Electrochemical corrosion characterization of nickel aluminides in acid rain

Nickel aluminides have been extensively studied in recent decades to replace superalloys, in somecomponents of aircraft turbines, because they have excellent corrosion resistance. Many industrial cities havethe problem of air pollution, which has forced the study of the degradation of these alloys in the presence ofacid rain. The aim of this work is to study the electrochemical corrosion behavior of nickel aluminides in amedium of simulated acid rain. Potentiodynamic Polarization, Linear polarization resistance curves, Rp,Nyquist data and Bode curves obtained by electrochemical impedance spectroscopy were used to study thecorrosion behavior of two intermetallic compounds. The polarization curves show that both intermetallicNi3Al and NiAl have very similar corrosion potential, showing a slightly nobler behavior the NiAlintermetallic. The intermetallic Ni3Al has an active-passive behavior where the anode branch presents ageneral dissolution of the alloy, indicating that it is under cathodic control. NiAl intermetallic shows anactive dissolution region, followed by a passive behavior. At longer immersion times, Ni3Al intermetallic hasa higher polarization resistance, which means a lower corrosion rate.Keywords: Nickel Aluminides, Electrochemical impedance spectroscoy, Acid Rain, Nanoindentation