Corrosion is responsible for numerous damages mainly in the industrial scope. The best way to fight this damage is prevention. One of the most well-known and useful methods to avoid or mitigate destruction/degradation on the surface of metals is a corrosion inhibitor. Low cost, environmentally friendly, and non-toxic are some of the best features in the inhibitor, guar gum, used in this study. The study shows that the potential of the metal is shifted positively when the concentration of the inhibitor is increased. Low current density was also observed due to increasing the concentration of the inhibitor. Therefore, a low corrosion rate means low current density and more positive potential of the metal. Different concentrations of inhibitor are used and the optimum concentration that showed a low corrosion rate is 2.5 g/L. The efficiency of the optimum concentration is 65%. The result states that the guar gum is absorbed on the surface of the metal and gives an unchanging chelate five-membered-ring with ferrous cation Fe+2.

1. http://www.iaeme.com/IJMET/index.asp 1 editor@iaeme.com
International Journal of Mechanical Engineering and Technology (IJMET)
Volume 10, Issue 05, May 2019, pp. 1–6, Article ID: IJMET_10_05_001
Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=10&IType=5
ISSN Print: 0976-6340 and ISSN Online: 0976-6359
© IAEME Publication
INHIBITION EFFECT OF GUAR GUM ON
CORROSION OF STORAGE TANK FOR CRUDE
OIL IN BASRA REFINERY
Akram A. Al-Asadi
Corrosion Eng. Lab., Chemical & Petrochemical Techniques Engineering Department,
Basra Engineering Technical College, Southern Technical University
Basra / Iraq
Abdulrazzaq S. Abdullah
Corrosion Eng. Lab., Chemical & Petrochemical Techniques Engineering Department,
Basra Engineering Technical College, Southern Technical University
Basra / Iraq
Layla Balasem Almalike
Corrosion Eng. Lab., Chemical & Petrochemical Techniques Engineering Department,
Basra Engineering Technical College, Southern Technical University
Basra / Iraq
ABSTRACT
Corrosion is responsible for numerous damages mainly in the industrial scope.
The best way to fight this damage is prevention. One of the most well-known and
useful methods to avoid or mitigate destruction/degradation on the surface of metals is
a corrosion inhibitor. Low cost, environmentally friendly, and non-toxic are some of
the best features in the inhibitor, guar gum, used in this study. The study shows that
the potential of the metal is shifted positively when the concentration of the inhibitor is
increased. Low current density was also observed due to increasing the concentration
of the inhibitor. Therefore, a low corrosion rate means low current density and more
positive potential of the metal. Different concentrations of inhibitor are used and the
optimum concentration that showed a low corrosion rate is 2.5 g/L. The efficiency of
the optimum concentration is 65%. The result states that the guar gum is absorbed on
the surface of the metal and gives an unchanging chelate five-membered-ring with
ferrous cation Fe+2
.
Key words: Corrosion, Mild steel, Green Inhibitor, Natural inhibitor, Guar gum
Cite this Article: Akram A. Al-Asadi, Abdulrazzaq S. Abdullah, Layla Balasem
Almalike, Inhibition Effect of Guar Gum on Corrosion of Storage Tank for Crude Oil
in Basra Refinery, International Journal of Mechanical Engineering and Technology
10(5), 2019, pp. 1–6.
http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=10&IType=5

