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Corrosion and corrosion inhibition of cast Iron in hydrochloric acid (HCl) solution by cantaloupe (Cucumis melo) as green inhibitor

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The effect of cantaloupe juice and seed extracts on corrosion of cast iron in 1.0 M hydrochloric acid (HCl) solution using hydrogen evolution measurements (HEM) and mass loss measurements (MLM) were investigated. Cantaloupe extracts inhibited the corrosion of cast iron in 1.0 M HCl solution. The inhibition efficiency increased with concentration of the extracts. The adsorption of the inhibitor molecules on cast iron surface was in accordance to Langmuir adsorption isotherms. In absence of inhibitors, the corrosion rate of cast iron increases with HCl concentration. The fractional reaction order observed in HCl solution indicates the formation of intermediates through the dissolution process or multiple steps mechanism of cast iron dissolution in HCl solution.
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Vol. 9(3), pp. 39-49, March, 2015
DOI: 10.5897/AJPAC2015.0607
Article Number: 2A845A651545
ISSN 1996 - 0840
Copyright © 2015
Author(s) retain the copyright of this article
http://www.academicjournals.org/AJPAC
African Journal of Pure and Applied
Ch
emistry
Full Length Research Paper
Corrosion and corrosion inhibition of cast Iron in
hydrochloric acid (HCl) solution by cantaloupe
(Cucumis melo) as green inhibitor
Khadijah M. Emran1*, Arwa O. Al-Ahmadi2, Bayan A. Torjoman2, Najla M. Ahmed2 and
Sara N. Sheekh2
1Chemistry Department, Faculty of Science, Taibah University, Saudi Arabia.
2Chemistry Department (Applied Chemistry), Faculty of Science, Taibah University, Saudi Arabia.
Received 10 January, 2015; Accepted 27 January, 2015
The effect of cantaloupe juice and seed extracts on corrosion of cast iron in 1.0 M hydrochloric acid
(HCl) solution using hydrogen evolution measurements (HEM) and mass loss measurements (MLM)
were investigated. Cantaloupe extracts inhibited the corrosion of cast iron in 1.0 M HCl solution. The
inhibition efficiency increased with concentration of the extracts. The adsorption of the inhibitor
molecules on cast iron surface was in accordance to Langmuir adsorption isotherms. In absence of
inhibitors, the corrosion rate of cast iron increases with HCl concentration. The fractional reaction order
observed in HCl solution indicates the formation of intermediates through the dissolution process or
multiple steps mechanism of cast iron dissolution in HCl solution.
Key words: Cantaloupe (Cucumis melo), corrosion, cast iron, HCl concentrations, adsorption isotherm.
INTRODUCTION
The use of inhibitors is one of the best options of
protecting metals against corrosion, especially green or
eco-friendly inhibitors. Now, this field has been promising
and effective, and it can be extracted by simple and
inexpensive procedures. Comparisons have been made
through the years between the toxic inorganic inhibitors
such as; chromates, pomegranate, and cyanide, or
synthetic organic compounds and the natural inhibitors, it
observed that the natural inhibitors could potentially serve
as an effective substitute for the corrosion inhibitors
without constituting risk for human health or the
environment in which people live in (Shanableh, 2011).
Many of these natural inhibitor substances can be
extracted from different parts of plants: seed, fruit and
leaves. Anyway, the plant extracts are considered as a
rich source of environmentally acceptable corrosion
inhibitors. For being that it can be extracted by simple
procedures, which can keep the environment healthier
with low cost and can be applied in various aggressive
environments that make it a major importance in research
*Corresponding author. E-mail: kabdalsamad@taibahu.edu.sa
Author(s) agree that this article remain permanently open access under the terms of the Creative Commons Attribution
License 4.0 International License
40 Afr. J. Pure Appl. Chem.
Figure 1. Cantaloupe (Cucumis Melo).
and studies.
Acidic solutions are widely used in various industries
for pickling ferrous alloys and steel. They are also used in
oil and gas production to stimulate and increase the oil
and gas flow to disqualify encrustations in production
wells. Among various acids, the hydrochloric acid is
mostly used for this purpose. Due to the extremely
aggressive nature of acidic media, localized pitting
corrosion starts to occur on the metal surface, over time,
produces damage and destruction for products (Gadow
and Fouda, 2014). In contrast, the particles of inhibitor
are commonly used to reduce acid attack on the substrate
metal by blocking active sites against deterioration.
Various natural plants are now used in many industries
to protect steel in hydrochloric acid (HCl) solution,
example, Garcinia Mangostana extract (Kumar et al.,
2010), Black pepper extract (Damani et al., 2010),
Fenugreek seed (Bouyanzer et al., 2010), Fennel
(Foeniculum Vulgare) (Lahhit et al., 2011) and Grap
Pomace (Rocha et al., 2012).
Cantaloupe (Cucumis melo) figure 1, a kind of
muskmelon fruit belonging to the family Cucurbitaceae
table 1, which is native to India and Africa. The unique
aroma of cantaloupe is composed of many volatile
compounds, biosynthetically derived from; fatty acids,
carotenoids, amino acid and terpens (Nattaporn and
Pranee, 2011; Milind and Kulwant, 2011). This article
report the effect of cantaloupe juice and seed extracts as
corrosion inhibitors of cast iron in 1.0 M HCl solution,
using hydrogen evolution measurements (HEM) and mass
loss measurements (MLM). In our knowledge, this is the
first time that cantaloupe juice and seed extracts have been
used as inhibitor of cast iron in HCl solution. Reinforced by
the discussion of other study, common adsorption isotherms
determine a process and nature of inhibitors adsorption,
aim to choose the best adsorption isotherm curves that fit
with experimental data (Figure 1 and Table 1).
