Corrosion behavior of uniaxially cold-pressed Fe2Mo intermetallic in 0.5M H2SO4

The effect of sintering pressure and temperature on the corrosion resistance of uniaxially cold-pressed Fe2Mo intermetallic alloy in 0.5M H2SO4 has been evaluated using electrochemical techniques at room temperature. The intermetallic Fe2Mo powder was sintered at 750 °C at 607, 884 and 1223 MPa and at 900 °C at 480, 540, 822, 873 and 1040 MPa to produce different porosities. Electrochemical techniques included potentiodynamic polarization curves, electrochemical noise in current, evolution of the free corrosion potential (Ecorr) with time and linear polarization resistance to know the change of the corrosion rate with time. Results showed that all the alloys showed a passive region of several hundreds of millivolts wide, and that, regardless the compacting pressure or temperature, practically neither the Ecorr nor the anodic current density values were affected by these variables, which rapidly reached a steady-state value. At 750 °C, the corrosion rate increased as the sintering pressure decreased, probably due to the retention of electrolyte inside the porous. At T = 900 °C, this was not so evident, but it followed a similar tendency. Thus, the electrochemical noise reading showed that precisely at the lowest compacting pressure for 750 °C, where is expected the highest porosity density, the corrosion type is a localized one, probably pitting, whereas in all the other compacting conditions, where a lower porosity density is expected, the corrosion type is uniform generalized one.