Asia Pacific Journal of Research Vol: I Issue XV, July 2014

ISSN: 2320-5504, E-ISSN-2347-4793

Page | 32

INHIBITION EFFECT OF ECO-FRIENDLY EXTRACT OF ACALYPHA INDICA ON

DISSOLUTION OF MILD STEEL IN HYDROCHLORIC ACID MEDIUM

A.Srinivasulu

1*, P.K.Kasthuri

2 and B.Koteshwar Rao

3

1Department of Atomic Energy, Heavy Water Plant, Manuguru-507116, India

2Department of Chemistry, L.R.G.Government Arts College for Women, Tirupur- 638604, India

3Department of Atomic Energy, Heavy Water Plant,Manuguru-507116, India

Correspondence should be addressed to A.Srinivasulu,achus.paru@gmail.com

ABSTRACT

The influence of the addition of acid extract of Acalypha indica on the corrosion of mild steel in 1M

HCL was studied by weight loss measurement. The inhibition efficiency increases with extract concentration

and immersion period. The effect of temperature studied indicates that inhibition efficiency increased with

temperature. The negative value of the free energy of adsorption indicates spontaneous adsorption. The

positive values of entropy and enthaply of adsorption observed are also characteristic of strong

interaction of inhibitor with the metal surface. The inhibitor obeys Temkin adsorption isotherm. The

inhibition activity is due to the adsorption of active components which are found in the Acalypha indica

extract.

Key Words: Mild steel, Acalypha indica, Plant extract, Corrosion inhibitor, Hydrochloric Acid

Inhibitors, Temkin adsorption

1. Introduction

Mild steel is a structural material widely used in automobiles, pipes and used in most of the

industries. Mild steel suffers from severe corrosion in aggressive medium of acids and pickling process

and descaling operations. Hence, hydrochloric acid is the medium generally being used for pickling mild

steel. About 90 % of pickling problems can be solved by introducing appropriate pickling inhibitor to the

medium [1-2]. The recent and growing trend is using plant extracts as corrosion inhibitors [3-11] were

Asia Pacific Journal of Research Vol: I Issue XV, July 2014

ISSN: 2320-5504, E-ISSN-2347-4793

Page | 33

reported to be effective acid corrosion inhibitors because of their biodegradability and eco-friendliness.

Generally, organic compounds containing hetero atoms like O, N and S are normally found to have higher

basic properties and electron density, which assist in corrosion inhibition to reduce the corrosion of mild

steel.

In this study, the plant extract of Acalypha indica have been selected to study anticorrosion on mild

steel in acidic medium. It is a small annul shrub generally occurs as a troublesanc weed in gardens and

roads sides throughout the plains of india. ). It belongs to the family Euphorbiaceae. Sparciflorine. Earlier

work on this plant showed the presence of an alkaloid acalyphine, cyanogenic glucoside and 3-cyano-3- β-

D-glucopyranosyloxy-2-hydroxy-4-methoxy-1-methyl-6(2, 3-dihydro) pyridine (cyanogenic glycoside),

triaetonamine, and also HCN (Adolf Nahrstedt Jens et al 1982). Reinvestigation of this plant led to the

isolation of acalyphamide, succinimide, β-sitosterol, and aurantiamide acetate (Banitalapatra et al 1981).

Phytochemical screening tests were performed as described in previous works (Kumar et al 2007).

Hydrochloric acid extracts of Acalypha indica were subjected to preliminary phytochemical testing for the

detection of bio active components. Results indicate the presence of an alkaloid, saponins and glycosides.

Hence the acid extracts of Acalypha indica can be used to study the corrosion inhibition effect on mild

steel in hydrochloric acid medium.

