Effect of Chromium on the Corrosion Behavior of Powder-Processed Fe-0.35 wt % P Alloys

The corrosion behaviour of phosphoric irons (i.e. Fe-P alloys containing low phosphorous in the range 0.1 to 0.7 wt. %) with/without addition of chromium, prepared by powder forging route was studied in different environments. The various environments chosen were acidic (0.25 M H2SO4 solution of pH 0.6), neutral/marine (3.5 % NaCl solution of pH 6.8) and alkaline (0.5M Na2CO3 + 1.0 M NaHCO3 solution of pH 9.4). The corrosion studies were conducted using Tafel Extrapolation and Linear Polarization techniques. The studies compare electrolytic Armco iron with phosphoric irons. It was observed that, chromium improved the resistance to corrosion in all the environments. Corrosion rates were higher in acid medium due to the enhanced hydrogen evolution and hence, the cathodic reaction. The corrosion rates were minimal in alkaline medium and low in neutral solution