Table 1. Scientific classification of cantaloupe (Cucumis Melo).
Kingdom
Plantae
Subkingdom
Tracheobionta
Super Division
Spermatophyta
Class
Mangoliophyta
Family
Cucurbitaceae
Genus
Cucumis L.
Species
C. Melo var. Cantalupensis
EXPERIMENTAL
Materials and solutions
Test was performed on cast iron specimen with weight percentage
compositions in Table 2. The cast iron specimen was manufactured
as cylindrical and purchased from ATTAIH Company, KSA. Before
all measurements, the specimen was polished with a series of
abrasive
paper finding a coarse to remove roughness and rust.
After that, the sample was washed by double-distillated water and
acetone, and finally dried for weighted. The HCl solution was
studied for Analar grade reagents. The solution was freshly
prepared by double-distilled water in range (0.5 to 2.0 M)
concentration by analytical dilution of stock solution (37%).
Cantaloupe extracts preparations
The juice extract of cantaloupe was obtained by putting fresh pulp
for five cantaloupes in the blender, then filtered to get homogenous
solution. While, the stock solution of seed extract was prepared by
boiled weight grams of dried seed in 600 ml from double-distilled
water for 90 min. The extract filtered and completed to 500 ml by
double-distilled water. Both extracts kept freshly in refrigerator.
Gravimetric and volumetric measurements
The measurements were carried out by tow method; hydrogen
evolution (HEM), and mass loss (MLM). Evolved H2 was collected in
a calibrated tube by downward displacement of water over time.
The temperature was adjusted at room temperature 27°C by
thermostat. The rates of HEM (R, ml/cm2.min) and MLM ( ,
g/cm2.min) were calculated as related in Equations (1) and (2),
respectively (Mathur and Vasudaven, 1982; El-Etre, 2003):
(1)
(2)
Where is the displacement of evolved gas, t is the time for
evolved gas in minute, W1 and W2 are the mass of cast iron
specimen before and after immersion in tested solution,
respectively, tf is the final time of experiment and A is the surface
area of cylindrical specimen in cm2.
The specimen was immersed in 1.0 M HCl solution in presence
inhibitors at 27°C. The inhibition efficiency (%IE) and degree of
Emran et al. 41
Table 2. Chemical compositions of cast iron specimen with weight percentage (%W).
%Si
%Mn
%P
%S
Remain
2.40 - 2.70
0.60 0.70
0.17 0.26
0.04 0.06
Fe
HCl solution
27°C
Figure 2. Volume of evolved H2 per unit area versus exposure time for cast iron
corrosion in various concentrations of HCl solutions at 27°C.
surface coverage ( ) were calculated from both HEM and MLM by
Equations (3), (4), (5) and (6) respectively (Oguzie, 2007).
(3)
(4)
(5)
(6)
Where are the HEM and MLM in the absence inhibitor,
respectively. While and are HEM and MLM in presence
inhibitor, respectively.
The corrosion rate for MLM (C.R, mmy) of the cast iron was also
calculated by using the following (Equation 7) (Quraishi et al.,
2009):
(7)
Where W is the weight loss of the metal (mg), A is the surface area
of the metal specimen (cm2), t is the exposure time (h) and D is the
density of the metal (g/cm3).
RESULTS AND DISCUSSION
Behavior of cast iron (CI) corrosion in various
concentrations of HCl solutions at 27°C
The data plotted for volume of evolved H2 per unit area
against time in minutes for 0.5 to 2.0 M of HCl
concentrations at 27°C, is presented in Figure 2. The
slopes of such lines were estimated in Table 3, taken as
rates of cast iron corrosion reacted with HCl solution as
corrosive environment using HEM. It is clear after
inspection through duration experiment; the volume of
evolved H2 gas per unit area (V/A) increase upon
increasing concentration.
The rates of corrosion of cast iron in various
42 Afr. J. Pure Appl. Chem.
Table 3. The corrosion rates of HEM & MLM for corrosion of cast iron in various concentrations of HCl solutions at 27°C.
HCl Concentration(M)
0.5
1.0
1.5
2.0
RHEM (mL.cm-2.min)
0.030
0.054
0.070
0.084
RMLM (g.cm-2.min)
6.90x10-5
1.06x10-4
1.28x10-4
1.71 x10-4
C.R. (mmy)
49.59
73.53
88.77
119.34
Figure 3. Rate (a) HEM (b) MLM of cast iron corrosion against various concentrations of HCl solutions at 27°C.
concentrations of HCl solutions resulted from HEM,
constructed that by MLM after weight specimen; which
were characterized by rapid effervescence, this influence
is shown in Figure 3. The C.R. (mmy) of cast iron
increase with increasing acid concentration, this indicates
that cast iron corrosion in HCl is concentration
dependent. It can also be observed from the Table 3 and
Figure 3 a very good agreement between values of
corrosion rates obtained from the three methods.
This result was expected, because with increased
acidic concentration; both acidity and Cl- anions
concentration are increased too. This observation agrees
with the fact that the rate of chemical reaction, diffusion,
and ionization activates with increased concentration (Al-
Tturkustani et al., 2010).
