The types of electrolytic pink treatment and the principle of coloring

When the anodic oxide film of aluminum sulfate is electrostained with tin or nickel salt, the amount of tin or nickel metal in the micropores is generally 50-200. As the amount of metal is released increases, the resulting colors range from champagne to light to dark bronze to black. A variety of hues in between the above colors can be obtained by controlling the amount of metal precipitation.

The hair color principle of electrolytic coloring is actually inferred to have two physical phenomena. The first is the metal particles dispersed in the pores of the transparent aluminum anodic oxidation film, and the color is formed by the scattering effect of human light. The second is when the thickness of micropores is thin and the porosity is large, the metal particles filled in the micropores form a layer of spongy metal film, and the color is formed due to the interference of human light.

The second mechanism of electrolytic coloring is the formation of double anodized aluminum films under different conditions, forming a unique shape of microporous connections. When the second anodic aluminum oxide film is formed, its porosity is larger and its thickness is smaller than that of the first anodic oxide film. The filling metal in the micropore itself plays a role similar to the role of metal film, and the color of this film is presented through the optical interference between the film and the base metal.

For example, after the anodizing treatment of aluminum sulfate (I electrolysis), the anodizing treatment of aluminum phosphate (2 electrolysis), the anodizing film of aluminum phosphate is between the aluminum matrix and the anodizing film of aluminum sulfate. The pore size of anodic oxide film of aluminum phosphate is different from that of anodic oxide film of aluminum sulfate, so the pass shape of double anodic oxide film of aluminum phosphate is "bottle shape". Then the metal precipitates in the micropores of the anodic oxidation film of aluminum phosphate, and the flask micropores are filled with metal to a certain thickness. Therefore, the color of interference light changes with the amount of metal deposition (i.e., the thickness of metal precipitation layer) in the micropore.

Sometimes further aluminum anodizing steps are added, for example, aluminum anodizing in oxalic acid solution (4 electrolytic treatments). This results in an increase in the thickness of the barrier layer below the metal layer causing the optical interference effect. The interference effect in this case can make the originally lighter color darker.