 68 pp 1ndash13 2013

[59] X Li S Deng and X Xie ldquoExperimental and theoretical studyon corrosion inhibition of oxime compounds for aluminium inHCl solutionrdquo Corrosion Science vol 81 pp 162ndash175 2014

[60] I Ahamad R Prasad and M A Quraishi ldquoAdsorption andinhibitive properties of some new Mannich bases of Isatin der-ivatives on corrosion of mild steel in acidic mediardquo CorrosionScience vol 52 no 4 pp 1472ndash1481 2010

[61] R Rosliza W B Wan Nik and H B Senin ldquoThe effect ofinhibitor on the corrosion of aluminum alloys in acidic solu-tionsrdquoMaterials Chemistry and Physics vol 107 no 2-3 pp 281ndash288 2008

[62] S K Milonjic ldquoA consideration of the correct calculationof thermodynamic parameters of adsorptionrdquo Journal of theSerbian Chemical Society vol 72 no 12 pp 1363ndash1367 2007

[63] P Mourya S Banerjee andMM Singh ldquoCorrosion inhibitionof mild steel in acidic solution by Tagetes erecta (Marigoldflower) extract as a green inhibitorrdquo Corrosion Science vol 85pp 352ndash363 2014

[64] P Mohan and G P Kalaignan ldquo1 4-Bis (2-nitrobenzylidene)thiosemicarbazide as effective corrosion inhibitor for mild


steelrdquo Journal of Materials Science and Technology vol 29 no11 pp 1096ndash1100 2013

[65] H Ju Y Ju and Y Li ldquoBerberine as an Environmental-FriendlyInhibitor for Hot-Dip Coated Steels in Diluted HydrochloricAcidrdquo Journal of Materials Science amp Technology vol 28 no 9pp 809ndash816 2012

[66] I Danaee M N Khomami and A A Attar ldquoCorrosion ofAISI 4130 steel alloy under hydrodynamic condition in ethyleneglycol + water + NOminus2 solutionrdquo Journal of Materials Science andTechnology vol 29 no 1 pp 89ndash96 2013

[67] E A Noor and A H Al-Moubaraki ldquoThermodynamic study ofmetal corrosion and inhibitor adsorption processes in mildsteel1-methyl-4[41015840(-X)-styryl pyridinium iodideshydrochlo-ric acid systemsrdquo Materials Chemistry and Physics vol 110 no1 pp 145ndash154 2008

Submit your manuscripts athttpswwwhindawicom

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


Table 1 Composition of aluminium alloy 5083 (AA5083)

Element Mg Mn Fe Si Zn Cr Ti Cu AlWeight percent wt 45 07 04 04 025 015 015 01 Remaining

In marine industry metals like aluminum alloy playtremendous roles in which they are used widely for ship-building chemical plant and offshore structure [22 23] Theincreasing sector demand for higher speed performances andcheap assembly technology has made aluminum alloy as oneof the best choices as a structural material for boats vesselsand components [24 25] The advantages of aluminum inmany ways have propelled it into one of the widely usedmetals in the marine industries

To better understand the inhibitive behavior of natu-ral products Lawsonia inermis as corrosion inhibitor wasinvestigated via electrochemical impedance spectroscopy andpotentiodynamic polarization Meanwhile the optical studywas conducted by using Fourier transform infrared (FTIR)and the quantum chemical calculationwas done to determinethe synergism behavior of the inhibitor

2 Experimental

21 Surface Preparation of Aluminum Alloy 5083 (AA5083)AA5083 with the dimension of 25mm times 25mm times 3mm waspolished by using emery paper with different grades (600900 and 1200) Then the samples were cleaned with acetoneand rinsed with distilled water dried in air and then storedin desiccators prior to use Table 1 shows the composition ofAA5083 [26]

22 Extraction of Lawsonia inermis (Henna) The fresh leavesof Lawsonia inermiswere dried at room temperature and thencrushed into powder form Lawsonia inermis powder wasmixed with ethanol and left for a week Then the mixturewas extracted by means of the rotary evaporator The residueleft in the flush was used directly by diluting it to 20 litersof seawater with respect to inhibitor concentration Seawaterwas collected at Universiti Malaysia Terengganu beachfrontThe composition of South China Sea seawater is shown inTable 2

