Tracking

Finishing Services

Alodine

Chromate Conversion Coating

At a glance

Applicable Materials

Colors

Clear, Gold

Applications

Tools, hardware, electrical systems

Thickness

0.25-1.0 µm0.00001-0.00004 inches

About the Process

Chromate conversion coating, more commonly known as chem film or by its brand name Alodine, is a chemical coating that passivates and protects aluminum from corrosion. It is also used as a base layer before priming and painting parts. The standard most commonly specified in engineering applications is MIL-DTL-5541F, which refers specifically to coating of aluminum alloys.

This protective layer is much thinner than an anodizing layer, and while both are created by immersion of parts into a bath, Alodine is a simple chemical coating and the process does not use electrical current.

Alodine is a slightly cheaper process than anodizing, though it is more prone to scratches, wear, and cosmetic damage. The most common color of the coating is an iridescent greenish-gold, and thus it may also be used for cosmetic purposes. However, this color comes from hexavalent chromium, which is toxic, so for RoHS compliance needs, there are clear versions of the coating available as well.

Design considerations

  • Plugging threaded/reamed holes not required unless tolerances are very tight, as thickness change is minimal.
  • Alodine coatings offer a much greater electrical conductivity than bare aluminum
  • Media Blast parts before Alodine to create a more consistent coating that hides small machine marks

YOU MIGHT ALSO BE INTERESTED IN

CNC Robotics: Technologies & Key Trends Explained

CNC robotics combines the accuracy and programmability of CNC machines with the versatility and flexibility of robots. Learn more about it here.

Learn More

New Urethane Casting Options Mean Greater Speed and Uncompromised Quality

Need show models and low-volume proof of concept for 10 or more parts? Urethane casting is a great option. Fictiv has supported Urethane Casting for many years, but we’ve just expanded the program to make it even better. We now offer more ways to make Urethane Casting with Fictiv easier than ever. This expansion includes: […]

Learn More