PURPOSE: To provide a weather resistant iron casting with which the hand intrinsic to the iron casting is exposed and maintained, generation of red rust is suppressed and easy maintenance is possible and a process for producing the casting.

CONSTITUTION: Pig iron and steel scrap are used as main raw materials. An Fe-Si alloy, graphite, etc., are added thereto and the mixture is melted by heating. The molten metal is subjected to a spheroidization treatment and is then subjected to an inoculation treatment with an Fe-Si alloy just prior to casting. The molten metal is cast into a casting mold for a bolt of M20×90 to be used for fastening of cast iron products to be exposed outdoors, by which the molten metal is molded to the spheroidal graphite cast iron. Such bolt is heated up to an austenitization temp. of 1130K by using a batch furnace and is held for 0.5 to 1 hour to austenitize the entire part. The bolt is thereafter immersed for 0.5 to 1 hour in a salt bath furnace consisting of 50% potassium nitrate and 50% sodium nitrate kept at 620K temp. and is pulled up. The bolt is then cooled with air and is subjected to an austempering treatment. The bolt is immersed for about two months in an aq. 5% iron sulfate soln. so as to be forcibly corroded, by which the mixed layer of the product of corrosion and acicular metal is formed on the surface of the bainite structure.