A noble metal is ordinarily regarded as a metallic chemical element that is generally resistant to corrosion and is usually found in nature in its raw form. Gold, platinum, and the other platinum group metals are most often so classified. Silver, copper, and mercury are sometimes included as noble metals, but each of these usually occurs in nature combined with sulfur.
Chalcopyrite, which is copper iron sulfide (CuFeS2), is the most abundant copper ore mineral
One half of a ruthenium bar. Size ~ 40 × 15 × 10 mm Weight ~44 g
Rhodium: 1 g powder, 1g pressed cylinder, 1 g pellet.
Palladium
Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials by chemical or electrochemical reaction with their environment. Corrosion engineering is the field dedicated to controlling and preventing corrosion.
Corrosion on exposed metal, including a bolt and nut
Galvanic corrosion of an aluminium plate occurred when the plate was connected to a mild steel structural support.
Gold nuggets do not naturally corrode, even on a geological time scale.
Normal microstructure of Type 304 stainless steel surface