Aluminum alloys are widely used in many fields such as construction, automobiles, and electronics due to their light weight, high strength, and good corrosion resistance. In order to further improve the performance and aesthetics of aluminum alloys, anodizing has become a common method.
Aluminum alloys can be divided into several series according to their alloy composition, such as 1 series (pure aluminum sheet), 5 series (Al-Mg alloy), 6 series (Al-Mg-Si alloy), 7 series (Al-Zn-Mg-Cu alloy), etc. Due to the difference in their composition, different series of aluminum alloys have different colors after anodizing.
1 series aluminum alloy (pure aluminum): The pure aluminum content is above 99%. Due to its high purity, the anodizing effect is the best. In bright anodizing, after brightening and anodizing, the higher the purity of the aluminum, the better the anodised aluminum sheet’s surface reflectivity. In protective anodizing, the corrosion resistance of the anodized film is also significantly improved, usually showing a silvery-white luster, pure and bright color.
5 series aluminum alloy (Al-Mg alloy): It is a deformed aluminum alloy that cannot be strengthened by heat treatment. It has good corrosion resistance and can be welded. Generally speaking, the color of 5 series aluminum alloy after anodizing is mostly silver-gray. When the magnesium content is greater than 5%, the anodized film will be slightly dull.
This series of aluminum alloys are often used in fields with high corrosion resistance requirements such as food industry, chemical industry, shipbuilding and marine environment. The color effect after anodizing can meet the needs of beauty and durability in these scenarios.
6 series aluminum alloy (Al-Mg-Si alloy): It is a deformable aluminum alloy that can be strengthened by heat treatment. It is widely used in engineering. For example, 6063 aluminum alloy is the most widely used extruded aluminum alloy. When bright anodizing, 6463 aluminum alloy is usually recommended, with an aluminum content of at least 99.7%.
The lower the impurity elements (such as iron and manganese) in the alloy, the smaller the brightness loss after anodizing. The anodized film of 6 series aluminum alloy generally presents a light gray or yellow-gray tone. When used in the construction field, it is recommended that the thickness of the anodized film should not be higher than 10um, because as the film thickness and current density increase, the anodized film will lose light and darken.
However, by controlling the appropriate process parameters, 6 series aluminum alloy can also obtain a better anodized appearance effect, and because of its good comprehensive performance, it is widely used in architectural decoration, electronic equipment housing, etc.
7 series aluminum alloy (Al-Zn-Mg-Cu alloy): It is produced by heat treatment pre-stretching process, has the characteristics of high hardness and strong bending resistance, and is often used in fields with extremely high material performance requirements such as aviation industry.
After 7 series aluminum alloy is anodized, if hard anodized, the surface treatment will appear golden yellow. However, some elements in its alloy composition may also cause problems such as uneven color during the anodizing process, and more precise control of process conditions is required to ensure color consistency.
Natural coloring method: The process is relatively simple and the cost is low; but the color types are relatively limited, mainly concentrated in some natural colors, such as silver, gold, bronze, etc.
Electrolytic coloring method: The color obtained by electrolytic coloring has good light resistance and corrosion resistance, and the color fastness is high. By adjusting the parameters such as the type, concentration, electrolysis time and voltage of the metal salt in the electrolyte, the depth and hue of the color can be precisely controlled. Its cost is relatively high.
Organic dye dyeing method: It can obtain extremely rich color selection, bright colors and high saturation, which can meet various personalized design needs. However, the light resistance and weather resistance of organic dyes are relatively poor.
Inorganic pigment filling method:
The color obtained by the inorganic pigment filling method has high light resistance, heat resistance and corrosion resistance, and is particularly suitable for outdoor applications that require high color durability. Welcome to inquire color anodized aluminum from us directly.