xiehe model

Surface preparation is the final stage of the manufacturing process. There are a range of methods applicable at this stage, one of the well-known methods being anodizing. This is because it produces parts that are both aesthetically pleasing and durable. There are two key parts every manufacturer must pay attention to when anodizing parts. The first is how to color aluminum and use the right aluminum color. Anodizing colors are key as they convey a great deal of information about the characteristics of the final product. Here's an in-depth look at anodizing and how it can be used to color aluminum parts.

What is the basic principle of anodizing process?

To correctly understand the various colors and matching techniques of anodized aluminum, one must first master the principles of the techniques. Aluminum anodizing is an electrochemical process that needs to be coated with a wear-resistant oxide layer after cnc machining. This improves the quality and aesthetics of the product. Enhanced features include increased durability and corrosion resistance. During the reaction, the aluminum part acts as the anode and the inert part acts as the cathode. The reaction takes place in an acidic electrolyte.

What are the types of anodizing process?

There are three main anodizing processes. Each differs in the strength of the coating. They vary by electrolyte, electrodes and energy used in the process.

Type 1 anodized anodized aluminum parts

We call this the light anodizing process. It requires the use of aluminum alloy parts as the anode and chromic acid as the electrolyte. Positive particles are produced at the anode when current passes through the electrolyte. This creates tiny grooves in the surface, which then oxidize to form an oxide layer. The parts we make with this process have better heat and corrosion resistance than ordinary aluminum parts.

Type 2 anodized

This process uses sulfuric acid instead of chromic acid as the electrolyte. Sulfuric acid is more potent and therefore has a better injection of positive aluminum particles than the first process. Therefore, it has deeper microscopic grooves and a thicker oxide layer. These properties contribute to better paint retention.

Type 3 anodized

This is the ideal anodizing process for the manufacture of heavy aluminum alloy parts. Unlike other forms of anodizing, it uses high voltage and strong acid.

Color of Anodized Aluminum Alloy Parts

The color of anodizing is different from that of other methods such as paint and powder coating. Because anodizing involves a range of variables, the task of achieving color consistency is even more difficult. The anodizing process is generally open to all colors within the rainbow spectrum. However, their use depends on many factors such as grade, size and finish. At Skyworth, we follow the following steps when using the anodizing process.

Cleaning and etching of aluminum

This procedure begins by cleaning the aluminum parts with detergent in a rinse tank. Afterwards, we etch the parts to give them a polished and glossy finish. Etching helps us remove trace metals that can cause errors in the process.

Endowed with film

We anodize after cleaning the aluminum parts. We can choose from the processes mentioned earlier. Another thing to look out for includes the type of metal alloy. This determines the size and shape of the hole. At the same time, solution concentration, tank temperature and voltage control determine the pore depth.

Add color

There are four methods of adding color to anodized aluminum alloy parts. The first is electrolytic coloring, which involves immersing the part in a solution of metal salts. Once we fill in the pores, it will provide enough coating strength to resist UV rays. However, there is no limit. Anodized color we can use. The most common colors are bronze and black. The second method is dip-dyeing. It requires putting parts into a dye jar.

After filling the pores with the dye, we boil the surface in deionized water to end the reaction. Dip dyeing allows us to use a large number of color variants. However, it does not provide excellent UV resistance.

The third method is overall coloring. It combines coloring and anodizing to color aluminum components in black and bronze. Last but not least, we have interference coloring, which enlarges the pore structure. Deposition of the metal results in lightfast colors ranging from green, blue, yellow to red. Colors are produced by optical interference effects rather than light scattering effects.

Sealed

This is the final stage of anodizing where we trap the dye molecules in the pores. Sealing aids prevent the uptake of unwanted molecules in the pores. We seal in hot water at 93 degrees Celsius. The formation of hydrated alumina crystals helps to seal the pores. Also, we end up depositing metal salts inside the pores.

How to color match?

Unlike painting, color matching is subtractive rather than additive. In general, the color that any material emits is the color that light reflects off of it. This is what happens with anodized color, only a small amount is added. The anodized coating does not reflect light, but transmits it to the aluminum of the base surface. The base metal then reflects it back into the film and to the exterior. Therefore, the anodized layer acts as a filter rather than a reflector which is crucial in color matching, making color matching anodized aluminum parts very onerous. If you have any other questions, please do not hesitate to contact us.