2.5ml Ethanol is used on plant extracts of locus bean (parkiabiglobosa) and banana sap (musaparadisiaca) as corrosion inhibitors for mild steel in 1M dilute HCl was investigated using weight loss techniques. Corrosion tests were first carried out for 1 and 3 hrs of immersion time respectively at various concentrations of extracts (0.5ml, 1.0ml, 1.5ml, 2.0ml and 2.5ml) and 2.5ml were used as corrosion inhibitors and at different temperatures (38oC, 45oC and 55oC). Results showed that the minimum corrosion rate obtained for 1 hr at 38oC with extract of Pakiabiglobosa is 0.85×10-4g/cm3/min and efficiency of 18.75% for 1hr, while at 55oC the corrosion rate was 4.37×10-4 g/cm3/min and efficiency of 33%. With ethanol extract of banana sap, minimum corrosion rate and efficiency recorded at 38°C were (4.16×10-4 g/cm3/min and efficiency of (22.1%), while at 55oC they were (0.83×10-4 g/cm3/min) and (7.6%) respectively. From these results, it is concluded that extracts of locust bean and banana sap can be successfully used as corrosion inhibitors in specified acidic medium.

1. Effect of plant extracts on corrosion rate of mild steel in acidic medium
IRJMSE
Effect of plant extracts on corrosion rate of mild steel in
acidic medium
Bawa Bamaiyi1
and MU Peni2
1
Federal Polytechnic, Kaura Namoda, Zamfara State, Nigeria.
2
Waziri Umaru Federal Polytechnic, Birnin Kebbi, Kebbi State, Nigeria.
2.5ml Ethanol is used on plant extracts of locus bean (parkiabiglobosa) and banana sap
(musaparadisiaca) as corrosion inhibitors for mild steel in 1M dilute HCl was investigated using
weight loss techniques. Corrosion tests were first carried out for 1 and 3 hrs of immersion time
respectively at various concentrations of extracts (0.5ml, 1.0ml, 1.5ml, 2.0ml and 2.5ml) and
2.5ml were used as corrosion inhibitors and at different temperatures (38
o
C, 45
o
C and 55
o
C).
Results showed that the minimum corrosion rate obtained for 1 hr at 38
o
C with extract of
Pakiabiglobosa is 0.85×10
-4
g/cm
3
/min and efficiency of 18.75% for 1hr, while at 55
o
C the
corrosion rate was 4.37×10
-4
g/cm
3
/min and efficiency of 33%. With ethanol extract of banana
sap, minimum corrosion rate and efficiency recorded at 38°C were (4.16×10
-4
g/cm
3
/min and
efficiency of (22.1%), while at 55
o
C they were (0.83×10
-4
g/cm
3
/min) and (7.6%) respectively. From
these results, it is concluded that extracts of locust bean and banana sap can be successfully
used as corrosion inhibitors in specified acidic medium.
Keywords: Ethanol, locus bean, banana sap, corrosion, inhibitors, efficiency, hydrochloric acid.
INTRODUCTION
Of all metallurgical problems that face civilization, only a
few can be economically more important than the
prevention of metallic corrosion. Environmental attack on
metal produces a destructive effect on their physical and
mechanical properties which consequently, contributes to
economic loses, impairs the safety of operating
equipment and invariably depletes our metal reserves
(Njoku, 2002).
Due to the problems arising from corrosion, several
methods of corrosion control and preventions have been
innovated: use of protective coatings, proper selection of
material, alloying, proper design, cathodic protection, the
use of inhibitors, etc. The method used for any specific
application is based on economic considerations, nature
of the corrosive environment, efficiency and cost
consideration (Rozenfeld, 1981). According to Gosta,
1982 and Schmitt, 1984, inhibitors are used in a wide
range of applications such as in oil pipelines, domestic
central heating systems, industrial central cooling
systems, corrosion protection of machines, in power
generating plant, metal extraction, oil extraction, chemical
processing and protection of metals operating under
corrosive environment. Inhibitors are also used in the
chemical removal of surface oxides from metal surface by
immersion in acid solution; a process referred to as
pickling. Ferrous oxides dissolve readily in acid solutions
during pickling in such a way that the oxides are attacked
first making it easier for scale removal (Rozenfeld, 1981).
Development in pickling techniques (ultrasonic pickling)
does not eliminate the use of inhibitors but rather proffers
solution to the problems of environmental pollution and
improvement of pickling yield (Goode et al, 1996).
