ISSN: 2320-5407 Int. J. Adv. Res.

5(3), 1457-1467

Journal Homepage: - www.journalijar.com

Article DOI: 10.21474/IJAR01/3653

DOI URL: http://dx.doi.org/10.21474/IJAR01/3653

RESEARCH ARTICLE
CORROSION INHIBITION OF MILD STEEL USING ALOE BARBEDENSIS MILLER SKIN EXTRACT IN
0.5 MHCL.

Annie Preetha. M and Dr. Felicia Rajammal Selvarani.

……………………………………………………………………………………………………....
Manuscript Info Abstract
……………………. ………………………………………………………………
Manuscript History Mild steel is employed widely in most industries due to its low
cost and availability in ease for the fabrication of various reaction
Received: 10 January 2017 vessels such as cooling tower tanks, pipelines etc. It can be subjected to
Final Accepted: 02 February 2017 aggressive and unfavorable environmental conditions, making it
Published: March 2017
susceptible to corrosion. From the economic and environmental view,
plant extracts area n excellent alternative as inhibitors because of their
Key words:- availability, biodegradability, non toxicity and environmental friendly.
Mild Steel Aloe barbedensis The rich source of anthraquinone and other chemical composition of
Miller,EDX,EIS Aloe Vera has been resulted a wide range uses in different sector. The
present study deals with the inhibition effect of biodegradable,
nontoxicand eco-friendly. Aloe Vera leaf extracton corrosion of mild
steel in HCl. The corrosion inhibition of mild steel in the presence
of Aloe Barbedensis Miller in 0.5 MHCl was studied by weight loss
measurement; electrochemical techniques (Potent iodynamic
polarization, A Cimpedance). The maximum efficiency was found to be
81% at 150 ppm. From the result of weight loss studies, the mode of
adsorption is found to be physisorption. Kinetic and thermodynamic
parameters were calculated and discussed. Potentiodynamic
polarization studies indicate that Aloe Barbedensis Miller acts as a
mixed type of inhibitor. The surface morphology has been analyzed.
Copy Right, IJAR, 2017,. All rights reserved.
……………………………………………………………………………………………………....

Introduction:-
Corrosion is the destruction of material resulting from an exposure and interaction with the environment. It is a
major problem that must be confronted for safety, environmental and economic reasons in various chemicals,
mechanical, metallurgical, biomedical and medical engineering applications and more specifically in the design of a
much more varied number of mechanical parts. Several efforts have been made using corrosion preventive
practices and the use of green corrosion inhibitors is one of them. Natural products have been studied extensively as
corrosion inhibitors both in product mixtures extracted from natural sources such as plants or essentially pure
products derived from animals or plants (i.e,vitamins and amino acids)[1].From the economic and environmental
view points, plant extracts are an excellent alternative as inhibitors because of their availability and biodegradability.
These extracts contain a variety of natural products such as essential oils, tannins, pigments, steroids, terpenes,
flavones and flavonoids, among other well-known active substances used as CIs.In general, these compounds contain
conjugated aromatic structures, long aliphatic chains such as nitrogen, sulfur, and oxygen heteroatoms with free
electron pairs that are available to form bonds with the metal surface; in most cases, they act synergistically to
exhibit good efficiency regarding the corrosion protection.Aloe Vera is an important medicinal plant which

Corresponding Author:- Annie Preetha. M. 1457

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belongs to the family of Liliacea. A more recent review concludes that the cumulative evidence supports the use of
Aloe barbadensis miller for the healing of first to second degree burns. Aloe Vera plant is used for corrosion
protection of metal in acidic medium since it was found for environmental eco-friendly and available in affordable
price. The Aloe Vera leaves contain several free anthraquinones and phenolic compounds that aid in absorptive
processes in metal surface. The rich source of anthraquinone and other chemical composition of Aloe Vera has been
resulted a wide range uses in different sector. In most of the studies related to Aloe Vera gel alone was taken and the
outer part of the skin was considered as a waste material. In the present study the outer part of Aloe Vera alone was
taken to investigate the inhibitive effect for the corrosion of mild steel in 0.5M HCl.

