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Conversion Coating & Chem Film

Chem Film Services for Advanced Manufacturers

Conversion Coatings - often referred to as Chem Film or Chromate - are a category of surface treatments that can bring a variety of benefits, including surface corrosion protection even at low electrical resistances, increased paint adhesion capability, and decorative purposes.

Chem Films are created via electrochemical or chemical reaction of metals, where the chosen treatment superficially converts the material into a thin adhering coating of an insoluble compound.

At AOTCO, we offer both Hexavalent Chem-film and, RoHS Hex-Free Chem-film coatings

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Benefits

Conversion Coatings are uniquely flexible in that, depending on your final surface finishing goals, Chem Film treatments can be appropriate for pre-process, post-process and as a finishing process itself.

Frequently Asked Questions

Conversion Coating Specs AOTCO Provides:
  • ASTM B449 [Nadcap Accredited]
  • MIL-C-5541 [Nadcap Accredited]
  • MIL-DTL-5541 [Nadcap Accredited, ROHS Compliant]
  • MIL-DTL-5541 Type II [Nadcap Accredited]
  • MIL-DTL-81706 [Nadcap Accredited, ROHS Compliant]
  • MIL-C-13924
  • MIL-DTL-13924
Types of Conversion Coatings

Hexavalent Chem Film (“Type I”)

  • The traditional process used in creating a Conversion Coating
  • Contains hexavalent chromium
  • Typical color specification (class) for traditional hexavalent chromate ranges from “clear” to “gold”

ROHS Chem Film (“Type II”)

  • A more environmentally friendly option
  • Does not contain Lead, Cadmium, Hexavalent Chromium, Mercury or PBB/PBDE compounds
  • ROHS chem-film is always “clear” in color, but longer exposure to the solution can make the coat more visibly discernible in daylight

Note: If no type is specified, Type I will be used.

Classes of Conversion Coatings

Class 1A

  • For maximum protection against corrosion on unpainted items, and increased adhesion on painted items
  • These coatings will generally be thicker and darker in appearance
  • Class 1A is commonly used on tanks, tubing, and component structures where only exterior protection is required

Class 3

  • For protection against corrosion where low electrical resistance is required
  • These films are generally lighter in appearance, and of a thinner thickness in order to maintain low electrical resistance
  • Class 3 is frequently used in electrical components such as circuit boards or connectors.
Metals Suited to Chem Film Treatments
  • Steel Alloys (black oxide is a common treatment)
  • Aluminum
  • Beryllium
  • Magnesium
  • Zinc
“Alodine” (Chem Film) vs. Anodize
  • Alodine is a trade name for chemical conversion coating of aluminum
  • Because the name sounds like anodize, there is sometimes confusion between the two coatings
  • While both are coatings created by immersion, the Chem Film treatment is much thinner than Anodizing and is created without use of electrical current
  • Unlike anodizing, Chem Films provide a conductive coating and are sometimes used in conjunction with masking in anodized parts
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Looking for Specs?

Learn more about the specifications AOTCO offers, including NADCAP-accredited and RoHS-compliant ones.
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