23 Fourier Transform Infrared Analysis (FTIR) and Ultravio-let Visible Spectroscopy (UV-Vis) FTIR was carried out usingThermo Nicolet 380 FTIR Spectrometer The spectrometerwas used to identify the functional groups of Lawsoniainermis by observing at the vibrationalmotion of bonds in themolecule An infrared light was passing through the samplethat was placed on the germanium crystal The frequencywas ranging from 4000 to 675 cmminus1 with spectra resolutionof 4 cmminus1 following the work done as reported elsewhere[27]The FTIR data was recorded in the transmittance modeThe transmittance and reflectance of the infrared rays atdifferent frequencies were translated into an IR absorptionplot consisting of reverse peaks The spectral pattern wasanalyzed and matched according to IR absorption table toidentify the functional group contained in the Lawsonia

Table 2 Composition of seawater from South China Sea

Parameter ReadingpH 7492Temperature (∘C) 2946Conductivity (mScm) 5256Salinity (ppt) 3158Dissolved oxygen (mgL) 7086Turbidity (NTU) 005

O

O

HO

Figure 1 Molecular structure of Lawsonia inermis

inermis Figure 1 shows themolecule structure of lawsone thatis the central component in Lawsonia inermis [16 28]

AUV-Vismeasurementwas performed using an in-housebuilt cell which allowed the transmission of light throughthe cell UVVis spectroscopy (Lambda 265 Perkin Elmer)recorded the absorbance between 200ndash800 nm in transmis-sion mode where ethanol was used as the background

24 Electrochemical Impedance Spectroscopy (EIS) EIS wasused to study the impedance characteristic as well as capac-itance behavior of AA5083 in the presence and absenceof henna The EIS measurement was performed by usingalternating current (AC) signal of impedance measurementsby means of Autolab PGSTAT302N with respect to the opencircuit potential (OCP) All the potentials referred wererelative to saturated calomel electrode (SCE)The impedancemeasurements used a frequency range of 1 kHz down to10mHz The results were analyzed using the fit program ofNOVA 110

Open circuit potential (OCP) measurement was con-ducted to investigate the potential of electrode at varioustemperatures OCP was run for 1800 s while the limit 119889119881119889119905was set to 1120583VsThe average potential was taken as the OCPof the electrode

25 Potentiodynamic Polarization (PP) Potentiodynamicpolarization (PP) is the most common polarization methodused for measuring corrosion resistant The cell used was aconventional three electrodes with a platinum wire counterelectrode (CE) and AgAgCl as a reference electrode (RE)The working electrode (WE) is in the form of a square



119894corr =119887119886 times 119887119888

2303119877119901 (119887119886 + 119887119888) (1)






119894corrtimes 100 (3)



120579 =120578 ()100 ()

(4)






Tran

smitt

ance

(au

)

102

100

098

096

094

092

090

088

086

084

3960

3376912

29777

16334922362488

144835

17222061265137

1045281

862067

3630 3300 1650

877496

904496

6601320 9902970 2640 2310 1980














1


2H2 (6)







0010203040506070809

1

200 250 300 350 400 450 500 550 600

Abso

rban

ce

Wavelength (nm)

Lawsonia inermisHNQ

418 nm

342nm

286 nm













119885CPE =1

1198840 (119895120596)119899 (12)













0

1000

2000

3000

4000

5000

6000

7000

8000

0 1000 2000 3000 4000 5000 6000 7000 8000

1000 ppm

800 ppm

600 ppm

400 ppm

200 ppm

0 ppm


minusZ998400998400

(Ωmiddotcm

2)

(a)

0

10

20

30

40

50

60

70

80

90

01 1 10 100 1000

1000 ppm

800 ppm

600 ppm

400 ppm

200 ppm

0 ppm

logf (Hz)

Phas

e ang

le (∘

)

(b)

1

10

100

1000

10000

01 1 10 100 1000

1000 ppm

800 ppm

600 ppm

400 ppm

200 ppm

0 ppm

logf (Hz)

logZ

(Ωcm

2)

