Evaluation of Corrosion of a Fe-40Al-2RE Intermetallic Alloy in NS4 Solution

Abstract

The corrosion study of Fe-40Al+2% Rare Earths (RE) intermetallic alloy in NS4 solution at room temperature was carried out. The intermetallic alloy was previously produced by melting in an induction furnace. The alloy microstructure is constituted by a minority phase of Fe3Al, homogeneously dispersed in the majority phase of FeAl. The effect of pH condition was presented in the corrosion mode, at pH 5 the sample showed uniform corrosion, while at pH 3 and 7 some pitting sites were observed, however the metallic samples showed uniform corrosion on the exposed areas. The anodic dissolution mechanism occurred preferentially in the FeAl phase observed at pH 3, which corresponds to the majority phase or alloy microstructure. Electrochemical results were complemented with the microstructure and chemical characterization by scanning electron microscopy, energy dispersion spectroscopy and X-ray diffraction analysis.

Assessment of the Corrosion Behavior of FeAl Based Intermetallics in NaCl Solution

“…The effect of a third alloying element to the FeAl base intermetallics has been studied in order to improves the mechanical properties (1-3,10), similarly, iron aluminides (Al-Fe) have presented a good performance against corrosion in NaCl saline solutions (6,7). The corrosion resistance behavior of iron aluminides is improved with the addition of some microalloying elements, particularly those that modify the microstructure, such as the case of Li here evaluated, as was reported previously (8,9). In those reports, the common characteristic was the formation of a continuous layer of corrosion products grown on the surface, as well the decreasing of the minority Fe 3 Al phase; which promotes the reducing of the galvanic microsites formed with the matrix phase.…”

“…Moreover, the addition of grain refining micro-alloys as the case of Li addition (1-3) has a beneficial effect on corrosion performance in various aqueous media. In the Fe-40Al alloy system, where the minority Fe 3 Al phase was homogeneously dispersed in the FeAl matrix, the effect of the addition of micro-alloys reduced the presence of the minority phase, improving the corrosion resistance (8,9). In this sense, in this work the evaluation of the electrochemical behavior of intermetallic materials based on Fe-Al (40 at.…”

Corrosion Assessment of Fe-Ni-Al Based Alloy in Saline Solution

“…Nevertheless, in both aqueous conditions, the addition of Fe to the base alloy NiAl promotes a beneficial effect on the corrosion resistance. Similarly, the FeAl phase has shown excellent behavior against corrosion in aqueous solutions, such as, for example, in the NS4 solution at pH 3, pH 5 and pH 7, the base intermetallic Fe 60 Al 40 (13) presented i corr values below 10 µA/cm 2 , and under the three pH conditions, at pH 5 present the best performance in corrosion resistance kinetics. In this sense, according to the results obtained, the authors consider that the Fe-Ni-Al alloy represents a candidate for potential applications in coastal environments…”

“…The combination of these three elements (Fe, Ni and Al) in a ternary system has also been studied because of the properties of the nickel aluminides and the modifications in the mechanical (3,4) and microstructural (5,6) properties obtained with the incorporation of the iron in the Ni-Al system. In this sense, some corrosion studies have been carried out on the behavior of the both Fe-Ni-Al (7) and Fe-Ni-Al-Cr (7,8) alloys in molten salts; and some corrosion resistance studies on both Fe-Al based and Ni-Al binary alloys at high temperature (9,10) and several corrosion assessment in aqueous solutions (11)(12)(13)(14) for the binary alloys. According to above described, in this work, the study of the corrosion of a Fe-Al-Ni base intermetallic alloy in a saline solution at room temperature was carried out by electrochemical techniques.…”