Electrochemical response of Fe_65.5Cr₄Mo₄Ga₄P₁₂ C₅B_5.5 bulk amorphous alloy in different aqueous media

Abstract

A bulk amorphous Fe 65.5 Cr 4 Mo 4 Ga 4 P 12 C 5 B 5.5 alloy was investigated for its electrochemical behaviour in different electrolytes. The investigations showed substantial differences in response between the rapidly quenched and cast samples of the same composition. Annealing of the cast samples improved their corrosion resistance, which was possibly due to structural relaxation processes. The alloy was found to have very good resistance to neutral and slightly acidic chloride solutions in the rapidly quenched form.The passivation observed could not be attributed to any metal/metalloid oxide and was most probably due to an adsorbed oxygen layer. No chromium or molybdenum enrichment was observed at the surface. However, a sub-surface phosphorus enrichment was observed in rapidly quenched samples, in the as-received state as well as after electrochemical treatments, which may be responsible for their improved corrosion resistance.

Corrosion behavior of bulk metallic glasses in different aqueous solutions

“…As for the sample annealed in 927 K, which responds to a crystalline state, the defects such as boundary, displacement, differing phases and crystal imperfection will act as nucleation sites for corrosion and induce the decease of its corrosion resistance. Interestingly enough, our results are very different from Chattoraj et al research work [10]. They have investigated rapidly quenched and cast Fe 65.5 Cr 4 Mo 4 Ga 4 P 12 C 5 B 5.5 samples of the same composition, which shows that annealing of the cast samples improved their corrosion resistance.…”

“…No chromium or molybdenum enrichment was observed at the surface. However, a sub-surface phosphorus enrichment was observed in rapidly quenched samples [10]. In fact, localized corrosion is dependent upon the chemical characteristic of the surface film [17][18][19].…”

“…Very recently, Lu et al [5], reported that they cast "amorphous steel" in bulk form with a critical sample thickness as large as 12 mm in FeCr(Co)MoMnCB system, and also Fe 65.5 Cr 4 Mo 4 Ga 4 P 12 C 5 B 5.5 amorphous rectangular bars with a cross-section of 2 mm×2 mm and a length of 30 mm was reported by Stoica et al [9]. Due to the inherent microstructural homogeneity and lack of surface irregularities, BMGs demonstrate promising potential in engineering applications [10]. In particular, the corrosion behavior of Fe-based BMGs is of great importance to more extended application.…”

Mechanical behavior of Fe65.5Cr4Mo4Ga4P12C5B5.5 bulk metallic glass

“…Because of the absence of crystalline anisotropy, the Fe 65.5 Cr 4 Mo 4 Ga 4 P 12 C 5 B 5.5 amorphous alloy exhibits good soft magnetic properties, characterized by a low coercive force and a high permeability [2]. The presence of Cr and Mo in the composition not only improves the glass-forming ability, but also increases the corrosion resistance of the material in comparison with conventional steels used for magnetic applications [3,4]. Besides the good soft magnetic properties, such alloys also require good mechanical strength for possible use in magnetic devices as magnetic sensors, magnetic valves or magnetic clutches.…”

Effect of cobalt on the corrosion behaviour of amorphous Fe-Co- Cr-B-Si alloys in dilute mineral acids

“…In 1974, Naka, Hashimoto and Masumoto brought into evidence both the corrosion resistance and the inertness in various aqueous electrolytes [1][2][3][4][5][6] . It is believed that all sources of localized corrosion disappear in the absence of common structural defects such as the grain boundaries, dislocations and segregations [7][8][9][10] .…”