Comparative study of Levofloxacin and its amide derivative as efficient water soluble inhibitors for mild steel corrosion in hydrochloric acid solution

Int J Ind Chem DOI 10.1007/s40090-016-0083-y RESEARCH Comparative study of Levofloxacin and its amide derivative as efficient water soluble inhibitors for mild steel corrosion in hydrochloric acid solution Turuvekere K. Chaitra1 • Kikkeri N. Mohana1 • Harmesh C. Tandon2 Received: 17 December 2015 / Accepted: 24 April 2016 Ó The Author(s) 2016. This article is published with open access at Springerlink.com Abstract The influence of 8-fluoro-3-methyl-9-(4-methylpiperazin-1-yl)-6-oxo-2,3-dihydro-6H-1-oxa-3a-aza-phenalene-5-carboxylic acid or levofloxacin (P1) and newly synthesized 8-fluoro-3-methyl-9-(4-methyl-piperazin-1yl)-6-oxo-2,3-dihydro-6H-1-oxa-3a-aza-phenalene-5-carboxylic acid-(5-methyl-pyridin-2-yl)-amide (P2) on corrosion inhibition of mild steel in 0.5 M hydrochloric acid solution was studied using weight loss and electrochemical techniques. Inhibition efficiency of P1 and P2 increased with concentration and decreased with temperature in the concentration range 0.14–0.35 mM in the temperature range 303–333 K. Thermodynamic parameters for dissolution and adsorption process were studied. Increase in energy of activation after the addition of inhibitors indicated formation of barrier film which prevents charge and mass transfer. Free energy of adsorption showed that the type of adsorption was neither physical nor chemical but comprehensive. The adsorption of the P1 and P2 on the mild steel surface was found to obey the Langmuir isotherm. Impedance measurement showed that there is increase in the polarization resistance and decrease in double layer capacitance after the addition of inhibitors. From polarization study as the shift in corrosion potential is more than 85 mV, both P1 and P2 are anodic type of inhibitors. Scanning electron microscope images confirm the formation of inhibitory film on mild steel surface. Quantum chemical calculation results well correlated with & Kikkeri N. Mohana 1 Department of Studies in Chemistry, Manasagangotri, University of Mysore, Mysuru 570006, Karnataka, India 2 Department of Chemistry, Sri Venkateswara College, Dhaula kuan, New Delhi 110021, India experimental results. Lower values of energy gap, ionization potential and hardness, higher value of softness make P2 better inhibitor compared to P1. Keywords Corrosion  Mild steel  Levofloxacin  Electrochemical techniques  Quantum chemical parameters  SEM Introduction Corrosion is a natural destructive phenomenon where pure metals interact with the environment to form non-desirable metallic compounds. Protection of metals from corrosion is one of the major economic issues. Mild steel (MS) is an important metal which is widely applied in oil wells, constructional materials, automobiles and many other industries due to its excellent mechanical properties and low cost [1]. Hydrochloric acid solutions (approximately 0.5–1 M) are widely used in several industrial processes, some of the important fields of application being acid pickling of steel, chemical cleaning and processing, ore production and oil well acidification [2]. Corrosion of MS when exposed to aggressive acids, such as hydrochloric acid and sulfuric acid results in such damage that needs either repair or replacement of the part leading to huge loss of resources. Corrosion of MS is worth investigating because such corrosions cause damage to pipelines, bridges, marine structures and construction materials bringing heavy economic losses worldwide. Corrosion is also one of the major concerns in the durability of materials and structures; and studies are continuously carried out to develop effective methods for corrosion control [3]. There are a number of methods for corrosion control but the choice depends on economics, safety requirements and 123 Int J Ind Chem technical considerations. Mitigation of MS corrosion is achieved through such means as galvanisation, organic coating (enamel, polymer, oils etc.) and using corrosion inhibitors [4–6] which form film by adsorbing on the metal surface. The organic corrosion inhibitors although proved to be the best for the protection of MS, but they are restricted in some cases because of their toxicity. Therefore, the best means of protection is to adapt an inhibitor which is eco-friendly, easily soluble and effective at low concentration. The class of organic compounds which satisfy these conditions are drugs and their derivatives which are highly water soluble. Corrosion inhibition studies of many drugs, such as blactam antibiotics {penicillin G [7], ampicillin [8], amoxicillin [9]}, quinolones {ofloxacin [10], ciprofloxacin [11], quinoline [12]}, tetracyclines {doxycycline [13]}, sulphonamides {sulfamethazine [14], dapsone [15] antifungal {ketoconazole [16]}, antiviral {rhodanine [17]}, have been reported. Levofloxacin is a member of the fluoroquinolone class of antibacterial used in the treatment of chronic bronchitis, respiratory tract infection, pneumonia, skin infection and urinary tract infection [18]. Its structure has extended pelectron systems, good number of hetero atoms and two electron donating methyl groups which facilitate its adsorption on the MS surface. Fluoroquilones have been established as potential class of inhibitors, P1 and P2 which belong to the same class are expected to give good inhibition because similar molecules tend to behave alike [19]. Eddy et al. [20] studied derivatives of fluoroquinolone (ofloxacin, amifloxacin, enofloxacin, pefloxacin) on MS corrosion in sulfuric acid medium by gravimetric technique supported by quantum chemical calculations and obtained inhibition efficiency up to 94 %. Levofloxacin was previously studied by Pang et al. [21] as MS corrosion inhibitor in sulfuric acid medium by weight loss and electrochemical methods and maximum inhibition efficiency obtained was 90 %. In this study, Levofloxacin is being studied as MS corrosion inhibitor in HCl medium using gravimetric and electrochemical techniques at lower concentrations and the results are supported by theoretical studies. Comparison of inhibition efficiency of Levofloxacin with its synthesized derivative has been made to study the effect of an extra heterocyclic ring and an amine group transformed into amide bond present in P2. In continuation of our previous work [22–26] the present paper reports the comparative study of the anticorrosion potential of levofloxacin (P1) and its newly synthesized amide derivative (P2) in 0.5 M HCl media using weight loss method, electrochemical impedance spectrosocpy (EIS) and potentiodynamic polarization measurements. Morphological study has been done using scanning electron microscope (SEM). Quantum chemical 123 calculations were done and different parameters, such as energies of highest occupied molecular orbital (EHOMO) and the lowest unoccupied molecular orbital (ELUMO), the energy gap (DE), hardness (g), softness (r), electron affinity (A), electronegativity (v), ionization potential (I) of P1 and P2 were determine (...truncated)