Rhenium (chemical symbol Re), with an atomic number of 75 and a density of 21.04g/cm³, is one of the rarest elements in Earth’s crust, with an average estimated abundance of one part per billion. It is a byproduct of the extraction processes of molybdenum and copper. Rhenium is a silvery-white metal, ranking second in melting point among all metals and fourth in density. It exhibits good ductility and has wear resistance second only to osmium. It maintains good plasticity at both high and low temperatures. Its tensile strength and creep resistance surpass those of refractory metals such as tungsten, molybdenum, and niobium. In high-temperature environments, rhenium retains excellent strength, hardness, and ductility, possessing very good mechanical properties. At room temperature, rhenium metal is resistant to acids and bases but reacts with hydrogen peroxide, nitric acid, and hot sulfuric acid. Rhenium does not undergo oxidation when exposed to temperatures below 300°C in air.