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 FeMo intermetallic alloy in 0.5M H2SO4 has been evaluated using electrochemical techniques at room temperature. The intermetallic Fe2MO powder was sintered at 750 degrees C at 607, 884 and 1223 MPa and at 900 degrees 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 (E-corr) 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 E-corr nor the anodic current density values were affected by these variables, which rapidly reached a steady-state value. At 750 degrees C, the corrosion rate increased as the sintering pressure decreased, probably due to the retention of electrolyte inside the porous. At T = 900 degrees 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 degrees 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. (c) 2005 Published by Elsevier B.V.