Stainless steel is deeply appreciated for its advantages such as corrosion resistance, durability, and environmental friendliness. However, its widespread application has been limited due to its cold and monotonous appearance. Colored stainless steel emerged to address this issue, as it not only maintains the physical, chemical, and mechanical properties of regular stainless steel but also offers a variety of colors that remain long-lasting. Its introduction satisfies the modern society’s demand for colorful diversity, leading to increasingly broader applications.
Origin of Colored Stainless Steel
Colored stainless steel is not achieved by painting or coating steel with paint or spray, nor is it colored using dyes like colored aluminum. Colored stainless steel itself is colorless, and its colors are obtained due to the presence of a transparent and dense oxide film on the surface. When light shines on this film, the resulting colors are the outcome of the interference between the reflected light and the refracted light passing through the film. The color displayed on the surface of colored stainless steel depends on factors such as the chemical composition, structural organization, smoothness, thickness of the oxide film, and incident light.
Types of Colored Stainless Steel:
(1) Chemical oxidation coloring method: This method involves the formation of the oxide film color in a specific solution, which includes methods like dichromate process, mixed sodium salt process, sulfuration process, acidic oxidation process, and alkaline oxidation process. The “INCO” method is commonly used, but to ensure consistent color for a batch of products, it requires the use of reference electrodes for control.
(2) Electrochemical oxidation coloring method: Colors are obtained by electrochemically forming the oxide film in a specific solution.
(3) Ion deposition oxide coloring method: Stainless steel parts are placed in a vacuum coating machine for vacuum evaporation plating. For example, titanium-gold-plated watch cases and watch bands generally exhibit a golden color. This method is suitable for mass production as the high investment and cost make it uneconomical for small-batch products.
(4) High-temperature oxidation coloring method: This method involves immersing the workpiece in specific molten salts and maintaining it at certain process parameters to form a certain thickness of oxide film, resulting in various colors.
(5) Gas-phase pyrolysis coloring method: This method is relatively complex and has limited industrial application.
3.Application of colored stainless steel
Colored stainless steel, with its vibrant colors, has gradually become an excellent decorative material, showcasing a sense of elegance and luxury when used for decoration. Moreover, colored stainless steel exhibits better resistance to salt spray corrosion than regular stainless steel, withstanding over 10 years of exposure to salt spray. Its colored surface layer can withstand temperatures of up to 200°C and is resistant to fading under more than 30 years of UV exposure.
Colored stainless steel is an environmentally friendly decorative material that does not contain methanol or other organic substances, is non-radiative, and is corrosion-resistant, durable, making it suitable for a wide range of applications. Currently, it is mainly used for exterior walls and window frame decoration in buildings, such as large architectural decorations (e.g., bus stations, train stations, subway stations, airports), hotel and office building decorations, public facilities, and residential interiors. In the field of arts and crafts, combining colored stainless steel with printing techniques allows the production of three-dimensional, fade-resistant relief murals, hanging screens, etc., using etching, grinding, and halftone techniques. Colored stainless steel is also applied in elevators, hardware appliances, kitchen and bathroom utensils, cabinets, advertising signs, daily necessities, etc., greatly increasing the added value of products and providing a distinct competitive advantage in the market.