Aluminum plates that have been coated with chemical film treatment.

Chemical Film (Chem. Film)

Chromate conversion coatings are commonly used on parts in the aircraft, electronics, and components industries, where it is often called chem film, chemical film, or the well-known brand names of Iridite® or Bonderite® (formerly known as Alodine).  It is a widely used process to protect aluminum from corrosion, and to assure good paint adhesion or preserve electrical conductivity.

Chromate conversion coating on aluminum is applied to passivate aluminum alloys to slow the formation of white corrosion. The process uses various chromium compounds which may include hexavalent (Cr6) chromium or non-hexavalent (Cr3) chromium.

The industry has developed non-hexavalent / trivalent, less toxic alternatives in order to comply with the Restriction of Hazardous Substances (RoHS) legislation.

Chem Film can be used as a primer for subsequent organic coatings. Untreated metal, especially aluminum, is difficult to paint or glue without a primer. Chem filmed parts retain their electrical conductivity to varying degrees, depending on coating thickness.

In addition to Aluminum applications, it is also used with steel, zinc, cadmium, silver, copper, titanium, tin and magnesium alloys.

The process may also be used to add color for decorative or identification purposes, usually giving a greenish yellow iridescence to white or gray metals. When applied over zinc, the protective effect of chem film can be indicated by color, from clear blueish, to yellow, gold, olive drab and black. In general, darker coatings provide a higher degree of corrosion resistance.

Chem Film Services We Offer

  • Barrel and Rack Processing
  • Trivalent RoHS compliant Chem Films

Barrel Processing provides an even, uniform coating. Parts are submerged in a plating solution and rotated slowly. Barrel processing increases defense against corrosion and offers a cost-effective solution for plating a high volume of small, sturdy parts such as nuts, bolts and fasteners, while also performing well for plating parts of differing sizes and shapes.

Rack Processing includes attaching parts to metal racks with hooks, wires or spring fingers, allowing parts to remain stationary during immersion into the plating solution. Rack processing is ideal for delicate parts not able to endure the tumbling action produced by barrel processing. Rack processing can also work well for large or complex components, plating intricate details with incredible precision. This method is favored by industries where a superior finish is crucial, such as automotive, medical and electronics.

Trivalent RoHS compliant Chem Films utilize trivalent chromate chemistry, versus hexavalent chromate chemistry.

Chem Film Benefits

  • Corrosion and Oxidation Protection
  • Highly Adhesive for Painting
  • Cost Effective
  • Does Not Interfere With Impedance
  • Appearance

 Chem Film Coating Applications

  • Industrial
  • Military applications
  • Aerospace
  • Electronics
  • Maritime
  • Medical
  • Automotive 
A black zinc metal finish is applied to fasteners.

THE DIFCO DIFFERENCE

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