Rhodium |
|||
 Technical specifications:
|
Rhodium is a member of the platinum metals group. The other members include platinum, palladium, ruthenium, iridium, and osmium.
It was first isolated in 1803 by English chemist William Wollaston. Due to the distinctive red color of the dissolved rhodium compounds, Wollaston named the new metal Rhodium based on the Greek word rhodon meaning "rose". Primary sources for rhodium are in Russia, South Africa, and Canada. The industrial extraction of rhodium is complicated by the fact that it occurs naturally with numerous other native ores. Mixed with other metals such as platinum, silver and nickel, the separation and refinement of rhodium ores are quite expensive. Only about 9-10 metric tons are produced annually worldwide. As of this writing, its trading range on the world spot metals market are quite volatile. Among numerous other physical characteristics such as hardness, and high reflectivity, rhodium has an extraordinary resistance to most acids and corrosive substances. It is one of the few "white" metals that will remain bright and reflective under all atmospheric conditions at ordinary temperatures. As a result, electroplated surfaces that utilize rhodium plating remain scratch resistant, bright and attractive for years. Rhodium can be plated onto just about any metal surface. Primarily, our customers utilize rhodium to plate metals that are easily tarnished such as sterling silver, nickel, and copper alloys. The plating thickness for decorative rhodium platings used by jewelry manufacturer can range from .05 microns to 1.5 microns. For most decorative applications, a thickness from .10 microns to .50 microns are utilized for maintaining long term "brightness". Industrial platings for specialized applications may utilize thicknesses up to 5.0 microns. However, rhodium finishes above 2.0 microns have a tendency to be brittle and will need special annealing processes to relieve the stress within the rhodium plated layer. Among the "white" decorative platings, rhodium is considered "best in class" in terms of toughness and wear resistance. Most items plated with at least .5 microns of rhodium are usually more scratch resistant than prior to being plated! Electroplated rhodium has a hardness ranging from 400-550 vickers which makes it very resistant to incidental abrasions. Over sterling silver objects, rhodium plating can prevent the formation of fine scratches that occur from normal handling and cleaning. How does the brightness of polished rhodium compare to silver? One of the minor cosmetic trade-offs for plating rhodium onto silver is that the rhodium finish will not be as bright or reflective as the original silver finish. Rhodium reflects about 72%-80% of the light rays that strike it. Silver reflects up to 95% of all incidental light that strikes it. However, over the long term rhodium will stay "brighter" than silver because of its superior resistance to tarnishing and scratching. |
||
|
