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Color anodizing is the process of anodizing a metal and then adding a dye to it before the metal is sealed. To anodize, the metal is placed in an electrolyte vat and electricity is run through the electrolyte, causing an oxide layer to form. After the oxide is formed, dyes can be applied to the metal, depending on the metal’s pore size. Aluminum is the most common metal used in color anodizing, but there are several other metals that can be used, including titanium and magnesium. While anodizing has several important benefits, adding color is mostly to help distinguish parts and to make parts look better for consumers.
Anodizing is a process in which a very thin oxide layer is formed on top of a metal that increases its surface hardness and changes the size of its pores. This also is used to make parts for a battery, specifically the anode. The metal is first placed in an electrolyte solution, which has free roaming ions. Electricity is pushed through the solution, which excites the ions and causes them to cling to the metal’s surface, resulting in the new coat.
Color anodizing occurs next. After the regular anodizing is finished, the pore density of the metal changes. Depending on how long the metal is anodized, the metal and the anodizing method, the metal can be given different colors. Dyes are added directly to the metal, and the color will affix as it does with textiles. If the metal is not anodized beforehand, then the pores will be too small and dyes will run off the metal’s surface.
Only certain metals can be used in color anodizing, because these metals have to react freely to oxygen. If they cannot react with oxygen, then the oxidized layer will not correctly form and they cannot be dyed. The two most common metals are aluminum and titanium, because of their hardness and general uses outside of anodizing. Other metals include zinc, tantalum and magnesium.
Unlike regular anodizing, which offers some mechanical benefits, color anodizing is mostly used for cosmetic purposes. The dyed metal will still receive the mechanical benefits, such as increased surface hardness, but the metal is rarely used for this. Color-anodized metal is commonly used to help distinguish parts by their color, to make metal products more visually attractive in consumer products, and for costume jewelry. An environmental benefit is that this process creates less pollution and has less leftover materials than other dying processes.