This section provides an overview for black anodized aluminum as well as their applications and principles. Also, please take a look at the list of 4 black anodized aluminum manufacturers and their company rankings.
Black Anodized Aluminum is a type of color anodizing in which the surface of anodized aluminum is colored black with a dye.
Anodized aluminum is an aluminum that has undergone anodizing, in which the surface is covered with an oxide film by electrolysis on an anode. It is more resistant to corrosion than aluminum as it is.
The luster can be changed by processing before and after, etc. There are different types of anodized aluminum, such as matte black anodized aluminum and glossy black anodized aluminum. It is possible to choose the one that matches the features of the product to be used, such as the function and appearance decoration.
Black anodized aluminum has high corrosion and wear resistance, as well as high hardness and insulation properties, and is widely used for a wide range of products, from aluminum products and everyday items to electrical machinery, automobiles, and ships.
Specific products include household goods such as lunch boxes, water bottles, cooking utensils such as pots and pans, parts for automobiles and semiconductors, industrial equipment such as medical equipment, and interiors of ships and aircraft.
Glossy Black Anodized Aluminum and matte Black Anodized Aluminum are used for optical products.
Black Anodized Aluminum is produced in the following order:
1) Anodizing of the aluminum substrate
2) Dyeing of the anodized aluminum.
Anodizing is a treatment method in which an anodic oxide film is formed on the aluminum surface by electrolysis using aluminum as the anode. In the alumite treatment, the surface of the aluminum substrate is first dissolved in the electrolytic solution and then the alumite layer is formed, so the film consists of two layers: a nonporous barrier film and a porous film.
The anodized aluminum coating is hard and has excellent abrasion and corrosion resistance, and can protect the underlying aluminum substrate. While plating is a treatment method in which a metal film is deposited on the surface by electrolysis using the plated object as a cathode, anodizing is a method in which the aluminum substrate is used as an anode and electrolyzed itself.
As mentioned above, a layer of porous film is formed on the anodized aluminum coating. In the production of Black Anodized Aluminum, the material is fed into a dyeing tank and black dye is poured into these cavities, where it is absorbed by the cells, and once absorbed, the cavities are sealed by a perforation process.
The amount of dye adsorbed depends on the thickness of the anodized aluminum oxide film, so if a darker color is desired, the thickness of the film must be increased and the amount of dye adsorbed must be increased. Glossy black anodized aluminum and matte black anodized aluminum are pretreated using chemicals.
Luster black anodized aluminum has a gloss added to the anodized aluminum substrate. On the other hand, matte black anodizing removes the gloss by applying a matte finish.
Black Anodized Aluminum can be classified in terms of film thickness and dye.
The standard thickness of Black Anodized Aluminum is approximately 10~30 µm. If the film thickness is thin, such as 10 µm or less, the amount of dye adhering to the surface film is reduced and a sufficient effect cannot be obtained. Obtain an even black color, it is necessary to ensure a certain degree of film thickness.
Although a film thicker than 30 μm can be formed, it cannot be applied to physically restricted areas, such as the inside of long, narrow tubes or sharp edges. The performance of the film produced by black alumite treatment varies greatly depending on the material, so it is necessary to consider the film thickness while considering compatibility with the dye.
Organic chromium complex dyes are typical dyes for Black Anodized Aluminum. The dye molecule has a structure in which an organic ligand is bonded to metallic chromium in a 1:1 or 1:2 ratio.
The complexation of the organic ligand with chromium increases light and heat resistance compared to the single chromium ligand. Since the pore diameter of the film is several hundred Å, whereas the size of the dye molecules is approximately several tens of Å, the dye molecules penetrate into the pores of the film and are colored by adsorption.
The main organic ligands are aromatic rings, such as benzene and naphthalene, to which substituent groups showing chromogenic properties, such as nitro and azo groups, are attached. Dyes to which sulfonic acid, hydroxy, or amino groups are bonded have also been developed to enhance solubility in solvents.
In Black Anodized Aluminum, ultraviolet rays and heat in sunlight can decompose dye molecules, causing discoloration and fading. Therefore, in recent years, dyes that are resistant to ultraviolet rays have been developed.
*Including some distributors, etc.
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