Selective leaching, also called dealloying, demetalification, parting and selective corrosion, is a corrosion type in some solid solution alloys, when in suitable conditions a component of the alloys is preferentially leached from the material. The less noble metal is removed from the alloy by microscopic-scale galvanic corrosion mechanism. The most susceptible alloys are the ones containing metals with high distance between each other in the galvanic series, e.g. copper and zinc in brass. The elements most typically undergoing selective removal are zinc, aluminium, iron, cobalt, chromium, and others.
The most common example is selective leaching of zinc from brass alloys containing more than 15% zinc (dezincification) in presence of oxygen and moisture, e.g. from brass taps in chlorine-containing water. It is believed that both copper and zinc gradually dissolved out simultaneously and copper precipitates back from the solution. The material remaining is a copper-rich sponge with poor mechanical properties, and color changed from yellow to red. Dezincification can be caused by water containing sulfur, carbon dioxide and oxygen. Stagnant or low velocity waters tend to promote dezincification.
Corinthian bronze, also called Corinthian brass or æs Corinthiacum, was a highly valuable metal alloy in classical antiquity. It is thought to be an alloy of copper with gold or silver (or both), although it has also been contended that it was simply a very high grade of bronze, or a kind of bronze that was manufactured in Corinth. It is referred to in various ancient texts, but no known examples of Corinthian bronze exist today.
Of the known types of bronze or brass in classical antiquity (known in Latin as aes and in Greek as χαλκός), Corinthian bronze was the most valuable—even more valuable than gold. Statues, vessels, or other objects that were formed of this metal were priceless. Vases and other ornaments that were made by the Romans of this metal were of greater value than if they had been made of silver or gold. Those who accurately documented this metal, including Pliny the Elder, distinguished it into three kinds, depending on the metal that is added to the copper base: in the first, gold is added (luteum); in the second, silver (candidum); in the third, gold, silver, and copper are equally blended. Plutarch and Cicero both comment that Corinthian bronze, unlike many other copper alloys, is resistant to tarnishing. Pliny also refers to a fourth, dark alloy, known as hepatizon.