Electrochemical Adsorption Properties and Inhibition of Brass Corrosion in Natural Seawater by Thiadiazole Derivatives: Experimental and Theoretical Investigation

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.