The straight line shown in Figure 2 when a metal
reacted with aggressive solution caused rapid reaction
between acid, and air indicates a soluble passive layer
(oxide film) formed on the surface of cast iron. As well,
the presence of ''induction period'' at the beginning of the
interaction (this obvious at 0.5 M) means dissolution of
the formed oxide layer. It leads to none protection
occurring on the surface and prevented solution from
coming to the surface. This layer starts to fade rapidly
with increase concentration of aggressive solution
especially up to 2.0 M HCl solution. This concentration
gives very good identity in linearity, the attack on oxide
film by Cl- anions was instantaneous, forming local
thinning passive layer on metal surface, over time create
pitting localized corrosion (Al-Tturkustani et al., 2010).
Generally, the corrosion of iron in HCl solution revealed
that it (Popova et al., 2005) takes place with hydrogen
depolarization. The spontaneous dissolution of iron can
be described by anodic dissolution reaction (Equation 8),
accompanied by the corresponding cathodic reaction
(Equation 9):
(8)
(9)
The corrosion of metals in acidic solution is cathodically
controlled by the hydrogen evolution reaction which
occurs in two steps (Equations 10 and 11) according to
(Mathur and Vasudaven, 1982):
(10)
(11)
The rate determining step for the hydrogen evolution
Emran et al. 43
Table 4. Kinetics parameters of the Mathur and Vasudevan model and conventional model.
Mathur and Vasudevan model
Conventional model
ln k
B
R2
lnk
n
R2
-3.52
0.57
0.99
-2.88
0.60
0.99
-9.82
0.58
0.98
-9.15
0.63
0.98
reaction is the recombination of adsorbed hydrogen
evolution reaction which the recombination of adsorbed
hydrogen atoms form hydrogen molecules (Equation 11).
Corrosion rate data as a function of acid concentration
can be used to show the rate dependence of hydrochloric
acid concentration by Mathur and Vasudevan model
(Equation 12) and based on the kinetic equation
(Equation 13) (Mathur and Vasudaven, 1982):
BCkR lnln
(12)
CnkR lnlnln
(13)
Where R is the rate of metal dissolution, k is corrosion
rate constant, B and n is the reaction order and C molar
concentration of HCl solution.
The values of k, B and n obtained using HEM and MLM
data and listed in Table 4. The fractional order observed
in HCl solution may indicate the formation of
intermediates through the dissolution process (Zaafarany,
2012), or multiple steps mechanism of cast iron
dissolution in HCl solution.
Inhibition action of cantaloupe extracts as green
inhibitor in cast iron corrosion
The corrosion rates for cast iron in 1.0 M HCl in absence
and presence of cantaloupe extracts were determined by
using HEM and MLM. Figure 4 shows the variations of
evolved H2 with time during the corrosion of cast iron in
1.0M HCl for various concentrations of cantaloupe
extracts (a) juice and (b) seed at 27°C. The
corresponding values of corrosion rates were given in
Table 5 from slope of each line.
In comparison, blank solution (absence inhibitors) with
added various concentrations of inhibitors (%v/v) of juice
and seeds extracts; were noted with straight lines with
much lower decreased rather than blank solution. The
decline become even more with increased concentration
of juice or seeds extracts. This indicates to oppositely
occur when studied behavior of cast iron corrosion in HCl
solution and the passive layer (adsorption film) formed
presence inhibitor become insoluble, that inhibitors were
first adsorbed onto the surface after impede corrosion
process.
The adsorption of an organic adsorbate between
metal/solution interface can be represented as a
substitutional adsorption process between the organic
molecules in the aqueous solution Org(soln) and the water
molecules on the metallic surface H2O(ads) (Equation 14)
(Bockris and Swinkels, 1964).
(soln)2(ads ) (ads)2
soln)
(
OH x + OrgOH x + Org l
(14)
where Org(ads) are the organic molecules adsorbed on the
metallic surface, H2O(sol) is the water molecules in the
aqueous solution and x is the size ratio representing the
number of water molecules replaced by one molecule of
organic adsorbate. According to (Bockris and Drazic,
1962) the inhibition mechanism could be explained by the
Fe(inh)ads reaction as intermediates:
Inh + en + Fe Fe(Inh) Inh + Fe
+n
ads
(15)
With further clarification, the Fe(Inh)ads did not have
enough covered metal surface at low concentration of
inhibitor, maybe because the added low concentration of
inhibitors, or the rate adsorption is slow. So, the metal
dissolution takes place on sites more than the formed
Fe(Inh)ads. Otherwise, at high concentration of inhibitor on
the cast iron surface forms compact and coherent
inhibitor over layer, then reducing chemical attack for
metal (Branzoi et al., 2000; Singh and Quraishi, 2012).
The inhibitor efficiency of cantaloupe juice and seed
extracts may be due to presence of many organic
substance that acts as a good corrosion inhibitors,
branched-chain and aromatic amino acid (Gonda et al.,
2010; Nattaporn and Pranee, 2011; Milind and Kulwant,
2011). These compounds usually contain polar functions
with heteroatoms such as nitrogen, oxygen, sulphur and
phosphorus, and have triple or double bonds or aromatic
rings. These groups are more a donor of electron and it
offers itself the possibility to be a center of adsorption.
The adsorption of these organic compounds by deferent
centers of adsorption on the electrode surface makes a
barrier for mass and charge transfers. This situation
leads to a reduction in the double layer and a protection
of the metal surface from the attack of the aggressive
anions of the aggressive solution (Barouni et al., 2008;
Emran et al., 2014).
