P: ISSN No. 0976-8602 RNI No.  UPENG/2012/42622 VOL.- XII , ISSUE- I January  - 2023
E: ISSN No. 2349-9443 Asian Resonance
Effect of Temperature on Protective Propensity of Azadirachta Indica Fruit Extract on Acid Corrosion of Mild Steel
Paper Id :  17014   Submission Date :  19/01/2023   Acceptance Date :  23/01/2023   Publication Date :  25/01/2023
This is an open-access research paper/article distributed under the terms of the Creative Commons Attribution 4.0 International, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
For verification of this paper, please visit on http://www.socialresearchfoundation.com/resonance.php#8
Arvind Kumar Meena
Assistant Professor
Chemistry
Govt. Girls College
Karauli,Rajasthan, India
Abstract The protective propensity of ethanolic extract of Azadirachta indica fruit (EEAiF) on mild steel corrosion in 0.5N nitric acid has been investigated by weight loss technique at elevated temperatures in the range of 303 to 343 K. The inhibition efficiency (η%) has been observed significantly high (63.15%) at 303 K at concentration 0.45 %. The adsorption of inhibitor on mild steel surface have been found to obey Langmuir adsorption isotherm. It was observed to be physical , exothermic and spontaneous. The kinetic parameters such as activation energy (Ea), enthalpy of activation (ΔHact), entropy of activation (ΔSact) and thermodynamic parameters such as free energy of adsorption (ΔGads), enthalpy of adsorption (ΔHads), entropy of adsorption (ΔSads) were calculated. These Kinetic and Thermodynamic parameters indicate a strong interaction among the inhibitor and metal surface. The high protective impact is attributed owing to phytochemical constituents present in the Azadirachta indica fruit extract.
Keywords Mild Steel, Acid corrosion, Azadirachta Indica, Langmuir Adsorption Isotherm, Thermodynamic Parameters.
Introduction
Mild steel 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]. Azadirachta indica (Neem) is an evergreen medical plants having wide spectrum of biological and pharmacological activity. The chemical ingredients of Azadirachta indica fruit primarily are triterpenoid (metiantriol), azadirone, nimbin, nimbinin, azadirone, limocin, nimbidin, epoxyazadiradione etc. and the inhibitive effect is attributed owing to these phytochemical constituents present in the extract [8-12]. Azadirachta indica fruits extract is biodegradable and non-toxic therefore its applications would help to diminish the economic cost of corrosion monitoring as well as reduce the subsequent environmental threats. A huge number of scientific studies have been devoted to the corrosion of mild steel and the exploitation of natural products as a corrosion inhibitors as Capparis decidua [13], Tamarindus indica [14], Prosopis cineraria [15], Azadirachta indica [16], Acacia nilotica [17] for aluminium in acidic media. In the present work, the impact of elevation in temperature on protective propensity of Azadirachta indica fruit for acid corrosion of mild steel has been analysed at 12 hrs immersion period.
Aim of study Prevention ( reduced ) of acid Corrosion of mild steel by using Azadirachta indica fruit extract.
Review of Literature
A huge number of scientific studies have been devoted to the corrosion of mild steel and the exploitation of natural products as a corrosion inhibitors as Capparis decidua [13], Tamarindus indica [14], Prosopis cineraria [15], Azadirachta indica [16], Acacia nilotica [17] for aluminium in acidic media.
Methodology
Preparation of Test Coupons: Sheet of mild steel achieved locally and of 0.18 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. Coupons were polished to mirror finish by applying emery paper. Test solutions & Experimentation: The electrolytic solutions of HNO3 were prepared by using bi-distilled water. All chemicals used were of Analar grade. Ethanolic extraction of Azadirachta indica fruits ( EEAi F ) was achieved by usingy refluxing the dried fruits in soxhlet extractor [18-19]. Each coupons was suspended by the glass hook plunge into a beaker containing 50 ml of the test solution as well as various concentration of the inhibitor (EEAi F). The investigation has been carried out at various raised temperature (303K to 343K). Subsequently 12 hrs immersion time period, test coupons were washed with distilled water and dried thereafter hanging the cleaned coupons in desiccators in order to appropriate time period [20]. Weight Loss studies Table 1 indicates the value of inhibition efficiency (η%), Fractional surface coverage (θ ), Corrosion rate (ρcorr), Adsorption equilibrium constant (Kads) obtained at varying concentration of the inhibitors in 0.5N nitric acid solution for an immersion period of 12 hrs at various elevated temperature in the range 303 – 343 K. From the mass loss value (ΔM), the inhibition efficiency (η%) was calculated using the following equation. 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.
Tools Used Chemical, Mild Steel etc.
Statistics Used in the Study
Formula used in this study.
Analysis
Gravimetric ( Practical) Analysis.
Result and Discussion