2. EXPERIMENTAL PROCEDURE

2.1 Preparation of Mild steel specimen

Mild steel strips were mechanically cut into strips of size 1 cm x 5 cm x 0.2cm containing the

composition of 0.03% C, 0.259 % Mn , 0.027 % Si, 0.004 % P, 0.012 % S, 0.045 % Cr, 0.016 % Mb,

0.013 % Ni and the remainder Fe with 2 mm diameter hole near the upper edge of the specimens, were

polished with buffing, washed with Clark solution (1L of HCl + 50g stannous chloride + 20g antimony

trioxide), rinsed with distilled water, finally dried with filter paper and stored in a desiccators. The

coupons were weighed and fully immersed in 100 ml of acid solution with the help of glass hooks, with

and without inhibitor at different concentration. Accurate weight of the samples was taken using electronic

balance.

2.2. Preparation of the plant extract

Reagent grade acid was used for preparation of acid extract of Acalypha indica. Five percent of stock

solution of the extract was prepared by refluxing 50 g of the dried and crushed leaves and twigs of

Acalypha indica with 1000 ml of methanol for 3 hours and leaving it overnight. Next day the supernatant

liquid was filtered and the excess of alcohol was removed by distillation. Fifty grams of the resulting

resinous matter was made up to 1000ml using 1M HCL. Similar kind of preparation has been reported in

studies using aqueous plant extracts in recent years [12-16]. Experiments were carried out in 1M HCl at

298K temperature for 0.5, 2, 4, 6, 8, 24 and 48 hours respectively. The influence of temperature on the

corrosion of mild steel has also been studied at five different temperatures ranging from 298K to 343K in

absence and presence of the inhibitors at different concentrations (0.05, 0.1, 0.2, 0.3, 0.5, 0.7 and 0.9%) for

30 minutes. The inhibition efficiency (IE) was calculated using the following formula.

Asia Pacific Journal of Research Vol: I Issue XV, July 2014

ISSN: 2320-5504, E-ISSN-2347-4793

Page | 34

u i

U I

U

W WIE % 100

W

(1) Where, Wu and Wi are the weight losses in absence and presence of inhibitor respectively.

Asia Pacific Journal of Research Vol: I Issue XV, July 2014

ISSN: 2320-5504, E-ISSN-2347-4793

Page | 35

3. RESULT AND DISCUSSION

Table 1. Shows the values of percentage of inhibition efficiency (IE) obtained from weight loss

measurement for different concentrations of the extract in 1M HCl at 298 K temperature.

The percentage of inhibition efficiency increases with increase in the extract concentration

over the entire concentration range studied in all the cases. The maximum inhibition

efficiency of the extract was found to be 99.55% at a concentration of 0.7% and further

increase in concentration did not cause any appreciable change in the performance of

inhibitor. The results seem to be consistent more or less with an inhibition mechanism

involving chemisorption of some phytochemical ingredients in the leaf extract of Acalypha

indica.

Table 1. Inhibition efficiency of Ai extract on mild steel in 1M HCl for different immersion

periods, at room temperature, using weight loss method

Conc.

(%)

Inhibition efficiency (%)

1/2 hr 2 hrs 4hrs 6hrs 8hrs 24hrs

0.05 38.55 80.33 87.03 82.41 74.12 74.56

0.10 51.93 85.75 89.11 84.66 82.35 81.01

0.20 63.55 91.8 93.88 88.84 85.93 84.29

0.30 68.23 93.32 95.47 91.86 89.10 86.01

0.50 74.67 94.45 96.21 95.41 94.56 91.05

0.70 78.95 96.72 97.55 97.25 95.70 93.26

0.90 76.12 94.22 94.11 94.17 93.78 91.26

Asia Pacific Journal of Research Vol: I Issue XV, July 2014

ISSN: 2320-5504, E-ISSN-2347-4793

Page | 36

Figure 1. Inhibition efficiency of Ai extract on mild steel in 1M HCl for different immersion

periods, at room temperature, using weight loss method

Table 2: Preliminary photochemical screening of extract of Acalupha indica.