The plot rates of corrosion HEM and MLM versus
concentrations of juice or seeds extracts by (%v/v) at
44 Afr. J. Pure Appl. Chem.
Figure 4. Variations of evolved H2 for (a) juice (b)seed extracts of cantaloupe in 1.0 M
HCl solution at 27°C.
27°C were presented in Figure 5. It is obvious that the
added extracts into 1.0 M HCl solution caused noticeable
reduction in amount rates obtained on cast iron surface.
Seeds extract of cantaloupe has a great decrease in rate
of HEM followed by MLM at different concentrations than
juice extract. This is precisely what was interpreted in
Table 5. 2 ml (%v/v) of juice and seeds extracts,
significantly reduced the mass loss of cast iron with a
factor 2 and 2.6 times respectively, and arched to 5.87
and 8.71 times at 40 (%v/v) compared with blank
respectively. The values of inhibition efficiency of %
IEHEM, %IEMLM degree of surface coverage (THEM) and
TMLM were listed in Table 5. The surface coverage and
inhibition efficiency values increase with increasing
extract concentration (Figure 6). The maximum inhibition
efficiency %IE value of 91.11 and 91.16% for juice
extract at 50%(v/v), whilst in seeds extract were 91.30%
and 88.5% at 40%(v/v) by using MLM and HEM at 27°C,
respectively. This is due to the blocking active sites on
metal surface and decreasing the effective area of
corrosion attack by adsorption of effect compounds
present in cantaloupe, like; Vitamin, Phenolic
compounds, Terpenoids etc. (Nattaporn and Pranee,
2011; Milind and Kulwant, 2011).
Emran et al. 45
Table 5. Effect of inhibitors on the corrosion of cast iron in 1M HCl solution by using HEM and MLM at 27°C.
Inhibitor concentration
%(v/v)
HEM
MLM
R
HEM
(ml.cm
-2
.min)
%IEHEM T
T
HEM
R
MLM
(g.cm
-2
.min)
%IEMLM
T
MLM
Blank (1.0 M HCl)
0.054
-
-
1.06x10-4
-
-
Juice extract
2%
0.027
50
0.50
5.30 x10-5
50
0.50
10%
0.023
57.41
0.57
4.85 x10-5
54.25
0.54
15%
0.021
61.11
0.61
4.04 x10-5
61.89
0.62
20%
0.013
75.93
0.76
2.59 x10-5
76.04
0.76
30%
0.011
79.63
0.80
1.98 x10-5
81.32
0.81
40%
9.20x10-3
82.96
0.83
1.79 x10-5
83.11
0.83
50%
4.80 x10-3
91.11
0.91
6.13 x10-6
94.22
0.94
Seeds extract
2%
0.021
61.11
0.61
4.13 x10-5
61.04
0.61
5%
0.015
72.22
0.72
3.04 x10-5
71.32
0.71
10%
0.012
77.78
0.78
2.37 x10-5
77.64
0.78
15%
9.80 x10-3
81.85
0.82
2.07 x10-5
80.47
0.80
20%
9.30 x10-3
82.78
0.83
1.86 x10-5
83.11
0.83
30%
9.02 x10-3
83.30
0.83
1.69 x10-5
84.06
0.84
40%
6.20 x10-3
88.50
0.89
9.12 x10-6
91.39
0.91
Figure 5. Plots (a) RHEM (b) RMLM via concentrations (%v/v) of cantaloupe extracts in 1.0 M HCl solution at 27°C.
Adsorption isotherm and adsorption parameters
Adsorption isotherms are usually used to describe the
adsorption process. The most frequently used isotherms
include: Langmuir, Temkin and Flory-Huggins. The
adsorption isotherm provides important clues regarding
the nature of the metal inhibitor interaction, and inhibitor
molecules adsorb on the metal surface if the interaction
between molecule and metal surface is higher than that
of the H2O molecule and the metal surface (Shukla and
Ebenso, 2011). Langmuir isotherm was tested for its fit to
the experimental data according to Equation (16)
(Langmuir, 1917; Christov and Popova, 2004).
(16)
Where C is the concentration of inhibitor, K is the
adsorptive equilibrium constant, T is the surface
coverage.
Langmuir isotherm given band is represented in Figure
7, and listed in Table 6. Where plots of log C/T versus
logCinh, for juice and seed extracts were found straight
lines with a good square correlation coefficient (R2)
46 Afr. J. Pure Appl. Chem.
Figure 6. Variations of the inhibition efficiency for (a) HEM (b) MLM with concentrations of inhibitors %(v/v) in 1.0 M HCl solution at 27°C.
Figure 7. Langmuir adsorption isotherm for cast iron in 1.0M HCl solution of cantaloupe extracts as inhibitors by using (a)
HEM (b) MLM at 27°C.
Table 6. Adsorption parameters for adsorption of cantaloupe extracts on cast iron surface under effect 1M HCl solution by
using HEM MLM at 27°C.
Isotherm and extracts
HEM
MLM
R2
K
R2
K
Langmuir
Juice
0.992
0.41
slope= 0.80
0.989
0.40
Slope= 0.80
Seed
0.999
0.58
slope= 0.87
0.999
0.56
slope= 0.87
Temkin
Juice
0.845
15.48
a= -3.90
0.816
11.48
a= -3.69
Seed
0.961
741.31
a= -5.80
0.976
416.87
a= -5.45
Flory
-
Huggins
Juice
0.664
4.57
x= 1.18
0.576
0.15
x= 0.90
Seed
0.938
2.04
x= 2.17
0.895
1.29
x= 1.85
Emran et al. 47
Figure 8. Temkin adsorption isotherm for cast iron in 1.0 M HCl solution of cantaloupe extracts as inhibitors by using (a) HEM (b)
MLM at 27°C.
