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| Adsorption And Inhibitive Characteristics of Ethanolic Extract of Acacia Nilotica on the Corrosion of Aluminium in HNo3 Acidic Medium | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Paper Id :
17078 Submission Date :
2023-01-13 Acceptance Date :
2023-01-21 Publication Date :
2023-01-25
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| Abstract |
The corrosion inhibition of aluminium in 1.5M HNO3 by Acacia nilotica extract was explored applying the standard gravimetric technique at 303± 1 K temperature. The inhibition efficiency (η%) is found to increase with increasing concentration of Acacia nilotica extract. Maximum inhibition efficiency 70.92 % was obtained in fruit extract and minimum I.E.(η%) was obtained 64.4% in root bark at 303± 1K temperature. The outcomes obtained from experimental data were fit into the Langmuir adsorption isotherm. Adsorption parameters ( Kads & ΔG0ads ) were determined from experimental data. The mechanism of physical adsorption is proposed from the calculated values of adsorption parameters. Surface morphology analysis was performed by SEM & FT-IR to ascertain the anti- corrosive characteristics of the inhibitor. Adsorption parameters indicate a strong interaction among the Acacia nilotica extract inhibitor and aluminium surface. The results manifested that examined Acacia nilotica extract in 1.5M HNO3 acidic medium acted as benign anticorrosive agent.
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| Keywords | Aluminium, HNO3 Acid, Acacia Nilotica, SEM & FT – IR , Langmuir Adsorption. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Introduction |
Aluminium is applied broadly as a metal or alloy in numerous industrial applications. Acid solutions are applied in various industrial processes namely acid descaling and acid cleaning etc. Corrosion inhibitors are the substances added to the corrosive medium to reduce the rate of its attack on the metal or alloy [1] and these may be organic or inorganic compounds [2 - 4]. Numerous industries exploitation equipment made from metals under diverse circumstances ranging from mild to stiff chemical environments, making their surfaces susceptible to corrosion [5-6]. Investigation have shown that corrosion cannot be perfectly removed from metal surfaces due to the different environments in which metals are applied [7]. Corrosion is the disintegration of metal and its alloy by the chemical (wet or dry reaction) when the metals in contact with the moisture or environment. Corrosion of aluminium in nitric acid media is usual phenomena. Commonly the creation of metals is from ores or the compounds which occur naturally with greatly high energy of huge magnitude of energy [8]. Corrosion inhibitors are the classic choice to protect metal by the electrochemical attack.
To inhibit the corrosion the corrosion different synthetic corrosion inhibitors came into the existence but these are toxic and hazardous in nature [9]. Plant extracts are applied usually now a days as potential corrosion inhibitor. Naturally plant extracts are readily available, nontoxic in nature, cheap and eco-friendly. These plant extracts involves organic constituents or polar atoms such as N, O, S and P [10]. A protective oxide film is produced when these ( N, O, S and P) polar atoms works as a bridge among extract of plant and surface of metal [11]. Owing to organic constituents, plant extracts interact with the corroded metal by their electrons [12]. In view of which protective oxide layer is generated and the corrosion is controlled.
A numerous researchers studies have been dedicated to the corrosion of aluminium and use of natural products as a potential corrosion inhibitor Azadirachta indica [11], Justicia gendarussa [13], Ipomoea triloba [14] in order to aluminium in acidic media.
Acacia nilotica extract endows a benign protection to aluminium against corrosion. The no toxicity of this organic plant constituents, its antimicrobial characteristics and sustainable sources of production present as having a large scope of applications as green potential corrosion inhibitors. Alcoholic extract of Acacia nilotica pod contains alkaloids, Tannins, Glycosides, Terpenoids, Gallic acid, catechin and galloylated flavan-3,4-diol ( leucocyanidin) has been from pods [15- 18].
In the present work, the inhibitory efficacy of Acacia nilotica extract for 1.5M HNO3 nitric acid corrosion of aluminium has been analysed at 12 hrs immersion period.
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| Objective of study | Reduced / inhibition of the corrosion rate of aluminium metal applying Acacia nilotica plant extract used as potential corrosion inhibitor. |
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| Review of Literature | A numerous researchers studies have been dedicated to the corrosion of aluminium and use of natural products as a potential corrosion inhibitor Azadirachta indica [11], Justicia gendarussa [13], Ipomoea triloba [14] in order to aluminium in acidic media. |
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| Methodology | Preparation of Test Coupons:
Sheet of aluminium achieved locally and of 0.20 cm thickness was mechanically cut into coupons of 2.54 × 1.52 cm2 size containing a hole of about 0.12 mm diameter near the upper edge in order to the purpose of hanging in the test solution. Different strips were polished to mirror finish by applying different grades emery paper.
