In order to make the surface of stainless steel more bright and eye-catching, the study of stainless steel surface coloring is attracting the attention of stainless steel manufacturers in various countries. This is to immerse the stainless steel in a certain solution, so that the surface of stainless steel to generate oxidation wax or sulfide film and present different colors of the method. Inco method is to soak stainless steel in a solution containing sulfuric acid 500 g / l and chromic anhydride 250 g / l, the solution temperature of 90 to 100 ℃, so that the surface of stainless steel to generate a thick 0.05 to 0.5 micron film. The growth rate of the film varies with the composition of the solution, stainless steel surface conditions, coloring depth and temperature. In order to strengthen the film, the primary film to be in a solution containing chromic anhydride 250 g / l and sulfuric acid 2.5 g / l, at room temperature for hard film treatment. The advantages of this method are easy control of coloring, high abrasion resistance of the colored film and suitability for mass production.

The principle of the appearance of different colors is shown in Figure 1, due to this interference phenomenon of light, so that the surface of stainless steel into a certain color. As the thickness of the film becomes thicker, the surface will become bronze, blue, golden yellow, red and green in turn. The surface of the original stainless steel plate used for chemical coloring can be BA surface, mirror surface, etched surface and various hairline processing surface.

Inco method belongs to the chemical coloring. In addition, in recent years, Japan has also researched and developed the ion plating method and ion injection method and other electrochemical coloring methods.

The principle of ion plating method is shown in the figure. With this method, the adhesiveness and reactivity of the film are improved due to the ionization of some of the gas-phase particles under the true setting and the movement energy becomes larger.

The spray method is to ionize the inert gas and other gases at low pressure, and the cations impact with the cathode target phase, so that the particles comprising the target plate fly out and are deposited on the opposite anode substrate to form a thin film.

Both methods are processed in a vacuum vessel of 10-3 to 10-1 Pa. The use of TiN with its composite film can be obtained golden yellow, the use of TiAlN film can be obtained bronze color, blue, the use of TiAlCN film can be obtained black.

These colored stainless steel sheets are widely used as architectural decoration, daily appliances and artwork.