0.992, 0.999 for HEM, and 0.989, 0.999 for MLM,
respectively. The slopes lines for each method and
extracts are arched unity, it is assumed that the inhibition
of cast iron corrosion in 1.0 M HCl by cantaloupe extract
occurs by monolayer adsorption at appropriate sites on
the metal, the metal surface contains a fixed number of
adsorption sites and each site holds one adsorbate, and
no interaction between adsorbate molecules. From the
intercepts of the straight lines logC/T axis for juice and
seeds extracts, K value calculated were 0.41 and 0.58
Lmol-1 for HEM, and 0.40 &0.56 Lmol-1 for MLM,
respectively. For Temkin adsorption isotherm, the
degree of surface by using HEM and MLM is related to
logarithmic inhibitor concentration (C) according to (Equ.
17) (Christov and Popova, 2004):
(17)
where K is the adsorption equilibrium constant and (a) is
the attractive parameter. Plots of θ against log C, as
presented in Figure 8 gave linear relationship, which
shows that adsorption data fitted Temkin adsorption
isotherm at seed extract (R2= 0.961 and 0.976) for HEM
and MLM more than juice (R2= 0.845 and 0.816) for HEM
and MLM, respectively. Adsorption parameters obtained
were recorded in Table 6. The values of interaction
parameter (a) was negative in all cases, which indicate
that repulsion exists in the adsorption layer. Flory-
Huggins adsorption isotherm can be expressed according
to (Equation 18) (Christov and Popova, 2004):
(18)
Where x is the number of inhibitor molecules occupying
one site, or the number of water molecules replaced by
one molecule of the inhibitor. The value x substituted by a
given inhibitor molecule adsorbed surface by plots of
) against by using HEM and MLM,
were shown in Figure 9. The values of the size parameter
x are positive 1.18 and 2.17 of HEM, 0.90 and 1.85 of
MLM for juice and seed cantaloupe extracts, respectively
as shown in Table 6. The values of x
x
1 for juice
extract, implied that one inhibitor molecule replaces one
water molecule, while, the values of x
x
x
x
1 for seeds
extract, means that one inhibitor molecule replaces more
than one water molecule. The x obtained for the seeds
extract were higher than those obtained for the juice
extract, suggesting that the adsorption behavior of the
seeds extract is better than that of the juice extract in
Flory-Huggins isotherm. According to the fit experimental
data (R2), the better adsorption isotherm of juice and
seeds extracts of cantaloupes is Langmuir isotherm.
Conclusion
The results obtained from HEM and MLM of corrosion
and corrosion inhibition of cast iron in various
concentrations HCl solutions (0.5-2.0 M), under 27°C;
can be deduced:
(1). The corrosion rate of cast iron increase with increase
concentration of HCl solution.
(2). Juice and seed extracts of cantaloupe acts as good
natural inhibitor for corrosion of cast iron in 1.0 M HCl
solution.
48 Afr. J. Pure Appl. Chem.
Figure 9. Flory-Huggins adsorption isotherm for cast iron in 1.0M HCl of cantaloupe extracts as inhibitors by using (a) HEM (b) MLM at
27°C.
(3). The inhibition efficiency increase with increase
concentration of inhibitors %(v/v), with maximum value
obtained in juice extract 91.11 and 94.22 at 50%(v/v),
while in seed extract 88.50 and 91.39 at 40%(v/v) for
HEM and MLM, respectively.
(4). Seed extract good natural inhibitor than juice extract
of cantaloupe.
(5). The square correlation coefficient (R2) was used to
choose the adsorption isotherm that fits experimental
data. The adsorption of cantaloupe juice and seed
extracts molecules on cast iron surface in 1.0M HCl
follows Langmuir adsorption isotherm.
Conflict of Interest
The authors have not declared any conflict of interest.
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... The effectiveness of organic inhibitors, however, depends on the nature and the condition of the metallic surface, the chemical composition and structure of the inhibitor [9]. All plant products are organic in nature and their constituents are tannins, organic and amino acids, saponins, alkaloids, flavonoids, glycosides and pigments are known to exhibit inhibiting action [10][11][12][13][14][15][16][17]. ...
... This effect has been observed since the earliest days of inhibitor technology and continues to be a potent tool in the development of acid inhibitors for specialized uses [18,19]. The synergistic inhibition between halide ions and some organic compounds has been investigated [10,20,21]. ...
... It was assumed that many organic inhibitors in acidic electrolytes become protonated, changing into cations according to the scheme [21]. According to the previous works, if S 1 approaches 1, it implies no interaction between the inhibitor compound existences, if S 1 > 1, it implies synergistic effects between the inhibitor and the halide and if S 1 < 1, it also implies that antagonistic interaction prevails, which may be attributed to competitive adsorption [10]. From the results presented in Table 7, there were synergistic effects between the extract and halide ion investigated and greater than 1 and increase with increase in temperatures from 35 to 80 °C. ...
