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Stainless steel AISI 304 surfaces were studied after a mild anodic polarization for oxide growth in the presence and absence of two derivatives of vitamin B2 (riboflavin and flavin mononucleotide) that can be secreted by metal‐reducing bacteria and act as a chelating agent for iron species. The alterations in oxide chemistry were studied by means of surface‐sensitive techniques such as X‐ray photoelectron spectroscopy and time‐of‐flight secondary ion mass spectrometry analysis. The complementary electrochemical characterization revealed a preferential growth of an oxide/hydroxide iron‐rich film that is responsible for an altered pit initiation and nucleation behavior. These findings suggest that as the corrosion behavior is determined by the interplay of the chemical and electronic properties, only a mild anodic polarization in the presence of redox‐active molecules is able to alter the chemical and electronic structure of the passive film formed on stainless steel AISI 304. This helps to achieve a profound understanding of the mechanisms of microbially influenced corrosion (MIC) and especially the possible effects of the redox‐active biomolecules, as they may play an important role in the corrosion susceptibility of stainless steel surfaces.

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a Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and high-resolution scanning electron microscopy are wellacknowledged tools in materials characterization. The ability to map chemical species on the surface of an investigated sample with often low mass detection limits makes ToF-SIMS an essential tool in fields where many question marks concerning degradation processes and damage mechanisms exist. The aim of this paper is to describe the power of data fusion of ToF-SIMS and high-resolution scanning electron microscopy results employing computational methods for multivariate data analysis such as principal component analysis. As a case study the investigation of hydrogen distribution in an artificially charged duplex stainless steel microstructure is presented aiming on a better understanding of hydrogen embrittlement.

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In the current research, the effect of heat treatment on the morphology of the dispersoids and their phase composition were investigated in three Cr-rich ferritic oxide dispersion strengthened (ODS) steels: PM2000, MA956, and ODM751. The steels were aged at 475°C for times ranging from 100 to 1,000 h. The microstructure was characterized using transmission electron microscopy. Study of the as-recrystallized samples revealed nano-scale Y-Al-O complex-oxide particles dispersed in the ferritic matrix. These dispersoids, which differ in size (10-160 nm) and geometry (polygonal and spherical), were identified as Y 4 Al 2 O 9 , YAlO 3 , and Y 3 Al 5 O 12 . After heat treatment, a significant change in the morphology, size, and distribution of the dispersoids was observed. Changes in the phase composition of the oxide dispersoids were also observed: YAlO 3 (with perovskite structure) was identified as the most dominant phase, indicating that it is probably the most stable phase in the Cr-rich ferritic ODS steels.

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