Weight Loss studies

Table 1 indicates the value of inhibition efficiency (η%), Fractional surface coverage (θ ),  Corrosion rate (ρcorr), Adsorption equilibrium constant (Kads) obtained at varying concentration of the inhibitors in 0.5N nitric acid solution for an immersion period of 12 hrs at various elevated temperature in the range 303 – 343 K.

From the mass loss value (ΔM), the inhibition efficiency (η%)  was calculated using the following equation.

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. Corrosion Parameters for mild steel in 0.5N HNO3 in Absence and Presence of Various concentrations of Ethanolic Extract of Azadirachta indica fruits (EEAiF) from Weight Loss Measurements at elevated temperatures for 12 hrs immersion period.

Effective area of specimen 7.72 cm2 Immersion time 12 hrs

Temperature

       (K)

EEAiF

Conc.  

(%)

Weight

 Loss 

ΔM 

 (mg)

Corrosion

Rate 

(ρcorr)

 (mmpy)

Fractional 

Surface 

Coverage  ( θ )

Adsorption

Equilibrium

Constant     (Kads )

 

 

 

303 + 1

Blank

318.6

55.79

     -

      -

0.09

210.4

36.84

0.3396

5.7133

0.18

185.4

32.46

0.4180

3.9900

0.27

174.3

30.52

0.4529

3.0659

0.36

140.5

24.60

0.5590

3.5208

0.45

117.4

20.56

0.6315

3.8082

 

 

 

313 + 1

Blank

370.4

64.86

     -

       -

0.09

257.5

45.09

0.3048

4.8711

0.18

230.6

40.38

0.3774

3.3672

0.27

219.8

38.48

0.4065

2.5366

0.36

191.5

33.53

0.4829

2.5938

0.45

164.4

28.78

0.5561

2.7837

 

 

323+1

Blank

425.6

74.52

     -

     -

0.09

305.5

53.49

0.2821

4.3655

0.18

280.3

49.08

0.3414

2.8794

0.27

260.8

45.66

0.3872

2.3400

0.36

242.7

42.49

0.4297

2.0927

 

0.45

209.1

36.62

0.5086

2.3000

 

 

333 + 1

Blank

500.0

87.60

      -

     -

0.09

374.6

65.59

0.2512

3.7266

0.18

354.8

62.12

0.2908

2.2777

0.27

339.2

59.39

0.3220

1.7588

0.36

306.4

53.65

0.3875

1.7572

0.45

258.8

45.32

0.4827

2.0735

 

 

 

343 + 1

Blank

590.5

103.40

    -

    -

0.09

458.4

80.27

0.2237

3.2011

0.18

435.8

76.31

0.2619

1.9711

0.27

412.6

72.25

0.3012

1.5962

0.36

395.2

69.20

0.3307

1.3722

0.45

345.2

60.45

0.4154

1.5788

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 and decreased with elevation in  temperature from 303 K to 343 K in 0.5N 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. The values of Kads and ΔG0ads are shown in table 2 for Azadirachta indica  fruit extract.

Fig.1: Langmuir adsorption isotherm curve for mild steel in 0.5N HNO3 with fruit extract of Azadirachta indica at different elevated temperatures at 12 hrs immersion period.