*Corresponding author: Bawa Bamaiyi, Federal
Polytechnic, Kaura Namoda, Zamfara State, Nigeria. Email:
bawabamaiyi@yahoo.com
International Research Journal of Materials Science and Engineering
Vol. 2(1), pp. 012-018, June, 2015. © www.premierpublishers.org. ISSN: 1539-7897x
Research Article

2. Effect of plant extracts on corrosion rate of mild steel in acidic medium
Bamaiyi and Peni 012
Inhibitors are employed predominantly for corrosion
control in closed systems as a cost-efficient alternative to
the use of high corrosion-resistant materials. Due to the
environmental requirements that are currently imposed
on the development of cleaner inhibitors; vegetable
tannins (a class of natural, non-toxic, biodegradable
organic compounds that can be obtained at reduced cost)
have been proposed. This work relates recent uses of
several vegetal tannins in corrosion protection,
particularly as corrosion inhibitors of mild steel in acidic
media. Practical criteria for the selection of corrosion
inhibitors are not only their inhibition efficiency but also
safety of use, economic constraints and capability with
other chemicals in the system and environmental
concerns (Rahim and Kassim, 2008).
Chromates are generally accepted as effective corrosion
inhibitors that can passivate metals by forming a mono-
atomic or polyatomic oxide film at the electrode surface.
However, the main disadvantage is the toxicity of the
chromium (VI) oxidation state and this is the reason for
search for less toxic alternatives (Rozenfield, 1981).
Current studies have shown that vegetal tannins are
good inhibitors for metals and alloys in acidic media and
their inhibition mechanisms are dependent on the
aggressive environment and the pH value. However
extensive corrosion protection studies by these tannins
evaluated via electrochemical techniques, accelerated
tests, weight loss measurements and molecular modeling
are limited to iron and steel substrates.
Background of the study
Inhibitors have found a wide range of applications in
metallurgical processes such as in the rolling mills where
rolled products are being de-scaled through the process
technically referred to as „pickling‟, which employs the
use of mineral acids such as hydrochloric (HCl) and
tetraoxosulphate VI acids (H2SO4) (Kassim, 2008). Acid
corrosion inhibitors are used to ensure that the attack on
the metal is minimized as much as possible. In many
industries, the need to use constructional materials
safely, but cost-effectively, is a primary consideration.
Frequently, physical requirements can be satisfied easily,
but corrosion effects seriously complicate the selection of
suitable materials. Generally, increased corrosion-
resistance can only be obtained at increased cost.
However, the actual material-related costs incurred in a
project will depend on the corrosivity of the environment
concerned, the required designed life, the physical
requirements of the material, and the readily available
stocks. Industrial use of corrosion inhibitors is, therefore,
now broad-based and extensive (Rahim and Kasim,
2008).
The choice of mild steel for this research is not
unconnected with their unique qualities such as excellent
formability, comparative cheapness, availability and their
diverse usage in engineering applications (Njoku, 2002).
HCl is a well-known standard corrosion inhibitor for
carbon steels in acidic environment and was, therefore,
chosen for comparative purpose and verification of
results.
The choice of hydrochloric acid is connected with its
predominant use in chemical treatment of steel e.g. for
pickling of rolled products and as etchant during
macro/microscopic examination of metals. The acid is
mostly used for pickling because it makes rinsing of
pickled materials easy due to high solubility of chloride in
water (Ohio, 1982).
The choice of plant extracts for this research is due to the
recent discovery that some plant extracts like cocoyam
leaf (xanthasoma) are used as corrosion inhibitors in
certain environments. For a plant extract to be used as
inhibitor, however, the plant should be cheap, non toxic
and readily available (Abiola and Oforka, 2004). The
choice of the extract of locust bean (Pakiabiglobosa) and
banana sap(musa paradisiacal) for this research work is
specifically based on the fact that both plants are readily
available in Nigeria and particularly their non-toxic in
nature. Their median lethal dose (LD50) is greater
than500mg
-1
(Abalaka, 2014).
Aims and objectives of this research
The aim of this research work is to investigate the effect
of corrosion inhibition of locust bean tree
(Parkiabiglobosa) and banana sap (musa paradisiaca) on
mild steel in hydrochloric acid solution.
