Project Description

Aluminum surface oxide film

How does the thickness of the oxide film on the surface of aluminum affect the surface color

Aluminum is a crucial industrial material, when exposed to the atmosphere, aluminum metal readily forms an oxide film that covers its surface. The generation and control of the oxide film have become an important research area in aluminum processing since the thickness of the oxide film can enhance the corrosion resistance, adjust the appearance color, and improve the gloss of aluminum.

Regarding the effect of oxide film thickness on the surface color of aluminum, typically, when the thickness of the oxide film on the aluminum surface is small, the reflection, refraction, and interference effects of light are weak. A large amount of light penetrates the oxide film and reflects back, resulting in a light or bright color on the aluminum surface, such as silver-gray.

When adjusting the appearance color of aluminum by controlling the thickness of the oxide film, environmental factors, processing techniques, and required application performance should also be considered. Besides affecting surface color, the oxide film can also enhance the hardness, corrosion resistance, and mechanical properties of aluminum, thus improving its overall utilization efficiency.

As the thickness of the oxide film increases, the reflection, refraction, and interference effects of light between aluminum surface and light also increase. The increase in oxide film thickness leads to a complex phase relationship between the transmitted light through the oxide film and the aluminum surface, resulting in deeper colors on the surface of aluminum. This is because some light is absorbed, while others are reflected, leading to a decrease in the intensity of light within a specific wavelength range.

Here is a table showing the correlation between oxide film thickness and aluminum surface colors:

Oxide Film Thickness (nm)                              Color
< 5                                                                    Light gray or silver-white
5 – 15                                                               Transparent
16 – 25                                                             Metallic luster
26 – 50                                                             Light golden yellow
51 – 100                                                           Light orange-yellow
101 – 200                                                        Medium brown
201 – 350                                                        Dark brown
350                                                                    Black

It should be noted that this table is only for reference and is influenced by various factors such as environmental conditions, processing technology, and equipment differences in practical applications.