Research Journal of Chemical Sciences ______________________________________________ ISSN 2231-606X Vol. 5(8), 28-34, August (2015) Res. J. Chem. Sci. International Science Congress Association 28 Eco-Friendly Corrosion inhibition of Mild steel in Hydrochloric acid using Leptadenia pyrotechnica as a Green inhibitorGajendra singh1*, Arora S.K. and Mathur S.P.2 Dept. of Chemistry, S.P.C. Govt. College, Ajmer, INDIA Dept. of Pure and Applied Chemistry (Ex.), M.D.S. Univ., Ajmer, INDIAAvailable online at: www.isca.in, www.isca.me Received 26th July 2015, revised 3rd July 2015, accepted 18th August 2015 AbstractMass loss technique has been used to study the corrosion inhibition efficiency of mild steel in HCl solution by using the stem, fruit and root extract of Leptadenia pyrotechnica. The results show that all the extracts under study are good corrosion inhibitors, among which stem extract is the most effective. Corrosion inhibition efficiency increases with increasing concentration of inhibitor and it also increases with increasing concentration of HCl solution. Inhibition efficiency was found maximum up to 93.07% for mild steel with 0.8% stem extract.Keywords: Corrosion, mild steel, mass loss method, thermometric method, inhibition efficiency. Introduction Mild steel is extensively used in different industries by virtue of its good structure, properties, mechanical workability and low cost. Acid solutions are used in the industrial processes, acid cleaning, acid descaling, acid pickling and oil well acidizing. Since it suffers severe corrosion in corrosive environment, it has to be protected. Presence of hetero atom (S, N and O) with free electron pairs, aromatic rings with delocalized -electrons, alkyl chains with high molecular weight and substituent group in organic compound generally improve the inhibition efficiency. It is noticed that organic compounds show higher inhibition efficiency as compared to inorganic. A number of naturally occurring substances like Henna, Tamarind, Tea leaves, Garlic, Beet-root, Pomegranate juice and peels, Eucalyptus leaves extract, Curry leave and very popular ayurvedic powder Mahasudarshana churna have been reported as corrosion combating material2-8. Corrosion inhibition efficiency of Eugenia jambolana, Adhatoda vasica, Prosopis juliflora, Datura Stromonium, Hibiscus Cannabinus12, Ocimum sanctum, Cordia dichotoma has also been reported. Recently the use of naturally occurring substances like Brahmi, Bhringaraj, Molasses, Pumpkins, Black tea, Pennisetum glaucum, Allium cepa and Araucaria columnaris have been evaluated as effective green corrosion inhibitors9-22. In the present studies the inhibitive effects of ethanolic extract of stem, fruit and root of Leptadenia pyrotechnica have been tested. Leptadenia pyrotechnica (common name – Kheep) is an erect, ascending shrub with green stem and pale green alternating bushy branches with watery sap. Chemical constituents: Three terpenes (phytol, squalene and taraxerol), five sterols (cholesterol, campasterol, stigmasterol, sitosterol and fucosterol), fifteen fatty acids (C14-C25), eleven n-alkanol (C29-C39) has been isolated from extract of Leptadenia pyrotechnica 23. Moustafa et al. reported the isolation of twenty four alkaloids and three glycoside from the aerial parts of the Leptadenia pyrotechnica24. Almost all of the alkaloids belonged to heterocyclic group including pyridine, pyrrole, pyrazine and indole types. CHCHCHCHCH CHCHCH Taraxerol Stigmasterol Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 5(8), 28-34, August (2015) Res. J. Chem. Sci. International Science Congress Association 29 Material and MethodsMild steel having composition of 0.14% C, 0.11% Si, 0.35% Mn, 0.75%Ni, 0.025% P, 0.03% S and the rest of Fe, specimens used in the mass loss experiments were