Stainless Steel In Natural Seawater Research Articles

The impact of alloying element Cu on corrosion and biofilms of 316L stainless steel exposed to seawater.

Copper-containing stainless steel (SS) has been reported to mitigate biofilms in industrial and clinical environments. However, the impact of copper released from copper-containing SS in natural seawater on biofilms and corrosion is still unclear. In this study, three kinds of 316L SS were immersed in natural seawater for 6months, and the pitting depth decreased in the order: 316L-Cu SS (annealed) > 316L SS > 316L-Cu SS (aged). The biofilm thickness and number of sessile cells on the surface of 316L-Cu SS (annealed) and 316L SS were similar but notably greater than those of 316L-Cu SS (aged). Furthermore, the results of the community analysis indicated that the addition of copper in 316L-Cu SS (aged) reduced the diversity and richness of the microbial community, resulting in a significant reduction in the number of genera constituting the biofilms. Copper ions exhibit a broad-spectrum bactericidal effect, effectively reducing the abundance of dominant populations and microbial genera in the biofilms, thereby mitigating pitting corrosion induced by microorganisms. In addition, the PCoA scatter plot showed that time also played an important role in the regulation of microbial community structure.

When material science meets microbial ecology: Bacterial community selection on stainless steels in natural seawater

The passive film depends on the alloy's composition and the exposure conditions. How the surface composition affects the selection of microbial biofilms though, has not been fully elucidated or incorporated into the analysis of corrosive biofilms. The degradation of stainless steel (SS) exposed to natural seawater was studied to understand how the oxide layer composition of SS could affect the selection and variability of the bacterial community. To accomplish this goal, austenitic and superferritic SS grades were exposed to natural seawater on the central coast of Chile. The deterioration of steel and qualitative description of biofilm formation was monitored at different exposure periods. Biofilms were evaluated based on massive sequencing analysis of the bacterial community and subsequent ecological studies. The results revealed that variability of the calculated corrosion rate correlated with the similarity of the bacterial community within samples from each SS and its corrosion inferred capacity. The associated bacterial families showed a higher representation in SSs with a more significant increase in the Fe/Cr ratio over the exposure time. These findings revealed that iron content in the oxide layer represents a key feature of the surface composition for selecting bacterial assemblages in marine environments.

Reduction of potential ennoblement of stainless steel in natural seawater by an ecofriendly biopolymer

The effect of biofilm formation on passive stainless steel in seawater environments is of primary importance since it leads to potential ennoblement of surfaces and subsequently to localized corrosion such as pitting and crevice corrosion. This study aims at developing an ecofriendly alginate biopolymer containing both non-toxic calcium and a limited amount of biocidal zinc ions which inhibits this effect. For this purpose, calcium alginate containing less than 1 % of zinc ions localized in the vicinity of the steel surface in natural and renewed seawater is demonstrated to reduce significantly the ennoblement process of steel. After 1 month of immersion, a mass loss of only 4 % of the active material is observed authorizing thereby long-term protection of steel in real environment.

Study of poly(3,4-ethylendioxythiphene) as a coating for mitigation of biocorrosion of AISI 304 stainless steel in natural seawater

In this work the poly(3,4-ethylenedioxythiophene) (PEDOT) was evaluated to mitigate biocorrosion of conventional stainless steel (SS), grade AISI 304, under exposure to natural seawater. PEDOT was obtained electrochemically onto the steel and coated coupons were immersed in flow-through exposure rig fed with fresh seawater. Corrosion performance of the coupons SS and SS/PEDOT was characterised using electrochemical analysis of open circuit potentials and polarization curves measured on samples retrieved after 7, 35 and 210 days of exposure. For the same retrieval times, the evolution of the biofilm was inspected by scanning electron microscopy (SEM), and microbiological analysis by denaturing gradient gel electrophoresis (DGGE) and fluorescence microscopy. Results indicate that PEDOT delays the growth of the biofilm on the modified steel surface by at least 35 days, producing a less variable bacterial community over time as compared to the uncoated steel surface. In addition, PEDOT retains electrochemical stability throughout the exposure, which is mainly attributed to the intrinsic properties of the conducting polymer.