(c)






CPE

Rct

Rs


minus07

minus08

minus09

minus10

minus11

600 ppm800 ppm

1000 ppm

400 ppm

200 ppm

0 ppm

0 50 100 150

Time (s)

Pote

ntia

l (V

)



119902119890 = 119902max119870119871119862119890

1 + 119870119871119862119890 (13)


119888119890119902119890=

1

119902max119870119871+

119888119890119902max

(14)





PP EIS PP EIS3275 3247 9 9








10E minus 03

10E minus 04

10E minus 05

10E minus 06

10E minus 07

10E minus 08



logi

(120583A

cm

2)

1000 ppm

800 ppm

600 ppm

400 ppm

200 ppm

0 ppm

Eb


0

200

400

600

800

1000

1200

1400

0 200 400 600 800 1000 1200

EISPP

C120579

C (ppm)






4 Conclusion




+

+

+

+

+

+

eminus

eminus

eminus

eminus

eminus

eminus

eminus

eminus

OHP

Met

al

Solu

tion

(a)

++

+

+

OHP

H+

H+

Met

al

Solu

tion

(b)




(Org)

(Org)

H+

H+







Competing Interests


Acknowledgments


References

















































































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of



119894corr =119887119886 times 119887119888

2303119877119901 (119887119886 + 119887119888) (1)






119894corrtimes 100 (3)



120579 =120578 ()100 ()

(4)






Tran

smitt

ance

(au

)

102

100

098

096

094

092

090

088

086

084

3960

3376912

29777

16334922362488

144835

17222061265137

1045281

862067

3630 3300 1650

877496

904496

6601320 9902970 2640 2310 1980














1


2H2 (6)







0010203040506070809

1

200 250 300 350 400 450 500 550 600

Abso

rban

ce

Wavelength (nm)

Lawsonia inermisHNQ

418 nm

342nm

286 nm













119885CPE =1

1198840 (119895120596)119899 (12)













0

1000

2000

3000

4000

5000

6000

7000

8000

0 1000 2000 3000 4000 5000 6000 7000 8000

1000 ppm

800 ppm

600 ppm

400 ppm

200 ppm

0 ppm


minusZ998400998400

(Ωmiddotcm

2)

(a)

0

10

20

30

40

50

60

70

80

90

01 1 10 100 1000

1000 ppm

800 ppm

600 ppm

400 ppm

200 ppm

0 ppm

logf (Hz)

Phas

e ang

le (∘

)

(b)

1

10

100

1000

10000

01 1 10 100 1000

1000 ppm

800 ppm

600 ppm

400 ppm

200 ppm

0 ppm

logf (Hz)

logZ

(Ωcm

2)

(c)






CPE

Rct

Rs


minus07

minus08

minus09

minus10

minus11

600 ppm800 ppm

1000 ppm

400 ppm

200 ppm

0 ppm

0 50 100 150

Time (s)

Pote

ntia

l (V

)



119902119890 = 119902max119870119871119862119890

1 + 119870119871119862119890 (13)


119888119890119902119890=

1

119902max119870119871+

119888119890119902max

(14)





PP EIS PP EIS3275 3247 9 9








10E minus 03

10E minus 04

10E minus 05

10E minus 06

10E minus 07

10E minus 08



logi

(120583A

cm

2)

1000 ppm

800 ppm

600 ppm

400 ppm

200 ppm

0 ppm

Eb


0

200

400

600

800

1000

1200

1400

0 200 400 600 800 1000 1200

EISPP

C120579

C (ppm)






4 Conclusion




+

+

+

+

+

+

eminus

eminus

eminus

eminus

eminus

eminus

eminus

eminus

OHP

Met

al

Solu

tion

(a)

++

+

+

OHP

H+

H+

Met

al

Solu

tion

(b)




(Org)

(Org)

H+

H+







Competing Interests


Acknowledgments


References

















































































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of








1


2H2 (6)







0010203040506070809

1

200 250 300 350 400 450 500 550 600

Abso

rban

ce

Wavelength (nm)

Lawsonia inermisHNQ

418 nm

342nm

286 nm













119885CPE =1

1198840 (119895120596)119899 (12)













