Switching from Homogeneous to Localized Corrosion in Stainless-Type Amorphous and Nano-Crystalline Steels

Amorphous stainless-type steels with high Cr content provide next to some applications as corrosion protective coatings an interesting playground for fundamental studies of electrochemical corrosion behavior (1-4). Starting from an ultimately homogeneous glassy version, partially and fully nanocrystalline states with large elemental heterogeneity depending on the crystallization can be derived by simple heat treatments (1,2). The amorphous materials Fe_65-xCr_xMo₁₄C₁₅B₆show relative low passive currents which significantly increase after partial crystallization owing in part to a related nano-scaled roughness of the passive films (Fig.1). For low-Cr contents we have as well observed  a clear switch from the typical homogeneous corrosion of these alloys to a clearly localized attack. We will discuss this phenomenon in the light of atom probe tomography (Fig.2), microscopy, and electrochemical measurements.

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