Volume 23 Preprint 37


Chemical. electrochemical and quantum mechanical evaluations of antibiotics/drugs as potential corrosion inhibitors in acidic environment-A review

S.Karthikeyan

Keywords: corrosion, inhibitors, drugs, antibiotics, electrochemical

Abstract:
Corrosion inhibition of metals and alloys is a major action of technical, economic, environmental, and aesthetical significance. The use of inhibitors is one of the best option of contending metals and alloys against environmental impact. The toxicity of organic and inorganic corrosion inhibitors to the environment has provoked the search for eco-friendly corrosion inhibitors like green corrosion inhibitors as other more environmental friendly corrosion inhibitors, most of which are biodegradable and do not possess heavy metals or other harmful functional atoms and groups in their molecular structure. Antibiotic is considered to have the potential to combat corrosion of several metals such as carbon steel, Aluminium, zinc, tin and copper in acidic environments . It behaves as an inhibitive agent in different corrosive media. Numerous techniques such as Mass loss method, Electro chemical polarization study and AC impedance spectra have been used to evaluate the corrosion inhibition performance of antibiotics. The formation of corrosion inhibitor barrier layer has been analysed by IR spectroscopy, atomic force microscopy, scanning electron microscopy and auger electron spectroscopy. Adsorption of antibiotics on metal and alloy surfaces obeys Langmuir, Temkin isotherm, depending on nature of metal and corrosive environment and adsorption could be of chemisorption, physisorption or both processes. Electrochemical Polarization study demonstrated that antibiotics may act as anodic or cathodic or mixed mode of inhibition based on chemical nature of metals and operating environment. This paper discusses several antibiotics being used as inhibitors against corrosion of metals in different environments and the screening of inhibitors using electrochemical methods have been dealt in a detailed way.

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ISSN 1466-8858 Volume 23, Preprint 37 first submitted 27 May 2020 Chemical. electrochemical and quantum mechanical evaluations of antibiotics/drugs as potential corrosion inhibitors in acidic environment-A review S.Karthikeyan* * Department of chemistry, School of Advanced Science, Vellore Institute of Technology, Vellore-632014, India E-mail : skarthikeyanphd@yahoo.co.in Abstract Corrosion inhibition of metals and alloys is a major action of technical, economic, environmental, and aesthetical significance. The use of inhibitors is one of the best option of contending metals and alloys against environmental impact. The toxicity of organic and inorganic corrosion inhibitors to the environment has provoked the search for eco-friendly corrosion inhibitors like green corrosion inhibitors as other more environmental friendly corrosion inhibitors, most of which are biodegradable and do not possess heavy metals or other harmful functional atoms and groups in their molecular structure. Antibiotic is considered to have the potential to combat corrosion of several metals such as carbon steel, Aluminium, zinc, tin and copper in acidic environments . It behaves as an inhibitive agent in different corrosive media. Numerous techniques such as Mass loss method, Electro chemical polarization study and AC impedance spectra have been used to evaluate the corrosion inhibition performance of antibiotics. The formation of corrosion inhibitor barrier layer has been analysed by IR spectroscopy, atomic force microscopy, scanning electron microscopy and auger electron spectroscopy. Adsorption of antibiotics on metal and alloy surfaces obeys Langmuir, Temkin isotherm, depending on nature of metal and corrosive environment and adsorption could be of chemisorption, physisorption or both processes. Electrochemical Polarization study demonstrated that antibiotics may act as anodic or cathodic or mixed mode of inhibition based on chemical nature of metals and operating © 2020 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of1 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 it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 23, Preprint 37 first submitted 27 May 2020 environment. This paper discusses several antibiotics being used as inhibitors against corrosion of metals in different environments and the screening of inhibitors using electrochemical methods have been dealt in a detailed way. Keywords : corrosion, inhibitors, drugs, antibiotics, electrochemical Introduction Corrosion is electrochemical phenomenon which is the destruction of metals by environment. It is a constant and continuous problem, often difficult to eradicate completely. Prevention would be more practical and