2. Inhibition Effect of Guar Gum on Corrosion of Storage Tank for Crude Oil in Basra Refinery
http://www.iaeme.com/IJMET/index.asp 2 editor@iaeme.com
1. INTRODUCTION
The most important engineering material used these days throughout the world is mild steel.
A long-standing struggle of scientists and engineers is to combat metal corrosion. One of the
utmost applicable helpful actions in this respect is the applying of suitable inorganic and
organic corrosion inhibitors. Nowadays, inorganic inhibitors having phosphate, oxygen
atoms, heavy metals, and chromate are used widely to prevent such corrosion. Some of these
organic inhibitors are environmentally and poisonous damaging. Consequently, many
researchers have put considerable effort into obtaining a suitable, environmentally friendly
inhibitors in various corrosive mediums. A study reported that natural products used as a
green inhibitor, such as extract of plant, biopolymers, proteins, and amino acids shows good
resistance to corrosion.1-9
Many studies are conducted using some macromolecules, natural polymers, known as
green inhibitors.10
Figure 1 shows the structure of complex of guar gum and iron. Guar gum
also called guaran, which is a compound of the polysaccharide having repetitive heterocyclic-
pyrane moiety in its structure. Guar gum is considered as a good inhibitor because of its
structure. 11,12
In 1M sulfuric acid solutions for 1 day, Abdullah is investigating it as a
corrosion inhibitor for mild steel.12
This study indicated that enhancing concentration of the
guar gum leads to increasing the efficiency of the inhibition process.
Figure 1. Structure of guar gum
The target of this research is the investigation of the guar-gum inhibition influence as a
natural polymer on carbon steel in water solution collected from a tank-2204 placed in Basrah
Crude Oil Refinery. In order to simulate the condition of the field of the tank-2204, many
experiments are conducted at room temperature. Guar gum, which is a natural polymer, used
as corrosion inhibitor in the 1M acetic acid in 2240 tank water for 20 hours.
2. MATERIALS AND METHODS
2.1. Materials
Table 1 exhibits the chemical composition of carbon steel (0.18 % C) 1cm2 used in this study.
This chemical composition is analyzed in the laboratory of the Basrah University, Mechanical
Engineering Department.
Table 1 Analysis of the chemical composition of carbon steel
Element C Si Mn P S Cr Cu Fe
Wt% 0.18 0.13 0.44 0.013 0.019 0.12 0.24 Remainder

3. Akram A. Al-Asadi, Abdulrazzaq S. Abdullah, Layla Balasem Almalike
http://www.iaeme.com/IJMET/index.asp 3 editor@iaeme.com
2.2. Inhibitor Electrolyte Solution
Guar gum solution was made through dissolving a 2.5 g of guar gum in 1 L of tank-2204
water, which its parameters are shown in Table 2. The tank-2204 water analysis is provided
by the Al-Shaiba Crude Oil Refinery in Basrah. Utilizing an analytical dilution of the stock
solution to prepare the concentrations of 0.1 g/L , 0.5 g/L , and 1.5 g/L.
Table 2 Analysis of chemical- physical parameters of tank-2204 water
Parameters PH
Conductivity
Us-cm-1
CaCO3
mg/L
Ca+2
mg/L
Mg+
mg/L
CL-
mg/L
Na+
mg/L
Value 7.9 4490 1058 232 116 998 638
Parameters
HCO3
mg/L
Suspended solid
mg/L
SiO3
mg/L
C.O.D
mg/L
B.O.D
mg/L
Turbidity
mg/L
T.D.S
mg/L
value 214 4 6 21 9.7 5.8 3027
2.3. Sample Preparation
Polishing of the mild steel specimen was carried out by using sand paper 100, 180, 220, and
400 grits, respectively. Then, the samples were rinsed with water in order to evade any
probable alteration in the mild steel’s microstructure. After that, they were rinsed with alcohol
such as isopropanol in order to avoid any contamination.
2.4. Electrochemical Measurements
A counter electrode (CE) which is platinum rod, a working electrode (WE) which is a carbon
steel specimen, and reference electrode (RE) which is a saturated-calomel electrode (SCE) are
utilized for conducting an electrochemical method. The electrolyte solution’s temperature
was sustained at room temperature. The carbon steel sample is polished, degreased, and
rinsed.
3. RESULTS AND DISCUSSION
The inhibition’s mechanism of guar-gum on mild steel is occurred by adsorption at the
electrode/solution interface. As mentioned, guar-gum has heterocyclic pyrane moiety. The
adsorption of guar gum is possible due to the existence of atom of the hetero-oxygen in its
structure. Such adsorption could happen by coordinate-type-linkage via the transport of sole
pairs of oxygen atoms’ electron to the mild steel’s surface. This will lead to obtaining a
unchanging chelate-five-membered ring with ferrous cation Fe+2
. Because of proximity factor
present in such chelation amid O1 and O2 with Fe+2
, it appears to be inextricably linked as
shown in Figure 1.
Influence of different concentrations of guar gum inhibitors (0.1, 0.5, 1.5, and 2.5 g/L) on
the anodic and cathodic polarization of mild steel in 1M acetic acid in 2204 tank water was
researched. Typical polarization curves without and within several concentrations of guar
gum inhibitor at 298K are shown in Figure 2. Figure 2 illustrations that increasing the
inhibition’s concentration decreases the current densities. Also, examination of curves
indicates that increasing the concentrations of the inhibitor leads to a move in the metal’s
potential to be more positive. In addition, a lack of electrons is the reason for the shifting of
the potential of the metal. As a result, the anodic reaction is sped up and the cathodic reaction
is slowed, as shown in Figure 2. Corrosion rate relays on current-density and the potential of
the metal. Furthermore, low current density and more positive potential of the metal means a
lower corrosion rate. Hence, the optimum concentration for the guar gum inhibitor is 2.5 g/L

