Microbiologically Influenced Corrosion in UNS S31653: Detection and Analysis Using Electrochemical Noise Technique

Abstract

Austenitic stainless steels are susceptible to microbiologically influenced corrosion (MIC), and biofilms of slime-forming bacteria can affect the integrity of the passive film of the stainless steel components. An attempt was made to detect and analyze the MIC on UNS S31653 using electrochemical noise (EN) technique. The progress of MIC was monitored in natural reservoir water, concentrated with biofilm-forming microbes along with 0.5 M sodium chloride (NaCl) and nutrients, as well as in a similar media minus microbes (made sterile by autoclaving) using two nominally identical UNS S31653 cylindrical specimens for about 3 weeks, where current and potential noise signals were collected at 1 Hz sampling frequency. Analysis of the shot-noise parameters like frequency of corrosion events, average charge in each event, true coefficient of variation, and noise resistance showed that initiation and propagation of MIC was marked by significant changes in these parameters. The presence of crevice corrosion as well as small pits were observed in the specimen exposed to the natural water confirming MIC; this observation concurred well with the bacterial density, which increased as a function of time. The specimen exposed to sterilized water showed just a few incipient pits.

Corrosion behavior of carbon steel in the presence of sulfate reducing bacteria and iron oxidizing bacteria cultured in oilfield produced water

“…SRB may propagate quickly in the locally anaerobic environment beneath the iron rich tubercles produced by IOB [24]. The interaction between SRB and IOB could accelerate the pitting corrosion process of carbon steel [25].…”

A Critical Appraisal of the Interpretation of Electrochemical Noise for Corrosion Studies

“…EPN transients are typically characterized by a relatively fast rise and slow (e.g., exponential) decay of the absolute value of the EPN signal. 6,8,[10][11]23,[48][49][50][63][64]80,84 Stable pitting corrosion generates an ECN signal that is characterized by large transients (typically larger than for metastable pitting). These can remain at a high value for a longer time than for metastable pitting (e.g., in the order of one hundred to several hundreds of seconds) before decreasing again.…”

Identification of steel corrosion associated with sulfate‐reducing bacteria by electrochemical noise technique

“…[ 24 ] Localized corrosion is expected to have a low characteristic frequency and high characteristic charge. Chandrasatheesh et al [ 37 ] and Pujar et al [ 39 ] showed that localized corrosion of stainless steel associated with MIC corresponded to shot noise parameters.…”

“…Asymmetry of the paired electrodes, possibly due to the variability of bacterial activity, biofilm, corrosion films, and aeration levels can result in macrocell polarization that will be reflected in these values. The standard deviation (σ) would ideally qualify the magnitude of the isolated noise transient events deviating from the mean, although larger values [37] Time domain, R n , shot noise 316 L stainless steel Iron-oxidizing bacteria, 1% NaCl Low f n and large q n corresponding to pitting corrosion -Homborg et al [38] Hilbert spectra of time domain Pujar et al [39] R n , shot noise UNS S31653 Stainless steel Slime-forming bacteria, 0.5 M NaCl Low f n and large q n corresponding to crevice -R n did not distinguish corrosion Zaveri et al [40] associated with wide noise bands could mask those phenomena. The localization index (LI) was defined as σ I /rms I and would ideally identify localized processes; however, interpretation of this value can be complicated due to the presence of bidirectional transients and the relative number of transient events in a time record.…”

“…[24] Localized corrosion is expected to have a low characteristic frequency and high characteristic charge. Chandrasatheesh et al [37] and Pujar et al [39] showed that localized corrosion of stainless steel associated with MIC corresponded to shot noise parameters. Due to the relatively few reported cases of bridge structural steel elements with deterioration associated with MIC, there has not been wide awareness of the risk for this form of corrosion for the submerged elements in natural waters, let alone the possibility for accelerated localized corrosion that is not accounted in design with sacrificial metal thickness and cathodic protection systems.…”