Corrosion Resistance of Alloys of the Al–Cu–Fe–(Si, B) System in Mineralized Saline and Acid Solutions

• Published in: Materials science (New York, N.Y.) N.Y.), 2019-09, Vol.55 (2), p.291-298
• Main Authors: Sukhova, O. V., Polons’kyi, V. A., Ustinova, K. V.
• Format: Article
• Language: English
• Subjects: Acid resistance; Acids; Alloy systems; Alloying; Alloys; Characterization and Evaluation of Materials; Chemistry and Materials Science; Copper; Corrosion and anti-corrosives; Corrosion resistance; Corrosion resistant alloys; Gravimetric analysis; Hydrogen chloride; Iron; Materials Science; Metallography; Pits; Quantitative metallography; Saline solutions; Silicon; Sodium sulfate; Solid Mechanics; Specialty metals industry; Structural Materials; Sulfuric acid
• ISSN: 1068-820X; 1573-885X
• DOI: 10.1007/s11003-019-00302-2

We study the influence of alloying with 4–7 at.% Si and/or 1–3 at.% B on the corrosion behavior of Al– Cu–Fe quasicrystalline alloys in the solutions of HCl, H 2 SO 4 , HNO 3 , and H 3 PO 4 (pH 1.0) acids and in 3.0 M NaCl and 0.2 M Na 2 SO 4 (pH 7.0) solutions of salts. We use the methods of quantitative metallography, electron microscopy, and gravimetric analysis. It is shown that the studied alloys corrode especially intensely in the solutions of HCl and H 2 SO 4 acids, while the least intense corrosion is observed in a solution of HNO 3 . The corrosion resistance in acids increases as the content of phases enriched with iron in the structure of alloy decreases. Corrosion mainly occurs in the areas with the λ -Al 13 Fe 4 phase or ψ –λ and ψ –(τ, η, θ) interfaces. As compared with the acid solutions, the alloys corrode much slower in saline solutions. In these solutions, we also observe the process of selective corrosion of iron from the Al–Cu–Fe–(Si, B) alloys but the dissolution of phases is more uniform than in acid solutions. On the surfaces of alloys, we observe the formation of the areas of brown rust and pits. The bottoms of the pits are covered with porous copper layers. For the major part of samples and pits, their corrosion in NaCl solutions is stronger than in Na 2 SO 4 solutions. The positive influence of alloying with Si or/and B on the corrosion resistance of alloys is revealed. The compositions of alloys with the highest corrosion resistances are determined. The Al 55 Cu 25 Fe 12 Si 7 B 1 and Al 53 Cu 25 Fe 12 Si 7 B 3 alloys are recommended for operation in acid and saline solutions, respectively.