What Is Rhodium Plating?
Rhodium is a silver-white, hard metal with high reflectivity. Rhodium metal usually does not form oxides. Molten rhodium absorbs oxygen but releases it during solidification. Rhodium has a higher melting point and lower density than platinum. Rhodium is insoluble in most acids, it is completely insoluble in nitric acid, and slightly soluble in aqua regia. The element symbol Rh, derived from rhodon, means "rose", because the solution of rhodium salt showed the reddish color of the rose, which was discovered and separated by Wollaston in 1803. Rhodium is a platinum-based element. [1]
- Kangxi dictionary
- The pronunciation of "Word Complement" is unknown. Wang Shenzhi cast a large iron coin, commonly known as rhodium. [2]
- Platinum group metals have high melting points, high strength, stable electric heating, high resistance to electric spark erosion, excellent corrosion resistance, high temperature and oxidation resistance, and good catalytic activity. They are widely used in automotive exhaust purification, chemical industry, aerospace, and glass fiber , Electronics and electrical industries, although the amount is small, but it plays a key role, known as "industrial vitamin".
- In addition to making alloys, rhodium can be used as a bright and hard coating on other metals, such as silverware or camera parts. Evaporating rhodium onto the glass surface to form a thin layer of wax creates a particularly good mirror surface.
- (1) High catalytic activity and selectivity, and long life. Rhodium and its alloys, rhodium-containing compounds, and complex catalysts can be used in the production of aldehydes and acetic acid, automotive exhaust purification, ammonia oxidation of nitric acid production, organic chemical synthesis of plastics, artificial fibers, drugs, pesticides, and fuel cell electrodes.
- (2) The reflectance to visible light is high and stable. Commonly used for the coating of special industrial mirrors, searchlights, radars and other reflective surfaces.
- (3) High melting point, oxidation resistance, corrosion resistance, and one of the most stable metals. It can be used as a corrosion-resistant container. It can be used in the atmosphere at a high temperature of 1850 ° C. Pure rhodium crucibles can be used to produce calcium tungstate and lithium niobate single crystals.
- (4) Rhodium plating has high hardness (7500 9000MPa), wear resistance, corrosion resistance, and stable contact resistance. Rhodium-plated composite materials are excellent electrical contact materials. Rhodium can also be used in the plating of jewelry and other industrial instruments and gas-sensitive components.
- (5) Modification. Rhodium can form a solid solution with metals such as platinum and palladium to strengthen the matrix, improve the melting point, recrystallization temperature and corrosion resistance of the matrix, and reduce oxidation and volatilization losses. Among them, platinum-rhodium alloy is an excellent precious metal temperature measurement material; Compounds formed with titanium, zirconium, hafnium, tantalum, niobium and other metals have a dispersion strengthening effect on rhodium-containing alloys and increase thermal stability; adding rhodium to iridium can improve the processing properties of iridium.
- (6) The work hardening rate is high, and it can be cold worked after hot working to a certain size.
- (7) Expensive, except for special use, usually only used as an additive element. [1]
- Rhodium was discovered in 1803 by William Wollaston. He worked with Smithson Tennant in a commercial investment, mostly to produce pure platinum for sale. The first step in this procedure is to dissolve ordinary platinum in aqua regia (nitric acid + hydrochloric acid). Not everything is dissolved in the solution, it stays
- Rhodium is present in platinum ore and can be collected during the refining process.
- China's platinum metal resources are relatively scarce. Platinum metal deposits are distributed in 10 provinces and autonomous regions. Gansu, Yunnan, Sichuan, and Heilongjiang have more reserves. These four provinces account for 94.6% of the national reserves. Other provinces such as Hebei, Qinghai, Xinjiang, Beijing, and Inner Mongolia also have some small mines, but the reserves are very small.
- Rhodium is a platinum-based element. Platinum-based elements exist almost completely in a simple substance state, and are highly dispersed in various ores, such as primary platinum ore, nickel copper sulfide ore, magnetite, and the like. Platinum-based elements coexist almost without exception, forming natural alloys. In the platinum-containing element ore, platinum is usually the main component, and the remaining platinum-based elements must be chemically analyzed before they can be found because of the small content. Because osmium, iridium, palladium, rhodium, and ruthenium all form ore with platinum, they are all found in the residue after extracting platinum from platinum ore. Apart from platinum and palladium, they are not only insoluble in ordinary acids, but also in aqua regia. Platinum is easily soluble in aqua regia, and palladium is also soluble in hot nitric acid. All platinum-based elements have a strong tendency to form complexes. From 1803 to 1804, shortly after discovering palladium in Wollaston, he dissolved the natural platinum ore in aqua regia, added sodium hydroxide solution, neutralized the excess acid, and then added ammonium chloride (NH4Cl) to precipitate platinum into platinum. Ammonium chloride ((NH4) 2 [PtCl4]), and then add mercury cyanide to precipitate palladium to palladium cyanide. After filtering off the precipitate, add hydrochloric acid to the filtrate to remove excess mercury cyanide and evaporate the solution dry,
- Blue Fancy Diamond Rhodium Plated Ring