Corrosion Inhibition of Cu Coated with Ni and Annealed with Flow of Oxygen in NaCl Solution as a Function of Annealing Temperature

In this work we report attempts to inhibit corrosion of Cu substrates in 0.6 M NaCl solution by coating with 100 nm Ni film and post-annealing with oxygen at different temperatures, in order to convert the nickel to nickel oxide. Electrochemical impedance spectroscopy (EIS) and polarization measurement analyses were used to obtain electrochemical data. The correctness of the EIS results was confirmed by Kramers-Kronig transformation, while fitting of the data (Nyquist and Bode diagrams) to suitable equivalent electrical circuits showed that the highest corrosion enhancement is achieved for the Ni/Cu sample annealed at 473 K, resulting in a 98% corrosion inhibition enhancement factor (η%). Polarization measurements also showed that this sample has the lowest corrosion current density, lowest corrosion rate and highest corrosion potential with a 97% corrosion inhibition efficiency factor (PE%). Consistent results are achieved for EIS and polarization measurements which are then correlated with the nanostructure of the films using X-ray diffraction and atomic force microscope analyses.