The morphologies and compositions of internal oxides on Ti60 alloy after corrosion under solid NaCl in H2O+O2 at 600 °C have been studied by TEM. The results show that microstructure has an effect on the internal corrosion process. The partial pressure of Cl2 was found to be higher inside the β strip and at the β phase/α platelet boundary, which promotes the corrosion process in αs grains located inside the β strip. Our results confirm that the internal oxides do not originate from the oxidation of chlorides. Titanium depletion caused by the Cl attack promotes oxidation of the matrix. •The influences of microstructure on internal partial pressure of Cl2 is proposed.•Oxidation of the metal chlorides is not responsible for internal oxidation.•Cl-induced alloy degradation accelerates the internal oxidation process.