Cranston
Cranston
401.943.9900 Mon - Fri 08:00 - 4:30 1425 Cranston St Cranston, RI 02920
Cranston
Cranston
401.943.9900 Mon - Fri 08:00 - 4:30 1425 Cranston St Cranston, RI 02920
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ISO 9001:2015
Certified
AS9100:2016
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MIL-DTL-5541 Chem Film: Type I and Type II, Class 1A and Class 3

Home » Technical Specifications » MIL-DTL-5541 Chem Film: Type I and Type II, Class 1A and Class 3

DiFruscia Industries applies chromate conversion coating (chem film) to aluminum to MIL-DTL-5541 (formerly MIL-C-5541), Type I and Type II, Class 1A and Class 3, under Nadcap accreditation for chemical processing (AC7108) and an AS9100D quality system.

What chem film does

Chem film converts the surface of aluminum into a thin protective film. It protects bare aluminum from corrosion, gives primer and paint a surface to grip, and keeps the surface electrically conductive for grounding and EMI shielding. See Aluminum Conversion Coating.

Types and classes

Callout What it means Notes
Type I Hexavalent chromate Yellow to tan iridescent, varies by alloy. Not RoHS compliant.
Type II Non-hexavalent (for example TCP-HP trivalent) Clear to faint blue or tan. RoHS compliant.
Class 1A Maximum corrosion protection, painted or unpainted Not intended for low electrical resistance
Class 3 Corrosion protection with low electrical contact resistance Grounding points, electronics enclosures, EMI shielding

What to expect

  • Virtually no dimensional change. Film thickness is 0.00001″–0.00003″, so close-tolerance features are unaffected.
  • Thin film. Not as hard as anodize, but it holds up to normal handling and non-cutting abrasion.
  • Appearance varies with type and alloy. Castings usually look lighter than wrought alloys.
  • Galvanic protection. The film slows galvanic action between dissimilar metals. For the most protection, treat both mating parts.

How to call it out on the drawing

  • Name the type and class, for example MIL-DTL-5541, Type II, Class 3.
  • Choose Type II where RoHS, ELV or WEEE apply or hexavalent chromium is not allowed.
  • Tell us about heat. Heat can reduce bare corrosion resistance, so tell DFI if parts will be baked or heat treated after coating.
  • Painting over it? Chem film is the usual base for MIL-PRF-23377 primer and MIL-PRF-85285 topcoat.

How the job runs

  1. Clean: an inhibited alkaline cleaner removes oils and soils.
  2. Deoxidize: an acid deoxidizer removes smut and oxides.
  3. Convert: a room-temperature conversion bath forms the film.
  4. Rinse and dry: a low-temperature dry protects the film.

Get a quote or a data sheet

Send the drawing and the spec callout to rfq@difruscia.com, or use Request a Quote. DFI’s technical data sheet for this process is available on request from Technical Specifications. Questions: 401.943.9900 or support@difruscia.com.

Values shown are typical results for reference only and are not specification limits. Results vary with alloy, part geometry, thickness and process parameters. Contact DFI to confirm the requirements for your application.