So far unexplored corrosion of titanium silicide (Ti5Si3) surface with acidified hydrogen peroxide is of interest due to its potential use in improving osseointegration of titanium implants coated by titanium silicides. Detailed examination of corrosion products by FTIR, Raman and XP spectroscopy, electron microscopy, XRD, BET and light scattering techniques allows recognition of hydrated nanocomposite TiOx/SiOx (x ≤ 2) phases composed of segregated amorphous SiOx species and TiOx–based networks containing Ti-O-Si and -O-O- bonds. The appearance of the TiOx networks depends on the extent of peroxidation. A less progressed peroxidation yields sub-μm-sized TiOx-based spheres which upon annealing develop anatase nanograins withstanding 800° C. A more progressed peroxidation produces larger mesoporous TiOx-based bodies which disintegrate upon sonication into micrometer-sized entities. The proposed mechanism of surface corrosion is based on the complementary use of analytical techniques. The one-step production of bioactive (hydrated TiOx and SiOx) species deserves to be explored in osseointegration studies of slightly corroded Ti5Si3-coated titanium implants.