Chromate

What is Chromate Conversion Coating?
Chromate conversion coating—also known as Chem-Film, Iridite, or Alodine—is a chemical process used to protect aluminum and other non-ferrous metals from corrosion. It creates a thin, gelatinous barrier on the surface that passivates the metal, slows oxidation, and enhances paint or primer adhesion. Over time, the coating hardens and becomes hydrophobic, providing increased durability while maintaining the metal’s electrical conductivity. It is commonly applied to aluminum alloys, zinc die castings, and aluminum die cast parts.

The Process
This conversion coating chemically reacts with the surface of the metal, forming a uniform layer that is typically around 0.00001″ thick. While the coating may appear clear, iridescent yellow, or light brown—depending on the material and process—it can be difficult to inspect visually, as small breaks in the film are not always visible. 

Chromate coatings are classified according to MIL-DTL-5541F standards:

• Type I contains hexavalent chromium
• Type II is hexavalent-free and RoHS compliant.

Classes of Chromate Coating

• Class 1A coatings are intended to provide maximum corrosion protection on aluminum and also serve as a primer base for paint or powder coating.
• Class 3 coatings offer moderate corrosion resistance while maintaining electrical conductivity, making them ideal for electronic components or parts that require grounding. This class is also used before anodizing, particularly when masking operations are needed.

Benefits of Chromate Conversion Coating

• Provides corrosion protection without adding significant thickness
• Improves paint and primer adhesion on aluminum surfaces
• Maintains electrical conductivity
• Offers self-healing properties for minor surface damage
• Available in RoHS-compliant (Type II) formulations
• Compatible with complex parts and masking operations

Where It’s Used
Chromate conversion coatings are commonly applied in aerospace components, aluminum stampings, electronic enclosures, connectors, and die cast housings. They are especially useful in applications that require both corrosion resistance and conductivity, such as grounding or shielding in electronic systems.

[REQUEST A QUOTE TODAY]