Plant Acalypha indica

Tannins -

Alkaloids +

Terpenoids +

Glycosides +

Flavanoids -

Saponins +

Anthraquinones -

Steroids -

Note: (+) -presence and (-) - absence

Table 3. Shows the values of percentage of inhibition efficiency (IE) obtained from weight loss measurement

for different concentrations of the extract in 1M HCl at 298K to 343K temperature. The inhibition efficiency

was found to increase with increasing temperature. Considering the influence of temperature on the behaviour

0.0 0.2 0.4 0.6 0.8 1.0

40

50

60

70

80

90

100

Inhi

biti

on e

ffic

ienc

y (%

)

Concentration (%)

1/2 hr

2 hrs

4 hrs

6 hrs

8 hrs

24 hrs

Asia Pacific Journal of Research Vol: I Issue XV, July 2014

ISSN: 2320-5504, E-ISSN-2347-4793

Page | 37

of acid extract of Acalypha indica, it is noted that the inhibition efficiency increased up to 333K temperature

and then slightly decreased. This may be due the fact that chemisorption increases with temperature due to the

strengthening of chemical bonds, and as a result inhibition efficiency increases with temperatures up to 333K

and thereafter the decomposition of the inhibitor may occur. This indicates the chemical adsorption of the

inhibitor on the metal surface. The maximum inhibition efficiency was found to be 89.54 % at 333K

temperature for 0.7% concentration of the extract. Energy of activation (Ea) was calculated with the help of

Arrhenius equation by Ebenso et al [4].

a2

1 1 2

Eρ 1 1Log

ρ 2.303 R T T

(2)

ρ1 and ρ2 are the corrosion rates at T1 and T2 temperatures respectively. „R‟ is a gas constant. The change in

free energy of adsorption for different higher temperatures in comparison with room temperature at various

concentration of inhibitor was calculated using the equation (3),

adsΔG 2.303 8.314 T Log K 55.5 (3)

θ

K1 θ C

Where,θ = Surface coverage of the metal surface,C = Concentration of the inhibitorin

percentage ,T = Temperature in Kelvin and K is the equilibrium constant.

Table 3: Inhibition efficiency of Acalupha indica extract on mild steel in 1M HCl for different

concentrations using weight loss method at different temperatures.

Table 4. Shows that the calculated average value of activation energy (Ea) over the temperature range of

298 K to 333K and free energy of adsorption (Gads) for mild steel

CONC.(%)

Inhibition Efficiency(%)

298K 313K 323K 333K 343K

0.05

54.71 90.99 92.99 93.67 90.41

0.1 66.10 92.06 93.84 94.10 93.37

0.2 75.10 94.70 95.74 96.31 95.76

0.3 78.37 96.00 97.05 97.14 96.89

0.5 81.35 97.23 97.88 97.64 97.20

0.7 90.26 98.36 98.89 99.12 97.65

0.9 88.67 96.51 96.28 97.29 95.68

Asia Pacific Journal of Research Vol: I Issue XV, July 2014

ISSN: 2320-5504, E-ISSN-2347-4793

Page | 38

ads

corrosion with and without inhibitor. Activation energy (Ea) value for blank is 67.01 kJ/mol and 55.31

kJ/mol for 0.7% concentration of the inhibitor. It is observed that the Ea value is less than that of the

uninhibited system. The magnitude of Ea obtained supports the assertion that chemical adsorption is

involved (Sankarapapavinasam et al. [10]. To explain the nature of the adsorption of the inhibitor,

adsorption isotherm model of Temkin was employed.

Table 4: Calculated values of activation energy Ea and free energy of adsorption for mild steel

corrosion in 1M HCl with and without acid extract of Acalupha indica.

Conc.

(%)

Ea

kJ/mol

(-ΔG)

(kJ/mol) Average (ΔH)

(kJ/mol)

(ΔS)

(kJ/mol) 298K 313K 323K 333K 343K

blank 67.01 - - - - - - 64.33 -

0.05 61.79 21.92 23.96 25.79 27.81 27.22 25.06 59.11 0.261

0.1 60.80 21.55 23.4 24.8 26.51 25.77 24.21 58.12 0.256

0.2 60.45 21.02 22.71 23.81 25.58 25.08 23.39 61.77 0.264

0.3 59.74 20.53 22.29 23.12 25.01 24.79 22.82 60.06 0.257

0.5 58.78 20.05 21.39 22.72 23.85 24.00 22.15 60.1 0.255

0.7 55.31 19.81 21.29 24.43 24.43 23.44 22.13 62.63 0.263

Fig 2. represents the against log C for mild steel in 1M HCl containing acid extract of

Acalypha indica for 4 hours at room temperature and 333K temperature. Straight lines suggest

that the inhibitor follows the Temkin adsorption isotherm. The negative values of (Gads)

indicated spontaneous adsorption and a string interaction of the compound on mild steel

surface.

