R. Khandelwal, R. Mathur, S.K. Arora, S.P.Mathur,
Keywords: Cordia dicotoma, Iron, Aluminium, Mass loss method, Thermometric method, corrosion inhibitor, inhibition efficiency.
Abstract:
The corrosion inhibitive effect of alcoholic extracts of different parts of plant cordia dicotoma on iron and aluminium has been studied in presence of hydrochloric and sulphuric acids by mass loss and thermometric methods. The observations were carried out at 299 ± 0.2 K in presence of different concentrations of fruit, leaves and stem extracts of Cordia dicotoma. The results reveal that the extracts of Cordia dicotoma are effective corrosion inhibitor for iron and aluminium in acidic media. The fruit extract is more potent than leaves and stem extract to inhibit the corrosion rate. The results exhibit that the Cordia dicotoma extract is better corrosion inhibitor for aluminium than iron.
The fruit extract show maximum inhibition efficiency up to 95 % in 0.5 N HCl for iron and up to 97% in 1.0 N H2SO4 for aluminium. The leaves extract exhibit maximum inhibition efficiency up to 89.88 % in 0.5 N HCl for iron and up to 89.47 % in 0.5 N H2SO4 for aluminium while the stem extract exhibit maximum inhibition efficiency up to 92.59 % in 0.5 N HCl for iron and up to 88.98 % in 0.5 N HCl for aluminium.
Because you are not logged-in to the journal, it is now our policy to display a 'text-only' version of the preprint. This version is obtained by extracting the text from the PDF or HTML file, and it is not guaranteed that the text will be a true image of the text of the paper. The text-only version is intended to act as a reference for search engines when they index the site, and it is not designed to be read by humans!
If you wish to view the human-readable version of the preprint, then please Register (if you have not already done so) and Login. Registration is completely free.
ISSN 1466-8858 Volume 12, Preprint 47 submitted 27 November 2009 Corrosion Inhibition Efficacy of Extracts of Plant Cordia dichotoma for Iron and Aluminium in Presence of Acidic Media R. Khandelwal, S.K. Arora, S.P. Mathur* Material research laboratory Govt. College, Ajmer (Raj.) Email: rakhi.gweca @gmail.com arorask_67@ yahoo.co.in ABSTRACT The corrosion inhibitive effects of alcoholic extracts of different parts of plant cordia dichotoma on iron and aluminium has been studied in presences of hydrochloric and sulphuric acid by mass loss and thermometric methods. The experiments were carried out at 299 ± 0.2 K in presence of different concentrations of dry fruit, leaves and stem extracts of Cordia dichotoma. The results reveal that the alcoholic extracts of Cordia dichotoma is a better corrosion inhibitor than that of toxic chemicals. The fruit extract is more potent than leaves and stem extracts to inhibit the corrosion rate. The results show that the inhibition efficacy of fruit extract is higher for aluminium as compared to the iron, but an average inhibition efficacy of fruit extract is higher for iron than aluminium. The fruit extract show maximum inhibition efficiency up to 95 % in 0.5 N HCl for iron and for aluminium it is 97% in 1.0 N H2SO4. The leave extract shows maximum inhibition efficiency up to 89.88 % in 0.5 N HCl for iron and for aluminium it is 89.47 % in 0.5 N H2SO4. The Stem extract shows maximum inhibition efficiency up to 92.59 % in 0.5 N HCl for iron and for aluminium it is 88.98 % in 0.5 N HCl. Introduction Metallic corrosion is a very common but serious problem