Abstract
Two nonionic surfactants based on tolyltriazole derivatives namely: 5-methyl-1 Decaethoxide-benzotriazole, TTA (12) and 5-methyl-1 Tetracosaethoxide-benzotriazole, TTA (24) were synthesized and evaluated as corrosion inhibitors for 65Cu-35Zn alloy dissolution in aerated seawater. The corrosion inhibition capability of these nonionic surfactants has been investigated in seawater solution using potentiodynamic polarization, electrochemical impedance spectroscopy, EIS, and scanning electron microscopic SEM/EDX measurements. According to both potentiodynamic polarization and EIS measurements, it has been found that the investigated tolyltriazoles compounds, TTAs, work as efficient inhibitors for 65Cu-35Zn corrosion and the protection aptitude raised by increasing the concentration of inhibitors. EIS measurements indicated that the charge-transfer resistances increase upon increasing the TTAs concentration. It was found that the percentage inhibition efficiency (eta%) increases by increasing the inhibitor concentration. Also, the results showed enhancement in inhibition efficiencies with decreasing the molecular size of the surfactant or the degree of ethoxylation at low concentration. At high concentration, the inhibition efficiency of the different inhibitors independent on the degree of ethoxylation. Potentiodynamic polarization curves indicated that the inhibitors under investigation act as mixed type. Finally, the surface characterization of the protective film formed on 65Cu-35Zn surface was examined by using SEM and energy dispersive X-ray, EDX, techniques. Adsorption of TTA, TTA(12), TTA( 24) on the surface of Cu-35Zn in seawater, follows the Langmuir adsorption isotherm. The adsorption free energy of inhibitors on 65Cu-35Zn alloy reveals a strong physical adsorption of the inhibitor on the metal surface..