5-(3-Aminophenyl)tetrazole - A new corrosion inhibitor for Cu-Ni (90/10) alloy in seawater and sulphide containing seawater

The inhibition performance of 5-(3-aminophenyl)tetrazole (APT) in controlling corrosion of Cu-Ni (90/10) alloy in synthetic seawater and synthetic seawater containing 10 ppm sulphide has been investigated. Electrochemical impedance, potentiodynamic polarization, cyclic voltammetry (CV) weight-loss and scanning electron microscopy (SEM)/energy dispersive X-ray analysis (EDX) studies were employed to evaluate the inhibitor performance. The results of impedance studies show that both charge transfer resistance and film resistance increase with an increase in APT concentration and at a concentration of 6.5 mM, APT functions as an excellent inhibitor with an inhibition efficiency of 99.72%. The phase angle Bode plots are more broadened and showed a phase maximum of 81° in the presence of APT. The APT film is highly protective even at a temperature of 60 °C. Potentiodynamic polarization studies inferred that APT functions as a mixed inhibitor. CV studies revealed that the protective APT film is stable even up to anodic potentials of +850 mV vs. Ag/AgCl. Weight-loss studies showed an inhibition efficiency of more than 99% in the presence of APT even after 30 days immersion period. SEM-EDX studies confirm the absence of any corrosion and presence of protective APT film on the alloy surface.