Rhodium black is a gray powder metal. It is pure and has no visible inclusions and oxidation color. Corrosion resistance is high, even insoluble in boiling Aqua regia. But hydrobromic acid corrodes rhodium slightly. Moist iodine and sodium hypochlorite can also corrode rhodium.
Boiling Point of Rhodium Black: Melting Point at 3727 C: Density at 1966 C: 12.41