attainable than complete removal. Corrosion protection of metals and alloys is a prime activity of technical, economic, environmental, and aesthetical significance. The use of inhibitors is one of the best choice of combating metals and alloys against detoriation against environmental impact. The toxicity of organic and inorganic corrosion inhibitors to the environment has provoked the search for eco-friendly corrosion inhibitors like green corrosion inhibitors as other more environmental friendly corrosion inhibitors, most of which are biodegradable and do not possess heavy metals or other harmful functional atoms and groups in their molecular structure. Inhibitors are chemical substances which when added in small quantity to a corrosive environment, Reduces the rate of corrosion to a considerable extent.. They reduce the corrosion by either performing as a barrier, by establishing an adsorbed layer or retarding the cathodic and / or anodic reactions i.e., oxidation of metal and evolution of hydrogen gas. Several researches have proven that antibiotics can be used as potential corrosion inhibitors because, through their functional groups, they form complexes with metal ions and on metal surfaces. Antibiotics fall under the category of eco-friendly compounds and hence claimed as Green corrosion inhibitors which are completely soluble in aqueous media and obtainable with high purity and relatively cheap. These properties would validate their use as corrosion inhibitors in various media. It has the efficacy to combat the corrosion of a wide variety of metals such mild steel, stainless steel, Aluminium zinc and nickel. Several techniques have been used to evaluate the corrosion inhibition performances of antibiotics and to analyse the nature of protective film formed on the metal surface. Carbocyclic and heterocyclic systems are omnipresent in drug structure. Five- and six-membered rings are quite common, but small ring systems occur with rational regularity (for example, the cyclopropane © 2020 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of2 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 it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 23, Preprint 37 first submitted 27 May 2020 ring in ciprofloxacin and the aziridine ring in mitomycin C). Of the five- and six-membered systems, the mainstreams of compounds are aromatic or pseudo-aromatic. Hence, substituted benzene rings are very recurrent, and heterocycles such as pyridines, furans, thiophenes, imidazoles, isoxazoles and others befall generally in antibiotics molecular structure. Due to above-mentioned structural ring closures, corrosion protection properties of many drugs have attracted too much attention in recent years. This review summary the existing research on several drugs used as corrosion inhibitors for various metals, highlighting a background for the classification on the basis of their performance in media. Depending on the nature of metal and nature of corrosive environment antibiotics obey different types of isotherms and perform as different type of inhibitor, namely anodic, cathodic or mixed type. Antibiotics as Potential Corrosion inhibitors Eddy et.al. 1,2 reported that Penicillin’s as mild steel corrosion inhibitors. They explained the inhibitory action of Penicillin G (Table 1a) and Penicillin V are chiefly through the physorption of the compounds on mild steel. It was further studied that the adsorption of Penicillin’s on the mild steel surface is realized by weak intermolecular interactions. Similar observation was made by Alder et al.3. This was attributed to the existence of amino and carbonyl moieties as well as nitrogen and sulphur atoms in the aromatic/cyclic structure of Penicillin’s. .Eddy and Ebenso4 have also investigated the synergetic effect of iodide ions of Pencillin G .They found that inhibition efficiency of Penicillin V is lower than Pencillin G due to the effect of synergism by Iodide ions. Hari Kumar and Karthikeyan5 found that the traces of a semisynthetic antibiotic, cloxacillin inhibited the corrosion of mild steel in acid medium. They have evaluated the inhibitory action of cloxacillin using weight loss, Tafel polarization, electrochemical impedance spectroscopy and hydrogen permeation studies. In their paper, hydogen permeation measurements indicated that the compound behaved as cathodic inhibitor, but predominantly under mixed control. Heterocyclic organic compounds namely ciprofloxacin and norfloxacin were used as corrosion inhibitor by Dubey, Potdar and Yogesh6 for protection of 304 stainless steel in 1.5 percent NaCl solution . The results obtained from electrochemical studies revealed that these compounds are very good corrosion inhibitors and showed their best performance at a concentration of 1800 ppb. Potentiodynamic curves indicated that