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Investigation of Terminalia avicennioides (T. avicennioides) extract as corrosion inhibitor for steel pipelines in acidic medium using gravimetric method with and without potassium iodide (0.5 M KI⁻) and statistical modelling was carried out. Qualitative and quantitative analyses were used to determine the phytochemical constituents of the extract. The inhibitor concentration, temperature and time were varied in the range of 2.5–15.0 g/L at 2.5 g/L interval, 35–80 °C at 15 °C interval and 12–72 h at 12 h interval in a static solution. Scanning electron microscope/energy dispersive spectroscopy (SEM/EDS) technique was used to characterize the coupon surfaces before and after corrosion tests. A statistical design for the corrosion process was carried out to determine which parameters (inhibitor concentration, temperature and exposure time) that were statistically significant using ANOVA. The results revealed the presence of tannins, saponins, glycosides, flavonoids, alkaloids with reasonable amounts. Inhibition efficiency results without and with KI⁻ at the optimum concentration of 10 g/L were 94.86 and 99.12%. Langmuir adsorption isotherm was followed. The activation energy in the presence of inhibitor was greater than 80 KJ/mol in the absence of inhibitor and physisorption in nature. The SEM/EDS revealed cracks, pitting and rough in the sample without inhibitor while the surface at optimum of 10 g/L of inhibitor and (0.5 M KI⁻) had smooth surface. ANOVA results showed that the inhibitor was the most significant parameter having the highest statistical influence of 78.39% followed by time (11.09%) and temperature (10.43%). Results therefore confirmed the high inhibition efficiency values obtained in the studies.
... Large numbers of organic extracts of plant materials have been used to prevent a variety of metals such as mild steel [17][18][19][20][21][22][23][24][25][26][27][28], various types of steel [29,30], cast iron [31] aluminum and its alloys [32][33][34], zinc and its alloys [35][36][37][38], copper [39][40][41], nickel [42,43] and tin [44,45]. ...
... According to corrosive medium, extracts of plant materials have been used to prevent corrosion of metals in various medium. Most studies were conducted in acidic medium [31] than in basic [34] and neutral medium [35]. Different parts of plants that include roots, leaves, bark, flowers and fruits (shell, juice and seed) were used to reduce the corrosion. ...
... Extract has been studies as nontoxic and eco-friendly corrosion inhibitor for Aluminum in acidic and alkaline solution. The corrosion impedeing effect of seed extracts of Cantaloupe on cast iron in 1M HCl solution utilizing hydrogen evolution measurements and mass loss techniques showed good efficiency as corrosion inhibitor (Emran et al., 2015). ...
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The inhibition of corrosion on mild steel in 1M HCl solution was evaluated by utilizing carrot (Daucus carota L.) peels (CP) extract. Study performed by gravimetric and Potentiodynamic polarization techniques. Various concentrations of CP extracts ranging from 0.05, 0.1, 0.2, 0.3, 0.4, and 0.5 (v/v) were used and corrosion rate (CR) on mild steel and inhibition efficiency (IE) were investigated at three temperatures (298K, 308K, and 323K). Corrosion rate increase with the increase in temperature. As inhibitor concentration increases, corrosion rate decreases and IE decreases at elevated temperature. The substantial reduction in CR with the increase in the concentration of CP extract was noted at studied temperatures. However, the increase in the CR at each CP extract along with the increase in the temperature tallied to the increase in kinetic activities at the electrolyte and metal interface. Results show that with the increase of 0.5 g/l CP extract, about 3 times lower CR of mild steel at studied temperatures than in pure 1M HCl solution affirm its robust inhibitive efficiency. Comparatively large change in the anodic Tafel slope and gradual decline in CR with an increase in the CP extract concentration confirmed the restricted dissolution of mild steel. Surface examination suggest that a layer of inhibitor material adsorbed on the surface of mild steel at low temperature is responsible for high IE and this phenomenon is characterized as chemisorption. Weight loss data used to test three well known adsorption isotherm Langmuir, Temkin and Freundlich models and found that data is fitted well to all the models to certain extent however Freundlich Isotherm is found to be best fitted with as the correlation coefficient (R2) values reaching to unity, which showed the applicability of the models to the process.
... This could also be attributed to the increasing rates of ionization and diffusion of active species in the corrosion process. Similar observation has been made by various workers on the corrosion of metals in both HCl and H 2 SO 4 solutions at high temperatures [31,32]. ...
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In the continuation of the possibility of using green corrosion inhibitor, Cardiospermum halicacabum (CH) leaf extract as corrosion inhibitor for steel pipeline in 0.5 M hydrochloric acid using both gravimetric and potentiodynamic polarization techniques was investigated. The leaves were characterized by both quantitative and qualitative analyses and Fourier Transform Infrared Spectroscopy. Characterization of the substrates before and after corrosion tests were investigated by scanning electron microscope equipped with energy dispersive X-ray spectroscopy. The inhibitor concentration, time and temperature were varied in the range of 5–25% v/v, 1–12 days and 30–60 °C at 5% v/v, 2 days, and 10 °C interval,, respectively. Linear regression equation and analysis of variance (ANOVA) were employed to investigate the influence of process parameters (temperature, inhibitor concentration and time). Corrosion rate increased with the increasing temperature and decreased with increases in both inhibitor concentrations and time,, respectively. Maximum inhibition efficiency of 98.56% occurred at the optimal value of 20% v/v of the inhibitor concentration. The CH results revealed phytoconstituents such as tannins, alkaloids, saponins, flavonoids with their contents and azoddicarbonnamide, trphenyl phosphine oxide, etc. which were responsible for the protection of steel pipelines in acidic environment. The coupons without green inhibitor were rough, and severe pits and cracks occurred, while the surface of steel pipeline with green inhibitor was smooth. The adsorption of the molecules of the green inhibitor on adsorbate’s surface obeyed Langmuir adsorption isotherm. The potentiodynamic polarization results showed that the green inhibitor acted as mixed-type inhibitor. The ANOVA results also showed that inhibitor concentration was the most important and followed over time for the anti-corrosion of the steel pipeline by the green inhibitor.
