Abstract
The application of expired drugs as corrosion inhibitors provides a cost effective and environmentally benign alternative to otherwise tedious and costly disposal/degradation process. In this context, we herein investigate the use of expired atorvastatin (EA) for corrosion inhibition of mild steel in 1 M HCl solution using weight loss, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (Tafel) methods. Fresh atorvastatin (FA) drug was also used for above studies for comparison purpose to understand whether there is any significant difference between the inhibition efficiency of the two after the expiration date of the drug. EIS analysis shows an increase in polarization resistance due to the adsorbed inhibitor molecules on metal surface. Potentiodynamic polarization indicates that both the EA and FA act as mixed-type inhibitors but predominantly behave as cathodic inhibitors. The adsorption of EA and FA on mild steel surface follows the Langmuir adsorption isotherm. SEM shows a smoother surface of mild steel in the presence of FA and EA drug in acidic solution. Both the fresh drug and its expired counterpart showed almost similar results in all the studies, thereby verifying the validity of the expired atorvastatin drug as a novel and efficient corrosion inhibitor for mild steel.
Highlights
Since the onset of industrial revolution, mild steel has been used as an alloy for a number of structural and industrial applications [1]
– 66.11 95.77 98.41 88.20 91.29 99.08 towards lower current density, indicating the suppression of both the cathodic and anodic reactions. This trend is corroborated by the data of inhibition efficiencies in Table 1 and suggests the adsorption of inhibitor molecules on the surface of mild steel and the formation of a protective film
This potential can be termed as desorption potential [23] and the results suggest that the corrosion inhibition process, under the present condition, is dependent on the electrode potential [22, 23]
Summary
Since the onset of industrial revolution, mild steel has been used as an alloy for a number of structural and industrial applications [1]. Researchers are mainly focusing on the use of non-toxic and ‘‘green’’ corrosion inhibitors, e.g., plant extracts and drugs to obviate the harmful effect of chemicals on environment [8,9,10]. Because of their non-toxic characteristics [18] and negligible negative impacts on the aquatic environment [19], drugs (chemical medicines) seem to be the ideal candidates to replace traditional toxic corrosion inhibitors [9]. A number of studies are available describing the application of drugs as efficient corrosion inhibitors [9,10,11,12,13,14,15,16,17]
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