these compounds have acted as anodic type of inhibitors. I.A. Adejoroa, F.K. Ojoa, b, S.K. Obafemib7 studied the influence of ampicillin drug on the corrosion of mild steel in HCl acid medium. Some antibiotic derivatives namely, neomycin sulphate and amoxicillin were investigated as corrosion inhibitors for carbon steel in 1 M HCl solutions was investigated by Fouda et al8. © 2020 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of3 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 it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 23, Preprint 37 first submitted 27 May 2020 Electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, electrochemical frequency modulation (EFM) and weight loss methods were used to study the inhibition action of carbon steel in 1 M HCl solutions at 30ºC. Electrochemical results showed that these compounds are efficient inhibitors for carbon steel and the efficiency reached to 81 %. The adsorption of these compounds on carbon steel surface followed the Freundlich adsorption isotherm. Polarization curves indicated that investigated antibiotic derivatives are mixed-type inhibitors. Raja and his co workers9 proved that The dissolution behaviour of SS 304 pipes in 2M Sulphuric acid with green inhibitor (namely neomycin) as corrosion inhibitor using Mass loss ,Potentiodynamic polarization, electrochemical impedance spectroscopy and hydrogen permeation studies. Polarization studies indicated that inhibitors are acted as mixed type. The adsorption of the compounds on SS 304 surface obeyed Langmuir adsorption isotherm. The corrosion inhibition of galvanized steel (GI steel)sheets in 5% NaCl with Esomeprazole (EPZ) as green inhibitor has been reported by Karthikeyan et al.,10 employing mass loss, Potentiodynamic polarization, electrochemical impedance spectroscopy , hydrogen permeation and quantum mechanical studies. All these techniques reveal that the EPZ inhibits the corrosion of galvanized steel in 5% NaCl medium. Polarization studies indicated that inhibitors are acted as mixed type inhibitor. The adsorption of the compounds on galvanized steel surface follows Langmuir adsorption isotherm. Fouda et al., 11 are of view that the addition of cefixime to the corrodent solution lowered the corrosion rate of carbon steel. Also , the inhibition efficiency of cefixime was found to increase with concentration and decreased with temperature. Adsorption of cefixime molecule on carbon steel surface was found to obey the Langmuir adsorption isotherm. The phenomenon of physical adsorption was proposed from the obtained thermodynamic parameters. The inhibition of mild steel corrosion in hydrochloric acid solution by ciprofloxacin drug as an ecofriendly and commercially available inhibitor was studied by Inemesit and his team12 by weight loss technique. It was found that the test drug had a promising inhibitory action against corrosion of mild steel in the hydrochloric acid medium .The inhibition efficiency was found to increase with a corresponding increase in the concentration of the inhibitor. It was also found that the adsorption as well as the the the inhibition process followed a first-order kinetics and obeyed Langmuir’s adsorption isotherm. Inhibition of nickel corrosion in 1 M HCl solution in the absence and presence of some Cephalosporin antibiotics derivatives was investigated by Fouda et al13 using potentiodynamic © 2020 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of4 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 it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 23, Preprint 37 first submitted 27 May 2020 polarization, electrochemical impedance spectroscopy (EIS), and electrochemical frequency modulation (EFM) techniques. The inhibitive action of these compounds was discussed in terms of blocking the electrode surface by adsorption of the molecules through the active centers contained in their structures following the Langmuir adsorption isotherm. The polarization measurement showed that these inhibitors are acting as mixed inhibitors for both anodic and cathodic reactions. Aziz14 and his co investigators have compared the inhibiting efficiency of antibiotic drugs (ciprofloxacin, cloxacillin, and amoxicillin) on the corrosion of mild steel in 1 mol· L? 1 HCl using mass loss measurement. The adsorption of drugs on the mild steel surface was found to be spontaneous and obeyed the Langmuir adsorption isotherm model. Imran Naqvi et al.,15 have reported the corrosion inhibition of mild steel in 1M HCl solution by Cefixime using weight loss measurement and electrochemical techniques i.e. Polarization Resistance, Potentiodynamic Polarization and Electrochemical Impedance Spectroscopy (EIS). The adsorption of Cefixime occurred according to Langmuir`s adsorption isotherm. Kinetic parameters (activation energy, and