Abstract
Corrosion of aluminum in aerated Arabian Gulf seawater (AGS) and 3.5% NaCl solutions and its inhibition by 3-amino-5-mercapto-1,2,4-triazole (AMTA) have been reported. The study was carried out using cyclic potentiodynamic polarization (CPP), current-time at constant potential (CT), and electrochemical impedance spectroscopy (EIS) measurements. Experimental results indicated that the presence of AMTA molecules inhibit the general and pitting corrosion of Al in both AGS and NaCl solutions by shifting the corrosion and pitting potentials of Al to the more noble values, decreasing the corrosion and passivation currents and corrosion rate, while increasing the surface and charge transfer resistances. This effect was remarkably increased by increasing the AMTA concentration to 5x10(-3) M. Although, AGS showed more aggressiveness towards Al than 3.5% NaCl, the inhibition efficiency of AMTA is higher for Al in AGS solution. The inhibition of Al corrosion by AMTA molecules is achieved by their adsorption then formation of a complex with the aluminum oxide preventing the formation of aluminum chlorides, AlCl(3), or chloride complexes, AlCl(4)(-) or even soluble oxychloride complexes, Al(OH)(2)Cl(2)(-), which lead to Al corrosion.