Corrosion studies on Fe- and Mg-based bulk-glass forming alloys

(Korrosionsstudien an Fe- und Mg-basierten massivglasbildenden Legierungen)   

A series of bulk amorphous steels (BAS) with castability of up to several centimeters thickness and extremely high strength and hardness has raised interest for structural applications. The corrosion behavior of a prominent example, (Fe44.3Cr5Co5Mo12.8Mn11.2C15.8B5.9)98.5Y1.5, was studied in different aqueous electrolytes. In acidic solutions, due to its single-phase nature, the BAS exhibits a much higher stability than the multiphase crystalline counterpart and the conventional steel X210Cr12. The acid corrosion process based on multiple micro-pit formation was analyzed in detail. With increasing pH value, the overall elemental composition of the alloy plays a more important role than structural particularities. The reactive elements Mo, Mn, Co are considered to cause a diminished corrosion stability of the BAS.
Metallic glasses based on the Mg-TM-RE system (TM= transition metal; RE= rare earth) show in many environments significantly reduced corrosion rates and improved anodic passivity as compared to Mg and conventional Mg alloys. However, they are very sensitive to local degradation phenomena like pitting and filiform corrosion. Moreover, these glasses exhibit a high capability for hydrogen absorption which causes materials embrittlement. On the other hand, some glasses are suitable for hydrogen storage.

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