Anodized Aluminum Introduction

Anodizing is an electrochemical process that thickens the oxide layer that naturally forms on the surface of aluminum. The thickness of the oxide layer grows from nanometers to micrometers, and anodizing can change the properties of aluminum products, resulting in higher corrosion resistance, coloring ability and consistent appearance. There are several types of anodizing: chromic acid anodizing (type I), sulfuric acid anodizing (type II), and hard coat anodizing (type III). For the purposes of this series of articles, we will focus on sulfuric acid anodizing (SAA), also known as Type II anodizing, as it is the most common method used for 70% of all anodized products.

Anodizing offers many benefits to aluminum, increasing the quality and versatility of the product. This includes improved durability, outstanding aesthetics and sustainability.

The thickened oxide layer is almost as hard as diamond, protecting the relatively soft aluminum material underneath. Since the anodic coating essentially converts the aluminum surface to aluminum oxide, it forms a chemical bond with the metal. Therefore, the surface layer is less likely to chip or peel. Most of the colors contained in the porous layer will have a high level of UV and weather resistance if treated properly.

Anodized layers are generally considered to have an attractive appearance. By itself, anodized surfaces are clear or "glass-like", giving your product a high-quality finish without the need for coloring. However, anodized surfaces can also add a range of beautiful colors.

Another benefit of anodizing is its metallic look that accentuates the aluminum itself. In contrast, painted surfaces can create a more plastic-like appearance.

Anodizing is the most environmentally friendly surface treatment process - especially when using sulfuric acid anodizing and chrome-free colors. By protecting the aluminum surface and preventing corrosion, anodizing extends the life of aluminum products, thereby reducing their life cycle costs. Additionally, anodized products can be recycled directly, unlike painted products, which must go through a pretreatment process to remove paint and harmful chemicals.

The anodizing process consists of several process steps, which can be divided into three stages: pre-treatment, anodization, and post-treatment.