mechanically cut from commercially available mild steel samples into coupons of 2.5cm x 1.55cm x 0.02cm with a small hole of about 2mm diameter near the upper edge. Specimens were cleaned by buffing to produce spotless finish and then degreased. Different concentration solutions of hydrochloric acid were prepared using double distilled water. The extract of stem, fruit and root of Leptadenia pyrotechnicawere obtained by drying, then finely powdered and extracted with boiling ethanol. The solvent is distilled off and the residue is treated using inorganic acid, where the bases are extracted as their soluble salt. The free bases are librated by the addition of any bases and extracted with various solvents, e.g. ether, chloroform etc. Each specimen was suspended by a glass hook and immersed in a beaker containing 50 mL of test solution with or without inhibitor at room temperature and left exposed to air. Evaporation losses were made up with distilled water. Duplicate experiments were performed for each and mean values of mass loss were calculated. The percentage inhibition efficiency was calculated as- Inhibition efficiency ( %) = (1)Where u and i are the mass loss of the specimen in uninhibited and in inhibited solution respectively.The degree of surface coverage () can be calculated as- Surface coverage () = (2)The corrosion rates in mmpy can be obtained by- Corrosion rate (mmpy) =  \r   \r  (3) Where mass loss is expressed in mg. Area is expressed in cm. Exposed time is expressed in hours and metal density is expressed in gm/cm. Inhibition efficiency was also calculated using thermometric method. This involves the immersion of specimen (dimension 2.5cm x 1.55cm x 0.02cm) in an insulating reaction chamber having 50 mL of test solution at an initial room temperature. Temperature change was observed at regular intervals using a thermometer with a precision of 0.1C. Initially the increase in temperature was slow, then rapid, attaining a maximum value and then decreased. The maximum temperature was noted. The inhibition efficiency was calculated as Inhibition efficiency ( %) =  (4) Where RN and RN are the reaction number in the free solution and inhibited solution respectively. Reaction number RN (K min-1) is given as: RN =  (5) Where Tm and Ti are the maximum temperature of solution and in initial temperature of solution respectively. t is time required (in minutes) to attain maximum temperature. The coefficient of correlations (r) between the inhibitor concentration and inhibition efficiency can be calculated by using the formula- r = ""\n"\n""\n%""\n (6) Where x is inhibitor concentration and y is inhibition efficiency. N is number of test sample. Results and Discussion The corrosion rate and inhibition efficiency measured from mass loss method for mild steel in hydrochloric acid solution with and without inhibitor are given in table 1. It is observed that the inhibition efficiency increases with increase in the concentration of inhibitor from 0.2% to 0.8%. Stem, fruit and root extract of Leptadenia pyrotechnica exhibit maximum inhibition efficiency up to 93.07%, 90.61% and 90.06% respectively in 1.5 N HCl. Reaction numbers (RN) and inhibition efficiency obtained by thermometric method are summarized in table-2. The results indicate that reaction number decreases with increasing concentration of inhibitor as well as that of acid. The maximum inhibition efficacies observed by thermometric measurement are 87.95%, 84.96% and 82.85% for the stem, fruit and root respectively. The value of correlation coefficient (r = 0.9748, 0.9984 and 0.9885) indicate that there is a high degree positive correlation between concentration and inhibition efficiency (%), which proves that the inhibition efficiency increases with increase in the inhibitor concentration. SEM Analysis: Figure-4 and figure-6 show almost same view of surface whereas figure-5 shows immense roughness which depicts that the mild steel surface has been adversely affected in HCl. Corrosion has been almost inhibited by extract of Leptadenia pyrotechnica which is indicated by almost same view of mild steel surface (figure-4 and figure-6).Conclusion The alcoholic extracts of Leptadenia pyrotechnica are found to be effective green inhibitor in acid media giving up to 93.07% efficiency and can safely be used as eco-friendly corrosion combating material. Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 5(8), 28-34, August (2015) Res. J. Chem. Sci. International Science Congress Association 30 Table–1 Mass loss data for mild steel in HCl with alcoholic extracts of plant Leptadenia pyrotechnica at 299 0.1K (Area of exposure – 7.75cmPlant part Inhibitor Concen. (%) 0.5N HCl 1.0N HCl 1.5N HCl Mass Loss m) Mg Inhibition Efficiency %) Corrosion Rate (mmpy) Mass Loss m) mg Inhibition Efficiency %) Corrosion Rate (mmpy) Mass Loss m) mg Inhibition Efficiency %) Corrosion Rate (mmpy) Stem Blank 775 - 15.4972 826 - 16.5170 895 - 17.8967 0.2 103 86.71 2.0596 139 83.17 2.7795 117 86.92 2.3396 0.4 93 88.00 1.8597 104 87.41 2.0796 94 89.50 1.8797 0.6 75 90.32 1.4997 96 88.38 1.9196 83 90.73 1.6597 0.8 61 92.13 1.2198 72 91.28 1.4397 62 93.07 1.2398 Fruit Blank 775 - 15.4972 826 - 16.5170 895 - 17.8967 0.2 325 58.06 6.4988 321 61.14 6.4188 195 78.21 3.8993 0.4 279 64.00 5.5790 283 65.73 5.6590 179 80.00 3.5793 0.6 246 68.26 4.9191 227 72.52 4.5392 136 84.80 2.7195 0.8 193 75.10 3.8593 199 75.91 3.9793 84 90.61 1.6797 Root Blank 775 - 15.4972 826 - 16.5170 895 - 17.8967 0.2 374 51.75 6.4988 417 49.51 8.3385 213 76.20 4.2521 0.4 356 54.06 5.5790 374 54.72 7.4786 198 77.88 3.9593 0.6 343 55.74 4.9191 341 58.71 6.8187 147 83.58 2.9395 0.8 255 67.10 3.8593 298 63.92 5.9589 89 90.06 1.7797 Table-2 Reaction Number (RN) and Inhibition efficiency ( %) for mild steel in HCl at 299 0.1 K with alcoholic extracts of plant Leptadenia pyrotechnica. (Area of exposure- 7.75 cmPlant part Inhibitor concentration 3N HCl 2N HCl 1N HCl (RN) ( %) (RN) ( %) (RN) ( %) Stem Blank 0.1137 - 0.1005 - 0.0921 - 0.2 0.0370 67.46 0.0352 64.98 0.0336 63.52 0.4 0.0344 69.74 0.0321 68.06 0.0289 68.62 0.6 0.0221 80.56 0.0223 77.81 0.0230 75.03 0.8 0.0137 87.95 0.0149 85.17 0.0145 84.26 Fruit Blank 0.1137 - 0.1005 - 0.0921 - 0.2 0.0395 65.26 0.0376 62.59 0.0367 60.15 0.4 0.0357 68.60 0.0367 63.48 0.0329 64.28 0.6 0.0260 77.13 0.0273 72.84 0.0267 71.01 0.8 0.0171 84.96 0.0177 82.39 0.0175 81.00 Root Blank 0.1137 - 0.1005 - 0.0921 - 0.2 0.0399 64.91 0.0396 60.60 0.0370 59.83 0.4 0.0381 66.49 0.0369 63.28 0.0308 66.56 0.6 0.0287 74.76 0.0301 70.05 0.0282 69.38 0.8 0.0195 82.85 0.0183 81.79 0.0201 78.18 Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 5(8), 28-34, August (2015) Res. J. Chem. Sci. International Science Congress Association 31 Table-3 Value of coefficient of correlation (r) between Inhibition efficiency ( %) and Inhibitor concentration of Leptadenia pyrotechnica for mild steel in 1.0 N HCl [Time- 24 hrs] Plant part Inhibitor concentration Inhibition efficiency X- ' ( Y- ) ( (dx) (dy) dx x dy r Stem 0.2 63.83 -0.3 -9.925 0.09 98.5056 2.9775 0.9748 0.4 72.53 -0.1 -1.225 0.01 1.5006 0.1225 0.6 77.85 0.1 4.095 0.01 16.7690 0.4095 0.8 80.81 0.3 7.055 0.09 49.7730 2.1165 ' ( * 0.5 + , = 73.755 X- ' ( = 0 Y- + , = 0 dx 2 = 0.2 dy=166.5483 dx x dy =5.626 Fruit 0.2 45.39 -0.3 -8.205 0.09 67.3220 2.4615 0.9984 0.4 50.92 -0.1 -2.675 0.01 7.1556 0.2675 0.6 56.82 0.1 3.225 0.01 10.4006 0.3225 0.8 61.25 0.3 7.655 0.09 58.5990 2.2965 ' ( * 0.5 + , = 53.595 X- ' ( = 0 Y- + , = 0 dx 2 = 0.2 dy=143.4773 dx x dy =5.348 Root 0.2 19.18 -0.3 -21.315 0.09 454.3292 6.3945 0.9885 0.4 31.73 -0.1 -8.765 0.01 76.8252 0.8765 0.6 