pre-exponential factor, ?) as well as thermodynamic parameters (enthalpy, entropy and free energy of adsorption) were also calculated. The effect on metallic corrosion of antibiotics containing the fused-ring structure of tetracycline (doxycycline and the dihydrate and hydrochloride salts of oxytetracycline) when present in 1% KCl solution was investigated by von Fraunhofer and Stidham 16 . They observed that corrosion potential and zero resistance ammetry results were variable and depended upon the nature of the metal and its surface condition. All three antibiotics appeared to stimulate the corrosion of Vitallium (cobaltchromium alloy), but corrosion inhibition was found for as-received titanium with all three antibiotics, for abraded titanium with doxycycline and for stainless steel with oxytetracycline dehydrate. Lakshmi et al.,17 have investigated the influence of sulfamerizine (SMZ) drug as anti-scalant in water containing 0.7 M Gypsum salt (CaSO4) and brine water (0.7 M) has been studied by weight loss, potentiodynamic polarization and A.C impedance measurements. The formation of protective layer of SMZ was justified by chronoamperometry technique. Quantum chemical methods confirmed the absorption of anti-scalant on steel. SEM studies evidenced the formation of stable anti-scalant film on steel in presence of gypsum salt water and brine water. The reduction of corrosion and hydrogen permeation through mild steel in 0. 5M H2SO4 and 1M HCl has been studied using weight loss measurements and various electrochemical techniques in the presence and absence of a green inhibitor viz., Carbenicillin (CBN) were studied by Karthikeyan et © 2020 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of5 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 it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 23, Preprint 37 first submitted 27 May 2020 al.18. The inhibitor was found to be more effective in H2SO4 than in HCl. Potentiodynamic polarization studies proved that the compound acted as a mixed inhibitor. Shukla et al.,19 found that Streptomycin inhibits the corrosion of mild steel in HCl solution. The inhibitor acted as cathodic inhibitor. The inhibitive action of lansoprazole (LPZ) on stainless steel 304 corrosion and permeation of hydrogen gas in 2N H3PO4 has been analyzed using weight loss, gasometric and electrochemical studies has been assessed by Karthikeyan20 et al. Hydrogen permeation and EIS measurements have confirmed that LPZ retards the corrosion of SS 304 effectively . Also, the authors have validated the performance of the inhibitor molecule through its effective adsorption on steel surfaces using theoretical values of EHOMO, ELUMO, ? E and dipole moment of inhibitor. Akpan and Offiong21 have reported that electrochemical investigation of the inhibitory action of Ciprofloxacin drug on the acid corrosion of mild steel and the adsorption of inhibitor obeyed langumuir adsorption isotherm. Hari kumar and Karthikeyan22,23 investigated that performance of torsemide and furosemide drugs as corrosion inhibitors for mild steel in 1 N HCl was thoroughly investigated by weight loss and electrochemical methods. The inhibition efficiencies of drugs obtained by all methods were in good agreement with each other. Torsemide exhibited higher inhibition efficiencies than furosemide in all the experimental studies. Polarization studies revealed that the inhibiting action of the compounds is under mixed control. The free energy of adsorption and the influence of temperature on the adsorption of inhibitors onto a mild steel surface have been reported. The adsorption of the compounds was found to obey the Langmuir adsorption isotherm. The mechanism of inhibition and formation of the Fe–inhibitor complex were confirmed by FT-IR and UV–visible absorption spectral analysis. The scanning electron microscopy (SEM) and atomic force microscopy (AFM) results established the formation of a protective layer on the mild steel surface. Quantum chemical calculations were applied to correlate the inhibition performance of inhibitors with their electronic structural parameters. 