Gold has outstanding corrosion resistance
Gold is used in an incredibly wide range of technologies. In each of the applications it is used, gold provides outstanding performance due to its unique technical properties. It combines high conductivity with corrosion resistance, and can be physically manipulated as it is both highly malleable and ductile. Gold is also a material of choice in medicine and dentistry as a consequence of its biocompatibility, and recent years have seen it emerge as a key nanomaterial.
The ability to efficiently conduct both heat and electricity is a key characteristic of gold, rendering it indispensable in modern electronics. Its electrical conductivity is surpassed only by copper and silver, but unlike these metals gold does not tarnish, making it the most reliable of conductive metals.
Gold’s resistance to corrosion is one of its most useful properties. Generally the only substance with sufficient power to corrode gold is a mixture of nitric and hydrochloric acid (aqua regia), and in everyday use gold does not tarnish. This quality makes gold ideal as a coating for contacts and connectors in electrical circuits where intimate contact between two metal surfaces is required to ensure electrical connectivity.
Gold is extremely malleable (the extent to which a material can undergo deformation in compression before failure). In its annealed (softened) state gold can be hammered cold into a translucent wafer 0.000013 cm thick. It is possible to beat one ounce of gold into a sheet covering over 9 square metres of 0.000018 cm thickness.
Gold is also ductile (the amount of extension which takes place before failure of a material in tension) and one ounce can be drawn into 80 km (50 miles) of thin gold wire (5 microns diameter). This is a key property for the production of bonding wire used in electronics.
Gold demonstrates excellent biocompatibility within the human body (the main reason for its use as a dental alloy), hence the number of direct applications of gold as a medical material. Gold also possesses a high degree of resistance to bacterial colonisation, which makes it the material of choice for implants that are at risk of infection, such as the inner ear.
A catalyst is a substance or material that accelerates the rate of a chemical reaction without itself being consumed by the reaction. Catalysts are an essential component of many different industrial processes used to produce chemicals, foodstuffs and other materials. Gold is an active catalyst for many commercially important reactions and its use in this field is growing.
It is important to draw a distinction between the properties of gold in its bulk form and properties it exhibits when present in the form of tiny nanoparticles. At the nanoscale, gold’s properties can be markedly different, as our recent publication, Gold for Good – Gold and Nanotechnology in the Age of Innovation , explains.
Gold’s unique nanoscale properties are leading to its use in a growing number of applications.