... Emran et al. (2014) reported the use of eco-friendly cantaloupe extract as a corrosion inhibitor for the protection of aluminum in acidic and alkaline solutions. The inhibitive effect of cantaloupe seed extract could also efficiently improve the corrosion resistance of cast iron in 1 M HCl solution (Emran et al., 2015). In this study, we utilize the Saudi origin sweet melon peel extract (SM extract) as an inhibitor and corrosion tendency of mild steel in 1 M HCl solution is monitored. ...
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Corrosion inhibition of mild steel by sweet melon (Cucumis melo L) peel (SM) extract in 1 M HCl solution was evaluated by weight loss and potentiodynamic polarization methods. Various SM extracts concentrations such as 0.05, 0.1, 0.2, 0.3, 0.4, and 0.5 g/l were added and corrosion rate (CR) of mild steel and inhibition efficiency (IE) were determined at various temperatures from 295 to 333 K. The appreciable decrease in CR with increase in SM extract concentration was observed at each temperature. However, the typically accelerated CR at each SM extract with the rise in temperature corresponded to the increased kinetic activities at the metal/electrolyte interface. By the addition of 0.5 g/l SM extract, ∼5 times lower CR of mild steel at high temperature (333 K) than in blank acidic solution confirmed its strong inhibitive efficacy. The relatively large variation in the anodic Tafel slope and progressive decrease in CR with an increase in the SM extract concentration validated the restricted dissolution of mild steel. The barrier characteristics of the SM extract layer and its chemical interaction with the surface was evaluated from the low activation energy (E a ) values that fluctuated from ∼20 to 23 kJ/mole. The increase in k ad increased from 0.602 to 1.053 (g/l) ⁻¹ and decrease in ΔG° ad (−3.74 to −4.91 kJ/mole) with an increase in temperature from 295 to 333 K assured the spontaneous interaction of SM extract molecules with the steel surface.
... We also surfer from acidic rain fall and metals exposed to work suits enabling environment for corrosion attacks. Among various acids, hydrochloric acids are mostly used for this purpose [5,6]. ...
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ABSTRACT Aim: The corrosion inhibition mechanism of aluminium Alloy AA5052 has been studied in acidic solution. The study used gravimetric and electrochemical impedance spectroscopy to verify the inhibition efficacy of Epiphyllum Oxypetalum Leaf Extract At Varied Concentrations. Study Design: Laboratory research was conducted at a maximum exposure time of nine (9) hours. Place and Duration of Study: The research was carried out at Material Science group laboratory, Abia State Polytechnics, Aba Abia State, Nigeria between May 2018 and July 2018. Methodology: Gravimetric technique was employed at varied temperatures to note the general inhibitive behaviour of the leaf. Electrochemical Impedance Spectroscopy (EIS) technique was employed to determine the electrochemistry process. The leaf extraction was done with reflux set up under 65°C. Results: An Optimal Inhibition Efficiency Value of 97% was obtained. The inhibition efficiency increased with increasing concentration of the inhibitor but decreases slightly with the increase in temperature. The electrochemical studies showed that the green leaf extract was able to alter the electrochemical mechanism of the corrosion process. The corrosion current densities icorr and mass electron/charge transfer were observed to reduce due to the presence of the inhibitor in the test solution. The thermodynamic parameters were studied. Adsorption mechanism of the inhibitor molecules obeyed Langmuir and Temkin adsorption models. The calculated adsorption Gibb’s free energy is negative showing that the adsorption process was spontaneous. OPTICAL micrograph was used to study the surface morphology of the metal surface. Vickers indentation studied on the metal showed how the inhibition process improved the mechanical hardness of the corroded metal. Conclusion: Epiphyllum oxypetalum extract has been developed as a corrosion inhibitor for aluminium alloy AA5052 in the hydrochloric acidic environment
... We also surfer from acidic rain fall and metals exposed to work suits enabling environment for corrosion attacks. Among various acids, hydrochloric acids are mostly used for this purpose [5,6]. ...
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The corrosion inhibition mechanism of Al alloy AA5052 was studied using gravimetric technique and potentiodynamic polarization in 0.5 M HCl. Reflux extraction technique was used on Newbouldia laevis leaf extract. The weight loss and the inhibition efficiency were calculated. The density current was of the inhibition system were reduced. An optimal inhibition efficiency of 87% was obtained. The green leaf extract was observed adsorbed on the surface according with Langmuir and Temkin adsorption isotherm models. The effects of temperature variations which led to thermodynamic parameters were studies. The negative adsorption energy, ∆Gads obtained suggested a spontaneous molecules adsorption on the metal surface. Light Micrograph was employed to study the surface morphology. The mechanical hardness strength of the metal was improved due to the protection of the leaf extract. Keywords Corrosion studies, Gravimetric, Potentiodynamic Polarization, Thermodynamic parameters and Green
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The corrosion inhibition of mild steel in 1 mol L−1HCl by barley grains and malting process residue extracts was investigated by weight loss measurements, polarization curves, electrochemical impedance measurements and scanning electron microscopy. The inhibition efficiency exceeded 92% in the presence of 100 mg L−1 extracts after 24 h immersion time for both extracts. The Ea decreased with the addition of the extracts, characterizing the chemical adsorption by the molecules present in the extracts on the surface.The high molecular weight fraction isolated from the barley grain extract also showed high inhibition efficiency, suggesting that macromolecules are probably responsible for the inhibitory action.