自然海水中におけるSUS304の長期動的すきま腐食観察

自然海水中におけるSUS304の長期動的すきま腐食観察

Corrosion potential and cathodic reduction efficiency of stainless steel in natural seawater

Stainless steels are widely used for different applications in seawater in the oil and gas and desalination industries. It is well known that the corrosion potential of stainless steel shifts to the noble direction (ennoblement) when exposed to natural seawater. The other significant effect of the biofilm on metallic surfaces is a dramatic increase of the cathodic reduction efficiency (e.g. cathodic reduction of dissolved oxygen), promoting the corrosion reactions and increasing the rate of corrosion propagation. Although, this has been widely studied in natural seawater at temperature ranging from 15 to 40 °C, very little is known on the effect of temperature (in a wider temperature range), dissolved oxygen content and chlorination level on the corrosion potential and the cathodic reduction efficiency of stainless steel in natural seawater. In this paper, corrosion potential and cathodic reduction efficiency of stainless steel are reported as a function of temperature (e.g. from 5 to 70 °C), dissolved oxygen content (e.g. from 20 ppb to saturation) and chlorination level (from 0 to 0.5 ppm). The results are discussed in terms of risk for crevice corrosion and bi‐metallic corrosion when coupling to other materials. In addition results from exposure in tropical sea are presented and compared to that of temperate seawater heated at the same temperature.

Sunlight-enhanced calcareous deposition on cathodic stainless steel in natural seawater

In replicate series of experiments in natural seawater, one in full darkness and the other in a 1:1 diurnal cycle with as little as ∼5% of natural solar illumination, sunlight promoted calcareous deposition on cathodic stainless steel surfaces. As exemplified by scanning electron microscopy, the deposit that formed under the natural diurnal cycle, in the presence of photosynthetic biofilms, was composed of finer calcareous crystals that provided more compact and more uniform surface coverage than the one formed in the dark. The light-enhanced deposit also possessed better scale properties, as suggested by X-ray analysis and electrochemical measurements. Sunlight enhancement of calcareous deposition looked all the more conspicuous when day and night regimes were examined independently. These results not only bear important implications for cathodic protection in marine waters, but also provide an intriguing analogy to coral reef calcification.

Corrosion pit growth on austenitic stainless steels in chloride containing solution: a quantitative approach

PurposeThe purpose of this paper is to quantitatively assess the pit growth rate on AISI 304L and AISI 316 austenitic stainless steels in natural seawater and 3.5 wt.% NaCl solutions through electrochemical measurements during the potentiostatic growth of pits.Design/methodology/approachA quantitative characterisation was carried out based on chronoamperometric measurements. The volume of dissolved metal per pit was calculated from the charge registered and Faraday's law, considering both, hemispherical and semi‐elliptical pit shapes and the density of the steels. Empirical growth laws for maximum pit depth as a function of polarisation time were obtained and compared with pits volumetric profile obtained from optical microscopy analysis and mechanical removal of material on both steels.FindingsElectrochemical‐based calculations of localised metal dissolution per pit present acceptable fit with the real volume of dissolved metal on hemispherical pits.Originality/valueThe paper presents the quantitative relationship of the corrosion pit growth rate of stainless steels in chloride containing solution determined by chronoamperometry (electrochemical technique) through the Faraday law's, with the mechanical removal of material (pit profile) through the density of metal.

Ennoblement of stainless steel in natural seawater – A new explanation

AbstractThe ennoblement of corrosion potential (Ecorr) of passive metal immersed in seawater was investigated with electrochemical technology and epifluorescence microscopy. The in situ observation showed that the bacteria number increased on the metal surface according to an exponential law which was in the same way with the ennoblement of Ecorr. At the same time, the anodic polarization current of high‐Mo stainless steel decreased in the initial days. According to the mix‐potential theory and the characteristics of polarization curves of high‐Mo steel in natural seawater, the ennoblement of corrosion potential may be induced by the decrease of the passive current density.

Measurements of the Localized Dissolution Rate During Potentiostatic Generation of Corrosion Pits in Austenitic Stainless Steel in Natural Seawater

not Available.

自然海水中に浸漬したステンレス鋼の電位貴化メカニズムの検討

自然海水中に浸漬したステンレス鋼の電位貴化メカニズムの検討

Detection of localized corrosion of stainless steels by optical interferrometry

An optical corrosion meter has been developed for materials testing and evaluation of different corrosion phenomena. The meter was based on principles of 3D holographic interferrometry for measuring microsurface dissolution, i.e. mass loss, and on those of electrochemistry for measuring the bulk electronic current, i.e. corrosion current of metallic samples in aqueous solutions. The early stage of pitting corrosion of UNS No. 304 stainless steel and crevice corrosion of UNS 316 stainless steel in natural seawater were monitored, in situ by the optical corrosion meter during the cyclic polarization tests. The observations of pitting corrosion were basically interferrometric perturbations detected on the surface of the UNS No. 304 stainless steel in seawater. In contrast, the observations of crevice corrosion were basically interferrometric perturbations detected on the surface of the UNS No. 316 stainless steel underneath a crevice assembly. Eventually, the interferrometric perturbations were interpreted as localized corrosion in the form of an early pitting or of an early crevice corrosion, of a depth ranging from 0.3 μm to several micrometers. Consequently, holographic interferrometry is shown to be a useful technique as a 3D-interferrometric microscope for monitoring pitting corrosion or crevice corrosion at the initiation stage of both phenomena for different metallic samples in aqueous solutions.

