Can zinc or copper alloys be treated with arc anodizing?

Fundamental Incompatibility of Zinc and Copper with Arc Anodizing

No, neither zinc nor copper alloys can be effectively treated with Arc Anodizing. This process is specifically designed for "valve metals" such as aluminum, magnesium, and titanium, which form a stable, dense, and adherent oxide layer that integrates with the substrate. The electrochemical behavior of zinc and copper prevents the formation of such a protective ceramic coating.

Why Zinc Alloys Are Not Compatible

Zinc alloys, including the various Zamak specifications used in Zinc Die Casting, react differently. The oxide layer formed on zinc is porous, non-uniform, and mechanically weak. It does not offer the same wear or corrosion resistance as the alumina ceramic created on aluminum. When subjected to the high voltages of arc anodizing, the process would likely result in a non-functional, powdery, or poorly adhered coating that fails to protect the component.

Why Copper Alloys Are Not Compatible

Similarly, copper and its alloys, such as the brasses and bronzes used in Copper Die Casting, form oxide layers (e.g., CuO, Cu₂O) that are brittle, non-protective, and prone to spalling. These oxides do not build up into a thick, hard, integrated layer. The process would be ineffective and could detrimentally affect the part's surface finish and dimensions.

Recommended Surface Treatments for Zinc and Copper

For zinc and copper alloys, entirely different surface finishing technologies are required to achieve corrosion resistance and aesthetic appeal:

• For Zinc Alloys: The standard and highly effective process is electroplating, most commonly with chromium, nickel, or brass, often followed by a clear chromate conversion coating to enhance corrosion resistance. Powder Coating is also an excellent option for a durable, colored finish.

• For Copper Alloys: While often left with their natural patina, these alloys can be protected with clear lacquers to prevent tarnishing. They can also be successfully treated with Powder Coating or, in some cases, plating.

Selecting the correct metal and its corresponding surface treatment is a critical function of our die castings Design service to ensure the final part meets all performance and durability requirements.