Table 2. Correlation coefficient (R2), slopes, Adsorption equilibrium constant(Kads) and Gibbs free energy (ΔGads) from Langmuir adsorption isotherm in 0.5N HNO3 with Fruit extract of Azadirachta indica at different elevated temperatures.

Temperature

      ( K )

Slope

R2

Kads

ΔG0ads

(KJ /mol )

303

0.712

0.9100

2.5876

-12.5145

313

0.6103

0.9250

1.7788

-11.9525

323

0.5598

0.9387

1.4220

-11.7332

333

0.5789

0.8495

1.2075

-11.6431

343

0.5085

0.8921

0.9082

-11.1804

Kinetic / thermodynamic treatment of Weight loss Results                                     

Energy of Activation

Elevation in temperature has significant influence on the corrosion phenomenon. The dependence of corrosion rate on temperature can be expressed by the Arrhenius equation.

log ρcorr.    =    log A  -  ( Ea  / 2.303 RT )

Where ρcorr is the corrosion rate, A is the frequency factor, R is the universal molar gas constant, Ea is the apparent activation of energy and T is the absolute temperature in kelvin.

Fig.2 for Azadirachta indica indicates the linear graph for plot of log ρcorr. versus 1 / T. Activation energy values Ea were estimated from slopes of log ρcorr. versus 1 / T . The slope of Arrhenius curve is equal to   – Ea / 2.303 R.

The positive sign for both Ea and ΔHact indicate the endothermic nature of corrosion process / phenomenon.

Other kinetic parameters of the corrosion reaction, namely, entropy ΔS and enthalpy ΔH of activation transition state were obtained from the transition state equation

ρcorr         =   ( RT / Nh ) e ( ΔSact /  R ) e ( - ΔHact / RT )

log  ( ρcorr / T )    =  [ log (R / Nh ) + ( ΔSact / 2.303 R ) ] - (ΔHact / 2.303RT )

Where  ρcorr.  is the corrosion rate , h is the plank’s constant, N is the Avogadro’ s number, R is the universal gas constant and T is the absolute temperature.

A plot of log ( ρcorr / T ) versus 1 / T give a straight line Fig.3 were obtained with the slope of ( - ΔHact / 2.303 R ) and intercept of [ log ( R / N h ) + ( ΔSact / 2.303 R ) ] from which the values of ΔHact and ΔSact respectively, were evaluated from the slope and intercept respectively from the linear plot . The estimated values of Ea, ΔHact and ΔSact are depicted in table 3 for mild steel in 0.5N HNO3.

                  

Fig. 2 : Arrhenius plots for mild steel corrosion in 0.5N HNO3 with fruit extract of Azadirachta indica at 12 hrs immersion period. 

 

 

Fig. 3 : Transition state plots for mild steel corrosion in 0.5N HNO3 with fruit extract of Azadirachta indica at 12 hrs immersion period.

Table 3 : Kinetic – thermodynamic parameters for mild steel corrosion in 0.5N HNO3 without and with fruit extract of Azadirachta indica at various concentrations at immersion time 12 hrs.

Concentration

  of Inhibitor

( % )

Activation

   Energy  

      Ea

(kJ / mol )

  Enthalpy

   ΔHact

 (kJ / mol)

  Entropy

    ΔSact

 (J / mol / K)

Heat of adsorption

Qads

 (kJ / mol)

Blank

13.11

10.45

-177.24

           -

0.09

16.52

13.88

-169.38

-12.1948

0.18

18.30

15.65

-164.62

-15.3943

0.27

18.45

15.79

-164.07

-14.2799

0.36

21.76

19.12

-155.27

-19.5128

0.45

22.39

19.74

-154.65

-17.6613

Thermodynamic Parameters : Thermodynamic adsorption parameters such as the enthalpy of adsorption ( ΔHads ) and the entropy of adsorption ( ΔSads ) were also determined from the experimental data. ΔH0ads and ΔS0ads are obtained using the following equation

ΔG0ads  =  ΔH0ads  -  T ΔS0ads                                                                                                                                       

The values of ΔS0ads was obtained from the slope and the intercept leads to ΔH0ads (table 4). The entropy (ΔS0ads) values are positive in almost all cases confirming that the corrosion process is entropically favourable.

