Relationship between Phase Occurrence, Chemical Composition, and Corrosion Behavior of as-Solidified Al–Pd–Co Alloys

Abstract

The microstructure, phase constitution, and corrosion performance of as-solidified Al70Pd25Co5 and Al74Pd12Co14 alloys (element concentrations in at.%) have been investigated in the present work. The alloys were prepared by arc-melting of Al, Pd, and Co lumps in argon. The Al74Pd12Co14 alloy was composed of structurally complex εn phase, while the Al70Pd25Co5 alloy was composed of εn and δ phases. The corrosion performance was studied by open circuit potential measurements and potentiodynamic polarization in aqueous NaCl solution (3.5 wt.%). Marked open circuit potential oscillations of the Al70Pd25Co5 alloy have been observed, indicating individual breakdown and re-passivation events on the sample surface. A preferential corrosion attack of εn was found, while the binary δ phase (Al3Pd2) remained free of corrosion. A de-alloying of Al from εn and formation of intermittent interpenetrating channel networks occurred in both alloys. The corrosion behavior of εn is discussed in terms of its chemical composition and crystal structure. The corrosion activity of εn could be further exploited in preparation of porous Pd–Co networks with possible catalytic activity.

Aqueous Corrosion of Aluminum-Transition Metal Alloys Composed of Structurally Complex Phases: A Review

“…The stresses were released during leaching, resulting in continuous tunnels inter-penetrating the surfaces of de-alloyed materials. A similar corrosion behavior was also found for the Al-Pd-Co alloys (Figure 18, [107]). The de-alloying of Al was more pronounced in the as-solidified alloys.…”

“… Microstructure of as-corroded Al–Pd–Co alloys: backscatter scanning electron microscopy images of Al 70 Pd 25 Co 5 ( a ) and Al 74 Pd 12 Co 14 ( b ) and confocal laser scanning images of Al 70 Pd 25 Co 5 ( c ) and Al 74 Pd 12 Co 14 ( d ). Reproduced from reference [ 107 ]. …”

“… Corrosion parameters of Al–Pd, Al–Co and Al–Pd–Co alloys in aqueous NaCl (0.6 mol L −1 ). Data is compiled from references [ 81 , 82 , 84 , 105 , 107 ]. …”

Annealing of Al-Zn-Mg-Cu Alloy at High Pressures: Evolution of Microstructure and the Corrosion Behavior

“…Existing studies have shown that in this aluminum alloy system, intermetallic compound MgZn 2 will act as an anode particle with a higher potential than the substrate [ 54 , 55 ]. The intermetallic compound plays an important role in affecting the electrochemical corrosion process of alloys [ 56 , 57 ]. In this study, the second phase MgZn 2 was first oxidized as the anode particle, and then resulted in a micropit, which initiated the pitting process [ 58 ].…”

Special Issue: Recent Advances in Corrosion Science

“…The search for alloying additives enhancing the corrosion resistance without sacrificing the desired characteristics continues, intending to reduce alloy corrosion rate and bring measurable economic profits. Within this Special Issue, you will find multiple original research papers strictly devoted to this issue for both ferrous [2][3][4] and non-ferrous metals [5][6][7][8]. The influence of novel microscopy tools, which enable the direct observation of local corrosion processes, cannot be overestimated.…”