Definition - What does Noble Metal mean?
A Noble Metal is a metal which is resistant to oxidation and corrosion in moist air. Chemically Noble Metals include rhodium, silver, osmium, ruthenium, gold, platinum and iridium. Copper, mercury and rhenium are also included in the list of Noble Metals. Other metals such as tantalum, niobium and titanium are highly resistant to corrosion but are not Noble Metals. Although Noble Metals are valuable because they are found rarely in the Earth's crust and are very useful in high technology, ornamentation and metallurgy, they are not considered as precious metals.
Petropedia explains Noble Metal
The group of several metallic chemical elements is considered as Noble Metals, which have a great resistance to corrosion and oxidation at high temperatures. They are opposite to the base metals as they readily corrode and oxidize. Some of these metals including mercury, platinum, gold and palladium can be easily dissolved in highly concentrated blend of nitric and hydrochloric acid, in aqua regia. Antimony is not a Noble Metal as it is considered to be a metalloid. The term Noble Metal has distinct meanings in various fields of application and study. Because of this reason there are different lists of these metals in every field.