Effect of carbon on corrosion resistance of powder-processed Fe-0·35%P alloys

The corrosion behaviour of phosphoric irons containing 0.35 wt % P, 2% copper, 2% nickel, 1% silicon, 0.5% molybdenum, with/without 0.15% carbon prepared by powder forging route were 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 (0.5 M Na2CO3 + 1.0 M NaHCO3 solution of pH 9.4). The corrosion studies were conducted using Tafel extrapolation and linear polarization methods. The studies also compare Armco iron with phosphoric irons. It was observed that the addition of carbon improved the corrosion resistance of a Fe-0.35%P-2%Ni-2%Cu-1%Si-0.5%Mo alloy in all the environments. Corrosion rates were highest in acid medium, minimal in alkaline medium and low in neutral solution. SEM/EDAX was used to characterize the compositions.