4. Inhibition Effect of Guar Gum on Corrosion of Storage Tank for Crude Oil in Basra Refinery
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because of a lack of electrons thus the shift the potential of the metal more positively leading
to a slower the corrosion rate.
Figure 2.Curves of polarization of carbon steel in 1Molar acetic acid in at different concentrations
of guar gum inhibitor in 2204 tank water at 298K.
Table 3 presents the various electrochemical parameters without and within numerous
concentrations of the guar-gum inhibitor, such as corrosion-potential (Ecorr), corrosion-
current density (icorr), and the computed inhibitor efficiency (%). The computed efficiency of
the inhibitor could be estimated by using the following equation:
Ei = (icorr - icorr
inh
)/ icorr
Where:
Ei:is inhibitor efficiency (percentage)
icorr and icorr
inh
: are the values of the corrosion current-density in the absence and presence
of the guar-gum inhibitor.
They are measured by using the extrapolation of the cathodic Tafel slops to the corrosion-
potential. Table 3 presents the values of the corrosion rate (mm/yr), inhibitor efficiency (E%),
and the coverage of the surface (θ) obtained by inhibitor efficiency per 100 for corrosion of
carbon steel in 1M acetic acid and in the existence of inhibitors tested at altered
concentrations.
Table 3 Parameters of potentio-dynamic polarization and corresponding of the inhibition efficiency
for corrosion of carbon steel without and within guar-gum inhibitor.
Conc.
Ecorr
mV
Icorr
mA/cm2
CR
mm/yr
IE θ
0 -524.1 0.00006130 0.711564792 0 0
0.1 -568.3 0.00002731 0.317011981 55.44861338 0.554486134
0.5 -565 0.00003098 0.359613006 49.46166395 0.494616639
1.5 -561.3 0.00002496 0.289733396 59.2822186 0.592822186
2.5 -568.5 0.00002126 0.246784135 65.31810767 0.653181077

5. Akram A. Al-Asadi, Abdulrazzaq S. Abdullah, Layla Balasem Almalike
http://www.iaeme.com/IJMET/index.asp 5 editor@iaeme.com
Figure 3 demonstrates the corrosion rates of mild steel without and within altered
concentrations of guar gum (green inhibitor) in 1M of acetic acid. The optimum corrosion rate
is ascertained in the existent of 2.5 g/L of guar gum.
Figure 3. Corrosion rate of carbon steel in 1Molar acetic acid without and within altered
concentrations of guar gum as corrosion inhibitor.
Figure 4 shows the efficiency of the guar-gum as a corrosion inhibition in the presence of
1M of acetic acid in 2240 tank water and the highest efficiency is observed in the existence of
2.5 g/L of guar-gum.
Figure 4. Efficiency of carbon steel in 1Molar acetic acid without and within altered concentration of
guar gum as corrosion inhibitor.
0.
0.2
0.4
0.6
0.8
0. 0.8 1.5 2.3 3.
CR(mm/y)
Concentration (g/L)
0.
17.5
35.
52.5
70.
87.5
0. 0.8 1.5 2.3 3.
Efficiency(%)
Concentration (g/L)

6. Inhibition Effect of Guar Gum on Corrosion of Storage Tank for Crude Oil in Basra Refinery
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4. CONCLUSIONS
Experiments are carried out in order to investigate the influence of the green inhibition, guar
gum, on the corrosion of mild-steel in the weak acid medium in 2240 tank water. The result of
this study can be concluded as follow:
 The presence of the atom’s hetero-oxygen in the structure of guar gum is a factor that allows
adsorption on the mild steel’s surface.
 As a result, the adsorption process gives an unchanging chelate-five-membered ring with
ferrous cations Fe2+
and it appears to be inextricably linked.
 The result shows that the decreasing of the current-densities is associated with enhancing the
inhibition’s concentration, and also leads to shifting the potential of the metal more positively
due to the lack of electrons.
 It is observed that the cathodic reaction is slowed, and the anodic reaction is sped up.
 The optimum concentration for the guar gum inhibitor and high efficiency is observed in the
existence of 2.5 g/L of natural polymer, guar-gum as a corrosion inhibitor.
 This inhibitor, it could be used in such medium and acts an anodic inhibitor.
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