Gold does not oxidize at normal temperatures, which means that it retains its conductivity and solderability. It is primarily used in the electronics industry for connectors, printed circuits, transistors, and integrated circuits – anywhere that contact resistance, solderability, or wire bonding is crucial. Alloying gold with small amounts of cobalt can dramatically increase its hardness and wear characteristics. The excellent physical and chemical properties offset the price of gold. There are four types of gold surface coating: pure, hard, electroless, and immersion gold.