How is titanium’s colored surface formed?
The colored surface of titanium is caused by surface oxidation to form titanium dioxide. Titanium dioxide oxide films of different thicknesses refract different colors of light, thus forming many different colors. Generally, the coloring oxidation of titanium is divided into normal pressure method, anodizing method and deposition method. Today we will introduce the most commonly used anodizing method.
Titanium anodizing, titanium and its alloys are placed in the corresponding electrolyte (such as sulfuric acid, chromic acid, oxalic acid, etc.) as anode, and electrolysis is performed under specific conditions and applied current. The titanium or its alloy on the anode is oxidized, forming a thin layer of titanium oxide on the surface. Its thickness is 5 to 30 microns, and the hard anodized film can reach 25 to 150 microns. Anodized titanium or its alloy has improved hardness and wear resistance, up to 250-500 kg/mm2, good heat resistance, hard anodized film melting point up to 2320K, excellent insulation, impact resistance, breakdown voltage up to 2000V, Enhanced corrosion resistance, no corrosion in ω=0.03NaCl salt spray for thousands of hours. The thin oxide film has a large number of micropores and can absorb various lubricating oils, making it suitable for manufacturing engine cylinders or other wear-resistant parts; the film has strong adsorption capacity and can be colored into various beautiful and bright colors. Non-ferrous metals or their alloys (such as titanium, magnesium and their alloys, etc.) can be anodized. This method is widely used in mechanical parts, aircraft and automobile parts, precision instruments and radio equipment, daily necessities and architectural decoration, etc. Generally speaking, titanium or titanium alloy is used as the anode and a lead plate is used as the cathode. Put titanium and lead plates together into an aqueous solution containing sulfuric acid, oxalic acid, chromic acid, etc. for electrolysis, and an oxide film is formed on the surfaces of the titanium and lead plates.
Pure titanium products have a dense oxide film on the surface and can adapt well to various environments at room temperature. Therefore, no spraying is required, and pure titanium kettles are highly corrosion-resistant. Faced with outdoor weak acid or weak alkaline environments, pure titanium kettles can easily cope with them. Whether it is river water, rainwater, rocks or vegetation, pure titanium kettles can be in direct contact with them without being corroded. Since the entire body of the kettle is not spray-painted, it takes on the unique gray color of pure titanium products. It can also be heated directly on a fire source to produce brilliant colors. Titanium kettles are colorful. The surface of titanium metal is covered with an extremely thin natural oxide film (titanium and oxide TiO2). This film can also turn into titanium rust because a transparent film with a high refractive index is formed on the surface. The film acts like a prism, refracting light and absorbing different wavelengths, and then you can see the color. Moreover, if the thickness of the oxide film is manually adjusted to 8~10um, thousands of similar colors can be displayed depending on the wavelength. Because this film is a transparent film with a high refractive index, it can display rich colors.
Photocatalyst was first discovered by Japanese scientists, and its effect was confirmed by Japanese scholar Guan Xiaonan as early as 1965. Later, Professor Kenichi Honda and his disciple Akira Fujishima of the University of Tokyo discovered the "Honda-Fujishima effect" in 1972, which can promote the electrolysis reaction of water by irradiating titanium dioxide electrodes with light, which caused a sensation. For more than 30 years, numerous technicians have worked hard on this road to practicality, and finally began to apply it to areas such as interior disinfection and antifouling a few years ago.
Photocatalyst is a new type of catalyst that uses nanoscale titanium dioxide as the main material and reacts under the irradiation of light. Photocatalyst has the power of decontamination and cleaning: it can not only be used to decompose dirt in water bodies and eliminate odors, but can also be sprayed on the inner and outer walls of buildings to resist the adhesion of dust and dirt for a long time and maintain a new state. . According to the development technicians, after this titanium dioxide absorbs ultraviolet rays from sunlight, internal electrons are excited, generating strong oxidizing power, destroying cell membranes, and capable of killing more than 99% of planktonic bacteria in the air. Moreover, it can also convert organic substances and harmful gases into harmless water, carbon dioxide, salt, etc. through oxidation-reduction reactions, thereby purifying water quality and purifying the air.
