Kovar is an iron-nickel-cobalt alloy with a density of 8.36g/cm3 and a coefficient of thermal expansion similar to that of hard (borosilicate) glass and ceramics. This makes it especially suitable for application which require a matched-expansion seal between metal and glass parts. Thus kovar is widely use in the electronics industry for metal parts bonding to hard glass envelopes for devices such as power tubes, x-ray tubes, etc., and other applications requiring glass-to-metal seals. Kovar is magnetic and can be plated with nickel and gold for use in corrosive environments as well