Chemical oxidation as repairing technique to restore corrosion resistance on damaged anodized titanium

• Published in: Surface & coatings technology Vol. 364; pp. 225 - 230
• Main Authors: Prando, Davide, Nicolis, Davide, Bolzoni, Fabio, Pedeferri, MariaPia, Ormellese, Marco
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 25.04.2019; Elsevier BV
• Subjects: Anodizing; Bromides; Chemical oxidation; Corrosion effects; Corrosion potential; Corrosion resistance; Damage localization; Hydrogen peroxide; Maintenance; Organic chemistry; Oxidation; Oxidation resistance; Oxide coatings; Pitting (corrosion); Sodium hydroxide; Submerging; Surface treatment; TiO2; Titanium; Titanium oxidation; Anodizing; Chemical oxidation; Titanium oxidation; Surface treatment; TiO2
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2019.03.005

Anodized titanium shows an excellent resistance to pitting corrosion. However, it could be subject to failure in case of local removal of the oxide film due, for example, to incorrect handling during transport, installation, or use. Depending on part size and usage, an electrochemical anodizing treatment could be not feasible. In this case, localized chemical oxidation treatment could be used to recover damaged film and restore corrosion resistance. Chemical oxidation was performed on titanium by immersion in NaOH 10 M and H2O2 10 M at temperature from room to 90 °C with duration ranging between 1 h and 72 h. Potentiodynamic tests in bromides 0.5 M were used to determine the effectiveness of the treatment in relation with the one obtained with anodic oxidation. Higher bath temperature led to faster growth of the film, however it has no effect on the final corrosion resistance. Breakdown potential in bromides increased with treatment duration. The establishment of a plateau occurs at earlier stage, as temperature is increased. Titanium samples anodized and then scratched, to simulate film mechanical removal, were recovered using chemical oxidation and initial corrosion resistance was restored. The suggested treatments for in-situ recovery are 72 h of exposure to NaOH or 6 h at H2O2 at room temperature. [Display omitted] •Commercially pure titanium was chemically oxidized in NaOH and H2O2 baths.•The maximum of corrosion resistance in NaOH was achieved after 12 h at 60 °C.•H2O2 kinetic is faster: the same resistance is achieved in 6 h at room temperature.•Both treatments can restore corrosion resistance on damaged anodized titanium.