The commonly used alloys aluminum 6061 and 7075, as well as cast aluminum A356, all have good coloring effects.
There is no necessary connection between die-cast parts and anodizing.
There are many types of cast aluminum, and it is not necessary to choose silicon-aluminum alloy (cast aluminum can be categorized into Al-Si, Al-Cu, Al-Mg, Al-Zn, etc., and can also contain rare earth elements). Even if silicon-aluminum alloy is chosen, anodizing is not impossible. Generally speaking, aluminum alloys contain silicon to some extent, such as 6061 containing 0.4-0.8% silicon, and 7075 containing 0.4% silicon; this level of silicon has a minimal impact on the anodizing of alloys (by the way, the copper content has little effect on the anodizing of aluminum alloys, but significantly affects hard anodizing and ceramic anodizing). However, when the silicon content in the alloy is very high (>7%), it will affect the anodizing of the alloy. This mainly manifests as a longer oxidation time and a darker film layer; these problems can be resolved through processing techniques (for example, using pulsed current for oxidation instead of direct current), which requires the surface treatment manufacturer to have certain technical capabilities. Therefore, cast aluminum ≠ silicon-aluminum alloy ≠ cannot be anodized.
Let’s also talk about the issue of coloring. The anodizing and coloring of aluminum alloys are two different processes, which is different from the bluing of steel. The bluing of steel is where the oxide film itself is blue, while coloring is done immediately after anodizing, and the oxide film itself is colorless and transparent. The oxide film obtained by sulfuric acid anodizing of aluminum alloys is most suitable for dyeing, and currently, organic dyes are commonly used for coloring. After coloring, the oxide film is treated with sealing. Additionally, there is also electrolytic coloring using heavy metal salts, but it is quite difficult to dye it red according to the original poster's requirements!
The process of chemically treating steel parts in a phosphoric acid solution to form a layer of water-insoluble protective film on the surface of the steel is called phosphating!
It mainly has the following characteristics:
1. The surface of the phosphating film is gray or dark gray.
2. The phosphating film, after filling, oiling, or painting treatment, has good corrosion resistance under atmospheric conditions.
3. The film layer has strong adsorption ability and is often used as the base layer for coatings.
4. The phosphating film has high electrical insulation properties.
5. After phosphating treatment, the mechanical properties, strength, and magnetic properties of the original metal remain basically unchanged.
6. The phosphating film has good lubrication performance.
7. The surface of nitrogen-diffused parts can be protected with a phosphating film.
8. The main feature of the phosphating film is that it can form a protective film on the inner surfaces of steel and on complex steel shapes.
9. The hardness and mechanical strength of the film layer are low, and it has certain brittleness.
Passivation generally refers to: in order to improve the protective and decorative performance of the galvanized layer, the galvanized item is treated by immersing it in a solution, forming a chemically stable layer on its surface. Passivation treatment can improve the protective performance and surface gloss of the galvanized layer.
Oxidation is generally divided into: oxidation of aluminum, aluminum alloys, and steel parts, differing only in the purposes that can be achieved and the solutions used.