Insights into the inhibition mechanism of 2,5-bis(4-pyridyl)-1,3,4-oxadiazole for carbon steel corrosion in hydrochloric acid pickling via experimental and computational approaches

Abstract

The addition of 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (4-POX) as organic corrosion inhibitor of carbon steel (CS) in 1 M HCl solution was assessed exploiting weight loss and electrochemical measurements as well as surface analyses. The gravimetric results showed that the 4-POX presents excellent anticorrosive properties on CS substrate, and its inhibition performance, ƞ(%), augmented with the 4-POX concentration to reach a maximum value of 93.6% at 1 mM afterwards 6 h embedding in 1 M HCl at 303 K. The AC impedance findings revealed that the addition of 4-POX to the corrosive medium leads to a decrease of the charge capacitance resulting in a systematic improve of the interface charge/discharge function and forms an adsorbed layer over the metal surface. Furthermore, SEM, water contact angle and XPS methods supported the development of a protective film over CS substrate surface afterwards addition of 4-POX. DFT calculations and MD simulations of 2,5-bis(n-pyridyl)-1,3,4 oxadiazole (n = 2, 3 and 4) derivatives were exploited to get better insight, about structural and electronic effects in relation to the anticorrosion properties and to envisage the interactions of the investigated inhibitors with metal surface atoms along with corrosive species. The cytotoxicity of 4-POX was also determined using the cell culture system.