4-Chloro-2-((furan-2-ylmethyl)amino)-5-sulfamoylbenzoic acid (FSM) and N- (isopropylcarbamoyl)-4-(m-tolylamino)pyridine-3-sulfonamide (TSM) drugs were tested as inhibitors by the same authors23 for mild steel corrosion in 1 N sulphuric acid solution by weight loss studies and electrochemical methods. The weight loss measurements were carried at different temperatures ranging from 303 to 333 K. The adherent film of FSM and TSM formed on metal surface obeyed Langmuir © 2020 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of6 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 it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 23, Preprint 37 first submitted 27 May 2020 adsorption isotherm. Fourier transform infrared spectroscopy and Ultraviolet–visible absorption spectral analysis were used to validate the mode of inhibition reaction to form complex between metal and inhibitor. The formation of protective layer on the mild steel surface was also confirmed by scanning electron microscopy (SEM) results. GeethaMani24 et al have examined the inhibitive action of an examined expired Ambroxol drug on the corrosion of mild steel in 1 M HCl and 1 M H2SO4 acid medium. According to them, inhibitor acted as a mixed type inhibition and followed Langmuir adsorption isotherm. The influence of Sulfalene (SFL) on corrosion and hydrogen permeation through Stainless steel 304 in 5% NaCl has been studied by Karthikeyan et al.,25 using weight loss measurements and various electrochemical techniques. Potentiodynamic polarization studies clearly indicated that SFL behaved as a mixed inhibitor. Hydrogen permeation studies and AC impedance measurements also proved an excellent performance of the compound in 5% NaCl. The adsorption of this compound on the mild steel surface obeyed Temkin's adsorption isotherm which was further validated by Quantum chemical calculations. Further the authors26 have evaluated the inhibition performance of Tobramycin (TBN) on stainless steel 304 dissolution and ingress of hydrogen gas in 2N H3PO4 and 2N HCl employing mass loss, gasometric and electrochemical studies. The antibiotic seems to be more effective in reducing the dissolution of steel in 2N H3PO4 than in 2N HCl. Potential- Current plots evidently pointed out that the inhibitor followed mixed mode of inhibition in acidic media. Hydrogen permeation and EIS measurements have confirmed that TBN retards the corrosion of SS 304 effectively in both the acids. The theoretical values of EHOMO, ELUMO, ? E and dipole moment in the presence of inhibitor confirmed its effective adsorption on SS 304 surface. The significance of Azithromycin (AZ) on corrosion of aluminium alloy 2024 in 0.1N Hydrochloric acid was examined by Lakshmi et al27 using weight loss measurements, Tafel polarization studies and scanning electron microscopy. The results indicated that AZ is a good inhibitor for aluminium alloy in 0.1N HCl and maximum efficiency obtained was 91% at 450ppm concentration of azithromycin. Potentiostatic Polarization analyses displayed that AZ works as a mixed type of inhibitor. Electrochemical impedance plots were used to examine the mechanism of corrosion. Quantum chemical studies were done for azithromycin and its various quantum chemical parameters were calculated . Also the influence of Roxithromycin (RZ) on corrosion of aluminium in 0.1N Hydrochloric acid was investigated by the same authors28. Abdallah et al29 have investigated the influence of three antihypertensive drugs namely Enalapril maleate, Atenolol and Etilefrine hydrochloride on the corrosion behavior of aluminum and three aluminum–silicon alloys in different concentrations of HCl solutions. The adsorption followed Langmuir adsorption isotherms. © 2020 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of7 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 it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 23, Preprint 37 first submitted 27 May 2020 It was found that the drugs compounds provided protection to Al and Al–Si alloys against pitting corrosion by shifting the pitting potential to more positive direction until critical drug concentrations (250 ppm). After this critical concentration the inhibition against to pitting corrosion started to decrease. The interfacial behavior of fluconazole (FLC) between aluminium and hydrochloric acid has been investigated by Obot and Egbedi30. The adsorption of the inhibitor on the aluminium surface is found to accord with Temkin adsorption isotherm. The correlation of inhibition effect and molecular structure of fluconazole was then discussed by quantum chemistry study to further provide insight into the mechanism of the inhibitory action. The same authors have also examined the performance of clotrimazole31 as the corrosion inhibitor for aluminium in hydrochloric acid medium. The compound was effectively adsorbed on Al surface and possesses a number of active centres concentrated mainly on the imidazole moiety of the molecule. The highest occupied molecular orbital (HOMO), and the lowest unoccupied molecular orbital (LUMO) were also found around the nitrogen atoms and the cyclic of the benzene rings. The effectiveness of expired Voltaren (EV) drug as corrosion inhibitor for aluminium in 1 M HCl was investigated by Abdel Hameed et al32. The Polarization measurements confirmed that the inhibiting action of the compound was mixed-type. The adsorption of the inhibitor was found to obey the Langmuir adsorption isotherm. Al-Shafey and his co-workers33 have studied the inhibition efficiency of the