The multi-color gradient effect of aluminum imitation stone relies on the deep integration of color matching technology and metal surface treatment processes. Its core lies in constructing naturally transitioning color layers through multi-layer coating, oxide film thickness control, and differences in dye adsorption. This process requires coordinated advancement across seven dimensions: substrate pretreatment, color layering design, oxidation process control, dye selection and adsorption, coating curing and protection, gradient boundary control, and effect verification and optimization, forming a complete color gradient realization system.
Substrate pretreatment is the foundation of color matching. Aluminum imitation stone materials typically use aluminum alloy as the substrate, and its surface needs to undergo processes such as degreasing, alkaline washing, and sandblasting to remove oil, oxide layers, and burrs, creating a uniform roughness. This step not only improves the adhesion of the coating but also provides conditions for the uniform growth of the subsequent oxide film. For example, sandblasting uses high-pressure jets of metal abrasive particles to form a micron-level uneven structure on the aluminum surface, which enhances the mechanical adhesion of the coating and reduces surface reflectivity through light scattering, making the gradient colors appear softer and more natural.
Color layering design needs to combine the characteristics of stone texture with optical principles. The color gradation of natural stone is usually caused by uneven distribution of mineral components. Aluminum imitation stone simulates this characteristic by breaking down the target color into multiple color layers. Designers use color wheel theory to select complementary or adjacent colors, and adjust the thickness and transparency of each color layer to achieve a visually natural transition. For example, a blue gradient might include three layers: dark blue, sky blue, and light blue. The thickness of each layer is distributed according to the saturation difference of the target color; the darker layers are thinner to avoid over-coverage, while the lighter layers are thicker to enhance coverage.
Controlling the oxidation process is key to creating a gradient in oxide film thickness. During the anodizing of aluminum alloys, oxide film thickness is positively correlated with electrolyte concentration, current density, and oxidation time. By controlling these parameters in segments, an oxide film layer of uneven thickness can be formed on the aluminum surface. For example, the oxidation time can be extended in areas requiring darker colors to achieve an oxide film thickness of over 20 micrometers, while the time can be shortened to less than 10 micrometers in lighter areas. Differences in film thickness result in varying dye adsorption amounts. Thicker film areas adsorb more dye molecules, resulting in darker colors; thinner film areas, with less adsorption, appear lighter, thus forming the basis for color gradation.
Dye selection and adsorption must balance color stability and compatibility. Aluminum imitation stone commonly uses organic dyes or metal complex dyes. Organic dyes offer vibrant colors but poor lightfastness, while metal complex dyes offer strong weather resistance but a narrower color gamut. In actual production, a mixture is used depending on the gradation requirements. For example, metal complex dyes are used in darker layers to improve durability, while organic dyes are used in lighter layers to enrich color expression. During adsorption, dye molecules diffuse into the pores of the oxide film; higher porosity results in greater adsorption. By adjusting the oxidation process to control porosity, the color transition effect can be further refined.
Coating curing and protection must ensure color durability. After multiple layers are stacked, high-temperature baking is required to cross-link and cure the resin, forming a dense protective film. This process not only fixes the color position but also improves surface hardness and chemical corrosion resistance. For example, after baking at 250℃, the surface hardness of a fluorocarbon coating can reach over 6H, effectively resisting ultraviolet rays, acid rain, and mechanical friction, ensuring that the gradient colors do not fade in outdoor environments for a long time.
Gradient boundary control relies on precision processing equipment. To achieve a natural color transition, gradient spray guns or laser engraving technology are used to create a micron-level mixing zone at the color layer boundary. Gradient spray guns adjust the nozzle air pressure and ink flow to gradually blend the two colors at the boundary; laser engraving, by controlling the energy density, creates indentations of varying depths on the oxide film surface, affecting the subsequent dye adsorption and thus forming a soft color transition band.
Effect verification and optimization are the final stage of quality control. A spectral analyzer is used to detect the color coordinates of each area to ensure they meet design requirements; a salt spray test chamber is used to simulate harsh environments to verify the coating's weather resistance; and a microscope is used to observe the oxide film structure to analyze the causes of color unevenness. Based on the test results, oxidation parameters, dye formulations, or spraying processes are adjusted until the ideal gradient effect is achieved. This closed-loop optimization process has enabled the multi-color gradient technology of aluminum imitation stone to move from the laboratory to large-scale production, providing the architectural decoration field with a new material that combines aesthetics and durability.
