5-Substituted 1H-tetrazoles as effective corrosion inhibitors for mild steel in 1 M hydrochloric acid

Abstract

The corrosion inhibition efficiency of (E)-3-phenyl-2-(1H-tetrazole-5-yl)acrylonitrile (PTA), (E)-3-(4-nitrophenyl)-2-(1Htetrazole-5-yl)acrylonitrile (NTA), and (E)-3-(4-hydroxyphenyl)-2-(1H-tetrazole-5-yl)acrylonitrile (HTA) on mild steel in 1 M HCl was tested using experimental and theoretical methods. The results show that the inhibition efficiency increases with the increasing concentration, and maximum values were obtained at a 40 mg L −1 concentration. The inhibition efficiency of the studied inhibitors follows the order HTA (98.69%) > NTA (96.60%) > PTA (93.99%). Polarization studies suggest that the tetrazoles behave as cathodic inhibitors. The adsorption of the tetrazoles on the mild steel surface obeys the Langmuir adsorption isotherm. In the present study, the values of the free energy of adsorption (− G 0 ads) vary from 34.92 to 39.71 kJ mol −1. The adsorption of the tetrazoles on the mild steel surface is supported by SEM, EDX and AFM studies. Quantum chemical calculations provide good support to the experimental results.

Synthesis, characterization and corrosion inhibition potential of two novel Schiff bases on mild steel in acidic medium

“…Potentiodynamic polarization studies were done by changing the WE potential from À250 mV to +250 mV with respect to the potential of RE at a perpetual sweep rate of 1.0 mV s À1 . The current density (i corr ) was derived by extrapolation of Tafel curves through which inhibition efficiency was derived using following equation: 9,12 h%…”

“…EIS studies were performed at the open circuit potential (OCP) in frequency range of 100 kHz to 0.01 Hz through AC current input having amplitude 10 mV peak to peak. The inhibition efficiency was calculated from polarization resistance (R p ; obtained from Nyquist plots) using following relationship: 9,12,45 h% ¼…”

“…DFT studies were performed using Gaussian 09 soware as described earlier. 12,43,44 Several outputs and descriptors such as energies of highest and lowest unoccupied molecular orbitals (E HOMO , E LUMO ), energy band gap (DE), electronegativity (c), global hardness (h), soness (s), and fraction of electron transfer (DN) have been calculated using following relationships: 12,[46][47][48]…”

“…A value of 0.2572 hartree was used for the c Fe , while h Fe was taken as 0 hartree for bulk Fe atom in accordance with the Pearson's electronegativity scale. 12,[46][47][48] In the present study, value of c Fe is replaced by its work function (f) as described earlier. [49][50][51][52][53] The values of f derived from DFT calculations which are 0.1436, 0.1771 and 0.1425 hartree for the Fe (100), Fe (110) and Fe (111), respectively.…”

“…[8][9][10] The adsorption of these inhibitors depends upon numerous factors such as nature of metal and electrolyte, electronic structure of the inhibitor, temperature, exposure time etc. 11,12 Recently, widespread studies of organic compounds show that these compounds exhibit various attractive linear and non-linear optical properties. 13,14 Schiff bases are generally synthesized by condensation reaction between aromatic aldehyde and primary amine (-HC]N-).…”