chem film

October 3, 2024

In the world of metal finishing, choosing the right surface treatment is crucial for ensuring the longevity and performance of your metal components. In this first part of our series, we will dive into the intricacies of chem film, exploring its properties, application process, and the benefits it offers. By understanding chem film, you can make informed decisions about its suitability for your specific needs and how it compares to other finishing methods.

What Is Chem Film?

Chemical film, commonly known as chem film, is a chemical process that facilitates the conversion of a metal’s surface into a protective layer through a series of chemical reactions. Unlike traditional plating methods that add a metal layer, chem film creates a protective coating by chemically interacting with the existing metal substrate. The main advantage of chem film finishes lies in their ability to inhibit further corrosion of metal surfaces, offering long-lasting protection.

Moreover, chem film treatments enhance the adhesion of organic coatings, making them an ideal pre-treatment step before applying paints or powder coatings. This improved cohesion ensures a more durable and uniform finish. In addition to corrosion resistance, chem film coatings play a crucial role in maintaining the electrical conductivity of metal surfaces, further enhancing their utility across various applications.

Types of Chem Film Coatings

Though there are various kinds of chem film coatings, they differ in the chemistry they use. The two methods most often used are type 1 and type 2 of the MIL-DTL-5541 standard, a military specification. Type 1 uses a chemical called hex chrome, known by its chemical name sodium dichromate, as it contains hexavalent chromium. Hex chrome is both hazardous to the environment and carcinogenic. Hence, the Environmental Protection Agency (EPA) and Occupational Safety and Health Administration (OSHA) require permits to use and dispose of the chemical.

Advantages of the MIL-DTL-5541 type 2 technique include:

  • Faster processing times.
  • Fewer steps in the process.
  • Room temperature processing. 

The type 2 technique uses titanium, trivalent chromium, or zirconium to replace hex chromium. Additionally, the type 2 chem film coatings technology has advanced considerably, making it safer and quicker.

As we conclude our exploration of chem film, it’s clear that this finishing technique offers numerous benefits, particularly in enhancing corrosion resistance and providing an excellent base for subsequent coatings. Whether you’re working in aerospace, automotive, or electronics, chem film stands out as a reliable choice for protecting aluminum components. Stay tuned for Part 2 of our three-part series, where we will delve into the world of anodizing.