Evaluation of some non-toxic thiadiazole derivatives as bronze corrosion inhibitors in aqueous solution

• Published in: Corrosion science Vol. 50; no. 9; pp. 2596 - 2604
• Main Authors: Varvara, Simona, Muresan, Liana Maria, Rahmouni, Kamal, Takenouti, Hisasi
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.09.2008; Elsevier
• Subjects: A. Bronze; Applied sciences; B. EIS; B. SEM; C. Corrosion; C. Kinetic parameters; Chemical Sciences; Corrosion; Corrosion environments; Corrosion prevention; Exact sciences and technology; Metals. Metallurgy; B. SEM; C. Kinetic parameters; C. Corrosion; B. EIS; A. Bronze; Bronze; Scanning electron microscopy; Copper base alloys; Corrosion protection; Corrosion inhibitor; Corrosion; Kinetics; Aqueous solution; Impedance; A. Bronze; B. EIS; B. SEM; C. Corrosion; C. Kinetic parameters
• ISSN: 0010-938X; 1879-0496
• DOI: 10.1016/j.corsci.2008.06.046

The inhibiting effect of four innoxious thiadiazole derivatives (2-mercapto-5-amino-1,3,4-thiadiazole (MAT), 2-mercapto-5-acetylamino-1,3,4-thiadiazole (MAcAT), 2-mercapto-5-methyl-1,3,4-thiadiazole (MMeT) and 2-mercapto-5-phenylamino-1,3,4-thiadiazole (MPhAT)) on bronze corrosion in an aerated solution of 0.2 g L −1 Na 2SO 4 + 0.2 g L −1 NaHCO 3 at pH 5 was studied by potentiodynamic voltammetry and electrochemical impedance spectroscopy. The corrosion parameters determined from the polarisation curves indicate that the addition of the investigated thiadiazole derivatives decreases both cathodic and anodic current densities, due to an inhibition of the corrosion process, through the adsorption of thiadiazoles on the bronze surface. The inhibiting effect of the investigated organic compounds appears to be more pronounced on the anodic process than on the cathodic one and, except for the case MPhAT, it is enhanced by the increases of the inhibitors’ concentration. The adsorption of the thiadiazole derivatives on bronze was confirmed by the presence of the nitrogen atoms in the EDX spectra of the bronze exposed to inhibitor-containing solutions. The magnitude of polarisation resistance values and, consequently, the inhibition efficiencies are influenced by the molecular structure of thiadiazole derivatives. The strongest inhibition was noticed in the presence of compounds with phenyl amino- or amino-functionalities in their molecules. The maximum protection efficiencies were obtained by addition of: 5 mM MAT (95.9%), 1 mM MAcAT (95.7%), 5 mM MMeT (92.6%) and 0.1 mM MPhAT (97%). EIS measurements also revealed that the inhibitor effectiveness of the optimal concentrations of thiadiazole is time-dependent.