0

1000

2000

3000

4000

5000

6000

7000

8000

0 1000 2000 3000 4000 5000 6000 7000 8000

1000 ppm

800 ppm

600 ppm

400 ppm

200 ppm

0 ppm


minusZ998400998400

(Ωmiddotcm

2)

(a)

0

10

20

30

40

50

60

70

80

90

01 1 10 100 1000

1000 ppm

800 ppm

600 ppm

400 ppm

200 ppm

0 ppm

logf (Hz)

Phas

e ang

le (∘

)

(b)

1

10

100

1000

10000

01 1 10 100 1000

1000 ppm

800 ppm

600 ppm

400 ppm

200 ppm

0 ppm

logf (Hz)

logZ

(Ωcm

2)

(c)






CPE

Rct

Rs


minus07

minus08

minus09

minus10

minus11

600 ppm800 ppm

1000 ppm

400 ppm

200 ppm

0 ppm

0 50 100 150

Time (s)

Pote

ntia

l (V

)



119902119890 = 119902max119870119871119862119890

1 + 119870119871119862119890 (13)


119888119890119902119890=

1

119902max119870119871+

119888119890119902max

(14)





PP EIS PP EIS3275 3247 9 9








10E minus 03

10E minus 04

10E minus 05

10E minus 06

10E minus 07

10E minus 08



logi

(120583A

cm

2)

1000 ppm

800 ppm

600 ppm

400 ppm

200 ppm

0 ppm

Eb


0

200

400

600

800

1000

1200

1400

0 200 400 600 800 1000 1200

EISPP

C120579

C (ppm)






4 Conclusion




+

+

+

+

+

+

eminus

eminus

eminus

eminus

eminus

eminus

eminus

eminus

OHP

Met

al

Solu

tion

(a)

++

+

+

OHP

H+

H+

Met

al

Solu

tion

(b)




(Org)

(Org)

H+

H+







Competing Interests


Acknowledgments


References

















































































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of



119885CPE =1

1198840 (119895120596)119899 (12)













0

1000

2000

3000

4000

5000

6000

7000

8000

0 1000 2000 3000 4000 5000 6000 7000 8000

1000 ppm

800 ppm

600 ppm

400 ppm

200 ppm

0 ppm


minusZ998400998400

(Ωmiddotcm

2)

(a)

0

10

20

30

40

50

60

70

80

90

01 1 10 100 1000

1000 ppm

800 ppm

600 ppm

400 ppm

200 ppm

0 ppm

logf (Hz)

Phas

e ang

le (∘

)

(b)

1

10

100

1000

10000

01 1 10 100 1000

1000 ppm

800 ppm

600 ppm

400 ppm

200 ppm

0 ppm

logf (Hz)

logZ

(Ωcm

2)

(c)






CPE

Rct

Rs


minus07

minus08

minus09

minus10

minus11

600 ppm800 ppm

1000 ppm

400 ppm

200 ppm

0 ppm

0 50 100 150

Time (s)

Pote

ntia

l (V

)



119902119890 = 119902max119870119871119862119890

1 + 119870119871119862119890 (13)


119888119890119902119890=

1

119902max119870119871+

119888119890119902max

(14)





PP EIS PP EIS3275 3247 9 9








10E minus 03

10E minus 04

10E minus 05

10E minus 06

10E minus 07

10E minus 08



logi

(120583A

cm

2)

1000 ppm

800 ppm

600 ppm

400 ppm

200 ppm

0 ppm

Eb


0

200

400

600

800

1000

1200

1400

0 200 400 600 800 1000 1200

EISPP

C120579

C (ppm)






4 Conclusion




+

+

+

+

+

+

eminus

eminus

eminus

eminus

eminus

eminus

eminus

eminus

OHP

Met

al

Solu

tion

(a)

++

+

+

OHP

H+

H+

Met

al

Solu

tion

(b)




(Org)

(Org)

H+

H+







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

1000

2000

3000

4000

5000

6000

7000

8000

0 1000 2000 3000 4000 5000 6000 7000 8000

1000 ppm

800 ppm

600 ppm

400 ppm

200 ppm

0 ppm


minusZ998400998400

(Ωmiddotcm

2)