causing considerable revenue loss throughout the whole world1. Iron is selected for many mechanical and © 2009 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 12, Preprint 47 submitted 27 November 2009 engineering purposes due to its properties such as strength, ease of fabrication, and cost. Aluminium also found to have variety of engineering applications because of lightness, strength, thermal and electrical conductivities, heat and light reflectivity and hygienic and non toxic qualities2, but both the metals and their alloys suffer from a serious corrosion problem. Corrosion commonly occurs at metal surfaces in the presence of oxygen and moisture involving two electrochemical reactions. Oxidation takes place at anodic site and reduction occurs at cathodic site. In acidic medium hydrogen evolution reaction predominates. Aluminium is a reactive metal according to electrochemical series (Eo = -1.66 V), yet it is unreactive in moisture due to the formation of a stable oxide film on its surface. Aluminium is not attacked by pure water but dissolves in aqueous acids with liberation of hydrogen gas. Corrosion inhibitors reduce or prevent the corrosion reactions. They are adsorbed on metal surface and form a barrier to oxygen and moisture by complexing with metal ions or by removing corrodent from the corrosive environment. Some of the inhibitors facilitate formation of passivating film on the metal surface 3. There are varieties of synthetic chemical corrosion inhibitors available but our present focus is on the naturally occurring green inhibitors which are eco-friendly, less expensive and having no side effects. Numerous naturally occurring substances such as Prosopis juliflora, 4 Eugenia jambolans,5 Lawsonia extract,6 Opuntia extract,7 Swertia aungustifolia,8 Ficus religeosa,9 Heena,10 Datura stromonium,11 and Calotropis plants 12 have been evaluated as potential green corrosion inhibitors. In the present paper we aimed to study by mass loss method and thermometric method, the effect of naturally occurring plant Cordia dichotoma on corrosion rate of the iron and aluminium in different concentrations of acid solutions. Description of inhibitor - Cordia dichotoma belongs to family Boraginaceae. Its common name is Indian cherry, lasura. Its chemical constitutions are mono and polysachharides, Beta-sitosterol, flavonol glycoside, taxifotin, 3-rhamnoside, 3-5dirhamnoside, distylin, 3-xyloside, allantoin. It is Astringent, anthelmintic, diuretic, demulcent and expectorant (fruit) and useful in the cough, chest diseases hence it relief from severe colic pain. Probably the alkaloid - Allantoin (Fig. 1) present in Cordia dicotoma is effective for corrosion inhibition activity in acidic media for iron and aluminium. © 2009 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 12, Preprint 47 submitted 27 November 2009 (Fig. 1) Allantoin Experimental MASS LOSS MEASUREMENTS: Specimen preparation Rectangular specimens of iron of dimensions 2.54 Χ 1.52 Χ .02 cm with a small hole of about 2mm diameter near the upper edge were employed for the determination of mass loss measurements. Surface preparation is of prime importance in mass loss method. To achieve uniform surface, a substantial thickness of metal surface should be removed by milling and turning by use of emery papers or by mean of mechanical grinding. Test solution preparation The solutions of 0.5N and 1N were prepared using doubly distilled water. The Fruit leave and stem extracts of