expired Phenytoin sodium drug (PSD) as corrosion inhibitor of carbon steel in 1 M HCl solution. The adsorption of phenytoin sodium obeyed Langmuir adsorption isotherm. Polarization curves indicated that they are mixed type of the inhibitors. Abdel Hameed34 had tested the expired ranitidine was tested as a corrosion inhibitor for mild steel in 1 M HCl. The adsorption of the inhibitor on the mild steel surface followed Langmuir adsorption isotherm model. The negative value of ? Gads (-40 kJ mol-1) indicated spontaneous chemical adsorption of Ranitidine drug on mild steel surface. The electrochemical and surface characterization studies on Azathioprine drug as corrosion inhibitor for carbon steel in HCl Solutions was cariedout by Fouda et. al35. The drug absorption on metal surface was obeyed Temkin’s isotherm. According to Hoseinpoor and Davoodi36, two anti thyroidal drugs namely methimazole (MMI) and propylthiouracil (PTU) could effectively reduced the corrosion of mild steel in 0.1 M HCl. .Also, inhibitor molecules directly adsorb at the surface on the basis of donor–acceptor interactions between the p-electrons, sulfur and oxygen atoms and the vacant d-orbitals of iron atoms.The adsorption process followed by MMI and PTU was Langmuir adsorption isotherm. Ameh and Sani37 are of view that , Cefuroxime axetil (CA) a pro-drug was used as corrosion inhibitor for aluminum in hydrochloric acid © 2020 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of8 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 it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 23, Preprint 37 first submitted 27 May 2020 solution .The authors have used the techniques such as thermometric, gasometric weight loss and scanning electron microscope (SEM) to screen the performance of the inhibitor. The adsorption of the inhibitor was also found to be spontaneous, exothermic and best fitted the Langmuir adsorption model. The influence of Ketosulfone as a green corrosion inhibitor for mild steel in 1 M HCl medium was studied by Matad et. al38. The Polarization measurements revealed that Ketosulfone acts as a mixedtype inhibitor. The adsorption of the inhibitor on the mild steel surface in acid solution was found to obey the Langmuir adsorption isotherm. The activation and thermodynamic parameters of dissolution and adsorption were calculated for this compound. Akpan and Offiong39 have evaluated inhibition of mild steel corrosion in acidic medium by amlodipine drug using chemical and electrochemical methods. The adsorption mode of the drug was found to be by monolayer chemisorption having found the experimental data obeyed the Langmuir adsorption isotherm. The corrosion inhibition of mild steel in acidic media using Trazodone (Tz) drug was studied by Manimegalai et. al40. Vaszilcsin et. al41 have examined the inhibitive action of expired Carbamazepine and Paracetamol tablets drugs for the corrosion of mild steel in acidic media. Meclizine hydrochloride was tested as a corrosion inhibitor for mild steel in 1 M HCl by Ishwara and Alva42. The adsorption of the inhibitor on the mild steel surface followed Langmuir adsorption isotherm model. The activation and thermodynamic parameters of dissolution and adsorption were calculated. Samide et al43 have examined the inhibition effect of two antibiotics namely Sulfathiazole and sulphonamide on the corrosion of mild steel in IN HCl medium. The authors have performed surface characterization studies using SEM and XPS. XPS analysis revealed that the corrosion product consists of an oxy hydroxide/oxide mixture and that the iron oxy hydroxide proportion is higher than the iron oxide proportion. The inhibition of the corrosion of zinc in 4 M HCI by Naproxen has been investigated by Emad Yousifl et al44. Ofoegbu and Ofoegbu45 have carried out trail studies on Chloroquine diphosphate as corrosion inhibitor for mild steel in 0.1M HCl. The adsorption of the inhibitor followed Langmuir adsorption isotherm. Narayana Hebbar and his coinvestigator46 studied the influence of Anthranilic acid on the corrosion of mild steel in 1M HCl. The studies indicated the mode of corrosion inhibition by this compound followed mixed type. Polyethelene Glycol-Anthranilic Acid Composite as Corrosion Inhibitor for Mild Steel in Acid Medium was studied by Banumathi et al47. Experimental results showed that the maximum inhibition efficiency was found to be 97%. The adsorption of compound was found to obey with Langmuir adsorption isotherm. Electrochemical studies confirmed the inhibitive nature of the PGA composite and also the mixed nature © 2020 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal of9 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 it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 23, Preprint 37 first submitted 27 May 2020 of the inhibitor. The polymer