The study of electrochemical behavior of approximation phases in the Al–(Cu)–Fe–Cr system is an important task in the context of developing new corrosion-resistant materials. Approximation phases, structurally close to quasicrystals but possessing a periodic lattice, can demonstrate unique electrochemical properties due to their complex atomic structure and chemical composition. The introduction of chromium into the Al–(Cu)–Fe system allows for targeted modification of the phase composition and microstructure, thereby influencing the electrochemical characteristics.
The electrochemical behavior of the approximation phases is studied using various methods, including potentiodynamic polarization, electrochemical impedance spectroscopy, and steady-state potential measurements. These methods allow us to evaluate the corrosion resistance of materials in various aggressive environments and to determine the corrosion mechanisms. The presence of chromium in the alloy can lead to the formation of a passive film on the surface, which significantly increases its resistance to electrochemical corrosion.
The corrosion properties of quasicrystalline phases, close in structure to crystalline ones, in the Al–Cu–Fe–Cr and Al–Cr–Fe systems are investigated in comparison with the behavior of stainless steel. A solution containing citric acid and chloride ions is used as an electrolyte. The electrochemical characteristics are assessed by measuring the open-circuit potential, determining the polarization resistance, and plotting anodic polarization curves. After completion of the electrochemical tests, the electrolytic solutions are analyzed, and the samples are examined by scanning and transmission electron microscopy.
During the electrochemical action, two types of corrosion are observed: uniform and pitting. The chemical composition of the samples plays a key role in their resistance to both types of corrosion in these aggressive conditions. Chromium seems to improve the electrochemical properties and increase corrosion resistance, while copper has the opposite, negative effect. Uniform corrosion leads to a change in the chemical composition of the surface due to the preferential dissolution of aluminum and an increase in the oxygen concentration. Some samples from the Al-Cr-Fe system show properties comparable to those of stainless steel.
The effect of chromium on the electrochemical behavior of approximation phases in the Al–(Cu)–Fe–Cr system is manifested in a change in the corrosion and pitting potentials, as well as in a change in the parameters of the passive film. Optimization of the alloy composition, including varying the chromium concentration, allows achieving maximum corrosion resistance under specific operating conditions. Analysis of electrochemical parameters in combination with microscopic studies of the surface after corrosion tests allows establishing the relationship between the structure of the material and its electrochemical behavior.
Author: D. Veysa, C. Rapin, X. Li, L. Aranda, V. Fournée, J. M. Dubois
Institute: Research Laboratory of Materials and Metallurgy UMR 7584 CNRS, INPL, UHP, Nancy School of Mines, Parc Sorup, F-54042 Nancy, France, Laboratory of Chemistry of Solid Minerals UMR 7555, Henri Poincaré University, F-54506 Vandoeuvre-lès-Nancy, France