Materials and Methods:-

Preparation of Mild Steel Specimens:-
The mild steel samples were obtained from a locally available industrial Fe-C steel with very low
concentrationofcarbon.Alargesheetofcoldrolled mild steel coupons have the following chemical composition 0.026%
Si, 0.006% P, 0.4% Mn, 0.1% C, 99.4%Fe.The mild steel samples, with an active surface of 1.2 × 4.0 × 0.3cm were
used for Mass loss measurements and 1cm× 1cm specimen for electrochemical measurements. The mild steel
samples were mechanically polished, washed in double distilled water and degreased with acetone and used for
the weight loss method and surface examination studies.

Weight – loss method:-

Determination of Corrosion Rate:-
Weight loss measurements were carried out using an ACCULAB Electronic balance with readability/sensitivity of
0.1 mg in 210g range. The specimens were immersed in beaker containing 100ml acid solutions without and
with different concentration of Aloe Barbedensis Miller leaves extract using hooks. At the end of exposure period,
specimens were cleaned according to ASTM G-81 and the weight recorded. The average mass loss of two parallel
mild steel specimens was obtained. The test specimens were removed and then washed with de-ionised water, dried
and reweighed[2].From the change in weight of specimens the corrosion rate was calculated using the
following relationship,

Corrosion Rate =87.6 × W / A × T ×D(mpy)

Corrosion Inhibition Efficiency (IE) IE = 100[1-(W2/W1)] %

Electrochemical Impedance Spectroscopy:-

Electrochemical measurements were run using a Potentiostat/galvanostat (Electrochemical system Model
Vertex.100mA.D) and a personal computer was used. IVIUM software was used for Electrochemical
Impedance Spectroscopy (EIS) and potentiodynamic polarization (PDP) analysis. The EIS measurements were
carried out using AC signals of amplitude 10 m V peaks-to-peaks at the open
circuitpotentialinthefrequencyrangeof10MHzto1Hz.The charge transfer Resistance (R ct)values have been calculated
from the difference in the impedance at low and high frequencies.The capacitances of the double layer (C dl) values
are estimated from the frequency(f)atwhichtheimaginarycomponentof the impedance (-Z”) is maximum and the
double layer capacitance (Cdl) was calculated by using following equation:

Obtained from the equation:Cdl = ½ × 3.14 × Rct× fmax

Potentiodynamic Polarization:-
After impedance spectrum was obtained, the potentiodynamic current potential curves was recorded immediately
by changing the electrode potential automatically taken from OCP value with scan rate of 5 m V /S [3].Tafel lines
extrapolation method was used for detecting Icorr and Ecorr values for the studied systems.

Scanning Electron Microscope and Energy Dispersive Spectroscopy Analysis:-

For surface morphological study of the uninhibited and inhibited mild steel samples were sent to SEM and EDX
analysis[4][5].

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Results and Discussion:-

Mass Loss Measurements:-
Effect of Inhibitor Concentration:-
Inhibition efficiency of mild steel with different concentration of Aloe Barbadensis Miller extract in 0.5M HCl at
room temperature are presented in Table 1.From the table, it is clear that the corrosion rate decreases with an
increase in inhibitor concentration ,i.e. the corrosion inhibition enhances with the inhibitor concentration. This
behavior is due to the fact that the adsorption and coverage of the inhibitor on the mild steel surface increase with
the inhibitor concentration. Maximum inhibition efficiency of 81% was shown at 150ppm in 0.5M HCl at 3 hour
immersion, period beyond 200 ppm the system remains constant. The high inhibitive performance of Aloe
Barbadensis Miller suggests a higher bonding ability of inhibitor on mild steel surface[6].

Table 1:- Corrosion rate of mild steel in 0.5M HCl.

S.no Concentration(ppm) Corrosion rate(mpy) Surface coverage(θ) % I.E
1 Blank 18 - -
2 50 6 0.66 66
3 100 5 0.72 72
4 150 3.4 0.81 81
5 200 3.7 0.79 79
6 250 3.6 0.80 80
7 300 3.6 0.80 80

7
6
5
Corrosion rate

4
3
2
1
0
0 50 100 150 200 250 300 350
Concentration(ppm)
Fig 1:- Corrosion rate of Aloe Barbadensis miller at different concentration.

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90
80
70
60
50
% I.E

40
30
20
10
0
0 50 100 150 200 250 300 350

Concentration(ppm)

Fig 2:- Inhibition efficiency of Aloe Barbadensis miller at different concentration.

