34
USING OF ALLIUM AMPELOPRASUM EXTRACT AS
CORROSION INHIBITOR
Hussein H. Ibrahim1, Abd- Alwahab A.Sultan2, Abdulkareem M. Jewad3, Intisar A. Abdulkareem4, Asaad H. Majeed5
1
South Oil Company, Basrah, Iraq
2
Petrochemical Engineering Department, Basrah Engineering Technical Collage, Basrah, Iraq
3
Healthy Technical Collage, basrah, Iraq
4
Petrochemical Industries Department, Technical Institute, Basrah, Iraq
5
Technical Institute, Basrah, Iraq
ABSTRACT
The inhibition of carbon steel corrosion by extract of Allium Ampeloprasum was studied by weight loss method. The inhibition efficiency of the inhibitor was found to increase with increasing content of the extract. Inhibition efficiency of 98.3% was achieved with 40% v/v of the extract in 1M hydrochloric acid during 3 hours at 25℃. Effect of temperature was also investigated and activation parameters were evaluated. The results showed that the extract adsorb on the surface of carbon steel through physical adsorption and the adsorption of the inhibitor obeys the Langmuir adsorption isotherm.
Keywords: Allium Ampeloprasum, Corrosion inhibition, Carbon steel, acidic media, adsorption
1. INTRODUCTION
Corrosion is the destructive attack of a metal by chemical or electrochemical reaction with the environment.
The basic cause of the corrosion of the metals is their tendency to return to their stable state. Nearly all metals are inherently unstable and it is their natural tendency to seek self-destruction by reacting with their environment to attain a state of lower energy by forming a metal compound. This is the state in which the majority of metals are found in nature [1].
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Volume 6, Issue 1, January (2015), pp. 34-41
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The three main reasons for the importance of corrosion are: economics, safety, and conservation. The cost of corrosion in industrialized countries has been estimated to be about 3–4% of the gross national product [2, 3].
Corrosion can compromise the safety of operating equipment by causing failure of, for example, pressure vessels and boilers, metallic containers for toxic chemicals, turbine blades and rotors. Loss of metal by corrosion is a waste not only of the metal, but also of the energy, the water, and the human effort that was used to produce and fabricate the metal structures in the first place [2]. Corrosion of metallic surfaces can be reduced or controlled by the addition of chemical compounds to the corrodent. This form of corrosion control is called inhibition and the compounds added are known as corrosion inhibitors. These inhibitors will reduce the rate of either anodic oxidation or cathodic reduction, or both. The inhibitors themselves form a protective film on the surface of the metal [4]. There are numerous inhibitor types and compositions. Most inhibitors have been developed by empirical experimentation [5]. Most synthetic corrosion inhibitors are expensive, toxic and hazardous compounds. The toxic effect of these inhibitors does not only affect living organisms but also poison the environment. Therefore, the use of natural products has gained popularity. Plants extracts constitute several organic compounds those act as antioxidants could be considered to generate cost effective source of corrosion inhibitor actives being renewable, widely available and they offer the advantage of imposing no hazard to the environment. In this study, extract of Allium Ampeloprasum was used as natural corrosion inhibitors.
2. EXPERIMENTAL 2.1 Specimen Preparation
Carbon steel specimens of size 6.5 cm x 2.5 cm x 0.3 cm containing a small hole of 3 mm diameter near the upper edge were employed for the weight loss test. Before each test, each specimen was polished with emery papers of 60, 1000, 1200 grades, washed with tap water followed by distilled water, dried with tissues, degreased with acetone and dried with tissues again.
2.2 Preparation of Plant Extract
Fresh Allium Ampeloprasum which was used in this study was collected from Al-Sarragi in Basrah city. The plant was washed with tap water several times followed by distilled water and put on the tissue to dry. Two grams of Allium Ampeloprasum was immersed in 100 ml of ethanol for three days. After three days the solution was filtered and used as natural corrosion inhibitor.
3. RESULTS AND DISCUSSION 3.1 Effect of Inhibitor Concentration
Various corrosion parameters such as corrosion rate and inhibition efficiency were obtained
from weight loss measurements for different inhibitor content (2%, 10%, 20%, 30% and 40%) for the corrosion of carbon steel in 1M HCl solution duration 3 hours at 25℃ (Table 1). Fig. 1 shows the variation of corrosion rate (mg cmhr) with content of extract in 1M HCl solution. From the plot it can be seen that corrosion rate of carbon steel was significantly lowered down in presence of extract and with the increase in content of the extract the corrosion rate decreased gradually. Corrosion rate of carbon steel in 1M HCl solution decreased from 0.8896 mg/cm^2.hr to 0.0151 mg/cm^2.hr in the presence of 40% of the extract.
Fig. 2 shows the variation of percentage corrosion inhibition efficiency against content of the extract. The results revealed that corrosion inhibition efficiency increases with increasing the extract content. The inhibition efficiency reached to 98.3026 in the presence of 40% v/v of the extract. This behavior can be attributed to the increase of surface covered θ and adsorption of natural compounds
36
on the surface of the carbon steel as the inhibitor content increases. Due to adsorption the corrosion sites of carbon steel get blocked and adsorbed film acts as barrier between carbon steel surface and corrosion medium.