 

Fig. 4 : Plot of  ΔG0 vs T  for various concentration of Azadirachta indica fruit extract in 0.5N HNO3 acid solution at 12hrs immersion period.

Table 4 : Thermodynamic parameters for mild steel corrosion in 0.5N HNO3 in the absence and presence of various concentrations of fruit extract of Azadirachta indica at elevated temperatures ( 303 – 343 K ) at immersion time 12 hrs.

Inhibitor Concentration        

                            ΔG0ads

       ΔH0ads

           ΔS0ads

303K

313K

323K

333K

343K

Blank

-

-

-

-

-

-

-

0.09

-14.51

-14.57

-14.74

-14.76

-14.77

-12.36

+ 0.0072

0.18

-13.60

-13.61

-13.62

-13.40

-13.39

-15.60

- 0.0064

0.27

-12.94

-12.87

-13.07

-12.68

-12.78

-14.48

- 0.0050

0.36

-13.29

-12.93

-12.77

-12.68

-12.35

-19.64

- 0.0212

0.45

-13.48

-13.11

-13.02

-13.14

-12.75

-17.75

- 0.0144
Findings Decrease in corrosion rate & increase in efficiency with increases with inhibitor concentration
Conclusion Following conclusions may be drawn on the basis of the results obtained from study of the effect of elevation in temperature on the protective propensity of Azadirachta indica fruit extract on acid corrosion of mild steel in 0.5 M HNO3. 1. Azadirachta indica fruit can be good inhibitor to impede acid corrosion of mild steel in 0.5 N HNO3 at 303 K with maximum inhibition efficiency of 63.15 % at is 0.45% concentration. 2. Elevation in corrosion rate at high temperature but with the additive, a reasonable decrease in corrosion rate was observed. 3. Activation energy Eact in aggressive medium alone (blank) was observed much lower as compared to that in inhibited test solutions. Eact of EEAiF was found in the range of 13.11 to 22.39 KJ / mol. 4. The adsorption of the extract on the mild steel was spontaneous and obeyed Langmuir adsorption isotherm at elevated temperatures. 5. Entropy of adsorption decreases with increase in EEAiF indicates association of inhibitor molecules. 6. Overall, it can be concluded that Azadirachta indica fruit extract can be used as green inhibitor to replace toxic chemicals used to impede mild steel corrosion in 0.5N HNO3 at elevated temperature up to 343 K.
Suggestions for the future Study Azadirachta indica fruit extract used as potential corrosion inhibitor therefore it applied broadly inhibitor
Acknowledgement Author is highly thankful to Department of Chemistry, Govt. Girls College, Karauli for providing necessary research facilities.
References
1. Shastri, V.S. (1998). “ Corrosion inhibitors : Principles and Applicationsˮ. John Wiley & Sons : England. 2. Iannuzzi, M. and Frankel, G.S. (2007). “ Mechanism of Corrosion Inhibitor of AA2024-T3 by Vanadates. Corrosion Scienceˮ. Vol. 49, pp. 2371-2391. 3. Yasakau, K.A., Zheludkevich, M.L., Ferreira, M.G.S. (2008). “ Lanthanide salts as corrosion inhibitors for AA5083 Mechanism and Efficiency of corrosion inhibitionˮ. J. Electrochem. Society, Vol. 155(5), pp. 169-177. 4. Yurt, A. Ulutas, H. and Dal, H. (2006). “ Electrochemical and Theoretical Investigation on the corrosion of Aluminium in acidic solution containing some Schiff basesˮ. Appl. Surf. Sci., Vol. 253(2), pp. 919-925. 