Effect of temperature:-
To show the effect of temperature on inhibition efficiency of Aloe Barbedensis Miller, Weight loss experiment was
performed in the temperature range of 308 to 328 K at optimum concentration. The variation of inhibition efficiency
with temperature at optimum concentration are listed in Table 2.From table 2, it is clear that corrosion rate is
temperature dependent and increases with increase in temperature[7],[8].
Table 2:- Effect of temperature on the CR of mild in 0.5 M HCl.
S.no Temperature Corrosion Corrosion Surface % I.E
(K) rate(Blank) rate(Inhibitor) coverage
1 308 22 5.3 0.76 76
2 313 31 9.1 0.71 71
3 318 41 10.8 0.73 73
4 323 50 15 0.70 70
5 328 75 26 0.65 65

Kinetic and Thermodynamic parameter for corrosion rate:-

The apparent activation energy (Ea) ,the enthalpy of activation (ΔH*) and entropy of activation (∆S*) for the
corrosion of mild steel in 0.5M HCl solution with and without inhibitor at different temperatures are calculated from
Arrhenius equation:

CR=A exp (Ea)/RT (1)

And from Transition state equation:
CR=RT/hNexp (∆S*/R)exp (-ΔH*/RT) (2)

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2
1.8
1.6
1.4 y = -2.570x + 9.690
R² = 0.989
1.2
Log CR

1
BLANK
0.8 y = -3.226x + 11.21
R² = 0.969 INHIBITOR
0.6
0.4
0.2
0
3 3.05 3.1 3.15 3.2 3.25 3.3
1000/T (K-1)

Figure 3:- Arrhenius plots of log CR Vs 1000/T(K-1)

The Arrhenius plot for mild steel immersed in 0.5M HCl with optimum concentration and blank solution is depicted
in fig.3.The Activation energy (Ea) is obtained from the slope (-Ea/2.303RT) and the values are listed in table 3.It is
evident from the increase in activation energy value in the presence of inhibitor that the reaction undergoes through
different mechanism which has a high E a value compared to uninhibited system. Hence the rate of corrosion is
decreases, as less reactants have that activation energy to reach the activation state.

Table 3:- Thermodynamic parameters for Mild steel in 0.5M HCl in the absence and presence of optimum
concentration of Aloe Barbadensis Millerleaves.
Ea (KJmol-1) ΔH* ΔS*
Blank 49.21 46.5 -68.18
Inhibitor 61.7 59.12 -39.07

0
-0.2 3 3.05 3.1 3.15 3.2 3.25 3.3

-0.4
-0.6
-0.8
Log CR / T -1 BLANK
y = -2.432x + 6.754
-1.2 R² = 0.987 INHIBITOR

-1.4
-1.6
y = -3.088x + 8.277
-1.8 R² = 0.966
-2
1000/T (K-1)

Figure 4:- Transition state plots of Log CR/T Vs 1000/T (K-1).

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A plot of log (CR/T) Versus 1000/T is shown in fig.4.Straight lines are obtained with slope (-ΔH*/2.303R) and
intercept of [log(R/Nh)+(ΔS*/R)] .The positive value of enthalpy of activation(ΔH*) in the absence and presence of
inhibitor at different temperatures reflects the endothermic nature of mild steel dissolution process, which indicates
that the dissolution of steel is difficult. It is evident from the table that the value of ΔH *increases in the presence of
the inhibitor than in the absence. This shows the higher protection efficiency of the inhibitor. This may be attributed
to the presence of high energy barrier for the reaction and hence there is rise in enthalpy of the corrosion process.

From Table 3, it is clear that there is an increase in the entropy of activation in the presence of inhibitor system
compared to its absence.The large negative value of entropy of activation in the absence of inhibitor shows that it
has more ordered arrangement in the transition state whereas in the presence of inhibitor system the entropy of
activation becomes less negative showing that the surface of the metal is covered with inhibitor molecules thus
moving the system towards less ordered arrangement.

