How to Do Color Matching for Anodized Aluminum Parts
Applying the surface finish is the final stage of the manufacturing process. There is an array of applicable methods at this stage, with one of the reputable ones being anodization. This is since it leads to the production of an aesthetically pleasing part that is also quite durable. There are two key parts that every manufacturer must be aware of when anodizing parts. The first one is how to color aluminum as well as the appropriate aluminum colors to use. Anodizing colors are key since they convey a great deal about the features of the end product. Here is an in-depth insight into anodizing as well as how to color aluminum parts using anodizing.
What’re The Basics of the Anodizing Process?
To properly comprehend the various anodized aluminum colors and matching processes we must first grasp the principle of the process. Aluminum anodizing is an electrochemical process that entails coating aluminum parts with a wear-resistant oxide layer. This improves the product’s quality and beauty. Among the enhanced features include enhanced durability and resistance to corrosion. During the reaction, the aluminum part acts as the anode with an inert part as the cathode. The reaction takes part in an acidic electrolyte.
What Are the Types of Anodizing Process?
There are three main anodizing processes. Each differs in terms of the coating intensity. They vary due to the electrolytes, electrodes, and energy in use during the process.
Type 1 Anodizing
We refer to this as the light type anodizing process. It entails the use of the aluminum part as the anode with chromic acid as the electrolyte. Positive particles arise from the anode after passing an electric current through the electrolyte. This results in microscopic grooves on the surface which then oxidize to form an oxide layer. The parts we make from this process have a better heat and corrosion resistance than normal aluminum parts.
Type 2 Anodizing
This process replaces chromic acid with sulfuric acid as the electrolyte. The sulfuric acid is more potent and thus has a better ejection of positive aluminum particles than the first process. It thus has a deeper microscopic groove with a thicker oxide layer. These features help in the better retention of paint.
Type 3 Anodizing
It is the ideal anodizing process for creating heavy aluminum parts. Unlike the other forms of anodizing, it uses a high voltage as well as a strong acid.
The Colors For Anodized Aluminum Parts
Anodizing colors differ from colors of other methods like paint and powder coat. It is more tasking to achieve color consistency since anodizing involves an array of variables. The anodizing process is usually open to all colors within the rainbow spectrum. Their use, however, depends on many factors like grade, size, and finish. At Creatingway, we follow the following steps when using the anodizing process.
Cleaning Etching of the Aluminum
This step starts by cleaning aluminum parts using detergent in rinsing tanks. Afterward, we etch the part to impart a polished and shiny surface. The etching helps us to remove trace amounts of metals that may cause errors during the process.
Imparting the film layer
We carry out anodizing after cleaning the aluminum part. We can choose from the previously mentioned processes. One other thing to look out for includes the type of metal alloy. This determines the size and shape of the pores. Meanwhile, the solution concentration, tank temperature, and voltage control determine pore depth.
There are four ways of adding anodized aluminum colors. The first one is electrolytic coloring which involves the immersion of the part in a solution of metal salts. Once we fill the pores it provides enough coating strength to resist UV rays. However, there is a limit to the no. Of anodizing colors, we can use. The most common colors are bronze and black. The second method is dip coloring. It entails placing the part in a tank of dye. After filling the pores with dye, we boil the surface in de-ionized water to end the reaction. Dip coloring allows us to use plenty of color variants. It, however, does not offer excellent UV resistance.
The third method is integral coloring. It combines coloring and anodizing to color aluminum parts in black and bronze shades. Last but not least, we have interference coloring which enlarges the pore structure. The deposition of metals results in light-fast colors varying from green, blue, yellow to red. The colors result from optical interference effects rather than light scattering effects.
It is the final stage of anodization, where we trap dye molecules in the pores. Sealing aids to prevent the absorption of undesired molecules in the pores. We achieve sealing in hot water at a temperature of 93 degrees Celsius. The formation of hydrated aluminum oxide crystals aids to seal the pores. In addition, we end up depositing metal salts within the pores.
How To Do Color Matching?
Unlike painting, color matching is subtractive and not additive. Normally, the color any material exudes is what light reflects on it. This is what happens in anodizing color with only a minor addition. Instead of reflecting the light, the anodized film transmits light to the aluminum at the base surface. Afterward, the base metal reflects it to the film and outside. The anodized layer thus acts as a filter rather than a reflector which is vital in color matching. This makes color-matching anodized aluminum parts quite tasking. Contact us now if you have any other inquiries.
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