Cordia dichotoma was obtained by dried, then finely powdered and extracted with boiling ethanol. To observe the influence of various parameters like inhibitor concentration, acid concentration and time, the corrosion inhibition efficiency (η) of the compounds has been calculated by mass loss method using following equation.13 η % = (∆ Mμ - ∆ Mi ) / ∆ Mμ × 100 Where ∆ Mμ is mass loss without inhibitor and ∆ Mi is mass loss with inhibitor. The degree of surface coverage (θ) can be calculated as – (θ) = (∆ Mμ - ∆ Mi) / ∆ Mμ The Corrosion rate in mili meter penetration year (mmpy) 14 can be obtained by following equation. Corrosion rate (mmpy) = (Mass loss × 87.6) / area × time × metal density © 2009 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 12, Preprint 47 submitted 27 November 2009 Where mass loss is expressed in mg, area is expressed in square cms of metal surface exposed, time is expressed in hours of exposure and metal density is expressed in gms/ cm 3. . THERMOMETRIC MEASUREMENTS: For the thermometric study15 the specimens of size 2.54 Χ 1.52 Χ .03 cm were immersed in 50ml of acid solution. The test was carried out in 0.5N HCl and 0.5 N H2SO4 solutions. The inhibition studies were carried out in the concentrations 0.12%, 0.24%, 0.36% 0.48% and 0.60% of the extract of natural products. Thermometer bulb and the test specimen were completely immersed in the test solution, which was kept in Dewar flask. The change in temperature was recorded at the successive intervals of 5 minutes with the help of thermometer with a precision of 0.1.C . The results were used to calculate reaction number (R.N.) and inhibition efficiency (η %). In this method, the variation of temperature is followed as a function of time. The test specimen is immersed in a cell containing the test solution along with the thermometer bulb, which is immersed in a dewar flask. Initially the temperature of the system remains constant. Reaction number can be calculated by the following equationRN = (Tm - Ti) / t Where Tm and Ti are initial and maximum temperatures respectively and t is the time in minutes to attain Tm in the experiment. Drastic corrosion is indicated by higher reaction number. The inhibitor efficiency can be calculated as – η % = (RNfree - RNi ) / RNfree × 100 Where RNfree and RNi are reaction number in blank and inhibited system respectively. The results are presented in Table 5 and 6. © 2009 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 12, Preprint 47 submitted 27 November 2009 Table 1 Mass loss and inhibition efficiency (η) for Iron and Aluminium in 0.5 N HCl (18hrs) with given inhibitor addition at 299 ± 0.2 K Inhibitor concentration Iron (%) ∆ M, (gm) η% Aluminium Corrosion ∆ M, rate (gm) η% Corrosion rate (mmpy) (mmpy) Fruit extract Unhibited 0.12 0.24 0.36 0.48 0.60 Leaves extract Unhibited 0.12 0.24 0.36 0.48 0.60 Stem extract Unhibited 0.12 0.24 0.36 0.48 0.60 0.02 0.010 0.009 0.007 0.004 0.001 50.00 55.00 65.00 80.00 95.00 0.0012 0.0006 0.0005 0.0004 0.0002 0.0001 0.121 0.024 0.021 0.020 0.019 0.010 80.16 82.64 83.47 84.30 91.74 0.0218 0.0043 0.0037 0.0036 0.0034 0.0018 0.089 0.033 0.027 0.021 0.014 0.009 62.92 69.66 76.40 84.26 89.88 0.0055 0.0020 0.0016 0.0012 0.0008 0.0005 0.121 0.25 0.022 0.021 0.019 0.013 79.34 81.82 82.64 84.30 89.47 0.0218 0.0450 0.0039 0.0037 0.0034 0.0023 0.054 0.028 0.024 0.023 0.020 0.004 48.15 55.56 57.41 62.96 92.59 0.0033 0.0017 0.0014 0.0014 0.0012 0.0002 0.121 0.027 0.024 0.023 0.022 0.014 77.68 