Using expired drotaverine for corrosion protection of steel in HCl solution

Abstract

In the last two decades, the scientific literature has widely covered the use of expired medicinal preparations for anticorrosion protection of metals. The aim of this work is to study expired Drotaverine (No-shpa) as a corrosion inhibitor for St3 carbon steel in a 1 M HCl solution. Drotaverine concentrations ranged from 20-80 mg/L.
Studies were conducted using gravimetry, potentiodynamic polarization, impedance spectroscopy, and scanning electron microscopy. Gravimetric studies of Drotaverine’s inhibitory effect were carried out at room temperature for 2 and 24 hours, and at 80°C for 0.5 hours, showing a protective effect (Z, %) of 72, 82, and 96%, respectively, at a concentration of 80 mg/L. The Z values calculated from polarization and impedance measurements were close to those determined gravimetrically. The surface coverage of the electrode by the inhibitor was estimated, and it was shown that Drotaverine adsorption conforms to the Langmuir isotherm. The calculated free energy of adsorption, equal to -29 kJ/mol, indicates physical adsorption of the drug on the steel surface with some contribution from chemisorption. Drotaverine causes a deceleration of both cathodic and anodic electrode reactions.