Gleco offers RoHS-compliant MIL-DTL-5541 chemical conversion coating for companies seeking cost-effective corrosion protection for aluminum parts that will eventually be powder coated or painted.
Chemical conversion coatings (also known as Chem Film treatments) can be clear or colored, applied pre-process, post-process, or as a finishing process depending on preference, part application, and operating environment. It creates a surface for the powder coat or paints to adhere to throughout the curing process. Without chemical conversion coating, paint won’t bond to the surface mechanically, risking delamination or flaking.
Chemical conversion coatings are opposite anodizing in the following ways:
- Chemical conversion coating preserves electric conductivity, while anodizing does not.
- Anodizing requires electricity, but chemical conversion coating does not.
- Chemical conversion coating is more cost-effective.
Chem Conversion Type I – Hexavalent Yellow Chromate Coating
Electroplating delivers specific benefits to the metals it coats, from rust protection to corrosion-resistance and lubricity to conductivity. Electroplated products can also be finished through chemical post-treatment processes to meet additional application requirements. One of the more popular of these options is yellow chromate coating. Gleco provides this spec option for companies seeking an aesthetic coating with exceptional wear-resistance in high-salt environments.
Hexavalent Yellow Chromate
Hexavalent yellow chromate produces an iridescent gold/yellow finish. It exhibits between 72 and 144 hours of salt spray corrosion resistance (between 72 and 144 hours). In addition, because hexavalent chromate plating is thick and self-healing, it maintains corrosion resistance when scratched.
One special consideration regarding hexavalent yellow chromate must be made; It is not Restriction of Hazardous Substances (RoHS) compliant.
Benefits of Yellow Chromate Coating
Yellow chromate coating offers several unique benefits over other finish colors. Specifically, it is:
- More cost-effective
- More corrosion-resistant
- Improved durability
It is also used to reduce the reactivity of these metals with water, serve as a primer for the adherence of paints and adhesives, and improve electrical conductivity.
Yellow Chromate Coating Applications
Yellow chromate coating is used in several industries, including the automotive, electronics, tool, and consumer products industries, to protect:
- Electrical contactors
- Hardware adapters
- Heat sink
- Mechanical components
- Aircraft parts
Chem Conversion Type II – Trivalent Clear Chromate Coating
Gleco Plating offers MIL-DTL-5541 Clear Chem Film coating for companies seeking additional corrosion protection for their aluminum and metal parts and products.
MIL-DTL-5541 Type 1 was the customary process for chem film coating for years. However, hexavalent chromium, the primary chemical involved, is now tightly regulated as environmentally hazardous by the EPA and as carcinogenic by OSHA. For this reason, Gleco does not offer Type 1 Clear Chem Film Coating.
Instead, we offer MIL-DTL-5541 Type 2, the newer, more acceptable process that uses trivalent chromium (for this reason, the process is sometimes known as hex-free chromating).
We apply our hex-free coating by dipping the component to brighten the surface material. Because the layer of transformed metal is very thin, this process will not fundamentally change the part’s dimensions.
Benefits of Clear Coatings
The primary benefits of a clear coating are protection against corrosion and potential oxidation of the aluminum surface.
Trivalent Clear Coating Applications
Clear chemfilm coatings are used by the automotive, aerospace, and manufacturing industries (among others) to provide corrosion-resistance for:
- Heat sinks
- Automotive wheels
- Aluminum hardware
- Aerospace parts
- Defense armaments
- Computer cabinetry
Chemical Conversions By Class
Following are a few typical uses of chemical conversion coatings by class:
- Class 1A chemical conversion coatings are used on tubing and component structures where only exterior protection is required to prevent corrosion and improve paint adhesion. These coatings are typically thicker and darker in appearance than Class 3 chemical conversion coats.
- Class 3 chemical conversion coatings are used on circuit boards and connectors in lower-resistance electrical and electronic applications to provide a corrosion-resistant film. These coatings are typically thinner and lighter in appearance than Class 1 chemical conversion coats (to ensure low electrical resistance).