Contact corrosion in titanium materials
In the active condition titanium is a relatively unnoble metal whose standard potential at <1.75 V lies between those of aluminum and magnesium. However, already at room temperature titanium forms a firmly adherent and dense passive layer on the surface which characterizes its corrosion properties.
In oxidizing and neutral media, as well as in reducing media containing amounts of oxidizing components (inhibitors) which allow formation of the passive layer and inhibit its destruction, titanium displays high corrosion resistance.
Due to this passive layer there is no significant difference in electrochemical potential between titanium and the corrosion resistant 18/8-CrNi steels, Monel and Hastelloy.
The risk of contact corrosion on surfaces of roughly the same size in seawater and chloride-containing solutions for example is therefore extremely slight. However galvanic contact of titanium with magnesium, aluminum, copper and their alloys can result in increased corrosive attack on these partner metals.
Deutsche Titan, Nov. 2000