80.16 80.99 81.82 88.98 0.0218 0.0048 0.0043 0.0041 0.0039 0.0025 © 2009 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 12, Preprint 47 submitted 27 November 2009 Table 2 Mass loss and inhibition efficiency (η) for Iron and Aluminium in 1.0 N HCl (18hrs), with given inhibitor addition at 299 ± 0.2 K Inhibitor concentration Iron (%) ∆ M, (gm) Fruit extract Unhibited 0.12 0.24 0.36 0.48 0.60 Leaves extract Unhibited 0.12 0.24 0.36 0.48 0.60 Stem extract Unhibited 0.12 0.24 0.36 0.48 0.60 η% Aluminium Corrosion ∆ M, rate(mmpy) (gm) η% Corrosion rate (mmpy) 0.074 0.026 0.024 0.022 0.021 0.013 64.86 67.57 70.27 71.62 82.43 0.0045 0.0016 0.0014 0.0013 0.0012 0.0008 0.132 0.032 0.030 0.028 0.024 0.017 75.76 77.27 78.79 81.82 87.12 0.0237 0.0057 0.0054 0.0050 0.0043 0.0030 0.074 0.040 0.035 0.032 0.030 0.029 45.95 52.70 56.76 59.46 60.81 0.0045 0.0024 0.0021 0.0019 0.0018 0.0017 0.132 0.035 0.031 0.030 0.027 0.019 73.48 76.52 77.27 79.55 85.61 0.0237 0.0063 0.0055 0.0054 0.0048 0.0034 0.074 0.054 0.050 0.049 0.045 0.041 27.03 32.43 33.78 39.19 44.59 0.0045 0.0033 0.0030 0.0030 0.0027 0.0025 0.132 0.036 0.032 0.031 0.030 0.021 72.73 75.76 76.52 77.27 84.09 0.0237 0.0064 0.0057 0.0055 0.0054 0.0037 © 2009 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 12, Preprint 47 submitted 27 November 2009 Table 3 Mass loss and inhibition efficiency (η) for Iron and Aluminium in 0.5 N H 2SO4 (18hrs), with given inhibitor addition at 299 ± 0.2 K Inhibitor concentration Iron (%) ∆ M, (gm) Fruit extract Unhibited 0.12 0.24 0.36 0.48 0.60 Leaves extract Unhibited 0.12 0.24 0.36 0.48 0.60 Stem extract Unhibited 0.12 0.24 0.36 0.48 0.60 η% Aluminium Corrosion ∆ M, rate(mmpy) (gm) η% Corrosion rate (mmpy) 0.398 0.115 0.098 0.089 0.065 0.020 71.10 75.38 77.64 83.67 94.97 0.0245 0.0071 0.0060 0.0055 0.0040 0.0012 0.038 0.021 0.012 0.009 0.007 0.002 44.74 68.42 76.32 81.58 94.74 0.0068 0.0037 0.0021 0.0016 0.0012 0.0003 0.398 0.116 0.099 0.092 0.080 0.041 70.85 75.12 76.88 79.90 89.70 0.0245 0.0071 0.0061 0.0056 0.0049 0.0025 0.038 0.023 0.013 0.012 0.009 0.004 39.47 65.79 68.42 76.32 89.47 0.0068 0.0041 0.0023 0.0021 0.0016 0.0007 0.398 0.118 0.102 0.094 0.082 0.051 70.35 74.37 76.38 79.40 87.18 0.0245 0.0072 0.0063 0.0058 0.0050 0.0031 0.038 0.025 0.015 0.013 0.010 0.005 34.21 60.53 65.79 73.68 86.84 0.0068 0.0045 0.0027 0.0023 0.0018 0.0009 © 2009 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 12, Preprint 47 submitted 27 November 2009 Table 4 Mass loss and inhibition efficiency (η) Iron and Aluminium in 1.0 N H2SO4 (18hrs), with given inhibitor addition at 299 ± 0.2 K Inhibitor concentration Iron (%) ∆ M, (gm) η% Aluminium Corrosion ∆ M, rate (gm) η% Corrosion rate (mmpy) (mmpy) Fruit extract Unhibited 0.12 0.24 0.36 0.48 0.60 Leaves extract Unhibited 0.12 0.24 0.36 0.48 0.60 Stem extract Unhibited 0.12 0.24 0.36 0.48 0.60 0.485 0.398 0.258 0.218 0.118 0.110 17.94 46.80 55.05 75.67 77.32 0.0299 0.0245 0.0159 0.0134 0.0072 0.0067 0.043 0.035 0.022 0.013 0.010 0.001 18.60 48.83 69.76 76.74 97.67 0.0077 0.0063 0.0039 0.0023 0.0018 0.0001 0.485 0.394 0.263 0.221 0.121 0.113 18.76 45.77 54.43 75.05 76.70 0.0299 0.0243 0.0162 0.0136 0.0074 0.0069 0.043 0.028 0.019 0.011 0.009 0.003 34.88 55.81 74.42 79.07 93.02 0.0077 0.0050 0.0034 0.0019 0.0016 0.0005 0.485 0.399 0.271 0.225 0.131 0.120 17.73 44.12 53.61 72.99 75.26 0.0299 0.0246 0.0167 0.0139 0.0080 0.0074 0.043 0.026 0.018 0.011 0.009 0.004 39.53 58.14 74.42 79.07 90.70 0.0077 0.0046 0.0032 0.0019 