Test solutions & Experimentation :
The electrolytic solutions of 1.5M HNO3 were prepared by using bi-distilled water. All chemicals applied were of Analar grade. Ethanolic extraction of Acacia nilotica extract was obtained by refluxing the dried fruits in soxhlet extractor [19]. Each coupons was suspended by the glass hook plunge into a beaker containing100 ml of the test solution and different concentration of the Acacia nilotica inhibitor. The investigation has been carried out at 303 K temperature. Since fixed intervals of immersion time period, test coupons were washed with distilled water and dried thereafter hanging the washed strips in desiccators in order to appropriate time period [19]. |
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| Analysis | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Result and Discussion |
Weight
Loss Studies The
value of inhibition efficiency (η%), Fractional surface coverage (θ ), Corrosion rate (ρcorr), Adsorption
equilibrium constant (Kads) obtained from experimental data
(Table.1) at varying concentration of the Acacia nilotica inhibitor in 1.5M
nitric acid solution in order to an immersion period of 12 hrs . From
the mass loss value (ΔM), the inhibition efficiency (η%) was calculated using the following equation
[20]. η% = [
( ΔMu - ΔMi ) / ΔMu
] ×
100 Where
ΔMu is mass loss without inhibitor and ΔMi is weight loss with inhibitor. The
corrosion rate (ρcorr) in millimetre penetration per year (mmpy) can be
determined by following equation ρcorr =
( ΔM × 87.6 )
/ area × time
× metal density Where
ΔM weight loss expressed in mg, area expressed in cm2 of metal
surface exposed, time expressed in hours of exposure and metal density
expressed in g / cm3. Table
1 - Kinetic parameters on corrosion of aluminium in 1.5M HNO3 with
and without ethanolic extract of varying concentration of fruit, stem bark and
root bark of Acacia nilotica at 303 0.1
K.
Effective area of Specimen : 7.72 cm2
Immersion period : 12 hrs.
 Fig. 1 Variation of inhibition efficiency with concentration of fruit, stem bark and root bark extract of Acacia nilotica for aluminium in 1.5M HNO3 at 12hrs immersion period.  Fig.
2. Langmuir adsorption isotherm curve for aluminium in 1.5M HNO3
with fruit, stem bark and root bark extract of Acacia nilotica at 12 hrs immersion
period. Outcomes
obtained from the table revealed that the addition of inhibitor to the acid had
diminished the corrosion rate (ρcorr). The inhibition efficiency (η%) increased
with increase in concentration of inhibitors in 1.5M HNO3 nitric acid solution. Adsorption
Isotherm Langmuir
adsorption isotherm graph was plotted between log (θ / 1- θ) and log C.
log (θ / 1- θ) =
log Kads + log C Where
Kads is adsorption equilibrium constant, the Kads value can be calculated from
the intercept line on the log (θ / 1 –θ ) axis and is related to standard free
energy of adsorption. The
values of ΔG0ads at all studied temperature can be evaluated from the equation
as follows ΔG0ads = -
2.303 RT log (55.5 Kads ) Where
R = 0.008314 KJ / mol is the universal gas constant, 55.5 indicate the molar
concentration of water in the solution whereas T is the absolute temperature in
Kelvin. SEM
Analysis SEM
observations were performed to endorse the creation of a protective oxide film
of the Acacia nilotica extract on the aluminium metal surface. The SEM images
obviously indicates in Figures 3 and 4,
the aluminium coupons exposed for 12 hours to 1.5 M HNO3
solution in the presence and absence of 0.45 % of the fruit extract.  Fig. 3 SEM image of aluminium in 1.5M HNO3 acid medium at 12 hrs.  Fig.4 SEM image of aluminium in 1.5M HNO3 with 0.45 % of the inhibitor concentration at 12hrs. |
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| Conclusion |
Following conclusions may be drawn on the basis of the outcomes obtained from experimental data on the inhibitory efficacy of Acacia nilotica extract on acid corrosion of aluminium in 1.5M HNO3 :
1. Acacia nilotica fruit extract can be good inhibitor to impede acid corrosion of aluminium in 1.5M HNO3 at 303 K with maximum inhibition efficiency of 70.92 % at 0.45 % inhibitor concentration in fruit extract.
2. The adsorption of the Acacia nilotica extract on the aluminium surfaces was spontaneous and obeyed Langmuir adsorption isotherms at 303± 1 K and occurred according to the mechanism of physical adsorption.
3. FT-IR / SEM images also supported the creation of protective oxide film on the aluminium metal surfaces.
4. Overall, it can be concluded that Acacia nilotica can be applied as a source of comparatively cheap, eco-friendly and influential inhibitor to replace toxic chemicals used to impede aluminium corrosion in 1.5M HNO3. |
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| Suggestions for the future Study | Acacia nilotica extract used as corrosion potential inhibitor owing to readily available, cheap, ecofriendly. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Acknowledgement | Author is highly thankful to the Department of Chemistry, Govt. Girls College, Karauli in order to providing necessary laboratory facilities and also grateful to Manipal University, Jaipur for SEM analysis facilities. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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