NICKEL IRON SEALING ALLOY 52 ; (Composition (Nominal): Ni 50 , Fe Balance . ;( Alloy 52 is a 50% nickel-iron alloy developed for glass-to-metal seals for some of the soft glasses and some ceramics. The alloy's rate of thermal expansion is virtually constant to a temperature of about 1050 °F (565 °C). ;(Specification : ASTM F30 ; ;(Product availability and request a QUOTE!