The specific aims and objectives of this research
work include:
a. To determine whether the plant extracts of locust
bean tree (Parkiabiglobosa) and Banana sap (musa
paradisiacal) could be used as corrosion inhibitor on mild
steel in acidic medium.
b. To first investigate the corrosive rate of the mild
steel rod using hydrochroric acid (HCl) after 1hour and 3
hours respectively.
MATERIALS AND METHODS
Apparatus and Equipment
The apparatus and equipments used in carrying out this
research include; desiccators, funnel, burette, retort
stand, water bath, emery papers ranging from 240 to 600
grades and an analytical mass balance.
A mild steel rod was sourced for this research work and
its chemical analysis was carried out using X-ray
fluorescence (XRF)
The result of the chemical analysis of mild steel is shown
in Table 1.

3. Effect of plant extracts on corrosion rate of mild steel in acidic medium
Int. Res. J. Mat. Sci. Engin. 013
Table 1. Chemical analysis of mild steel
Fe C Si Mn S P Cr V Al Ni
0.25 0.16 0.4 0.7 0.04 0.04 8 0.15 0.02 0.032
Source: Design of mild steel structure MIT-Department and Civil Engineering and Environment.
Table 2. Phytochemical composition screening of Parkiabiglobosa.
Chemical constituents in both plant Score indication
Petrol ether Chloroform Ethyl acetate Methanol Water
Alkaloids - - - - +
Glycosides - - - - ++
Saponins + - - + -
Tanins - - - ++ ++
Flauonoids - - + + -
Polyphenols - - - - -
Key
++: Present in abundance
+ : Present
- : active compound absent
Source: African Journal of Bio-medical Research Vol. 5/Ajaiyeoba
Table 3. Phytochemical screening of banana sap
Petrol ether Chloroform Ethyl acetate Methernol Water
Carbohydrate - - - - -
Reducing sugar - - - - -
Alkanoids + - - + -
Tannins - - - ++ ++
Flouonoids - - + + -
Tepenoids - - - + -
Phylobotanin - - - - -
Coumanins - - - + +
Cycloglycoside - - - + -
Total phenols + - - + +
Quinines - - - - -
Anthraquinones - - - - -
Steroids
Key: “++” Active compound copiously present
“+” Active compound present
“-“ Active compound absent
- - - - -
Source: Curr. Res. J. BioL. Sci. 5(1): 26-29, 2013
Three inhibitors were used during the course of this
research work. Two of the inhibitors were the plant
extract: Locust bean tree (Pakiabiglobosa) and Banana
sap (musaparadisiaca) while the third was a standard
inhibitor: Hydrochloric acid (HCl).
The extracts of locust bean tree (Pakiabiglobosa) and
Banana sap (musaparadisiaca) were extracted and the
phytochemical screening was carried out. Dry powders of
locust bean tree and banana sap were used for the
screening and extraction. The extraction (most important
constituent of the extracts i.e. tannin which is the main
constituent that brings about corrosion inhibition) was
extracted using Soxletextractor (Yawas et al, 2005). The
results of these analyses are shown in Table 2 and 3
respectively.
Methods
The acid solution in this research is 0.5M HCI. The
concentration of the acid is kept at constant throughout
this research. This concentration is chosen in order to
give room for reasonable amount of reactions to take
place within the selected time frame considering the
small area of the coupons. The concentrations of the
inhibitors is varied thus; 0.5ml 0.1ml 1.5ml 2.0ml and
2.5ml in distilled water for each of the inhibitors in order
to determine the effect of variation in inhibitor
concentrations on corrosion rate and inhibitor efficiency.

4. Effect of plant extracts on corrosion rate of mild steel in acidic medium
Bamaiyi and Peni 014
Figure 1. Corrosion rate in the absent of inhibitor after 1hr and 3hrs for banana sap
Figure 2. Corrosion rate in the absent of inhibitor after 1hr and 3hrs for Parkiabiglobosa
Mild steel in the form of a rod was sectioned into small
specimen sizes (coupons), of dimensions: 2.0cm x
1.5cm x 1.0cm. The coupons are abraded with series of
emery papers ranging from 220 to 600 grades in order to
expose the surfaces of samples. The abraded specimen
is then washed, de-greased, dried and weighed using an
analytical balance and stored in a desiccator to prevent
further interaction with the environment.
Before the commencement of the experiment, the acid
solution is prepared by diluting concentrated HCl in
distilled water to make 1MHCl solution. The solution
containing 0.1g/cm
3
of the extracts is prepared by
dissolving the dried extracts in distilled water in the
presence of ethanol to ease the dissolution process.
