The action of ethanol (EEAA), acid (AEAA), and toluene (TEAA) extracts from Artemisia annua and Artemisinin (ATS) on mild steel corrosion in H2SO4 solutions was investigated using gravimetric and gasometric techniques. The extracts and ATS functioned as good inhibitors, and their inhibition efficiencies (%IE) followed the trend: EEAA > AEAA > TEAA > ATS. %IE increased with increase in inhibitors concentration and decreased with increase in temperature. The enhanced %IE values of the extracts were attributed to synergistic effect of the components of the plant extracts with ATS. The adsorption of the inhibitors was consistent with Langmuir isotherm. Physisorption is proposed as the mechanism of inhibition. 1. Introduction Present trend in research on environmental friendly corrosion inhibitors is taking us back to exploring the use of natural products as possible sources of cheap, nontoxic, and ecofriendly corrosion inhibitors. These natural products are either synthesized or extracted from aromatic herbs, spices, and medicinal plants. Of increasing interest is the use of medicinal plant extracts as corrosion inhibitors for metals in acid solutions. This is because these plants serve as incredibly rich sources of naturally synthesized chemical compounds that are environmentally acceptable, inexpensive, readily available, and renewable sources of materials [1, 2]. These chemicals include alkaloids, flavonoids, terpenoids, glycosides, tannins, saponins, fats and oils, and carbohydrates, and so forth [3–11]. The complex composition of phytochemicals in plant extracts makes it difficult to attempt to assign the inhibition ability to a particular constituent. Some researchers have, however, ascribed the inhibition efficiency of these medicinal plants to their active components used for medical purposes [3]. We have recently attempted to assign the inhibition ability to some constituents by studying the inhibitive effect of different parts of a given plant with variable concentrations of the phytochemicals on acid corrosion [4–7]. Another most probable method would be the use of different solvents in the extraction process and comparing their inhibition efficiencies. This is yet to be explored in most of the reported work on corrosion inhibition of plant extracts. Artemisia annua is native to Asia, most probably China, but is currently cultivated in many countries including Nigeria, mainly as a source of artemisinin, an important natural sesquiterpene lactone with antimalarial effect against susceptible and multidrug resistant Plasmodium spp. The plant is a
References
[1]
R. M. Saleh, A. A. Ismail, and A. H. El Hosary, “Corrosion inhibition by naturally occurring substances. vii. the effect of aqueous extracts of some leaves and fruit peels on the corrosion of steel, Al, Zn and Cu in acids,” British Corrosion Journal, vol. 17, no. 3, pp. 131–135, 1982.
[2]
O. K. Abiola and A. O. James, “The effects of Aloe vera extract on corrosion and kinetics of corrosion process of zinc in HCl solution,” Corrosion Science, vol. 52, no. 2, pp. 661–664, 2010.
[3]
A. Y. El-Etre, “Inhibition of acid corrosion of carbon steel using aqueous extract of olive leaves,” Journal of Colloid and Interface Science, vol. 314, no. 2, pp. 578–583, 2007.
[4]
P. C. Okafor and E. E. Ebenso, “Inhibitive action of Carica papaya extracts on the corrosion of mild steel in acidic media and their adsorption characteristics,” Pigment and Resin Technology, vol. 36, no. 3, pp. 134–140, 2007.
[5]
P. C. Okafor, M. E. Ikpi, I. E. Uwah, E. E. Ebenso, U. J. Ekpe, and S. A. Umoren, “Inhibitory action of Phyllanthus amarus extracts on the corrosion of mild steel in acidic media,” Corrosion Science, vol. 50, no. 8, pp. 2310–2317, 2008.
[6]
I. E. Uwah, P. C. Okafor, and V. E. Ebiekpe, “Inhibitive action of ethanol extracts from Nauclea latifolia on the corrosion of mild steel in H2SO4 solutions and their adsorption characteristics,” Arabian Journal of Chemistry. In press.