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Corrosion inhibition effect of black pepper (BP) extract and its piperine isolated from BP on corrosion of C38 steel in 1 M HCl solution was investigated by weight loss method. Piperine was isolated by ethanol in yield 6 from ground BP. Results obtained from weight loss measurements indicate that the natural compounds tested exhibit higher efficiency exceeding 95% at 2g/L. The presence of piperine decreases hugely the corrosion rate and its inhibition efficiency (E%) increases with concentration to attain 99 % at 10(-3) M. Piperine adsorbs on the steel surface according Langmuir isotherm. Adsorption enthalpy were determined and discussed. Effect of temperature was also investigated and activation parameters were evaluated
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The corrosion rate of aluminum alloy at deferent concentrations of HCl and NaOH was deduced by chemical methods. It was found that dissolution rate of aluminum alloy depends on the concentration of corrosive media. The inhibition efficiency of Cantaloupe juice and seed extracts in 1.0M HCl was higher than that in 1.0M NaOH solutions. In both acidic and basic media, the increase in Cantaloupe extracts resulted in a increase both of the inhibition efficiency and the degree of surface coverage. Good corrosion inhibitor properties of cantaloupe extracts are due to presence of many organic substances. The adsorption of these organic compounds on the aluminum surface makes a barrier for mass and charge transfers. The adsorption of Cantaloupe juice and seed extract molecules on aluminium metal surface in 10.M HCl obey Langmuir's adsorption isotherm. In case of base media, the adsorption Cantaloupe juice obey Langmuir's isotherm and Temkin isotherm was fit to Cantaloupe seeds.
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The effect of Schiff base compounds, namely, ethylenediamine bis-isatin (EDBI), hexane 1,4-diamine bis-isatin (HDBI) and thiocarbohydrazide bis-isatin (TCBI) were investigated by gravimetric, potentiodynamic polarization, electrochemical impedance spectroscopy , atomic force microscopy and scanning electron microscopy . Although effect of molecular planarity on inhibition efficiency is observed from the results obtained between EDBI and HDBI. Adsorption of these inhibitors obeyed the Frumkin adsorption isotherm. It was found that efficiency order followed by inhibitor is TCBI>EDBI>HDBI. This fact strongly suggests that, an efficient corrosion inhibitor molecule should be large one, planar, having unoccupied d-orbital and also containing an extensive number of π-electrons.
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In the present work the corrosion inhibition of mild steel in hydrochloric solution by Black pepper extract (Piper nigrum fem. Piperaceae) was studied. The techniques employed for study were mass loss measurements, poten-tiodynamic polarisation, linear polarization resistance and electrochemical impedance spectroscopy (EIS). The results ob-tained revealed that Black pepper extract was a good corrosion inhibitor for mild steel in hydrochloric acid medium and maximum inhibition efficiency (98%) was found at 120 ppm at 35 ºC. Potentiodynamic polarization curves showed that black pepper extract is a mixed-type inhibitor. EIS showed that the charge transfer controls the corrosion process in inhib-ited solutions. Adsorption of the inhibitor on the mild steel surface followed Langmuir adsorption isotherm. The value of the free energy of adsorption, G ads , indicated that the adsorption of inhibitor molecules was typical of chemisorption. The results obtained show that the Black pepper extract which mainly contains alkaloid 'Piperine' could serve as an excel-lent green inhibitor for corrosion of mild steel in acid solutions.
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The effect of commercial pectinase, Pectinex® Ultra SP-L (10,292 PGU/ml), on volatile and functional bioactive compounds of flesh and placenta of fully ripe cantaloupe cv. Sunlady was studied. It was found that enzymatic degradation of cantaloupe flesh and placenta until the reducing sugar contents as 57.09-58.48 and 39.12-40.44 mg glucose/g FM, respectively, had more bioactive compounds than other conditions significantly (p≤0.05). Antioxidant activities of flesh and placenta detected by DPPH method were 9 and 4 times higher than the undegraded samples (control) (1.57, 0.66 ug FM/μg DPPH); and those measured by ABTS method were 3 and 2 times higher than undegraded samples (5.12, 7.88 μg Trolox equivalents/g FM). Total phenolic contents were 8 and 3 times higher than the undegraded samples (14.95, 39.72 mg gallic acid equivalents/100 g FM). Total flavonoid contents were 10 and 2 times higher than the undegraded samples (2.25, 12.24 mg catechin equivalents/100 g FM). Beta-carotene had increased from 68.15 to 76.71 μg/100 g FM in flesh and 97.23 to 181.89 μg/100 g FM in placenta. Dietary fiber changed from 0.65 to 0.76 g/100 g FM in flesh and 0.32 to 0.52 g/100 g FM in placenta. Prebiotic activities resulted from probiotic type L. acidophilus La5 in flesh and placenta were 0.15 and 0.14, respectively, and ones from B. lactis Bb12 were 0.34 and 0.33, respectively.. Furthermore, the main volatile compounds found in enzymatic degraded flesh were nonanal, cis-6-nonen-1-ol, and geranyl acetone as well as those found in placenta were ethyl acetate, nonanal, cis-3-nonen-1-ol, and cis-6-nonen-1-ol, etc. Therefore, fully ripe cantaloupe flesh and placenta extracted by enzyme can be a good material to be developed as food colorant with bioactive compound and to be used instead of synthetic agent in the future.
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