From these stocks of solutions, the following inhibitor
concentrations were prepared: 0.5ml, 1.0ml, 1.5ml, 2.0ml
and 2.5ml of distilled water.
The experimental setup consists of a beaker containing
the HCl solution. The experiment is first carried out at
38°C in the absence of an inhibitor .Two weighed steel
samples are suspended into the beaker containing the
HCl acid solution. The beaker is placed on a water bath
which has provision for regulating the temperature. The
corrosion rate is monitored after every one hour for three
hours, that is, the first sample is removed after 1 hour,
the second after three hours. Each of the samples
removed from the solution is washed, dried, re-weighed
and recorded. The same procedure is repeated at 45°C
and 55°C uninhibited as shown in fig. 1 and 2.
The same above procedure is carried out for the two
inhibitors whose concentration varied thus: 0.5ml, 1.0ml,
1.5ml, 2.0ml, and 2.5ml in distilled water. In the presence
of inhibitors, the experiment conducted at 38°C, 45°C,
and 55°C in other to evaluate the effects of change in
temperature on the corrosion rate and inhibitor efficiency
of the extract. The weight loss recorded is used to
determine parameters.
The corrosion in each case has been computed thus as
follows:
Corrosion rate (Cr) =
𝑊𝑒𝑖𝑔 𝑕𝑡𝑙𝑜𝑠𝑠
𝑆𝑢𝑟𝑓𝑎𝑐𝑒𝐴𝑟𝑒𝑎𝑋𝑇𝑖𝑚𝑒
=
𝑔
𝑐𝑚 2 /𝑚𝑖𝑛----------
(2.1)
Total surface area of the coupon = 2(1 × 𝑏 + 𝑏 × 1 + 𝑏 ×
𝑕) = 2(1.5 + 1.5 × 1) = 2(4) = 8𝑐𝑚2

5. Effect of plant extracts on corrosion rate of mild steel in acidic medium
Int. Res. J. Mat. Sci. Engin. 015
Figure 3. Corrosion rate in the presence of inhibitor after 1hr at different temperatures for
Parkiabiglobosa
Figure 4. Corrosion rate in the presence of inhibitor at different temperatures for ParkiaBiglobosa at 3hrs
The values of inhibitor efficiencies and surface coverage
are determined for each of the three inhibitors according
to Quraishi and Jamal (2002) as inflows:
IE = (r0 - r)/r0 x100(%)------------------------------(2.2)
Where; r0 = corrosion rate in the absence of an inhibitor
r = corrosion rate in the presence of an inhibitor.
The surface coverage θ, is calculated from the formula:
𝜃 = (r0 - r)/r0
RESULTS AND DISCUSSIONS
Corrosion rate of steel sample in the absence and
presence of inhibitor used at different temperature and
exposure time were calculated using equation 2.1. The
values of inhibitor efficiencies of the inhibitor were
calculated using equation 2.2. The values obtained using
the various equations were used to plot different graphs
as presented as shown below:
DISCUSSIONS
Visual observation of the two categories of coupons i.e.
with and without inhibitor after exposure reveals changes
in color of the coupons from bright surface to dull
surfaces. The changes in color were more intense in
coupons exposed to solution without the extract.
These shows that corrosion rate reduces with time but
increases with rise in temperature as shown in fig. 3, 4, 5
and 6.. Variations of corrosion rate were ranked (Cr) 55
o
C
> (Cr) 45
o
C > (Cr) 38
o
C which agrees with the findings of
Ayeni, 2007. It also indicates that as the exposure time
increases, the corrosion rate decreases.
The plant extract of Parkiabiglobosa at 38°C recorded a
maximum corrosion rate 1.62g/cm
3
/min after 1hr of
exposure and corrosion efficiency of 50% and after 3hrs
maximum corrosion rate of 5.76g/cm
3
/min and efficiency
of 38%. At 45°C, 6.08g/cm
3
/min was recorded and
corrosion efficiency of 33%. While at 55
o
C 8.75g/cm
3
/min
is the maximum corrosion rate and inhibitor efficiency is
38%. The reduction in corrosion rate with concentration

6. Effect of plant extracts on corrosion rate of mild steel in acidic medium
Bamaiyi and Peni 016
Figure 5. Corrosion rate in the presence of inhibitor after 1hr banana sap at different temperatures
after 1hr
Figure 6. Corrosion rate in the presence of inhibitor banana sap for 3hrs at different temperatures
Figure 7. Inhibitor efficiency at different concentrations and temperatures after 1hr Parkiabiglobosa
of Pakiabiglobosa indicates that at higher concentration
more of the inhibitor species are available to block
corrosion sites, forms films on the surface of the steel or
absorb themselves on the steel hence reducing the
corrosion rate. The increase in corrosion rate with
temperature is not unexpected. This is in accordance with
the effect of temperature on the rate of chemical reaction.