0.0016 0.0007 © 2009 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 12, Preprint 47 submitted 27 November 2009 Table 5 Reaction Number (RN) and Inhibition efficiency (η %) for Iron and Aluminium in 0.5 N HCl solution with given inhibitor addition at 299 ± 0.2 K Inhibitor Iron Aluminium concentration (%) Unhibited Fruit extract 0.12 0.24 0.36 0.48 0.60 Leave extract 0.12 0.24 0.36 0.48 0.60 Stem extract 0.12 0.24 0.36 0.48 0.60 RN 0.0750 η% - RN 0.0600 η% - 0.0178 0.0149 0.0110 0.0105 0.0100 76.27 80.13 85.33 86.00 86.67 0.0148 0.0120 0.0104 0.0088 0.0079 75.33 80.00 82.67 85.33 86.83 0.0189 0.0162 0.0121 0.0109 0.0104 74.80 78.4 83.87 85.47 86.13 0.0159 0.0122 0.0109 0.0092 0.0088 73.5 79.67 81.83 84.67 85.33 0.0192 0.0168 0.0128 0.0122 0.0118 74.4 77.6 82.93 83.73 84.27 0.0162 0.0134 0.0121 0.0095 0.0090 73.00 77.67 79.83 84.17 85.00 © 2009 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 12, Preprint 47 submitted 27 November 2009 Table 6 Reaction Number (RN) and Inhibition efficiency (η %) for Iron and Aluminium in 0.5 N H2SO4 solution with given inhibitor addition at 299 ± 0.2 K Inhibitor Iron Aluminium concentration (%) Unhibited Fruit extract 0.12 0.24 0.36 0.48 0.60 Leave extract 0.12 0.24 0.36 0.48 0.60 Stem extract 0.12 0.24 0.36 0.48 0.60 RN 0.0810 η% - RN 0.0510 η% - 0.0192 0.0161 0.0129 0.0112 0.0098 76.29 80.12 84.07 86.17 87.90 0.0122 0.0101 0.0092 0.0082 0.0070 76.08 80.20 81.96 83.92 86.27 0.0194 0.0165 0.0135 0.0119 0.0102 76.05 79.63 83.33 85.31 87.40 0.0125 0.0118 0.0098 0.0087 0.0077 75.49 76.86 80.78 82.94 84.90 0.0198 0.0175 0.0139 0.0122 0.0109 75.55 78.39 82.84 84.94 86.54 0.0128 0.0120 0.0101 0.0092 0.0081 74.90 76.47 78.23 81.96 84.11 © 2009 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 12, Preprint 47 submitted 27 November 2009 Result and Discussion Mass Loss Method Mass loss, inhibition efficiency and corrosion rate for iron and aluminium at different concentrations of HCl and inhibitors are given in Table 1 and 2. And for H2SO4 and inhibitor are given in Table 3 and 4. It is observed that the inhibition efficiency (%) increases with the increase in inhibitor concentration for both the metals iron and aluminium. The inhibition efficiency of alcoholic extracts of fruit, leaves and stem of Cordia dichotoma was calculated, and it is observed that the fruit extract shows the maximum inhibition efficiency. In 0.5 N HCl the fruit extract shows the maximum inhibition efficiency 95 % for iron and 91.47 % for aluminium. The leave extract exhibits maximum inhibition efficiency 89.88 for iron and 89.47 for aluminium. And the stem extract shows maximum inhibition efficiency 92.59 for iron and 88.98 for aluminium. In 1.0 N HCl all the three extracts show maximum inhibition efficiency at maximum inhibitor concentration. It is also observed that in 1.0 N HCl inhibition efficiencies are higher for aluminium as compared to iron. The fruit extract shows the maximum inhibition efficiency 87.12 % for aluminium 82.43 % for iron. The leave extract shows maximum inhibition efficiency 85.61 for aluminium 60.81 for iron. And the stem extract exhibits maximum inhibition efficiency 84.09 for aluminium 44.59 for iron. In 0.5 N H2SO4 the fruit extract shows the maximum inhibition efficiency 94.97 % for Iron and 94.74 % for aluminium. The leave extract shows maximum inhibition efficiency 89.70 for iron and 89.47 for aluminium, and the stem extract shows maximum inhibition efficiency 87.18 for iron and 86.84 for