Adsorption Parameter:-
The primary step in the action of inhibitors in solution is generally agreed to be adsorption on the metal surface. This
involves the assumption that the corrosion reactions are prevented from occurring over the area (or active sites) of
the metal or alloy surface covered by adsorbed inhibitor species, whereas these corrosion reaction occurred normally
on the inhibitor free area. Accordingly, the fraction of surface covered with inhibitor species (θ=%IE/100) can be
followed as a function of inhibitor concentration and solution temperature. The surface coverage (ө) data are very
useful while discussing the adsorption characteristics. When the fraction of surface covered is determined as a
function of the concentration at constant temperature, adsorption isotherm could be evaluated at equilibrium
condition. The dependence of the fraction of the surface covered ө on the concentration C of the inhibitor was tested
graphically by fitting it to Langmuir’s isotherm, which assumes that the solid surface contains a fixed number of
adsorption sites and each site holds one adsorbed species.

0.4
y = 1.191x + 0.014
0.35 R² = 0.998

0.3

0.25
Log C/

0.2

0.15

0.1

0.05

0
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35
C(g/L)
Figure 5:- Langmuir adsorption plot of Log C/ө Versus C.

Table 4:- Langmuir adsorption of Aloe Barbadensis Miller in 0.5M HCl on the mild steel.
Inhibitor Intercept Kads R2 ΔGadsᵒ(KJ/mol)
Aloe Barbadensis miller 0.014 71.428 0.998 -10.75

The equilibrium constant for the adsorption process is related to the standard free energy of adsorption by the
equation:

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ΔGadsᵒ= -RT lnK (3)

The value of K can be obtained by the following equation

C/θ =1/K+C, (4)

where C is the concentration of inhibitor (g/lit),θ is the surface coverage which is given as θ=%IE/100.A plot of C/θ
VS C gives a straight line, from the intercept of the straight line the value of K can be calculated and the value is
substituted in above equation and hence the ΔGᵒ value is obtained. The negative value of ΔGadsᵒ from Table 5 shows
that the adsorption process is spontaneous. Normally ,the magnitude of ΔG adsᵒ around -20 KJ/mol or less negative is
assumed for electrostatic interactions exist between inhibitor and the charge metal surface(i.e. physisorption).Those
around -40 KJ/mol or more negative are indication of charge sharing or transferring from organic species to the
metal surface to form a coordinate type of metal bond(i.e. chemisorption).The calculated ΔGadsᵒ value is -10.75
KJ/mol which is less than -20 KJ/mol indicates that the adsorption is physical adsorption.The data are also used to
study the El-Awady isotherm. The characteristic of the isotherm is given by:
Log (θ/1-θ) = log K+ y log C (5)

Where C is the concentration of the inhibitor, ө is the degree of surface coverage, K ad is the equilibrium constant of
adsorption process and Kad = K1/y.

0.8
y = 0.453x + 0.882
Log /1-

R² = 0.930 0.6

0.4

0.2

0
-1.4 -1.2 -1 -0.8 -0.6 -0.4 -0.2 0 0.2

Log C

Figure 6:- El-Awadyadsorption plot of Log(θ/1-θ)Versus Log C.

Table 5:- El-Awady adsorption of Aloe Barbadensis Miller in 0.5M HCl on the mild steel.
Inhibitor Kads 1/y R2 ΔGadsᵒ(KJ/mol)
Aloe Barbadensis miller 87.09 2.207 0.930 -11.25

In this model, the number of active sites y is included. Values of 1/y is less than one implies multilayer adsorption,
while 1/y greater than one suggests that a given inhibitor molecule occupies more than one active site. Curve fitting
of the data to the thermodynamic-kinetic model is shown in fig 6.The plot gives straight line which clearly show that
the data fitted well to the isotherm. The value of 1/y and Kad calculated from the El.Awady et.al model curve is
given in table 5.It is evident from table.7 that the value of 1/y is greater than unity showing that the inhibitor
molecule occupies more than one active site. The ΔGᵒ value can be obtained by substituting the value of Kad in
equation.3.The negative value of ΔGadsᵒ from Table.3shows that the adsorption process is spontaneous. The
calculated ΔGadsᵒ value is -11.25 KJ/mol which is less than -20 KJ/mol indicates that the adsorption is physical
adsorption.

SEM Analysis:-
The SEM mages were recorded to establish the interaction of inhibitor molecule with metal surface .Figure
7.represents the SEM images of (a) mild steel immersed in 0.5 M HCl, (b) mild steel immersed in the presence of
Aloe Barbedensis Miller in 0.5 M HCl covered with the inhibitors. Result shows that the phytochemical constituents
present in the Aloe leaves form a protective layer of the mild steel specimen and thereby reduce the corrosion rate.