-1.4 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Surf

ace

cove

rage

Log (Concentration)

298K

333K

Asia Pacific Journal of Research Vol: I Issue XV, July 2014

ISSN: 2320-5504, E-ISSN-2347-4793

Page | 39

4. Mechanism of Inhibition

The results of the preliminary phytochemical screening are shown in Table 4.19. The extract

was found to contain alkaloids, terpenoids, glycosides and saponins. FTIR spectrum of Ai residue

dissolved in 1M HCl (Figure 4.13) shows the presence of NH and C=O group of amide and aromatic

ring. When this spectrum is compared with FTIR spectrum of the mild steel after immersion in the

inhibitor (Figure 4.24) shows reduced weak absorption bands at same frequencies indicate that the

phytochemical compound is involved in complex formation with the metal through the functional groups

and π electrons of aromatic ring. Similar type of mechanism was reported by Soror (2004) in the study of

inhibition effect of Medipolymorphol, a new sterol isolated from the plant of Medicago polymorpha Roxb

on corrosion of 316 stainless steel in 5% HCl.

Figure 4.13 FTIR spectrum of Ai residue in 1M HCl

Asia Pacific Journal of Research Vol: I Issue XV, July 2014

ISSN: 2320-5504, E-ISSN-2347-4793

Page | 40

Figure 4.24 FTIR spectrum of mild steel after immersion of 1M HCl containing 0.7% Ai

extract

5.CONCLUSION

The extract of Acalypha indica leaves acts as good and efficient inhibitor for the corrosion of mild steel in1

M hydrochloric acid medium. The maximum inhibition efficiency was found to increase with

concentration, immersion period and temperatures studied. The adsorption of the extract of Acalypha

indica on mild steel obeys Temkin adsorption isotherm. The thermodynamic parameters such as

activation energy (Ea) and free energy of adsorption (Gads) obtained from this study indicated

spontaneous adsorption of inhibitor on the surface of the metal. The inhibitive action of the plant

extract may be due to strong chemisorptions of the active ingredients of the acid extract. Reference:

1. Ajmal M, Mideen A.S,Quarshi M.A (1994) “2-hydrazino-6-methyl-benzothiazole as an effective

inhibitor for the corrosion of mild steel in acidic solution”. Corro sci 36:79-84

2. Hoasry A.A, Saleh R.M,Eldin A.M.S (1972) “corrosion inhibition by naturally occurring

substances-1 The effect of Hibiscus subdariffa (Karkade) extract on the dissolution of Al and

Zn”. Corro sci 12(1):897-904

3. Chandrasekarn V, Muralisankar M (2006)”Adhatoda vasika alkaloids as inhibitor for

aluminiumcorrosion in acids”, J. Met. Matet Sc., 48(2): 93-102

4. Ebenso E.E (2004) “Effect of halide ions on the corrosion inhibition of mild steel in

1. H2SO4 using methyl red - Part 1. Bull”. Electro Chem 19(5) : 209-216

5. El-Etre A.Y, Abdallah M, El-Tantawy Z.E( 2005) “Corrosion inhibition of some metals using

Asia Pacific Journal of Research Vol: I Issue XV, July 2014

ISSN: 2320-5504, E-ISSN-2347-4793

Page | 41

Lawsonia extract”. Corr sci 47:385-389

6. Fraz Mojab, Mohammad Kamalinejad, Nayasaneh Ghaderi , Hamid Reza, Vahidipour (2003)”

Phytochemical screening of some species of Iranian plants”, Iran J of Pharm Rese 77-82