aluminium. In 1.0 N H2SO4 the fruit, leaves and stem extracts exhibit maximum inhibition efficiency 77.32, 76.70, 75.26 for iron while 97.67, 93.02, and 90.70 for aluminium. The efficiencies of inhibitors expressed as the relative reduction in corrosion rate can be quantitatively related to the amount of adsorbed inhibitors on the metal surface. It is assumed that the corrosion reactions are prevented from occurring over the active sites of the metal surface covered by adsorbed inhibitor, whereas the corrosion reactions occurs normally on the inhibitors free area. The inhibition efficiency is then © 2009 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 12, Preprint 47 submitted 27 November 2009 directly proportional to the fraction of surface covered with adsorbed inhibitor. This assumption has been applied to deduce the effect of concentration on adsorption of inhibitors. Generally the adsorption of organic molecules on metallic surface involves O, N, and S atoms. In the case of plant extracts of Cordia dichotoma, the N and O of the alkaloids may be responsible for adsorption. This process may block the active sits on metal surface, hence decreasing the rate of corrosion. Due to the higher electron density the N atom of the alkaloid acts as the reaction centre, resulting in the formation of a monolayer on the metal surface. Organic inhibitors with active portions generally contain large hydrocarbon chains or rings with positively charged amine N group at the one end. In acids and water the terminal primary, secondary and tertiary amines groups take additional hydrogen that gives them a net cationic charge. The polar amine group is adsorbed on the metal and hydrocarbon portion forms an oily water repellent surface film. The molecular dissymmetry helps these materials to act as surfactants and can stabilize emulsions of oil and water. The Organic corrosion inhibitor may function by – 1. 2. 3. Chemisorption on the metallic surface. Neutralizing the corrodent Adsorbing the corrodent They offer large coverage due to the long hydrocarbon chain and by the presence of –NH groups. Being hydrophilic in nature, the –NH group counteracted the effects of chain length and ensured higher solubility. It has been observed that the fruit extract of Cordia dicotoma has maximum inhibition efficiency as compared to leaves and stem extracts. This may be attributed to the presence of alkaloids. In the fruit extract the electron repelling hydroxyl group on the alkaloid is present; as a result the electron density at the N atom becomes more than the any other additives. This process increased the adsorptivity of the fruit extract on the corroding site of the metal. This explains the higher inhibition efficacy displayed by the fruit extract for 0.6 % concentration. © 2009 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 12, Preprint 47 submitted 27 November 2009 Thermometric Method Inhibition efficacies were also determined using thermometric method. Temperature change for iron and aluminium in o.5 N HCl and 0.5 N H2SO4 were recorded both in presence and absence of inhibitor. Results summarized in Table 5 for HCl and Table 6 for H2SO4 show a good agreement with the results obtained by mass loss method. The maximum inhibition efficiency was obtained with the highest concentration of inhibitor. The reaction number decreases with increase in the inhibitor concentration. Conclusion It is anticipated that the proposed investigation on green corrosion inhibitor