5. Caines, S., Khan, F., Shirokff, J. & Qiu, W. (2015). “Demonstration of increased corrosion activity for insulated pipe systems using a simplified electrochemical potential noise method ˮ. Journal of Loss Prevention in the Process Industries, Vol. 33, pp 39-51. 6. Ali, A. & Mahrous, Y. (2017). “ Corrosion inhibition of C-steel in acidic media from fruiting bodies of Melia azedarach L extract and a synergistic Ni2+ additive ˮ. RSC Advances, Vol. 7(38), pp. 23687- 23698. 7. Landolt, D. (2007). “Corrosion and Surface Chemistry of Metals ˮ, Ist Ed.,Taylor and Francis Group, New York, pp 400. 8. Okafor, P.C. Ebenso E.E. and Ekpe, U.J. (2010). “Azadirachta indica extracts as corrosion inhibitor for mild steel in acid medium ˮ. Int. J. Electrochemical society, Vol.5 pp. 978-993. 9. Sharma, S.K. and Jain, G. (2010). “ Corrosion inhibition and adsorption properties of Azadirachta indica ature leaves extract as green inhibitor for mild steel in HNO3 ˮ. Green chemistry Letters and Reviews, Vol. 3(1), pp. 7-15. 10. Loto, C.A., Loto, R.T. and Popoola, A.P.I. (2011). “ Effect of Neem leaf extract on the corrosion inhibition of mild steel in dilute acids ˮ. Int. J. Phy. Sci., Vol. 6(9), pp. 2249-2257. 11. Sangeetha, T.V. and Fredimoses. (2011). “ Inhibition of mild copper metal corrosion in HNO3 medium by acid extract of Azadirachta indica seed ˮ. E-J Chemistry, Vol. 8, pp. 51-56. 12. Eddy, N.O. and Mamza, P.A.P. (2009). “ Inhibitive and adsorption properties of ethanol extract of seeds and leaves of Azadirachta indica on the corrosion of mild steel in H2SO4 ˮ. Portug Electrochimica Acta, Vol. 27(4), pp. 443-456. 13. Meena, A.K. and Bairwa, B.S. (2021). “ Inhibitory efficacy of Capparis decidua extract on the corrosion of Al in various acidic media ˮ. Journal of Advanced Scientific Research, Vol. 12(1) Suppl 2. 14. Meena, A.K. and Bairwa, B.S. (2019). “ Use of Tamarindus indica extract as potential corrosion inhibitor for Al in acidic medium ˮ. Remarking an analisation. Vol. 3•, Issue 12• (Part-1 ). 15. Pratihar, P.S., Verma, P.S. and Sharma, A. (2016). “ Effect of temperature on inhibitive propensity of Prosopis cineraria leaves extract on acid corrosion of Aluminium ˮ. International Journal of Innovative Science, Engineering & Technology, Vol. 3 Issue12, pp. 286-291. 16. Sharma, A., Choudhary, G., Sharma, A. and Yadav, S. (2013). “ Effect of Temperature on Inhibitory efficacy of Azadirachta indica fruit on acid corrosion of Aluminium ˮ. International Journal of Innovative in Science, Engineering and Technology, Vol. 2, Issue12, pp. 7982-7992. 17. Yadav, S. and Sharma, A. (2013). “Effect of temperature on protective propensity of Acacia nilotica on acid corrosion of copper ˮ. Review of Research, Vol. 2, Issue. 7, pp. 12. 18. Sharma, A., Verma, P.S., Sharma, I.K. Nair, R.N. (2009). “Proc. World Acad. Sci. Eng. Technol ˮ. (PWASET). Vol. 39, pp. 745. 19. Nair, R.N., Sharma, S., Sharma I.K. Verma, P.S. & Sharma, A. ( 2010). “ Inhibitory efficacy of Piper Nigrum Linn. Extract on corrosion of AA1100 in HCl ˮ. RASAYAN J. Chem., Vol. 3(4), pp. 783-795. 20. Sharma, A., Choudhary, G., Sharma, A and Yadav, S. (2013). “ Effect of temperature on inhibitory efficacy of Azadirachta indica fruit on acid corrosion of aluminium ˮ. IJIRSET ( International Journal of Innovative Research in Science, Engineering and Technology. Vol.2, Issue 12pp. 7982 -7992.