Stainless steel is popular because of its advantages of "corrosion resistance, durability and environmental protection", but its application field is greatly limited due to its cold and monotonous color. Colored stainless steel came into being as the times require. It not only maintains the physical, chemical and mechanical properties of primary color stainless steel, but also has colorful and permanent colors. Its appearance meets the requirements of modern society for color diversification, and its application is becoming more and more extensive.

1. Origin of Colored Stainless Steel

Colored stainless steel is neither painted or plastic sprayed on steel to obtain color, nor dyed with dyes like colored aluminum. Colored stainless steel itself is colorless. The color is obtained because there is a layer of colorless and transparent dense oxide film on the surface. When light shines on the film, its reflected light interferes with the light refracted through the film. The color of the color stainless steel surface depends on the chemical composition, structure, finish, film thickness and incident light of the surface oxide film.

2. Colored stainless steel is divided into the following categories:

(1) Chemical oxidation coloring method: refers to the color of the film formed by chemical oxidation in a specific solution, including dichromate method, mixed sodium salt method, sulfurization method, acid oxidation method and alkaline oxidation method. In general, "Inco" method is used more frequently. However, to ensure the color consistency of a batch of products, reference electrodes must be used for control.

(2) Electrochemical oxidation coloring method: It refers to the color of the film formed by electrochemical oxidation in a specific solution.

(3) Ion deposition oxide coloring method: put stainless steel workpieces in a vacuum coating machine for vacuum evaporation plating. For example, the titanium plated watch case and band are generally golden yellow. This method is suitable for processing large quantities of products. Because of large investment and high cost, small batch products are not cost-effective.

(4) High temperature oxidation coloring method: It is used to immerse the workpiece in a specific molten salt to maintain a certain process parameter, so that the workpiece can form an oxide film of a certain thickness and show a variety of colors.

(5) Gas phase cracking coloring method: it is relatively complex and less used in industry.

3. Application of Color Stainless Steel

Colored stainless steel has gradually become a very good decorative material because of its gorgeous color. It can be used to decorate with elegant quality. In addition, the salt spray corrosion resistance of color stainless steel is better than that of ordinary stainless steel, which can resist salt spray corrosion for more than 10 years. Its color surface can withstand the temperature of 200 ℃, and can resist ultraviolet light for more than 30 years without discoloration.

Colored stainless steel is an environment-friendly decorative material. It does not contain organic substances such as methanol, has no radiation, and has a wide range of applications due to its corrosion resistance and durability. At present, it is mainly used for decoration of exterior walls and window frames of buildings, such as large-scale architectural decoration (bus station, railway station, subway station, airport, etc.), hotel and building business decoration, public facilities, and new residence decoration; In the arts and crafts industry, the combination of color stainless steel and printing can adopt the process of etching and grinding as well as dot method to produce three-dimensional relief murals and hanging screens that will never fade; It can also be used in elevators, hardware and household appliances, kitchen and toilet appliances, cabinets, advertising signs, daily necessities, etc., which can greatly improve the added value of products and has obvious market competitive advantages.