SurTec 650 TCP

Colloquially also called ChrmitAL TCP.

Surtec 650 TCP (Trivalent Chromium Passivation) was developed by Naviair in collaboration with the United States Department of Defence.

Surtec 650 TCP is an alternative to the chromium (VI)-containing plating for aluminum components – colloquially known under the trade name Aludine.

The Surtec 650 TCP is a chemical surface treatment/conversion coating which maintains the surface and adds new chemical and technical features to it.


  • It is RoHS convertible
  • Maintains the conductivity of the surface
  • Improves corrosion protection
  • Improves the adherence ability of the aluminum for organic coatings such as paint, lacquer, adhesive, etc.
  • Heat-resistant op to 100°C with a minimal loss of corrosion resistance.
  • Low contact resistance; < 0,8 mOhm/cm2
  • Binds itself chemically to the aluminum and creates a thin coating on its surface


  • Tools, office machinery, electronics, etc.

Structure and appearance after treatment

  • The metal look is maintained.
  • The chrome plating is light to dark yellow.
  • The look of the surface depends on the pre-treatment chosen.
  • Surtec 650 TCP has a transparent look with a faint tint of blue/green.


  • The weight is 0,08 g/m2 (0,05 to 0,20 g/m2)


  • An indicator colour cannot be added to the surface treatment.
  • The quality of the surface treatment can only be demonstrated by exposing a test piece to a destructive spray.


  • Both aluminum, alloys, and castings can be surface treated with SurTec 650 TCP.

TCP meets the requirement for Mill 5541 and is documented on the QPL list.

As SurTec 650 TCP is applied on the aluminum by submerging in baths, the materials must be mounted on a suspension tool before the treatment. For this reason, it is important, already during the construction phase, to make sure the materials are constructed so they can be mounted sufficiently.

HAI’s laboratory has a new A-scott S 450 salt spray chamber at its disposal. This is one of the most modern salt spray testers for corrosion testing in the world.

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