Cast irons are basically binary alloys of iron and carbon having carbon exceeding its maximum solid solubility in austenite but less than the carbon content of iron carbide. However, like steels, cast irons have varying quantities of silicon, manganese, phosphorus and sulphur. Silicon plays an important role in controlling the properties of cast irons and for this reason, the term cast iron is usually applied to a series of iron, carbon and silicon alloys. Special purpose cast irons include white and alloy cast irons which are mainly used for applications demanding enhanced abrasion, corrosion or heat resistance. In present study, corrosion resistant cast irons are of our interest.

A detailed review of literature disclosed that corrosion resistant alloy cast irons currently in use is a compound of high percentage of silicon, nickel and chromium. Hence is called as chromium-molybdenum irons. It is widely used for oxidizing purpose. However, it shows low mechanical strength and shock resistance. Hence it is less useful for applications related with high mechanical strength and shocks. Ni-resist irons are useful in various types of ambient. It has low strength and become unsuitable at temperature higher than 780°C. High Ni- austenitic gray irons also suffer from corrosion due to graphite. High chromium irons is useful in all types of mold depending on chromium content. It demonstrates good resistance against attrition, abrasion and oxidation. The jostle resistivity of high chromium irons can be improved by reducing carbon content.   

Low cost substitutes for these cast irons may be aimed at substituting the scarce elements namely nickel and/or molybdenum partly or fully. Nickel can be replaced partially by manganese and copper. Manganese also controls austenite like nickel completely. Hence it can be used to refine pearlite and promote the formation of any desired matrix (bainite or martensite or austenite) in the as-cast condition. It has a mild carbide-forming tendency. The carbide morphology of manganese bearing chromium irons was found to be similar to that observed in high chromium irons because both manganese and chromium have a similar carbide-forming tendency. Copper cannot fully stabilize austenite and is effective only in the presence of another austenite stabilizer.

The possibility of evolving low cost corrosion resistant white irons is based on the fact that the difference of electrochemical potential between austenite and graphite is higher than that between austenite and carbide and it is a reason of reduction in graphitic corrosion which is a typical problem in high alloyed corrosion resistance gray irons. The mixture of materials is preferred due to the fact that the elements are locally available and effective in production of corrosion resistant white irons. It is assumed that iron-manganese-chromium-copper white irons are capable to resist corrosion, wear and corrosive-wear.

The present study essentially comprised a detailed investigation of certain newly designed Fe-Mn-Cr-Mo white irons, containing 10% Mn-6% Cr-3.0% C,0.3%Mo, The investigation was aimed at developing cheaper corrosion resistant white cast irons having corrosion resistance similar to expensive highly alloyed Ni-Resist irons. The study comprised assessing the heat treatment response of the experimental alloy with a view to establish interrelation between structure and properties. Hardness measurements, optical and scanning metallography, quantitative metallography, electron probe micro analysis and differential thermal analysis were carried out to correlate structure, properties and corrosion rate. However corrosion rates in 6% NaCl solution were found comparable to that of Ni-Resist irons.