may be useful for preventing losses caused due to corrosion. The extracts of Cordia dichotoma are found to be an effective inhibitor for both the metals iron and aluminium in acidic media giving IE up to 95.00% in HCl, 97.67 % in H2SO4 It is also concluded that at lower acid concentrations extracts of Cordia dichotoma are more potent to inhibit corrosion in iron but at higher acid concentrations extracts are more effective inhibitors for aluminium. On the basis of the results it is concluded that the alcoholic extracts of Cordia dichotoma may de use as ecofriendly corrosion inhibitors without any toxic effect and pollution. © 2009 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 12, Preprint 47 submitted 27 November 2009 References 1. R. Chowdhary , T.Jain, M.Rathoria and S.P.Mathur : Bull.Electrochem., 20, 67, (2004). 2. T. Sethi, A. Chaturvedi, R.K.Upadhayay and S.P.Mathur : Polish J Chem. 82,591,(2008). 3. T. Sethi, A. Chaturvedi, R.K.Upadhayay and S.P.Mathur : J. chil.Chem. Soc., 52, 1206, (2007). 4. R. Chowdharyand S.P. Mathur: J. Electrochem. Soc. India, , 54, 1, (2005). 5. S.A.Verma and G,N. Mehta : Trans. SAEST, 32, 89, (1997). 6. Y.El-Etre,M.Abdallah and Z.E.El-Tantway : Corrosion Science, 47, 385, (2005). 7. A.Y.El-Etre : Corrosion Science, 45, 2485, (2003). 8. S.J.Zakvi and G.N. Mehta : Trans. SAEST, 23, 407,(1988). 9. T.Jain,R.Chowdhary and S.P.Mathur : Mater. Corros, 57, 422, (2006). 10. A. Chetouani and B. hammouti: Bull.Electrochem. 19, 23, (2003). 11. G.S.Verma, P. Anthony and S.P. Mathur: J. Electrochem. Soc. India, 51, 173, (2002). 12. Sudesh Kumar, S.Arora, M.Sharma, P.Arora and S.P. Mathur : J. chil.Chem. Soc., 53, 1718, (2009). 13. J.D.Talati and D.K.Gandhi : Indian J.Technol. , 29, 277 (1991). 14. R.H.Hausler : Proc. Int. Conf. on ‘Corrosion inhibition’ dallas, TX, USA : 1983, 7,16 15. K.Aziz, A.M. ShamsEL-DIN, Corros. Sci. 5,489, (1965). © 2009 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 12, Preprint 47 submitted 27 November 2009 inhibition efficiency (η%) Variation of inhibition efficiency with inhibitor concentration for Iron in 0.5 N HCl (18hrs) 100 fruit 80 leaves 60 stem 40 20 0 0.12 0.24 0.36 0.48 0.6 Inhibitor concentration (%) © 2009 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 12, Preprint 47 submitted 27 November 2009 Variation in inhibition efficiency with inhibitor concentration for Alum inium in 0.5 N HCl (18hrs) nhibition efficiency (η %) 100 fruit leaves 80 stem 60 40 20 0 0.12 0.24 0.36 0.48 0.6 Inhibitor concentration (%) © 2009 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 12, Preprint 47 submitted 27 November 2009 Variation of inhibition efficiency with the inhibitor concentration for Iron in 1.0 N H2SO4 (18hrs ) Inhibition efficiency (η%) 100 fruit 80 leaves 60 stem 40 20 0 0.12 0.24 0.36 0.48 0.6 Inhibitor concentration (%) © 2009 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 12, Preprint 47 submitted 27 November 2009 Variation of inhibition efficiency with the inhibitor concentration for Alum inium in 1.0 N H2SO4 (18hrs) Inhibition efficiency (η %) 100 fruit leaves 80 stem 60 40 20 0 0.12 0.24 0.36 0.48 0.6 Inhibitor concentration (%) © 2009 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of Corrosion Science and Engineering. It will be reviewed and, subject to the reviewers’ comments, be published online at http://www.jcse.org in due course. Until such time as it has been fully published it should not normally be referenced in published work.