The electrochemical behavior of brass in natural seawater in the absence and presence of thiadiazole derivatives, namely, 2-amino-5-(4-methoxyphenyl)-1,3,4-thiadiazole (AMOPTD), 2-amino-5-(4-methylphenyl)-1,3,4-thiadiazole (AMPTD), 2-amino-5-(4-pyridinyl)-1,3,4-thiadiazole (APTD), and 2-amino-5-(4-nitrophenyl)-1,3,4-thiadiazole (ANPTD), has been investigated by electrochemical techniques such as potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The optimum concentration of the studied inhibitors showing the highest inhibition efficiency was also evaluated at five different temperatures in the range between 303 and 343 K. The inhibition efficiency was found to increase with increase in concentration of the inhibitors but decrease with rise in temperature for all the studied inhibitors except ANPTD. Thermodynamic and kinetic parameters for the adsorption process were determined. Quantum chemical approach was further used to calculate some electronic properties of the molecule in order to confirm any correlation between the inhibitive effect and molecular structure of the studied inhibitors. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) analysis confirms that dezincification was minimized to a greater extent in the presence of the investigated inhibitors. Scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS), and Fourier transform infrared spectroscopy (FT-IR) observations of the brass surface confirmed the existence of such an adsorbed film.

The electrochemical behavior of brass in natural seawater in the absence and presence of oxadiazole derivatives, namely 2,5-bis-(4-aminophenyl)-1,3,4-oxadiazole (BAPOD), 2,5-bis-(4-bromophenyl)-1,3,4- oxadiazole (BBPOD), 2,5-diphenyl-1,3,4-oxadiazole (DPOD), and 2,5-bis-(4-nitrophenyl)-1,3,4-oxadiazole (BNPOD) has been investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The inhibition efficiency of the inhibitors was also evaluated at different temperatures. The inhibition efficiency was found to increase with increase in concentration of the inhibitors but decrease with rise in temperature for all the inhibitors except BNPOD. Inductively coupled plasma atomic emission spectroscopic (ICP-AES) analysis confirmed that dezincification was minimized to a greater extent in the presence of the inhibitors. Scanning electron microscopy (SEM), energy dispersive x-ray analysis (EDX) and Fourier transform infrared spectroscopy (FT-IR) observations of the brass surface confirmed the existence of an adsorbed film.

The corrosion inhibition of thiadiazole derivatives for brass in natural seawater has been evaluated by potentiodynamic polarisation and electrochemical impedance spectroscopic techniques. It was found that the inhibition efficiency of the thiadiazole derivatives, namely, 2-amino-5-ethyl-1,3,4- thiadiazole(AETD), 2-amino-5-ethylthio-1,3,4-thiadiazole(AETTD) and 2-amino-5-tert-butyl-1,3,4- thiadiazole (ATBTD) increases with increase in concentration. The adsorption of thiadiazole derivatives on brass surface exposed to inhibitor-containing solutions was confirmed using SEM/EDX spectra and FT-IR spectra. Adsorption of these inhibitors on brass surface followed Langmuir adsorption isotherm. ICP-AES analysis confirms that dezincification was minimized to a greater extent in the presence of these inhibitors.