Effect of austempering temperature and time on corrosion behaviour of ductile iron in chloride and acidic media

The aim of this paper is to study the effect of heat treatment temperature and time on the corrosion behavior of ductile iron in 0.5 M NaCl and 0.5 M H₂SO₄.

Ductile iron samples of known composition were austenized at temperatures 800°C and 850°C, and austempered at 300°C and 350°C for periods of 30, 45 and 60 min to convert them to austempered ductile iron (ADI). The corrosion behavior of these ADI samples in 0.5 M NaCl and H₂SO₄ was measured using the conventional weight loss method. The metallographic examination of the samples was carried out to study the morphology of their corroded surfaces.

Ductile iron is susceptible to corrosion in both acidic and chloride media, while attack by acid media is mainly at the grain boundaries, that from the chloride is pitting. The corrosion behavior of the material is affected by the compositional structures of the materials as well as the austempering temperature and time it was subjected to.

Ductile iron has the potential to replace costlier materials in many engineering and structural applications.

The results revealed that the corrosion of ADI in both acidic and chloride media were strongly dependent on the structure of the material, which in turn was affected by the austempering temperature and time.