Electrochemical corrosion characterization of nickel aluminides in acid rain

Engelbert Huape Padilla,Claudio Aguilar Ramírez,Luis Béjar Gómez,Ariosto Medina Flores,Ismeli Alfonso López

doi:10.1590/s1517-707620180002.0335

Abstract

Nickel aluminides have been extensively studied in recent decades to replace superalloys, in some components of aircraft turbines, because they have excellent corrosion resistance. Many industrial cities have the problem of air pollution, which has forced the study of the degradation of these alloys in the presence of acid rain. The aim of this work is to study the electrochemical corrosion behavior of nickel aluminides in a medium 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 the corrosion behavior of two intermetallic compounds. The polarization curves show that both intermetallic Ni3Al and NiAl have very similar corrosion potential, showing a slightly nobler behavior the NiAl intermetallic. The intermetallic Ni3Al has an active-passive behavior where the anode branch presents a general dissolution of the alloy, indicating that it is under cathodic control. NiAl intermetallic shows an active dissolution region, followed by a passive behavior. At longer immersion times, Ni3Al intermetallic has a higher polarization resistance, which means a lower corrosion rate. Keywords: Nickel Aluminides, Electrochemical impedance spectroscoy, Acid Rain, Nanoindentation.

Highlights

Nickel aluminides such as NiAl and Ni3Al have received considerable attention for high temperature structural and coating applications in aerospace field [1,2,3], and due to high temperature strength, high corrosion resistance, high thermal and electrical conductivity, high melting temperature (1638°C), high Young’s module (240GPa) have been regarded as a promising candidate for the high temperature applications [4,5]
Ni-base superalloys, Co alloys and steels are widely used in applications such as aircraft turbine blades and power plants due to present good corrosion resistance at elevated temperatures, the lower density (5.86g/cm3) than superalloys and excellent high temperature oxidation resistance, allowed nickel aluminides being extensively studied in the past decades to replace superalloys [6,7,8]
No precipitates were observed in this intermetallic alloy, confirmed by X-ray diffraction pattern, where crystal structure corresponding to Ni3Al alloy and no second phases were detected, see Fig. 2a

Summary

Introduction

Nickel aluminides such as NiAl and Ni3Al have received considerable attention for high temperature structural and coating applications in aerospace field [1,2,3], and due to high temperature strength, high corrosion resistance, high thermal and electrical conductivity, high melting temperature (1638°C), high Young’s module (240GPa) have been regarded as a promising candidate for the high temperature applications [4,5]. Ni-base superalloys, Co alloys and steels are widely used in applications such as aircraft turbine blades and power plants due to present good corrosion resistance at elevated temperatures, the lower density (5.86g/cm3) than superalloys and excellent high temperature oxidation resistance, allowed nickel aluminides being extensively studied in the past decades to replace superalloys [6,7,8]. Nickel aluminides have excellent corrosion resistance in most environments, are being used as biomedical metallic materials to replace alloys such as stainless steel, most of the used materials for human implants include. PADILLA, E.H.; FLORES, A.M.; RAMIREZ, C.A. Matéria, v.23, n.

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