Effect of bacterial biofilm on 316 SS corrosion in natural seawater by eis

The electrochemical behavior of AISI 316 stainless steel in natural seawater collected from Canary Archipelago was investigated. A comparative study on a large number of samples immersed during three weeks in this environment with and without sulfate-reducing bacteria (SRB) was made. Open circuit potential measurements, cyclic polarization, Scanning Electron Microscopy (SEM) and Electrochemical Impedance Spectroscopy (EIS) were used. The obtained results permitted an interpretation of the contribution of biofilms to corrosion of stainless steel and a mechanism of the process is checked.

ステンレス鋼の海水中での微生物腐食とその抑制に及ぼす表面性状の影響

ステンレス鋼の海水中での微生物腐食とその抑制に及ぼす表面性状の影響

海水中におけるステンレス鋼の微生物腐食

海水中におけるステンレス鋼の微生物腐食

Microbially influenced corrosion of stainless steels in natural seawater

Microbially influenced corrosion of stainless steels in natural seawater

海水中におけるステンレス鋼の微生物腐食機構

Stainless steels, such as types 316L and 304 have high susceptibilities to pitting and crevice corrosion in natural seawater even though they have low susceptibilities in synthetic seawater. Recently, this type of corrosion has been recognized as a kind of Microbially Influenced Corrosion (MIC) in aerobic aqueous environments. The mechanism of MIC on stainless steels in natural seawater is studied by the electrochemical and biological techniques. Measurements of cathodic polarization curves of stainless steels were carried out in natural and synthetic seawater. The corrosion potential of stainless steels was measured in seawater and culture medium of the bacteria isolated from natural seawater. The corrosion potential of stainless steels became noble in natural seawater compared with synthetic seawater, and the cathodic polarization behavior indicates that some substances exist, which have higher redox potential than that of oxygen. It has become clear that the susceptibility to corrosion of stainless steels in natural seawater is effected by bacteria in the mature biofilm. As a result of the experiment using isolated bacteria, the corrosion potential became noble in the logarithmic phase of bacterial growth. These results suggest that the aerobic metabolism of the bacteria causes the ennoblement of stainless steels. Hydrogen peroxide, which could be generated due to the reduction of oxygen in the presence of enzyme (oxidase), was detected in the mature biofilm. Hydrogen peroxide has a higher redox potential than that of oxygen. Therefore, this result supports the fact that the hydrogen peroxide, as an intermediate substance in the aerobic metabolism of bacteria in the biofilm, causes the ennoblement of stainless steels in natural seawater. The potential ennoblement and the occurrence of crevice corrosion of stainless steels were successfully reproduced in the laboratory by using the synthetic seawater with the addition of oxidase and substrate.

Applications of the scanning reference electrode technique to localized corrosion

A new commercially-designed instrument using the Scanning Reference Electrode Technique (SRET) has enabled the measurement of localized current densities in the vicinity of pits in Type 304 stainless steel in natural seawater. The results demonstrate the scope for improved quantitative models of localized corrosion using this technique.

Impact of biofouling on the electrochemical behaviour of 304 stainless steel in natural seawater

Biofilm formation on 304 stainless steel (S30400) does not necessarily result in an ennoblement of the corrosion potential. Instead, biofilms composed of aerobic and anaerobic bacteria from Gulf of Mexico water formed an anaerobic biofilm/metal interface and caused the corrosion potential to move in the negative direction. Biofilms from the same source containing photosynthetic diatoms in the presence of light produced aerobic biofilm/metal interfaces and a positive shift (ennoblement of the corrosion potential). Corrosion potentials of stainless steels exposed in natural seawater cannot be predicted without an understanding of the composition of the biofilm and its impact on interfacial chemistry. In this paper, measurements of corrosion potential, interfacial pH and dissolved oxygen have been correlated with SEM/EDAX surface analyses to evaluate the electrochemical behaviour of stainless steels exposed to Gulf of Mexico water. The interfacial chemistries that influence the corrosion potential are also d...

Cathodic Performance of Stainless Steels in Natural Seawater as a Function of Microorganism Settlement and Temperature

Abstract The modification of oxygen reduction rate induced by bacterial settlement on stainless steel (SS) surfaces immersed in natural seawater was studied as a function of temperature (25 C≤tempe...