This process is to seal off microscopic pores of anodic oxide film.
In this process there are pressurized steam sealing, boiling water sealing and added nickel acetate sealing, but 2 step sealing combined with added nickel acetate + boiling water is commonly used.
Cross-sections of sealed oxide film are as shown below pictures taken by electronic microscope.
- [Picture-1] Cross-section of unsealed oxide film (x70,000)
- [Picture-2] Cross-section of sealed oxide film (x150,000)