Which metals can be treated with arc anodizing?

Compatible Metals for Arc Anodizing: A Focused Substrate List

Arc Anodizing, also known as Plasma Electrolytic Oxidation (PEO), is a specialized high-voltage process that creates a ceramic coating on specific "valve metals." The range of compatible substrates is narrow but critically important for high-performance applications.

Primary Compatible Metals

The process is fundamentally designed for and most effectively applied to the following three metals and their alloys:

• Aluminum and Its Alloys: This is the most common and industrially significant substrate. The coating performance is highly dependent on the specific alloy. For optimal results, alloys with lower copper and silicon content, such as A360 for die casting or 6061 for machining, are preferred. They produce a more uniform, protective, and adherent coating compared to high-silicon alloys like A380.

• Magnesium Alloys: Arc anodizing is an exceptionally effective treatment for magnesium, providing a hard, wear-resistant, and corrosion-resistant ceramic layer that is vital for protecting this lightweight but highly reactive metal.

• Titanium and Its Alloys: The process is also highly compatible with titanium, where it creates a very durable oxide layer that enhances wear resistance and can be used to develop integral colors without dyes.

Incompatible Metals

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

• Zinc Alloys (e.g., Zamak): These cannot form a stable anodic ceramic coating via this process and 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 Steel): Arc anodizing is an electrochemical process for non-ferrous metals. Steel components undergo entirely different processes like powder coating, plating, or nitriding for surface enhancement.

Key Takeaway for Material Selection

The suitability of a metal for arc anodizing depends on its innate ability to form a stable, passivating oxide film that can be transformed into a ceramic by plasma discharges. When designing a component for this high-performance finish in our die castings Design service, the selection must be limited to aluminum, magnesium, or titanium to ensure a successful and functional outcome.