INFLUENCE OF MOLYBDENUM ON THE ANODIC-DISSOLUTION OF IRON IN ACIDIC SOLUTIONS

The anodic dissolution of pure iron and binary iron-molybdenum alloys (10 and 20 wt % Mo) in molar H2SO4 and HCl solutions was studied by d. c. polarization and a.c. impedance techniques. Molybdenum additive inf luences both the steady state polarization curves and the impedance sp ectra in the two media, the impact being stronger for the Fe-20 wt % M o alloy. In general, two-slope polarization curves are obtained for th e alloys; impedance spectra exhibit two time constants in addition to the charge transfer one implying the existence of two reaction interme diates. Differences between spectra measured in H2SO4 and HCl are disc ussed. A kinetic model advanced on the basis of literature data for pu re iron and molybdenum was able to reproduce quantitatively both the s teady state and a.c. impedance results for both alloys in the two medi a. Kinetic parameters for the anodic dissolution of Fe-Mo alloys are t hereby determined.