Performance of an anticonvulsant drug, expired gabapentin, on zinc corrosion in an acidic environment

Corrosion inhibitors that are both economical and environmentally beneficial have received a lot of interest in controlling the corrosion of metals. Regarding these parameters, the primary goal of this work is to assess the effectiveness of an expired gabapentin in controlling corrosion of zinc in 0.1 M HCl solution through chemical, i.e., weight loss method and electrochemical techniques, i.e., Tafel polarisation and EIS techniques. The result obtained in all the three methods is comparable. It has been found that corrosion inhibition efficiency increased with an increase in inhibitor concentration exhibiting maximum inhibition efficiency of 85% at 400 mg/L of the inhibitor used. The influence of temperature on % I.E was determined and observed that inhibition efficiency decreases with an increase in temperature. Tafel polarisation study indicates the mixed type behaviour of expired gabapentin. The experimental impedance data were fitted to theoretical values using equivalent circuit models, allowing for a better comprehension of the adsorption mechanism and the recommendation of a model that explains the electrochemical behaviour of the metal/solution interface under various conditions. The adsorption of gabapentin on zinc metal surface is the cause for the reduction of corrosion and follows the Langmuir model. The standard enthalpy of adsorption (Δ H 0 ads ) was found to be − 69 kJ/mol which clearly demonstrates gabapentin’s physical adsorption on the zinc surface. The higher activation energy ( Ea * = 17.29 kJ/mol) for zinc in the presence of the expired gabapentin inhibitor compared to blank is due to physisorption. FTIR, SEM, and EDX measurements were used to correlate the results with surface morphology analyses. Computational investigations using quantum mechanics DFT simulations in gas phase were carried out in parallel with the tests. According to the obtained results, expired gabapentin drug could be used and applied as a non-toxic green inhibitor for zinc corrosion in an acid environment.