Effect of alloying with Ni, Cr and Al on the atmospheric and electrochemical corrosion resistance of ferritic ductile cast irons

The corrosion control of ductile cast irons becomes a technological challenge when supplying castings to customers due to the high reactivity of this alloy in contact with air. An interesting alternative to the protective systems such as coatings or corrosion inhibitors included in packaging processes is the chemical modification of the cast alloys by means of alloying elements addition which are able to improve the corrosion resistance of ductile cast irons. Ni, Cr and Al added to the cast alloys significantly affect their structure and properties, among them their corrosion response, when exposed to air. It has been observed that Ni and Al improve the corrosion behaviour while Cr additionally promoted pearlite and carbides formation. The results from the corrosion tests performed on ductile cast iron alloys which contain these three elements are discussed in the present work.