Most of the gird components in a Glock pistol are treated with a nitriding development called "Tenifer", which increases http://www.gunslot.com/guns/glock-19 the surface hardness and makes the weapon resistant to corrosion and wear.
This was so revolutionary at the continuance that Remington dyed the plastic brown to resemble pulp and fitted a cosmetic sheet-metal cover on the receiver to make it appear to be plastic from steel. Further, the most extended custom of polymers in a appropriate was in the Ram-Line Syn Tech Exactor pistol with a tun made from steel-lined plastic.