When wetting is promoted by interfaces, the rate at which the liquid spreads over the solid substrate is controlled by the rate at which the well-wetted interfacial product can be formed along the liquid/solid/atmospheric triple line. If this reaction involves a reactive alloy addition to the liquid, the rate of spreading can be limited by two phenomena. A simplified analysis of diffusion- limited reactive spreading of Cu-Sn-Ti alloys on vitreous carbon was conducted based on the assumption that the interfacial reaction is strictly localized at the triple line. The addition of 3at.%Ti to Cu-15at.%Sn led to very good wetting on vitreous carbon. This was due to the formation, at the interface, of a continuous layer of TiC.