The plant extract of banana sap at 38°C recorded a
maximum corrosion rate 11.25g/cm
3
/min after 1hr of
exposure and corrosion efficiency of 62.8% and after
3hrs maximum corrosion rate of 5.41g/cm
3
/min and
efficiency of 94%. At 45°C, 4.16g/cm
3
/min was recorded
and corrosion efficiency of 46.3%. While at 55°C
1.37g/cm
3
/min is the maximum corrosion rate and
inhibitor efficiency of 46.3%. The reduction in corrosion
rate with concentration of banana sap indicates that
higher concentration more of the inhibitor species are
available to block corrosion sites, forms films on the

7. Effect of plant extracts on corrosion rate of mild steel in acidic medium
Int. Res. J. Mat. Sci. Engin. 017
Figure 8. Inhibitor efficiency at different concentrations and temperatures for Parkiabiglobosa after
3hrs
Figure 9. Inhibitor efficiency at different temperatures and concentrations after 1hr for banana sap
Figure 10. Inhibitor efficiency at different temperatures and concentrations after 3hrs for banana sap
surface of the steel or absorb themselves on the steel
hence reducing the corrosion rate. The increase in
corrosion rate with temperature is not unexpected. This is
in accordance with the effect of temperature on the rate
of chemical reaction.
The inhibitor efficiency of the Pakiabiglobosa in the acidic
medium after exposure of 1hr recorded the minimum
efficiency of 1.6% at 45°C and 95.0% is also recorded as
the maximum at 45°C with the concentration of 2.5ml of
the inhibitor shown in Figure 7. While after 3hrs minimum
efficiency is 5.4% at 38°C and the maximum of 54% at
55°C with concentration of 2.5ml of the inhibitor shown in
figure 8. This implies that the corrosion rates were found
to decrease with increase in inhibitor concentration and
the time of exposure as indicated in the fig. 3, 4, 5 and 6.
But increase with rise in temperature the inhibitor

8. Effect of plant extracts on corrosion rate of mild steel in acidic medium
Bamaiyi and Peni 018
efficiency was ranked Pakiabiglobosa having 95.0%. The
inhibitor efficiency of the banana sap in the acidic
medium after exposure of 1hr recorded the minimum
efficiency of 7.6% at 55% and 62.8% is also recorded as
the maximum at 38°C with the concentration of 2.5ml of
the inhibitor as shown in fig. 9. While after 3hrs minimum
efficiency is 6.7% at 55°C and the maximum of 94.4% at
38°C with concentration of 2.5ml of the inhibitor. as
shown in fig. 8. This implies that the time of exposure.
But increase with rise in temperature the inhibitor
efficiency were ranked banana having 94.4%
CONCLUSION
From the result of the weight loss measurement for the
investigation of the corrosion inhibition properties of the
plant extract Pakiabiglobosa and banana sap in
hydrochloric acid solution, the following conclusions were
made:
i. Pakiabiglobosa and banana sap extract are
effective corrosion inhibitors for mild steel in acidic
medium.
ii. The corrosion rates were found to decrease with
increase in inhibitor concentration and time of exposure,
but increase with rise in temperature. The inhibition
efficiencies of the inhibitors were ranked in the following
order: Pakiabiglobosa 95.0% > banana sap 94.0%
iii. The results shows that Pakiabiglobosa is better
inhibitor than banana sap extract in 1M HCl solution
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Accepted 28 May, 2015.
Citation: Bamaiyi B, Peni MU (2015). Effect of plant
extracts on corrosion rate of mild steel in acidic medium.
International Research Journal of Materials Science and
Engineering, 2(1): 012-018.
Copyright: © 2015 Bamaiyi and Peni. This is an open-
access article distributed under the terms of the Creative
Commons Attribution License, which permits unrestricted
use, distribution, and reproduction in any medium,
provided the original author and source are cited.