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Fig.7:- SEM micrograph of (a) Mild steel immersed in acid (b) Mild steel immersed in the presence of ABMLE in
0.5M HCl).

Energy Dispersive Spectroscopy:-

Energy dispersive x-ray analysis (EDX) technique was employed in order to get information about the composition
of the surface of the mild steel sample in the absence and presence of the inhibitor in 0.5 M HCl solution. The EDX
spectra of uninhibited and inhibited mild steel samples are shown in fig.8.

Fig.8:- EDX spectra of mild steel specimens (a) After immersion without inhibitor (b) After immersion with
inhibitor.

The percentage atomic content of various elements of the uninhibited and inhibited mild steel surface determined by
EDX is listed in table 6.The percentage atomic content of Fe for mild steel immersed in 0.5 M HCl solution is 79.69
% and those for mild steel dipped in an optimum concentration of Aloe Barbedensis Miller are 71.96 respectively.
From figure 8, the spectra of inhibited samples show that the Fe peaks are considerably suppressed, When compared
with the uninhibited mild steel sample. This suppression of Fe lines is due to inhibitory film formed on the mild steel
surface.

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Table 6:- .Percentage atomic contents of elements obtained from EDX spectra.
Mild steel Fe C O Si Ca Cr Ni Cu Zn
Blank 79.69 8.46 11.85 - - - - - -
Inhibitor 71.96 10.52 10.61 1.18 0.22 0.47 0.34 0.54 4.15

Electrochemical Impedance Spectroscopy:-

In general, as impedance diagrams for solutions examined have almost a semi circular appearance, it indicates that
the corrosion of mild steel is mainly controlled by a charge transfer process. The impedance data such as R s, Rp and
Cdl were estimated by assuming Randles circuit. The values of charge transfer resistance (R t) and double layer
capacitance (Cdl) were evaluated from Nyquist and Bode plots. The values of R t, Cdl and %IE derived from these
investigations are given in table 7.The existence of single semicircle showed that single charge transfer process
occurred during dissolution of mild steel which is unaffected by the presence of extract. It was found that addition of
extract increases the value of Rt and reduces the Cdl value[9]. The decrease in Cdl value attributed to increase in
thickness of electrical double layer. The increase in Rt value is attributed to the formation of protective film on the
metal-solution interface.

Table 7:- The Electrochemical Impedance Parameters of Aloe Barbedensis Miller in 0.5 M HCl at optimum
concentration.
System Rs(Ω) Rct(Ω cm2) Cdl(F cm-2)
Blank 20.9 31.19 6.39X 10-5
Inhibitor 20.31 108.3 5.780 X 10-5

The impedance behavior of mild steel in 0.5 M HCl in the absence and presence of inhibitor at optimum
concentration of Aloe Barbedensis Miller is shown as Nyquist plot in fig.10 and EIS parameter such as R s, Rct and
Cdl were derived from the Nyquist plot are given Table.7 The ω max represents the frequency at which the imaginary
component reaches the maximum. It is the frequency at which the real part (Zr) is midway between the low and high
frequency X-axis intercepts. It is clear from the result that the value of R ct increases from 31.19 Ω cm2(Blank) to
108.3 Ω cm2 on the addition of 150 ppm of inhibitor .The value of Cdl decreases from 6.39X 10-5 F cm-2 (Blank) to
5.780 X 10-5 F cm-2.The decrease in capacitance(Cdl) on the addition of the inhibitor may be due to increase in the
local dielectric constant and /or may be due to increase in the thickness of the double layer,showing that Aloe
Barbadensis Miller leaves inhibited Iron metal corrosion by adsorbing at metal/acid interfaces.

Fig 9:- Nyquist plot in absence and presence of optimum concentration of Aloe Barbadensis Miller.

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Linear Polarization Measurement:-

The inhibition behavior of Aloe Barbedensis Miller in 0.5M HCl in the presence and absence of the inhibitor at
optimum concentration are calculated by linear polarization Parameters and are given in Table.8.The efficiency
found by linear polarization shows good agreement with efficiency obtained from Tafel and EIS data.

