Stainless steel, with its advantages of “corrosion resistance, durability, and environmental friendliness,” has won people’s hearts. However, its application has been greatly restricted due to its cold and monotonous appearance. Colored stainless steel has emerged to address this limitation. It not only maintains the physical, chemical, and mechanical properties of traditional stainless steel but also boasts a vibrant and enduring array of colors. Its introduction fulfills the modern society’s demand for diversity in colors, leading to increasingly widespread applications.
- Origin of Colored Stainless Steel Colored stainless steel is not achieved by painting or spray-coating steel with color, nor is it colored through dyes like colored aluminum. Colored stainless steel itself is colorless; its color is obtained due to the presence of a transparent and dense oxide film on the surface. When light illuminates this film, the result is an interference phenomenon between the reflected light and the refracted light passing through the film. The color exhibited on the surface of colored stainless steel depends on factors such as the chemical composition of the oxide film, its structural organization, surface smoothness, film thickness, and the angle of incident light.There are several methods for coloring stainless steel as follows:
- (1) Chemical Oxidation Coloring Method: This involves forming a colored film through chemical oxidation in specific solutions, including methods like chromic acid anodizing, mixed sodium salt method, sulfuration method, acidic oxidation method, and alkaline oxidation method. The “INCO” method is commonly used, although maintaining consistent color for a batch of products requires the use of reference electrodes for control.
(2) Electrochemical Oxidation Coloring Method: This involves forming a colored film through electrochemical oxidation in specific solutions.
(3) Ion Deposition Oxide Coloring Method: This involves placing stainless steel workpieces in a vacuum coating machine for vacuum evaporation coating. For instance, watch cases and bands coated with titanium gold tend to appear golden. This method is suitable for large-scale production due to its high investment and cost, making it less economical for small batches of products.
(4) High-Temperature Oxidation Coloring Method: Involves immersing the workpiece in specific molten salts at certain process parameters to generate a certain thickness of oxide film, exhibiting various colors.
(5) Gas-Phase Pyrolysis Coloring Method: This method is more complex and finds limited application in industrial settings.
- Applications of Colored Stainless Steel Colored stainless steel, due to its vibrant hues, has gradually become an excellent decorative material, showcasing an aura of elegance and luxury when used for adornment. Moreover, colored stainless steel exhibits superior resistance to salt spray corrosion compared to conventional stainless steel, withstanding salt spray corrosion for over 10 years. Its colored surface layer can endure temperatures of up to 200°C and remain unchanged even after exposure to ultraviolet radiation for more than 30 years.
Colored stainless steel is an environmentally friendly decorative material that is free from organic compounds such as methanol and radiation. It is corrosion-resistant, durable, and boasts a wide range of applications. Currently, it is primarily used for exterior walls and window frame decoration of buildings, including large architectural embellishments such as bus stations, train stations, subway stations, airports, as well as for hotel and office building decoration, public facilities, and new home decoration. In the realm of decorative arts, combining colored stainless steel with printing techniques allows for processes such as etching, grinding, and dot pattern application to create unfading three-dimensional relief murals, hanging screens, and more. Additionally, it finds use in elevators, hardware appliances, kitchen and bathroom utensils, cabinets, advertising signage, everyday items, etc., significantly enhancing the added value of products and offering distinct competitive advantages in the market.