MIL DTL 5541 Chemical Conversion Coatings on Aluminum and Aluminum Alloys

EUROLAB laboratory provides testing and compliance services within the scope of MIL DTL 5541 standard. The MIL DTL 5541 standard applies to chemical conversion coatings formed by the reaction of chemical conversion materials on the surfaces of aluminum and aluminum alloys. This specification has been approved for use by all departments and agencies of the United States Department of Defense (DoD). Although specially prepared for DoD applications, the standard is also used in many commercial applications.

Chromate Conversion coatings have been used for over 50 years as a treatment to coated or fabricated surfaces to increase corrosion resistance and provide a good base for subsequent paint application. Chromate aluminum coatings are an inexpensive solution to prevent aluminum from oxidizing. They make excellent primers for painting and can be used alone as corrosion resistant metal surface coatings. Although primarily used for military/defense and aerospace applications, customers in all industries can benefit from chemical film coatings on their parts and components.

The MIL-DTL-5541 specification includes chemical conversion coatings that form protective coatings through chemical reaction with aluminum and aluminum alloy; These coatings cover the following types and classes:

Hexavalent Chromium Type

The type in this specification refers to chemical conversion coatings with or without hexavalent chromium as a constituent of the chemical.

• Type 1: Considers compositions containing hexavalent chromium. This film typically appears golden or brown in color, but in some cases may optionally be specified as colorless (No color is defined as "clear").
  
  
• Type 2: Handles compositions that do not contain hexavalent chromium. This film typically appears to have no color (No color is defined as "clear").

Corrosion Protection Class

The grade in this specification refers to the amount of corrosion protection in a given chemical conversion coating.

• Class 1A: Provides maximum protection against corrosion, whether painted or unpainted. This is a relatively thick coating used as a finishing touch or pre-treatment for paint or powder coating.
• Class 3: Provides corrosion protection where low electrical resistance is required. This is a thin coating that provides low contact resistance and the coating weight is as low as corrosion resistance. There may be some advantages to using this thinner film in bonding applications.

Chemical conversion coatings are RoHS compliant and designed for use on non-anodized aluminum and aluminum alloy surfaces. They are used in the repair of anodized coatings on aluminum. They are defined as a post-treatment to ion vapor deposition (IVD) aluminum used in many military platforms as an alternative to cadmium or a galvanic corrosion inhibitor.

Type I and II conversion coatings provide corrosion protection on unpainted items and also improve the adhesion of paint coating systems on aluminum and aluminum alloys. The conversion coatings covered by this specification exceed most commercially available products.

EUROLAB also provides MIL PRF 23377K testing services within the scope of other military testing services. Thanks to these services, businesses receive more effective, high-performance and quality testing services and provide safe, fast and uninterrupted service to their customers. Do not forget to contact EUROLAB for testing and certification services.