International Journal of Advanced Research in Engineering and Technology (IJARET)
Volume 8, Issue 2, March - April 2017, pp. 42–48, Article ID: IJARET_08_02_005
Available online at http://www.iaeme.com/IJARET/issues.asp?JType=IJARET&VType=8&IType=2
ISSN Print: 0976-6480 and ISSN Online: 0976-6499
© IAEME Publication
INHIBITION EFFECT OF PHOENIX
SYLVESTRIS EXTRACT IN 1M HCL SOLUTION
Hussein H. Ibrahim
South Oil Company, Basrah, Iraq
Abd-alwahab A. Sultan
Petrochemical Engineering Department, Basrah Engineering Technical Collage, Basrah, Iraq
Abdulkhaleq A. Hasan
Abdulkhaleq A.Hasan, Technical Institute of Basrah, Basrah, Iraq
ABSTRACT
The inhibitory effect of the ethanol extract of Phoenix Sylvestris on the carbon
steel in 1M HCl was studied by weight loss method. The corrosion inhibition efficiency
was found to increase with inhibitor content to obtain 97.91% with 40% of the extract
at 25℃ during 3 hours immersion time. The inhibition efficiency of the extract
decreased as temperature increased. The results showed that the adsorption of the
extract on the carbon steel obeys Langmuir isotherm. The activation parameters,
apparent activation energy (E ), the enthalpy of activation (∆H ) and entropy of
activation (∆S ) for the corrosion of carbon steel in 1M HCl in the absence and
presence of the extract were calculated and discussed.
Key words: Phoenix Sylvestris, Carbon steel, Corrosion inhibitor, HCl solution,
Weight loss.
Cite this Article: Hussein H. Ibrahim, Abd-alwahab A. Sultan and Abdulkhaleq A.
Hasan, Inhibition Effect of Phoenix Sylvestris Extract in 1M HCL Solution,
International Journal of Electronics and Communication Engineering and
Technology, 8(2), 2017, pp. 42–48.
http://www.iaeme.com/IJECET/issues.asp?JType=IJECET&VType=8&IType=2
1. INTRODUCTION
Corrosion of metals is a very common problem that has economic implications costing
billions of dollars each year. Corrosion is the destructive attack of a metal by chemical or
electrochemical reaction with the environment [1]. In fertilizers, petroleum, metallurgical and
other industries, corrosion of metallic components are likely during acid cleaning, pickling,
etching and related processes. Although there are several options in controlling corrosion of
metals, the use of inhibitors has been proven to be one of the best options [2]. Corrosion
inhibitors are substances which when added in small concentrations to corrosive media
decrease or prevent the reaction of metal with the media [3]. However, because of the toxic
nature, high cost and increasing awareness and strict environmental regulations of some of
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42
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Hussein H. Ibrahim, Abd-alwahab A. Sultan and Abdulkhaleq A. Hasan
industrial inhibitors, the exploration of natural product of plant origin as corrosion inhibitor is
currently receiving attention [4].
The present study is aimed at investigating the inhibitive properties of ethanol extract of
Phoenix Sylvestris on the corrosion of carbon steel in 1M HCl solution.
2. EXPERIMENTAL
2.1. Specimen Preparation
In this study carbon steel of composition (wt. %) Si (2), Mn (0.4), C (0.368), S (0.1), Cr
(0.07), Mo (0.012) and Fe (97.05) was used. The specimens were of size 2.5 cm x 1.5 cm x
0.3 cm containing a small hole of 4 mm diameter near the upper edge. Before each test, each
coupon was polished with emery papers of 60 and 1000 grades, washed with distilled water,
dried with tissues, degreased with acetone and dried with tissues again.
2.2. Preparation of Inhibitor
Phoenix Sylvestris was washed with distilled water and put on the tissue to dry. Four grams of
Phoenix Sylvestris were immersed in 200 ml of ethanol for two days. After two days the
solution was filtered and used as natural corrosion inhibitor.
3. RESULTS AND DISCUSSION
3.1. Effect of Inhibitor Concentration