is found to be highly efficient non-toxic and environmentally safe. Ananth kumar et al48 have analysed the performance of Mephentermine Sulfate drug solution to inhibit corrosion of mild steel in hydrochloric acid (HCl) media and the adsorption of inhibitor is found to follow Langmuir adsorption isotherm. The inhibition performance of mebendazole, a drug, on mild steel in molar hydrochloric acid solution was studied by Ahamad and Quaraishi49. The Adsorption of inhibitor obeyed Langmuir adsorption isotherm model. Recently Karthikeyan et al50 investigated the inhibitive effect of dicloxacillin on the corrosion of mild steel in acid medium and found that dicloxacillin acted as cathodic inhibitor. Further the authors have evaluated the influence of Cefalotin drug 51 on the corrosion resistance of Al-SiC composites in sea water . This study has confirmed that the compound retarded the dissolution of Al-SiC in sea water environment by acting as mixed inhibitor. The adsorption of the compound on composite surface followed Temkin’s adsorption isotherm. The quantum chemical analysis validated the inhibition action of the green inhibitor determined by electrochemical methods. According to N.V.Lakshmi et al 52., Sulfamerizine (SMZ) drug acted as anti-scalant in water containing 0.7?M Gypsum salt (CaS O4) and brine water (0.7?M) .The studies such as weight loss, potentiodynamic polarization and A.C impedance measurements were used for screening the inhibitor. The formation of protective layer of SMZ was justified by chronoamperometry technique. Quantum chemical methods confirmed the absorption of anti-scalant on steel. SEM photographs evidenced the formation of stable anti-scalant film on steel in presence of gypsum salt water and brine water. Surface characterization by SEM, AFM, and FTIR were used to understand the drug inhibitor behavior of specific drug against mild steel corrosion and their adsorption mechanism on the surface by Md. Zaved Hossain Khan and his co investigators 53 . Yulu shi etal 54 used three types of expired nitro imidazole antibiotics as potential corrosion inhibitors for the corrosion of mild steel in 1M HCl. Evaluation was carried out by mass loss and electrochemical techniques. The surface morphology and the composition of the elements of adsorption layer were investigated by scanning electron microscopy and energy dispersive spectrometer. The significance of an antihistamine drug viz., Cetrizine [CZN] on corrosion of Stainless steel 314 in 2N Sulphuric acid was studied by S.Karthikeyan et al 55 using mass loss measurements, Tafel polarization studies and impedance measurements. The inhibitor found to perform well in sulphuric acid medium and protected the corrosion of SS 314. S.Karthikeyan and his co workers 56 examined the inhibitive action of Dicloxacillin (DCX) on corrosion of mild steel in brine water (5% NaCl) using mass loss, gasometric © 2020 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal 10 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 it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 23, Preprint 37 first submitted 27 May 2020 measurements , potentiodynamic polarization and impedance studies. The studies clearly indicated that DCX acted as cathodic inhibitor. Diffused reflectance spectra and SEM images confirmed the formation of adsorbed film of inhibitor on metal and the adsorption prcess followed Temkin’s adsorption isotherm. Ehsan Naseri et al 57 adapted response surface method (RSM) to design electrochemical experiments for assessment of a green organic molecule, namely Clopidogrel from cardiovascular drugs class, as a corrosion inhibitor for mild steel in sulfuric acid solution. The adsorption mechanism of Clopidogrel was computed through quantum chemical calculations, confirming that this compound can replace water molecules from the surface upon its adsorption to the metal substrate. . P.A.Jeeva et al 58 are of view that Co-Amoxiclav drug had extensively retarded the corrosion of mild steel in 1N HCl medium even at very low concentration of inhibitor. It was found that a definite correlation existed between chemical and electrochemical studies for the inhibition action of Co-Amoxiclav molecules on the corrosion of mild steel in 1N HCl. A.K singh et al 59 have studied the influence of an expired cefdinir (CDR) drug which exhibited exceptional corrosion inhibiting potential in acidic medium. The inhibitive action of dichlorphenamide and its quantum mechanical behaviour for the corrosion of Al 7075 in 4N sulphuric acid was examined by G.Sundara mali et al 60 . The studies clearly demonstrated that said antibiotic has performed as cathodic inhibitor. The adsorption of the compound on Al 7075 surface obeyed Temkin’s adsorption isotherm. Quantum mechanical indicies such as ELUMO,EHOMO, Energy gap and dipolement values