7. Kalpana M, Mehta G.N (2003)” Evalution of Enicostemma axillare as

2. Biodegradable less toxic inhibitor for acid corro- sion of mild steel”. Bull.

3. Electrochem 19(8): 381-384

8. Kasthuri P.K, Arulanantham A, Natesan M (2006) “The effects of Acalypha indica extract as

corrosion inhibitor on the mild steel in 1M sulphuric acid”, J. Metallurgy and Mat. Sci 48(2):

109-116

9. Orubite-Okorosaye K, Oforka N.C (2004)”Corrosion inhibition of zinc on HCl using Nypa

fructicans Wurmb extract and 1,5-diphenyl carbazone” J Appl. Sci., Environ. Manag 9(2): 56-61

4. 10. Sankarapapavinasam S, Pushpnadev A.A, Ahmed M.F(1989) “Piperidine, piperidones and

tetrahydrothiopyrones as inhibitiors for the corrosion of copper in 1N H2SO4”, Corr Sci 32:

193-203

10. Shand S.H,Ismail A.A,El-Miligi A.A (1995) “ The effect of temperature on the corrosion and

corrosion inhibition of steel alloys in hydrochloric acid solution”,Bull, Electrochem 11(10): 462-469

11. El-Etre A.Y ( 2007) “inhibition of acid Corrosion of carbon steel using aqueous extract of olive

leaves”, J of coll & intf sci 314(2):578-583Corr sci 47:385-389

12. Anand .B, Balasubramanian.V(2011)“Corrosion behavior of mild steel in acidic medium in

presence of aqueous extract of Allamanda blanchetti”,E-J Chem 8(1) :226-230

13. Adolf Nahrstedt Jens D., Kant and Victory Wary (1982) „Acalyphine, A cyanogenic glycoside from

Acalypha indica‟, Phytochemistry, Vol.21, No.1, pp.101-105.

14. Husaain .M.H,Kassim .M.J (2010) “Electrochemical studies of mild steel corrosion Inhibition in

aqueous solution by Uncaria gambir extract”,J Phy Sci21:1-13

15. Illayaraja.G,Sasiekhumar A.R (2011) “Inhibition of mild steel corrosion in acidic medium by

aqueous extract of Tridax procumbens L”, E-J Chem 8(2):685-6

16. 17.Zucchi F. Hashi Omer I. and Trabanelli G. (1985) „Inhibitors of Pitting Corrosion of stainless

steel‟, Proceedings of the 6th

European symposium on Corrosion inhibitors, Anna University Ferrara

N.S.Sez.V.Suppl., No.8, p.1535.

17. Venkataraman (2002) „Influence of Aldimines on corrosion inhibition of mild steel in acidic media‟,

Ph.D. Thesis PSG College of Technology, Tamil Nadu.

Asia Pacific Journal of Research Vol: I Issue XV, July 2014

ISSN: 2320-5504, E-ISSN-2347-4793

Page | 42

18. Bani Talapatra, Shyama Prasad, Goswami and Sunil K. (1981) „Acalyphamide a new Amide and

other chemical constituents of Acalypha indica Linn.‟, Indian Journal of Chemistry, Vol.20 B,

pp.974-977.

19. Sanghvi M.J., Shukla S.K., Misra A.N., Padh M.R. and Mehta G.N. (1997) „Inhibition of

hydrochloric acid corrosion of mild steel by acid extracts of Embillica officianalis, Terminalia

bellirica and Terminalia chebula‟, Bulletin of Electro Chemistry, Vol.13, No.8-9, pp. 358 - 361.

20. Khaled K.F. (2008) „New Synthesized Guanidine Derivatives as a Green Corrosion Inhibitor for Mild

Steel in Acidic Solutions‟, Int. J. Electrochem. Science ,No.3, pp.462-475.

21. Jeyaperumal D., Muralidharan S.M., Subramaniam P., Venkatachari G. and Senthilvel (1997)

„Propargyl alcohol as hydrochloric acid inhibitor for mild steel-temperature dependence of critical

concentration‟, Anti Corrosion Methods and Materials, Vol.44, No.4, pp.265-268