Corrosion Inhibition Action of Glipizide against Mild Steel Corrosion in 1M Hydrochloric Acid: Experimental, Theoretical and Quantum studies

Glipizide an active drug molecule used in the treatment of type 2 diabetes was investigated for its corrosion inhibition action towards mild steel corrosion. Corrosion rate was measured in 1M hydrochloric acid solution by chemical and (weight loss) and electrochemical method (Tafel polarization and electrochemical impedance spectroscopy). Experimental results obtained were complemented with spectral analysis. The data obtained by tafel method reveals the mixed type of inhibitory action for Glipizide. The % IE reached a maximum of 89.13% at 40ppm inhibitor concentration. Glipizide presence in the studied corrosive media reduced the i(corr) and C-dl values which were obtained by tafel and EIS study. This may be attributed because of the formation of protective layer of Glipizide on the metal surface and may happen be the replacement of adsorbed H2O molecule from the metal surface. Further from the study, it has been found that the adsorption of the Glipizide on the metal surface is the main cause for the minimization of corrosion of mild steel and proposed to follow Langmuir adsorption model, thereby separates the metal surface from the rest of the corrosive medium. The calculated thermodynamic parameters indicated the spontaneity of adsorption, which was further confirmed by the surface analysis by SEM and FTIR study, SEM showed the formation of protective layer on the mild steel surface and FTIR results revealed the incorporation of Glipizide in mitigating the corrosion and is confirmed by the appearance of characteristic absorption peaks. The density functional theory (DFT) calculated indices (triangle E-gapp& E-HOMO) indicates the suitability of Glipizide towards corrosion control. Further, the theoretical data are in good agreement with experimental evidence.