Abstract:

Electrochemical studies of the effect of hydrodynamic conditions on corrosion inhibition of Cu–Ni (90/10) alloy in synthetic seawater and sulphide containing synthetic seawater by 1,2,3-benzotriazole (BTAH) are presented. Impedance, potentiodynamic polarization and cyclic voltammetric (CV) studies are employed in the present investigation. The studies are carried out by using Cu–Ni (90/10) alloy rotating disc electrode at different rotation speeds and at different immersion periods. Reynolds numbers at each rotation speed infer that the flow of seawater is laminar. With increasing rotation speed of the electrode immersed in seawater without sulphide and BTAH, both the charge transfer resistance (R_ct) and film resistance (R_film) are increased. However, in the presence of sulphide ions and without BTAH, both the R_ct and R_film are found to decrease with increasing rotation speed at identical immersion periods. Interestingly, when BTAH is added to seawater or seawater containing sulphide, both the R_ct and R_film are increased to such a great extent that an inhibition efficiency of 99.99% is obtained. In the presence of BTAH, the phase angle Bode plots are more broadened and the maximum values of phase angle are increased to a value close to 90° as the rotation speed is increased. The BTAH film is highly protective even under hydrodynamic condition also. Potentiodynamic polarization studies infer that BTAH functions as a mixed inhibitor under hydrodynamic conditions also. CV studies reveal that the protective BTAH film is stable even at anodic potentials of +850 mV vs Ag/AgCl.

Key words: CueNi (90/10) alloy, Rotating disc electrode, Seawater, Corrosion inhibition, Electrochemical studies, 1,2,3-Benzotriazole