An Electrochemical Study of the Effect of B on the Corrosion of Atomized Fe40Al Intermetallics in Molten Na_2SO_4

摘要

The hot corrosion resistance of sprayed and atomized and Fe40Al+10Al_2O_3 intermetallic materials with different boron contents (0.1, 0.2 and 0.4at. percent) has been evaluated in molten Na_2SO_4 at 1173 and 1273 K using polarization curves, open circuit potential and linear polarization resistance measurements. The results are supported by electron microscopy and micro-chemical studies. Generally speaking, the additions of up to 0.4B were berieficial, since, for short times, they made the E_(corr) value more active but, after some hours, all the E_(corr) values became nobler, even nobler than the alloy without boron and decreased both the anodic and cathodic current density, but did not promote the formation of a passive film, at least for short times. In terms of corrosion rate, additions of boron always decreased this value as opposed to the alloy without boron, specially at 1273 K, but the corrosion rate values decreased rapidly, attaining a constant value, which was consistent with the establishment of a protective alumina, Al_2O_3 layer and promoted Al depletion on the FeAl matrix which allows internal sulfidaton. It seems that the optimum amount of boron that gives the best corrosion resistance is 0.1B