(a)

0

10

20

30

40

50

60

70

80

90

01 1 10 100 1000

1000 ppm

800 ppm

600 ppm

400 ppm

200 ppm

0 ppm

logf (Hz)

Phas

e ang

le (∘

)

(b)

1

10

100

1000

10000

01 1 10 100 1000

1000 ppm

800 ppm

600 ppm

400 ppm

200 ppm

0 ppm

logf (Hz)

logZ

(Ωcm

2)

(c)






CPE

Rct

Rs


minus07

minus08

minus09

minus10

minus11

600 ppm800 ppm

1000 ppm

400 ppm

200 ppm

0 ppm

0 50 100 150

Time (s)

Pote

ntia

l (V

)



119902119890 = 119902max119870119871119862119890

1 + 119870119871119862119890 (13)


119888119890119902119890=

1

119902max119870119871+

119888119890119902max

(14)





PP EIS PP EIS3275 3247 9 9








10E minus 03

10E minus 04

10E minus 05

10E minus 06

10E minus 07

10E minus 08



logi

(120583A

cm

2)

1000 ppm

800 ppm

600 ppm

400 ppm

200 ppm

0 ppm

Eb


0

200

400

600

800

1000

1200

1400

0 200 400 600 800 1000 1200

EISPP

C120579

C (ppm)






4 Conclusion




+

+

+

+

+

+

eminus

eminus

eminus

eminus

eminus

eminus

eminus

eminus

OHP

Met

al

Solu

tion

(a)

++

+

+

OHP

H+

H+

Met

al

Solu

tion

(b)




(Org)

(Org)

H+

H+







Competing Interests


Acknowledgments


References

















































































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


CPE

Rct

Rs


minus07

minus08

minus09

minus10

minus11

600 ppm800 ppm

1000 ppm

400 ppm

200 ppm

0 ppm

0 50 100 150

Time (s)

Pote

ntia

l (V

)



119902119890 = 119902max119870119871119862119890

1 + 119870119871119862119890 (13)


119888119890119902119890=

1

119902max119870119871+

119888119890119902max

(14)





PP EIS PP EIS3275 3247 9 9








10E minus 03

10E minus 04

10E minus 05

10E minus 06

10E minus 07

10E minus 08



logi

(120583A

cm

2)

1000 ppm

800 ppm

600 ppm

400 ppm

200 ppm

0 ppm

Eb


0

200

400

600

800

1000

1200

1400

0 200 400 600 800 1000 1200

EISPP

C120579

C (ppm)






4 Conclusion




+

+

+

+

+

+

eminus

eminus

eminus

eminus

eminus

eminus

eminus

eminus

OHP

Met

al

Solu

tion

(a)

++

+

+

OHP

H+

H+

Met

al

Solu

tion

(b)




(Org)

(Org)

H+

H+







Competing Interests


Acknowledgments


References

















































































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


10E minus 03

10E minus 04

10E minus 05

10E minus 06

10E minus 07

10E minus 08



logi

(120583A

cm

2)

1000 ppm

800 ppm

600 ppm

400 ppm

200 ppm

0 ppm

Eb


0

200

400

600

800

1000

1200

1400

0 200 400 600 800 1000 1200

EISPP

C120579

C (ppm)






4 Conclusion




+

+

+

+

+

+

eminus

eminus

eminus

eminus

eminus

eminus

eminus

eminus

OHP

Met

al

Solu

tion

(a)

++

+

+

OHP

H+

H+

Met

al

Solu

tion

(b)




(Org)

(Org)

H+

H+







Competing Interests


Acknowledgments


References

















































































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


+

+

+

+

+

+

eminus

eminus

eminus

eminus

eminus

eminus

eminus

eminus

OHP

Met

al

Solu

tion

(a)

++

+

+

OHP

H+

H+

Met

al

Solu

tion

(b)




(Org)

(Org)

H+

H+







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















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

The Effect of Concentration of Lawsonia inermis as a ...downloads.hindawi.com/journals/apc/2017/8521623.pdf2 AdvancesinPhysicalChemistry Table1:Compositionofaluminiumalloy5083(AA5083)