Chemical oxidation as repairing technique of damaged corrosion resistance enhanced anodic oxide film

Titanium, as other light metals, shows enhanced corrosion resistance when properly anodized. This technique was already proved effective in several aggressive environments (mainly halides) in past works. However, it could be subject to failure in case of localized removal of oxide film due, for example, to incorrect handling during transport, installation, or use. Depending on part size and usage, a new 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 10M and H2O2 10M at temperature from room to 90°C with duration ranging between 1h and 72h. Potentiodynamic tests in bromides 0.5M 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 achievable. Samples pitting potential in bromides increased with treatment duration up to the establishment of a plateau that appears at lower time as temperature is increased. Titanium sample anodized and then scratched to simulate film mechanical removal was recovered using chemical oxidation and initial corrosion resistance was restored. The suggested treatments for in-situ recovery are 72h of exposure to NaOH or 6h at H2O2 at room temperature.