Corrosion rates of carbon steel samples were determined in 1M HCl solution at various
contents of the extract for 3 hours of immersion at 25℃. The values of percentage inhibition
efficiency and corrosion rate obtained from weight loss method at different contents of extract
at 25℃ are summarized in (Table 1). The corrosion rate is found to decrease with the extract
content. Figure1 shows the plot of corrosion rate (mg cm hr ) against content of extract
for the corrosion of carbon steel in 1M HCl solution during 3 hours at 25℃. The maximum
inhibition efficiency (97.91%) was obtained at 40% content.
From the results, it is seen that values of inhibition efficiency of Phoenix Sylvestris
extract for the corrosion of carbon steel increases as the content of the extract increases
indicating that the extract acts as corrosion inhibitor. Figure 2 shows the variation of
percentage corrosion inhibition efficiency against content of the extract. This behavior can be
attributed to the increase of surface covered θ and adsorption of natural compounds on the
surface of the carbon steel as the extract content increases.
Table 1 Corrosion parameters obtained from weight loss measurements
Content
weight loss (mg)
C.R (mg/cm^2.hr)
I.E %
0%
2%
10%
20%
30%
40%
28.8
9.6
9.1
6.8
2.3
0.61
0.8617
0.3143
0.2922
0.1948
0.0662
0.0180
---63.52
66.09
77.39
92.31
97.91
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Inhibition Effect of Phoenix Sylvestris Extract in 1M HCL Solution
Corrosion rate (mg/cm^2.hr)
1
0.8
0.6
0.4
0.2
0
0%
10%
20%
30%
40%
Inhibitor content
Inhibition efficiency %
Figure 1 Plot of corrosion rate of carbon steel against extract content in 1M HCl solution at 25℃.
93
83
73
63
0%
10%
20%
30%
40%
Inhibitor content
Figure 2 Corrosion inhibition efficiency of various extract contents in 1M HCl solution at 25℃.
3.2. Effect of Temperature
The influence of temperature on the corrosion behavior of carbon steel in acidic medium was
also studied in the absence and presence of the extract between 25 and 65℃ at 3 hours (Table
2).
The corrosion rate of carbon steel increases with temperature both in the absence and
presence of the inhibitor at a maximal content (40%). The presence of inhibitor leads to
decrease of the corrosion rate. Figure 3 represents this behavior clearly. The values of
corrosion inhibition efficiency of the extract decreased with increasing temperature. This is
due to increase rate of dissolution process of carbon steel and partial desorption of the
inhibitor from the metal surface with temperature [5]. Figure 4 shows the relation between
corrosion inhibition efficiency of the extract with temperature.
Table 2 Corrosion parameters obtained from weight loss test for carbon steel immersed in 1M HCl in
the absence and presence of 40% of the extract at different temperatures
Tem.
25
45
65
weight loss (mg)
28.8
0.61
51.6
8.4
69.3
29.6
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C.R (mg/cm^2.hr)
0.8617
0.0180
1.3927
0.2304
1.9965
0.6799
I.E %
---97.91
---83.45
---65.94
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Hussein H. Ibrahim, Abd-alwahab A. Sultan and Abdulkhaleq A. Hasan
C.R (mg/cm^2.hr)
2.5
2
1.5
1
Without inhibitor
With inhibitor
0.5
0
20
30
40
50
60
70
Temperature (C)
Inhibition Efficiency %
Figure 3 Plot of corrosion rate of carbon steel in 1M HCl without and with 40% of the extract against
temperature obtained from weight loss measurements.
100
95
90
85
80
75
70
65
60
20
30
40
50
60
70
Temperature (C)
Figure 4 Plot of inhibition efficiency of the extract (40%) in 1M HCl against temperature.
3.3. Activation Parameters of Inhibition Process
The apparent activation energy (E ), the enthalpy of activation (∆H ) and entropy of
activation (∆S ) for the corrosion of carbon steel in 1M HCl in the absence and presence of
the extract were calculated from Arrhenius equation and Arrhenius transition state equation
[6,7]:
log C. R = −
log
E
+ log J
2.303RT
(1)
C. R
R
∆S
∆H
= log
+
−
T
Nh 2.303R
2.303RT
(2)
A plot of logarithm corrosion rate of carbon steel obtained from weight loss
measurements versus the reciprocal of absolute temperature ranges (25 – 65℃), gives a
straight line as shown in fig. 5 with slope – E ⁄2.303R . On the other hand, a plot of
log C. R⁄T versus 1⁄T gives a straight line (figure 6) with a slope equal to − ∆H ⁄2.303R and
an intercept of log R⁄Nh + ∆S ⁄2.303R , from which the values of ∆H and ∆S were
calculated. The values of E , ∆H and ∆S are listed in (Table 3).
It is clear that the addition of the extract provokes an increase in the value of apparent
activation energy. The higher value of activation energy of the corrosion process, when the
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Inhibition Effect of Phoenix Sylvestris Extract in 1M HCL Solution
extract is added, when compared to activation energy for the medium without inhibitor, is
attributed to an electrostatic mechanism of the inhibitor [8]. The positive signs of enthalpies
reflect the endothermic nature of dissolution process.
Table 3 Activation parameters for the dissolution of carbon steel in 1M HCl in the absence and
presence of 40% of the extract.
Content
0.0
E
(KJ/mol)
17.6230
∆H
(KJ/mol)
16.2635
40%
76.5694
75.2099
0.5
Log C.R
0
y = -920.4x + 3.028
R² = 0.997
-0.5
Blank
-1
40%
-1.5
y = -3999.x + 11.76
R² = 0.963
-2
0.0029 0.003 0.0031 0.0032 0.0033 0.0034
1/T (K^-1)
Figure 5 Plot of log C.R against 1/T for carbon steel in 1M HCl in the absence and presence of 40%
of the extract.
-2
y = -849.4x + 0.316
R² = 0.997
Log C.R/T
-2.5
-3
-3.5
-4
Blank
y = -3928.x + 9.049
R² = 0.961
40%
-4.5
0.0029
0.003
0.0031 0.0032 0.0033 0.0034
1/T (K^-1)
Figure 6 Plot of log C.R/T against 1/T for carbon steel in 1M HCl in the absence and presence of 40%
of the extract.
3.4. Adsorption Isotherm
The effectiveness of organic compounds as corrosion inhibitors can be ascribed to the
adsorption of molecules of the inhibitors through their polar functions on the metal surface. In
this study, Langmuir adsorption isotherm was found to be suitable for the experimental
finding and has been used to describe the adsorption characteristic of this inhibitor.
Assumption of Langmuir adsorption isotherm is expressed in equation (3) [9]:
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Hussein H. Ibrahim, Abd-alwahab A. Sultan and Abdulkhaleq A. Hasan
C
θ
=
1
+C
K
(3)
was found to be linear as shown in Figure 7. This figure
The plot of θ versus C
indicates that the adsorption of the extract on carbon steel in 1M HCl solution obeys the
Langmuir adsorption isotherm.
0.5
R² = 0.977
Content/ɵ
0.4
y = 0.960x + 0.038
0.3
0.2
0.1
0
0
0.1
0.2
0.3
0.4
Content
Figure 7 Langmuir isotherm for the adsorption of the inhibitor on the surface of the carbon steel in
1M HCl solution at 25℃.
4. CONCLUSION

Phoenix Sylvestris extract showed inhibitive effect on carbon steel in HCl solution.

Inhibition efficiency increases with an increase in inhibitor content.

The adsorption of Phoenix Sylvestris extract obeyed Langmuir isotherm.

Activation energy increases in the presence of the extract which indicates the
physisorption of the extract on the carbon steel surface.

Inhibition efficiency of Phoenix Sylvestris extract decreases as the temperature increases.
SYMBOLS
A: Constant
C. R: Corrosion rate (mg. cm . hr )
C : Content of the inhibitor
E : Apparent activation energy (KJ.mol )
h: Planks constant (6.626*10
J. s)
H : Enthalpy of Activation (KJ.mol )
K: Binding constant of the adsorption reaction
N: Avogadro’s number (6.022*10 mol )
R: Gas constant (8.314 J. mol . K )
S : Entropy of activation (J. mol . K )
T: Temperature (K)
θ: Surface coverage
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Inhibition Effect of Phoenix Sylvestris Extract in 1M HCL Solution
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