Electrochemical stability of magnetron-sputtered Ti films on sintered and sintered/plasma nitrided Fe-1.5% Mo alloy

We report on the electrochemical stability of magnetron-sputtered Ti films on sintered and sintered/plasma nitrided Fe-1.5% Mo alloy. Open-circuit potential and potentiodynamic polarization measurements were carried out in pH 7 saline solutions together with scanning electron microscopy imaging. Magnetron-sputtered Ti films on sintered samples were found to be gradually more electrochemically stable as the Ti deposition time increased from 20 to 60 min, characterized by open-circuit potential and potentiodynamic polarization measurements and SEM micrographs. Sintered/plasma nitrided+Ti samples, however, presented the best electrochemical stability for an intermediate deposition time of 30 min, while films deposited during 60 min were found to be more easily corroded, probably due to a decrease in the film-to-substrate adhesion because of the presence of a nitride layer prior to coating. In the case of sintered/plasma nitrided+Ti samples whose deposition time was 20 or 30 min, the effect of the two layers (nitride and Ti) was clearly greater than the sum of the individual effects, characterizing a synergistic effect.