CAO: Chromic anodic oxidation

The BF5 process is covered by a patent and a trademark registered by SGI; it is a chromic anodizing process which is characterized by its simplicity and reliability of use.


Electrolytic conversion treatment applicable on aluminium alloys; its characteristics are as follows:

  • It forms a low thickness oxide film (2 to 7 μm), useful in the case of parts with tolerances, which has the advantage of being flexible and presenting better slip properties than oxide layers performed in a sulphuric medium.
  • Chromic acid does not attack the aluminium nor the alumina; this eliminates any danger in the event of retention on moulded parts or assemblies.
  • The oxide layer reproduces the structure of the metal and in so doing the history of the part. Hence it can be used to establish a check on material soundness..
  • It provides high corrosion resistance (750 hours in neutral salt spray, ISO 9227).
  • It enables good adhesion of paint systems.


These chromic anodizing lines satisfy aeronautical specifications perfectly and are certified by most customers: AIRBUS France, Alenia, Boeing helicopters, British Aerospace, CASA, Dassault Aviation, Dornier, Fabrique Federale d’Emmen, Gamesa, SAAB, SABCA, SNECMA, SONACA, Pratt & Whitney (Canada), etc.

Common uses

BF5 chromic anodizing is used for primary parts constituting aircraft fuselages and in precision engineering. It is also useful as temporary protection and receipt inspection of plate intended for the aeronautical industry. Finally, it can create savings in the event of subsequent hard anodizing.

New development.... Class III sealing

A new sealing process has been developed and patented in collaboration with Dassault Aviation. This process provides both high corrosion resistance of the anodizing and optimum adhesion of the paint system.