[7]
P. C. Okafor, E. E. Ebenso, and U. J. Ekpe, “Azadirachta indica extracts as corrosion inhibitor for mild steel in acid medium,” International Journal of Electrochemical Science, vol. 5, no. 7, pp. 978–993, 2010.
[8]
I. B. Obot, S. A. Umoren, and N. O. Obi-Egbedi, “Corrosion inhibition and adsorption behaviour for aluminuim by extract of Aningeria robusta in HCl solution: synergistic effect of iodide ions,” Journal of Materials and Environmental Science, vol. 2, no. 1, pp. 60–71, 2011.
[9]
M. Lebrini, F. Robert, and C. Roos, “Alkaloids extract from Palicourea guianensis plant as corrosion inhibitor for C38 steel in 1 M hydrochloric acid medium,” International Journal of Electrochemical Science, vol. 6, no. 3, pp. 847–859, 2011.
[10]
M. Lebrini, F. Robert, P. A. Blandinières, and C. Roos, “Corrosion inhibition by Isertia coccinea plant extract in hydrochloric acid solution,” International Journal of Electrochemical Science, vol. 6, no. 7, pp. 2443–2460, 2011.
[11]
A. O. James and O. Akaranta, “Inhibition of corrosion of zinc in hydrochloric acid solution by red onion skin acetone extract,” Research Journal of Chemical Sciences, vol. 1, no. 1, pp. 31–37, 2011.
[12]
M. Kohler, W. Haerdi, P. Christen, and J.-L. Veuthey, “Extraction of artemisinin and artemisinic acid from Artemisia annua L. using supercritical carbon dioxide,” Journal of Chromatography A, vol. 785, no. 1-2, pp. 353–360, 1997.
[13]
P. S. Covello, “Making artemisinin,” Phytochemistry, vol. 69, no. 17, pp. 2881–2885, 2008.
[14]
J. Ferreira and J. Janick, “Annual Wormwood (Artemisia annua L.) New Crop FactSHEET,” 2009, www.hort.purdue.edu/newcrop/cropfactsheets/artemisia.pdf, 23rd March, 2010.
[15]
J. Han, M. Ye, X. Qiao, M. Xu, B.-R. Wang, and D.-A. Guo, “Characterization of phenolic compounds in the Chinese herbal drug Artemisia annua by liquid chromatography coupled to electrospray ionization mass spectrometry,” Journal of Pharmaceutical and Biomedical Analysis, vol. 47, no. 3, pp. 516–525, 2008.
[16]
J. B. Harbone, Phytochemical Methods : A Guide to Modern Techniques of Plant Analysis, Chapman and Hill, London ,UK, 1973.
[17]
E. R. Sofowora, “Guidelines for research promotion and development in traditional medicine,” Nigeria Journal of Pharmacy, vol. 11, pp. 117–118, 1980.
[18]
G. E. Trease and W. C. Evans, A Textbook of Pharmacology, Baillier Tidally, London ,UK, 1996.
[19]
U. J. Ekpe, U. J. Ibok, B. I. Ita, O. E. Offiong, and E. E. Ebenso, “Inhibitory action of methyl and phenyl thiosemicarbazone derivatives on the corrosion of mild steel in hydrochloric acid,” Materials Chemistry and Physics, vol. 40, no. 2, pp. 87–93, 1995.
[20]
B. I. Ita and O. E. Offiong, “Inhibition of steel corrosion in hydrochloric acid by pyridoxal, 4-methylthiosemicarbazide, pyridoxal-(4-methylthiosemicarbazone) and its Zn(II) complex,” Materials Chemistry and Physics, vol. 48, no. 2, pp. 164–169, 1997.
[21]
P. C. Okafor, U. J. Ekpe, E. E. Ebenso, E. M. Umoren, and K. E. Leizou, “Inhibition of mild steel corrosion in acidic medium by Allium sativum extracts,” Bulletin of Electrochemistry, vol. 21, no. 8, pp. 347–352, 2005.
