Which materials are the most expensive to arc-anodize?

Material and Process Factors Driving Arc-Anodizing Costs

The cost of arc-anodizing is less about the base price of the raw metal and more about the process efficiency, energy consumption, and technical challenges associated with specific materials. While aluminum is the most common substrate, the expense can vary significantly, with certain non-aluminum metals and specific aluminum alloys commanding a higher price.

Most Expensive Materials for Arc-Anodizing

The highest costs are typically associated with materials that are difficult to process or require specialized, expensive electrolytes.

1. Titanium and Its Alloys: While compatible, titanium is often the most expensive substrate to arc-anodize. The process can require specialized electrolyte chemistries (e.g., phosphate-based instead of silicate-based) and precise control of electrical parameters to achieve specific colors or functional properties. Furthermore, the value of the titanium component itself is high, and any risk associated with processing a costly part is taken into account. The primary drivers are the specialized chemistry and lower process throughput compared to aluminum.

2. Magnesium Alloys: Arc-anodizing magnesium is crucial for corrosion protection but presents unique challenges. The process often requires more complex, hazardous, and expensive electrolyte formulations to handle magnesium's high reactivity. The power supply regime may also need to be tailored to prevent burning the substrate, potentially leading to longer cycle times and lower batch yields.

3. Challenging Aluminum Alloys: Among aluminum substrates, high-copper alloys (e.g., 2024) or high-silicon die-casting alloys like A380 are more expensive to process. Achieving a satisfactory, protective coating on these materials requires longer processing times and higher energy input to overcome the disruptive effects of copper or silicon, leading to a higher cost per part. Using a more compatible but less castable alloy like A360 can involve a higher initial material cost but often results in a more efficient and reliable anodizing process.

Key Cost Drivers Beyond Base Material

The final price is a function of several interacting factors:

• Energy Consumption: Arc-anodizing is inherently energy-intensive. Any factor that increases process time (like a difficult alloy or a very thick coating specification) multiplies the electricity cost.

• Part Geometry & Surface Area: Complex parts with a high surface-area-to-volume ratio cost more due to higher energy and electrolyte consumption, and the potential need for specialized fixturing.

• Coating Specification: A requirement for an exceptionally thick coating (e.g., >75µm) or one that must pass stringent quality testing like 1000-hour salt spray will significantly increase cost.