validated the performance inhibitor for Al 7075 in acidic solution. Ramakrishnan et al 61 have synthesised and characterized a novel antibiotic viz., thioctic acid (TA) conjugate [ Chemical name is 5-(1,2-dithiolan-3-yl)-N-(6-ethoxybenzo thiazol--2yl) pentanamide [TA2A-6E-BT], which was examined as green corrosion inhibitor for carbon steel (L80) sheets in Khuff gas media. They further screened the performance of the inhibitor employing experimental techniques viz. weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy and quantum mechanical studies. The inhibitor acted as mixed inhibitor. Mechanism Corrosion inhibition of mild steel , Aluminium, Al-SiC composites, Zinc, Nickel,Copper in acidic and sea water medium by antibiotics/drugs which were reported as potential green inhibitors could be be elucidated on the basis of molecular adsorption of inhibitor on to the metal surface. It is mostly © 2020 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal 11 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 it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 23, Preprint 37 first submitted 27 May 2020 deliberated that the corrosion inhibition of a metal is the adsorption of the inhibitor molecules at metal / solution interface. Organic compounds are adsorbed on the metal surface by, i) Electrostatic interaction between the changed molecules and charged metal ii) Interaction of electrons with the metal iii) Interaction of unshared pair of electrons in the molecule with the metal and iv) The combination of the all the effects. The inhibition efficiency of the inhibitors also depends on several parameters such as the adsorption centers, mode of interaction with metal surface, charge density, molecular size, and the formation of the metallic complexes .Physical adsorption of the inhibitor molecule required both electrically charged surface of the mild steel and charged inhibitor species in the corrosive solution. The inhibitor molecule is protonated in the acid medium. Thus they became cation, existed in equilibrium with the corresponding molecular form. It is well known fact that the steel surface bears positive charge in acid solution. The protonated inhibitor molecule could be attached to the mild steel surface by electrostatic interaction between negatively charged ions of electrolyte/corrosive media and protonated drug molecules. The decrease in the inhibition efficiency obtained with rise in the temperature supported the electrostatic interaction. CONCLUSIONS It has been proven that Antibiotics/ drug molecules are prominent corrosion inhibitors in aqueous media. The review paper detailed that significant research has been carried out employing antibiotics as corrosion inhibitors for different metals in different electrolyte. The results of the sequence of surveys have revealed that the methods involved in corrosion inhibition are unpredictable with respect to all classes of compounds so far explored and are not even constant or consistent with one inhibitor in © 2020 University of Manchester and the authors. This is a preprint of a paper that has been submitted for publication in the Journal 12 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 it has been fully published it should not normally be referenced in published work. ISSN 1466-8858 Volume 23, Preprint 37 first submitted 27 May 2020 a given system. Indeed, the overall process is a function of the metal, corrodent, inhibitor structure, and concentration, as well as temperature. This paper apprehended the role of antibiotics as inhibitor for the corrosion and summarized details fall from a decade of publications by several researchers (2004-2019) in this area of interest. However few more essential and basic research findings that date back to years have also been incorporated. This review is mainly converging on recent improvements in the field of green corrosion inhibition by drugs/antibiotics for metals in different environment and has been discussed in a detailed manner. References 1. Eddy N, Odoemelam S, Ekwumemgbo P. Inhibition of the corrosion of mild steel in H2SO4 by penicillin G. Sci. Res. Essays 2009;4(1):033-038. 2. Eddy N, Odoemelam S. Inhibition of the corrosion of mild steel in acidic medium by penicillin V potassium. Advances in Natural and Applied Sciences 2008;2(3):225-233. 3. Alder AC, McArdell CS, Golet EM, Ibric S, Molnar E, Nipales NS, Giger W. Occurrence and fate of fluoroquinolone, macrolide, and sulfonamide antibiotics during wastewater treatment and in ambient waters in Switzerland. 2001. 4. Eddy NO, Ebenso EE. Quantum chemical studies on the inhibition potentials of some penicillin compounds for the corrosion of mild steel in 0.1 M HCl. Journal of molecular modeling 2010;16(7):1291-1306. 5. Kumar SH, Karthikeyan S. 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