48.71 0.1 8.215 0.01 67.4862 0.8215 0.8 62.36 0.3 21.865 0.09 478.0782 6.5595 ' ( * 0.5 + , = 40.495 X- ' ( = 0 Y- + , = 0 dx 2 = 0.2 dy=1076.7189 dx xdy =14.652 Figure–1 Variation of inhibition efficiency (%) with inhibitor concentration (%) for mild steel in 1.5 N HCl of Leptadenia pyrotechnica (72 hrs) 1020304050607080901000.20.40.60.8Inhibition efficiency (%)Inhibitor concentration (%) Stem Fruit Root Research Journal of Chemical Sciences ___ ______________________________ Vol. 5(8), 28-34, August (2015) International Science Congress Association Langmuir adsorption isotherm for mild steel in 1.5 N HCl with alcoholic extracts of Variation of corrosion rate with inhibitor concentration (%) of plant 0.00000.20000.40000.60000.80001.00001.2000 log (/1-) 101520 blank Corrosion rate ______________________________ ___________________ International Science Congress Association Figure – 2 Langmuir adsorption isotherm for mild steel in 1.5 N HCl with alcoholic extracts of Leptadenia pyrotechnica Figure- 3 Variation of corrosion rate with inhibitor concentration (%) of plant Leptadenia pyrotechnica for mild steel in 0.5N HCl Figure- 4 SEM of pure mild steel 0.69900.39790.22180.0969 stem fruit root logC blank 0.20.40.60.8Inhibitor concentration stem fruit root ___________________ _______ ISSN 2231-606X Res. J. Chem. Sci. 32 Leptadenia pyrotechnica (72 hrs) for mild steel in 0.5N HCl stem fruit root stem fruit root Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 5(8), 28-34, August (2015) Res. J. Chem. Sci. International Science Congress Association 33 Figure- 5 SEM of mild steel in HCl Figure- 6 SEM of mild steel in HCl with inhibitor (0.8%) References1.Putilova I.N., Balizine S.A. and Baranmik V.P., Metallic corrosion inhibitor, Pergaman Press, London (1960)2.Chetopuani A. and Hammant B. I., Bulletin of Electrochem., 19, 23 (2003) 3.Rajam K., Rajendran M., Manivannan S. and Saranya R., J. Chem. Bio. Phy. Sci., , 1223 (2012) 4.El-Hossary A. A., Garwish M. M., Saleh R. M., Oriented Basic Electrochem. Tech., , 81 (1980) 5.El-Hossary A. A., Saleh R. M. and Sham El-Din A. M., Corrosion Science, 12, 897 (1972) 6.Ilusein P. K. A., Varkey G. and Singh G., Trans SAEST, 28, 2810 (1993) 7.Sharmila A., Prema A. A. and Sahagraj P.A., Rasayan J. Chem., , 74 (2010)8.Zakvi S. J. and Metha G. N., J. Electrochem. Soc. India, 37, 237 (1988)9.Verma A. S. and Mehta G. N., Trans SAEST, 32, 89 (1997) 10.Choudhary R., Jain T., Rathoria M. K. and Mathur S. P., J. Electrochem. Soc. India, 51, 173 (2002) 11.Verma G. S., Anthony P. and Mathur S. P., J. Electrochem. Soc. India, 51, 173 (2002) 12.Singh M. R. and Singh G., J. Mater. Environ. Sci., , 698 Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 5(8), 28-34, August (2015) Res. J. Chem. Sci. International Science Congress Association 34 (2012)13.KumpawaN. t, Chaturvedi A. and Upadhyay R. K., Res. J. Chem. Sci., , 51 (2012)14.Khandelwal R., Arora S. K., and Mathur S. P., E-Journal of Chemistry, , 1200 (2011) 15.Singh A., Ebenso E. E. and Quraishi M. A., Inter. J. Electrochem., , 3409 (2012) 16.Johnsirani V., Sathiyabama J., Rajendran S., Portugaliae Electrochimica Acta, 31(2), 95 (2013) 17.Iyasara I. C. and Ovri J. E. O., Inter. J. Engineer. Sci, , 346 (2013) 18.Anbarasi K. and Vasudha V. G., J. Environ. Nanotechnol., , 16 (2014)19.Gadow H. S. and Fouda A. S., Inter. J. Advance Res., , 233, (2014) 20.Mathur N. and Chippa R. C., Inter. J. Engineer. Sci. Res. Technol., , 845 (2014) 21.Suliman S., Nor-Anuar A., Abd-Razak A. S. and Chelliapan, Res. J. Chem. Sci., 2(5), 10, (2012)22.Brindha T., Revathi P. and Mallika J., Int. Res. J. Environment Sci., , 36, (2015) 23.Moustafa A. M. Y., Ahmed I.K. and Mahmoud A.S., J. Pharma. Toxico. , 681 (2007)24.Moustafa A. M. Y., Ahmed I. K. and Mahmoud A. S., Pharmaceutical Biology, 47, 994 (2009)