The interfacial reactivity between metal (titanium, aluminum and gold) and epoxy-diamine prepolymer has been studied. When epoxy-diamine mixtures are applied onto gold-coated substrates, coating properties are the same as epoxy-diamine bulk ones. However when they are applied on metallic substrates (Ti and Al) and cured, an interphase, having chemical, physical and mechanical properties quite different to polymer bulk ones is formed. Nuclear magnetic resonance (NMR), FTIR, polarized optical microscopy (POM), and inductively coupled plasma spectroscopy (ICP) analyses suggest that diamine monomers chemically react and dissolve the hydrated metallic oxide layer. Metallic ions diffuse through the liquid organic layer to form a organo-metallic complex by coordination binding resulting from the electron-rich nitrogen atom of amine groups donating its lone pair to the electron-deficient metallic center.