Preconditioning of AISI 304 stainless steel surfaces in the presence of flavins—Part I: Effect on surface chemistry and corrosion behavior

Abstract

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.

Preconditioning of AISI 304 stainless steel surfaces in the presence of flavins—Part II: Effect on biofilm formation and microbially influenced corrosion processes

“…The thickening of the oxide layer due to the preconditioning step in the presence of flavins was previously reported. [16] In presence of the bacteria, the pure steel samples show an oxide and biofilm growth with an increase in double-layer capacitance within 24 h of incubation after a phase of double-layer rearrangement in the first 6 h. The FMN sample does not exhibit a lag phase probably due to the high attractiveness of the surface for the bacteria and immediate settlement and oxide growth. After 24 h of incubation, the FMN sample has the lowest values in the phase angle (highest negative values-darkest blue range) over a wide frequency region pointing toward a thickened oxide film and a homogenous biofilm coverage.…”

“…This finding is supported by SEM images taken after the corrosion experiments. The control samples depicted in Figure 7 showed pit formation (see Part I [16] for a more detailed discussion). After incubation with bacterial culture, the pit form and size were different, as can be seen in Figure 8.…”

“…The comprehensive sample preparation and the detailed characterization of the substrates are reported elsewhere. [16] 2.2 | Cultivation of S. putrefaciens in a continuous culture S. putrefaciens CN32 (ATCC® BAA-1097™), facultative anaerobic metal-reducing bacteria, were grown in continuous culture to eliminate cultivation-related influences of batch cultures. For this purpose, a chemostat was installed, providing the bacterial culture at a set absorbance at 600 nm (A 600 ) of 0.1 in late exponential growth state for all investigations.…”

“…As presented in Part I, a detailed analysis of the surface chemistry and semiconducting properties has been performed by means of X-ray photoelectron spectroscopy (XPS) measurements and time-of-flight secondary ion mass spectrometry (ToF-SIMS) depth profiling before the incubation study to clarify the changes in the passive film chemistry and its effect on the corrosion properties. Briefly summarizing the results of Part I, [16] preconditioning in the presence of flavin molecules resulted in preferential growth of iron oxide/hydroxide-rich outer layers during passive film buildup.…”

“…[4,15] It has been demonstrated recently (in Part I) that the presence of RB and FMN during mild anodic polarization results in thickening of the passive film with an increase in Fe(II) oxyhydroxides, leading to changes in the pit nucleation and corrosion properties. [16] Xiao et al [17] investigated whether riboflavin has the ability to inhibit ferrihydrite transformation. O'Loughlin [18] studied the effect of electron transfer mediators on the bioreduction of lepidocrocite by S. putrefaciens CN32.…”