Potentiodynamic Polarization Measurements:-

The potentiodynamic polarization behavior of mild steel in 0.5 M HCl in the absence and in the presence of Aloe
Barbedensis Miller is shown as Tafel plot in fig.10 .The various electrochemical potentiodynamic parameters such
as corrosion potential(Ecorr),corrosion current density (Icorr),anodicand cathodic slope (βa and βc) are calculated from
Tafel plots and the values are listed in Table.8.It is seen that addition of Aloe Barbedensis Miller decreases the
corrosion current (Icorr) density from 420.9(Blank) to 101.8µA cm-2 and shifts the Ecorr from -426.8 to -396.8 m V
SCE. Even though the slight shift of E corr to less negative side makes one to think it as anodic inhibitor, but the large
shift in the cathodic slope points to the control of cathodic process. Hence it is a mixed inhibitor controlling both
cathodic and anodic process.

Table 8:- The potentiodynamic polarization and linear polarization parameters of Aloe Barbadensis Miller.
System Ecorr Icorr βa βc Rp
(m V /SCE) (µA cm-2) (m V /dec)
Blank -426.8 420 987 1023 51.6
Inhibitor -396.8 101 985 629 213.2

Fig10:-Tafel polarization curves for corrosion product of mild steel in 0.5M HCl in the absence and presence of
Aloe Barbadensis Miller.
Conclusion:-
Aloe Barbadensis Miller skin is good corrosion inhibitors for corrosion of mild steel in 0.5 M HCl
solution.Themaximumefficiencywasfoundtobe 81 % at 150 ppm.The adsorption of Aloe Barbadensis Miller on
mild steel surface obeyed the Langmuir and Al-Ewady Isotherm. The potentiodynamic studies reveal that Aloe
Barbedensis Miller is a mixed type inhibitor. The negative value of ΔGº shows that
adsorptionofAloeBarbadensismilleronmildsteel is a spontaneous process. The increase in E a value is proportional

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to the inhibitor concentration, indicating thattheenergybarrierforthecorrosioninteractionis also increased. The

results obtained from the Weight loss, electrochemical methods, SEM, EDX suggested that the mechanism of
corrosion inhibition is occurring mainly through adsorption process. EIS measurement results indicate that the
charge transfer resistance of the mild steel electrode increases and double layer capacitance decreases by increasing
the inhibitor concentration, showing the formation of the film.The SEM proves the formation of a film on the
surface of the metal.

References:-
1. Obot IB, Obi-Egbedi NO, Umoren SA, Ebenso EE. Synergistic and Antagonistic Effects of Anions and
Ipomoea invulcrata as Green Corrosion Inhibitor for Aluminium Dissolution in Acidic Medium. International
Journal of Electrochemical Science 2010;5(7) 994-1007.
2. C.S.Hsuand,F.Mansfeld,Corrosion57(2001)747.
3. Dr.J.D.Talati, Dr.N.H.Joshi, “Materials and corrosion”,(2004),vol. 31,issue 12,926-933.
4. Severin, Kenneth P., 2004, Energy Dispersive Spectrometry of Common Rock Forming Minerals.
Kluwer Academic Publishers, 225 p.– [5] Goldstein, J. (2003) Scanning electron microscopy and x-ray
microanalysis. Kluwer Adacemic/Plenum Pulbishers, 689 p.
5. Obot,I.B.,Obi-Egbedi,N,O.,Corrosion Science ,52(2010)198. [7]Rajalakshmi,R.Subjhashini,S.Leelavathi,S.,
Geethanjali,R.,J.Nepal chem.Soc.,25(2010)29.
6. I.Ahamad,R.Prasad and M.A.Quaraishi, Corrosion .Science. 52(2010)3033.
7. Ashassi-Sorkhabi H,Shaabani B,Seifzadeh D.Effect of some pyrimidinic Schiff bases on corrosion
of mild steel in HCl.Electrochem Acta2005;50:3446-52.
8. Bentiss F,Traisnel M,Lagrenee M.The substituted 1,3,4-oxadiazoles:a new class of corrosion
inhibitors of mild steel in acidic media.Corr.Sci 2000:42:127-46.
9. R.A.Prabhu,T.V.Venkatesha,A.V.Shanbhag,G.M.Kulkarni,R.G.Kalkhambkar,corrosion.science.50
(2008)3356-3362.

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