[22]
A. Y. El-Etre, “The inhibitive action of the mucilage extracted from the modified stems of prickly pears, toward acid corrosion of aluminum,” Corrosion Science, vol. 45, no. 11, pp. 2485–2495, 2003.
[23]
M. Abdallah, “Antibacterial drugs as corrosion inhibitors for corrosion of aluminium in hydrochloric solution,” Corrosion Science, vol. 46, no. 8, pp. 1981–1996, 2004.
[24]
P. C. Okafor, U. J. Ekpe, E. E. Ebenso, E. E. Oguzie, N. S. Umo, and A. R. Etor, “Extract of Allium cepa and Allium sativum as corrosion inhibitors of mild steel in HCl solution,” Transactions of the SAEST, vol. 41, no. 2, pp. 82–87, 2006.
[25]
T. Zhao and G. Mu, “The adsorption and corrosion inhibition of anion surfactants on aluminium surface in hydrochloric acid,” Corrosion Science, vol. 41, no. 10, pp. 1937–1944, 1999.
[26]
M. Abdallah, E. A. Helal, and A. S. Fouda, “Aminopyrimidine derivatives as inhibitors for corrosion of 1018 carbon steel in nitric acid solution,” Corrosion Science, vol. 48, no. 7, pp. 1639–1654, 2006.
[27]
S. S. Rehim, O. A. Hazzazi, M. A. Amin, and K. F. Khaled, “On the corrosion inhibition of low carbon steel in concentrated sulphuric acid solutions. Part I: chemical and electrochemical (AC and DC) studies,” Corrosion Science, vol. 50, no. 8, pp. 2258–2271, 2008.
[28]
A. A. El-Awady, B. A. Abd-El-Nabey, and S. G. Aziz, “Kinetic-thermodynamic and adsorption isotherms analyses for the inhibition of the acid corrosion of steel by cyclic and open-chain amines,” Journal of the Electrochemical Society, vol. 139, no. 8, pp. 2149–2154, 1992.
[29]
P. C. Okafor, V. I. Osabor, and E. E. Ebenso, “Eco-friendly corrosion inhibitors: inhibitive action of ethanol extracts of Garcinia kola for the corrosion of mild steel in H2SO4 solutions,” Pigment and Resin Technology, vol. 36, no. 5, pp. 299–305, 2007.
[30]
E. E. Oguzie, G. N. Onuoha, and A. I. Onuchukwu, “The inhibition of aluminium corrosion in potassium hydroxide by "Congo Red" dye, and synergistic action with halide ions,” Anti-Corrosion Methods and Materials, vol. 52, no. 5, pp. 293–298, 2005.
[31]
K. Gomma and M. H. Wahdan, “Effect of temperature on the acidic dissolution of copper in the presence of amino acids,” Materials Chemistry and Physics, vol. 32, no. 2, pp. 142–148, 1994.
[32]
S. Martinez and I. Stern, “Thermodynamic characterization of metal dissolution and inhibitor adsorption processes in the low carbon steel/mimosa tannin/sulfuric acid system,” Applied Surface Science, vol. 199, no. 1–4, pp. 83–89, 2002.
[33]
S. S. Abd El Rehim, M. A. M. Ibrahim, and K. F. Khalid, “The inhibition of 4-(2'-amino-5'-methylphenylazo) antipyrine on corrosion of mild steel in HCl solution,” Materials Chemistry and Physics, vol. 70, no. 3, pp. 268–273, 2001.
[34]
B. B. Damaskin, O. A. Petrii, and B. Batraktov, Adsorption of Organic Compounds on Electrodes, Plenum Press, New York, NY, USA, 1971.
[35]
A. Le Mehaute and G. Grepy, “Introduction to transfer and motion in fractal media: the geometry of kinetics,” Solid State Ionics, vol. 9-10, no. 17, pp. 17–30, 1983.
[36]
G. Reinhard and U. Rammet, in Proceedings of the Proceedings of the 6th European Symposium on Corrosion Inhibitors, p. 831, Ferrara, Italy, 1985.
