Metallic colours - Import export

The grey shiny niobium is not unlike tantalum, which also has a very high melting temperature. A striking difference to tantalum is its much lower density. The pure metal is easy to process due to its low hardness. However, it becomes much harder and more brittle due to minor carbon impurities. Niobium is a relatively base element. When exposed to air, a protective oxide layer forms around the metal, which protects it from further corrosion and provides additional resistance. These wafer-thin oxide layers on the metal surface cause the coloured iridescence that occurs when heating a compact piece with a burner. Niobium powder is pyrophoric and can therefore ignite by itself. Glowing niobium powder reacts with oxygen to form niobium(V)-oxide. The compact metal resists most acids at room temperature. After heating, however, almost all acids are able to decompose the metal.