Which metals are most compatible with arc anodizing?

Primary Metals for Arc Anodizing: Aluminum, Magnesium, and Titanium

Arc Anodizing is specifically designed for valve metals—those that form a stable, protective oxide layer. The most commercially significant and compatible metals are, in order of prevalence:

1. Aluminum and Its Alloys: This is the most common and industrially relevant metal for the process. The compatibility, however, is highly dependent on the specific alloy. The best results are achieved with alloys containing lower percentages of copper and silicon. For die casting, A360 is the preferred choice, while wrought alloys like 6061 (A96061) and 5052 are excellent for machined components. High-silicon alloys like A380 can be processed but yield a darker, less uniform coating with potentially reduced corrosion resistance.

2. Magnesium Alloys: Arc Anodizing is a highly effective treatment for magnesium, creating a hard, wear-resistant, and corrosion-resistant ceramic coating. This is critical for protecting this lightweight but highly reactive metal, often used in aerospace and automotive applications.

3. Titanium and Its Alloys: The process is also applicable to titanium, where it creates a very hard, durable oxide layer that enhances wear resistance and can be used to develop integral colors for medical and consumer goods without dyes.

Alloy Compatibility and Selection Criteria

The core principle is that the base metal must oxidize to form a stable, continuous ceramic layer. The presence of certain alloying elements directly impacts the coating's quality:

• Compatible Elements: Magnesium, Silicon (in moderate amounts), and Manganese generally support the formation of a good oxide layer when part of an aluminum alloy.

• Detrimental Elements: High levels of Copper and Iron are the most problematic. Copper-rich phases oxidize differently, creating weak spots in the coating that severely compromise corrosion protection. This makes many common high-strength alloys (e.g., 2024) poor candidates for protective arc anodizing.

Therefore, selecting the right Die Cast Aluminum Alloy is a fundamental engineering decision made during our die castings Design service phase.

Incompatible Metals and Materials

It is crucial to understand that most other common engineering metals are not compatible with arc anodizing:

• Zinc Alloys (e.g., Zamak): These cannot be anodized in this manner. They are typically protected with electroplating or powder coating.

• Copper, Brass, and Bronze: These metals do not form a suitable anodic oxide layer and require other surface treatments.

• Steels (including Stainless): Arc anodizing is an electrochemical process for non-ferrous metals. Steel components undergo entirely different processes like powder coating or plating for corrosion protection.