Adsorption and inhibition study of N-(5-methoxy-2-hydroxybenzylidene) isonicotinohydrazide Schiff base on copper corrosion in 3.5% NaCl

Corrosion inhibition ability of synthesized Schiff base namely, N-(5-methoxy-2-hydroxybenzylidene) isonicotinohydrazide (NMHI) on copper in 3.5% NaCl solution was studied via electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PP) and gravimetric study. Results showed NMHI to inhibit copper corrosion in chloride solution. The inhibition efficiency of NMHI was enhanced with an increase in the concentration but decreases with rising temperature. Maximum value of 97.7% inhibition efficiency was obtained with weight loss measurement at 303 K for the highest NMHI concentration (1 × 10^-3 M) used. Polarization studies indicated that NMHI acted as mixed kind of inhibitor. The Nyquist plot revealed that double-layer capacitance (C_dl) declined and charge-transfer resistance (R_ct) was enhanced with increase in NMHI concentrations, involving increased inhibition efficiency. NMHI adsorption onto the surface of copper obeyed Langmuir adsorption isotherm. Scanning electron microscopy (SEM) was used to characterize the morphology of uninhibited and inhibited copper surfaces.