Abstract:Corrosion studies of a commercially pure titanium in phosphoric acid solutions at 250 ℃ were carried out by immersion test in an autoclave. At lower phosphoric acid concentration (0.1 mol/L), the corrosion was mild. At higher phosphoric concentration (1.0 mol/L) corrosion, a 25 µm-thick white corrosion products layer was formed on the samples after 24 h immersion. XRD analysis shows that the white layer consists mainly of titanium oxide phosphate hydrate (π-Ti₂O(PO₄)₂∙2H₂O). The corrosion product shows the morphology of fiber bundles. A thermodynamic analysis of the formation of the corrosion product is presented.

Key words: titanium; corrosion; phosphoric acid; high temperature and high pressure; corrosion mechanism