Table 1: Corrosion parameters obtained from weight loss measurements
Content weight loss (mg) C.R (mg/cm^2.hr) I.E %
0% 30.00 0.8896 ---- 2% 10.10 0.3066 65.5350 10% 9.20 0.2792 68.6151 20% 7.50 0.2225 74.9887 30% 1.30 0.0377 95.7621 40% 0.51 0.0151 98.3026
Fig 1: Variation of corrosion rate of carbon steel without and with extract in 1M HCl solution at
25℃
Fig 2: Variation of percentage corrosion inhibition efficiency with the content of the extract in 1M
HCl solution at 25℃ 0 0.2 0.4 0.6 0.8 1 0% 10% 20% 30% 40% C o rr o si o n r a te ( m g /c m ^ 2 .h r) Inhibitor content 65 70 75 80 85 90 95 100 0% 10% 20% 30% 40% In h ib it io n e ff ic ie n cy % Inhibitor content
37 3.2 Effect of Temperature
The effect of temperature on the various corrosion parameters such as weight loss, corrosion
rate, inhibition efficiency were studied for the corrosion of carbon steel in 1M HCl solution duration 3 hours at temperatures 25, 45 and 65℃. The results indicated that the corrosion rate of carbon steel in the absence and presence of the extract increases with rise in temperature, although corrosion rate is lowered in the presence of the extracts compared to blank solution. Fig. 3 represents this behavior clearly. The values of corrosion inhibition efficiency of the extract decreased with increasing temperature. Fig. 4 shows the relation between corrosion inhibition efficiency of the extract with temperature. As explained previous these results can be attributed to the physical adsorption of the extract on the carbon steel surface in 1M HCl solution [6, 7].
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. weight loss (mg) C.R (mg/cm^2.hr) I.E %
25 30 0.8896 ---- 0.51 0.0151 98.3026 45 49.6 1.3279 ---- 9.4 0.2516 81.0472 65 79.3 2.3045 ---- 31.6 0.7264 68.4774
Fig 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
0 0.5 1 1.5 2 2.5 20 30 40 50 60 70 C o rr o si o n r a te ( m g /c m ^ 2 .h r) Temperature (C) without inhibitor with inhibitor
38
Fig 4: Plot of inhibition efficiency of the extract (40%) in 1M HCl against temperature
3.3 Activation Parameters of Inhibition Process
The activation energy (E ) and enthalpy of activation for the corrosion of carbon steel in the absence and presence of 40% v/v of the extract in 1M hydrochloric acid were calculated using Arrhenius equation and Arrhenius transition state equation [8, 9]:
log C. R = −2.303RT + log A (1)E logC. RT = logNh +R 2.303R! −∆S 2.303RT (2)∆H
A plot of logarithm corrosion rate of carbon steel obtained from weight loss measurements versus the reciprocal of absolute temperatures 25, 45 and 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 (Fig. 6) with a slope equal to − ∆H ⁄2.303R from which the values of ∆H were calculated. The values of E and ∆H are listed in Table 3.
The results showed that the activation energy increases in the presence of the extract. Higher activation energy for the corrosion process in the presence of inhibitor leads to conclusion that probably the inhibitor is found to be adsorbed on the surface of carbon steel by specific physical adsorption process [10, 11]. 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 %& (KJ/mol) ∆'& (KJ/mol) 0.0 19.8364 18.4789 40% 81.7583 80.3988 65 70 75 80 85 90 95 100 20 30 40 50 60 70 In h ib it io n e ff ic ie n cy % Temperature (C)
39
Fig 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
Fig 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
Addition of extract molecules which adsorbed on the carbon steel surface and the interaction between them can be described by adsorption isotherm. The data were tested graphically by fitting to Langmuir model. This model is given by [12]:
C()*
θ = 1
K + C()* (3)
By plotting values of ,-./θ versus C()* (Fig. 9) a linear plot was obtained indicating that the adsorption of the inhibitor is consistent with the assumption of Langmuir adsorption isotherm and the slope obtained is close to unity.
y = -1036.x + 3.411 R² = 0.983 y = -4270.x + 12.61 R² = 0.952 -2 -1.5 -1 -0.5 0 0.5 0.0029 0.003 0.0031 0.0032 0.0033 0.0034 lo g C .R 1/T (K^-1) Blank 40% y = -965.1x + 0.699 R² = 0.982 y = -4199.x + 9.899 R² = 0.951 -4.5 -4 -3.5 -3 -2.5 -2 0.0029 0.003 0.0031 0.0032 0.0033 0.0034 lo g C .R /T 1/T (K^-1) Blank 40%
40
Fig 9: Langmuir isotherm for the adsorption of the inhibitor on the surface of the carbon steel in 1M
HCl solution at 25℃
4. CONCLUSION
1. Allium Ampeloprasum extract acts as efficient corrosion picking inhibitor on carbon steel in 1M hydrochloric acid.
2. The extract showed maximum inhibition efficiency of 98.3% at the presence of 40% in v/v during 3 hours at 25℃.
3. The corrosion inhibition efficiency of the extract decreases with increasing temperature.
4. Activation energy increases in the presence of the inhibitor which indicates the physisorption of the extract on the carbon steel surface.
5. Allium Ampeloprasum extract adsorbs on the carbon steel surface according to the Langmuir isotherm.
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*1001 J. s) H : Enthalpy of Activation (KJ.mol)
K: Binding constant of the adsorption reaction N: Avogadro’s number (6.022*100mol) R: Gas constant (8.314 J. mol. K) S : Entropy of activation (J. mol. K)
T: Temperature (K) θ: Surface coverage R² = 0.970 0 0.1 0.2 0.3 0.4 0.5 0 0.1 0.2 0.3 0.4 C i n h /ɵ C inh
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