Effect of passive film on the galvanic corrosion of titanium alloy Ti60 coupled to copper alloy H62

Ti alloys exhibit high potential because of the compact passive film. However, the effect of passive film on galvanic corrosion is not clear. On the one hand, the great potential difference can accelerate the galvanic corrosion of other metals with low potential. On the other hand, the passive film can hinder the electrochemical reactions, inhibiting the galvanic corrosion. To clarify this question, the galvanic corrosion of titanium alloy Ti60 coupled to copper alloy H62 was studied using zero-resistance ammeter, scanning vibrating electrode technique, scanning electron microscopy, and potentiodynamic polarization measurements. The chemical composition and electrical properties of the passive film on Ti60 were detected using X-ray photoelectron spectroscopy and Mott-Schottky plots. The results indicate the galvanic corrosion of Ti60-H62 coupling is ignorable in spite of the great galvanic potential difference between them. It can be attributed to the low electron donor density of passive film, which inhibits the electron charge transfer process at the film/solution interface, causing the slow cathodic reaction rate on Ti60.