Enhanced antibacterial and corrosion resistance of copper-containing 2205 duplex stainless steel against the corrosive bacterium Shewanella algae.

2205 DSS is an excellent corrosion-resistant engineering metal material, but it is still threatened by microbiological corrosion. The addition of copper elements is a new approach to improving the resistance of 2205 DSS to microbiological corrosion. In this study, 2205-Cu DSS was compared with 2205 DSS to study its antimicrobial properties and resistance to microbiological corrosion in the presence of the electroactive bacterium Shewanella algae. The results showed that compared to 2205 DSS, the biofilm thickness and the number of live bacteria on the surface of 2205-Cu DSS were significantly reduced, demonstrating excellent antimicrobial properties against S. algae. Electrochemical tests and surface morphology characterization results showed that the corrosion rate and pitting of 2205-Cu DSS by S. algae were lower than that of 2205 DSS, indicating better resistance to microbiological corrosion. The good antimicrobial properties and resistance to microbiological corrosion exhibited by 2205-Cu DSS are attributed to the contact antimicrobial properties of copper elements in the 2205-Cu DSS matrix and the release of copper ions for antimicrobial effects. This study provides a new strategy for combating microbiological corrosion.

Enhanced corrosion of 2205 duplex stainless steel by Acetobacter aceti through synergistic electron transfer and organic acids acceleration.

Acetobacter aceti is a microbe that produces corrosive organic acids, causing severe corrosion of industrial equipment. Previous studies have focused on the organic acid corrosion of A. aceti, but neglected the possibility that it has electron transfer corrosion. This study found that electron transfer and organic acids can synergistically promote the corrosion of 2205 duplex stainless steel (DSS). Electrochemical measurement results showed that corrosion of 2205 DSS was more severe in the presence of A. aceti. Surface analysis indicated a thick biofilm formed on the steel surface, with low pH and dissolved oxygen concentrations under the biofilm. Corrosion intensified when A. aceti lacked a carbon source, suggesting that A. aceti can corrode metals by using metallic substrates as electron donors, in addition to its acidic by-products.

Harnessing active biofilm for microbial corrosion protection of carbon steel against Geobacter sulfurreducens.

Microbiologically influenced corrosion (MIC) caused by corrosive microorganisms poses significant economic losses and safety hazards. Conventional corrosion prevention methods have limitations, so it is necessary to develop the eco-friendly and long-term effective strategies to mitigate MIC. This study investigated the inhibition of Vibrio sp. EF187016 biofilm on Geobacter sulfurreducens on carbon steel. Vibrio sp. EF187016 biofilm reduced the corrosion current density and impeded pitting corrosion. A thick and uniform Vibrio sp. EF187016 biofilm formed on the coupon surfaces, acting as a protective layer against corrosive ions and electron acquisition by G. sulfurreducens. The pre-grown mature Vibrio sp. EF187016 biofilms, provided enhanced protection against G. sulfurreducens corrosion. Additionally, the extracellular polymeric substances from Vibrio sp. EF187016 was confirmed to act as a green corrosion inhibitor to mitigate microbial corrosion. This study highlights the potential of active biofilms for eco-friendly corrosion protection, offering a novel perspective on material preservation against microbial corrosion.

Accelerated corrosion of 316L stainless steel in a simulated oral environment via extracellular electron transfer and acid metabolites of subgingival microbiota.

316L stainless steel (SS) is widely applied as microimplant anchorage (MIA) due to its excellent mechanical properties. However, the risk that the oral microorganisms can corrode 316L SS is fully neglected. Microbiologically influenced corrosion (MIC) of 316L SS is essential to the health and safety of all patients because the accelerated corrosion caused by the oral microbiota can trigger the release of Cr and Ni ions. This study investigated the corrosion behavior and mechanism of subgingival microbiota on 316L SS by 16S rRNA and metagenome sequencing, electrochemical measurements, and surface characterization techniques. Multispecies biofilms were formed by the oral subgingival microbiota in the simulated oral anaerobic environment on 316L SS surfaces, significantly accelerating the corrosion in the form of pitting. The microbiota samples collected from the subjects differed in biofilm compositions, corrosion behaviors, and mechanisms. The oral subgingival microbiota contributed to the accelerated corrosion of 316L SS via acidic metabolites and extracellular electron transfer. Our findings provide a new insight into the underlying mechanisms of oral microbial corrosion and guide the design of oral microbial corrosion-resistant materials.

Microbially Influenced Corrosion of Steel in Marine Environments: A Review from Mechanisms to Prevention.

Microbially influenced corrosion (MIC) is a formidable challenge in the marine industry, resulting from intricate interactions among various biochemical reactions and microbial species. Many preventions used to mitigate biocorrosion fail due to ignorance of the MIC mechanisms. This review provides a summary of the current research on microbial corrosion in marine environments, including corrosive microbes and biocorrosion mechanisms. We also summarized current strategies for inhibiting MIC and proposed future research directions for MIC mechanisms and prevention. This review aims to comprehensively understand marine microbial corrosion and contribute to novel strategy developments for biocorrosion control in marine environments.

Synergistic Antibacterial Activity of Benzalkonium Bromide and Cu-Bearing Duplex Stainless Steel against Pseudomonas aeruginosa.

The bactericide benzalkonium bromide is widely used to kill Pseudomonas aeruginosa, which causes microbiologically influenced corrosion (MIC). However, the extensive use of benzalkonium bromide will enhance bacterial drug resistance and cause environmental pollution. In this study, benzalkonium bromide combined with Cu-bearing 2205 duplex stainless steel (2205-Cu DSS) was used to kill Pseudomonas aeruginosa; the germicidal rate of the combination of benzalkonium bromide and 2205-Cu DSS was 24.2% higher than that of using benzalkonium bromide alone, after five days. The antibacterial efficacy was evaluated using an antibacterial test and biofilm observation. The results showed that, in the presence of P. aeruginosa, the combination of 23.44 ppm benzalkonium bromide and 2205-Cu DSS showed the best antibacterial efficacy.

3D printed Ti-5Cu alloy accelerates osteogenic differentiation of MC3T3-E1 cells by stimulating the M2 phenotype polarization of macrophages.

Ti-5Cu alloy has been proved to have excellent mechanical properties and cell compatibility and has certain antibacterial properties due to the addition of Cu. However, there are few studies on the effects of Ti-5Cu alloy on macrophage polarization and immune-related bone formation. In this study, we prepared Ti-5Cu alloy by three-dimensional printing technology and found that Ti-5Cu alloy presented a much smoother surface compared with Ti. In addition, the CCK-8 results indicated the Ti-5Cu alloy had no cytotoxicity to RAW264.7 cells by co-culture. The results of inductively coupled plasma mass spectrometry showed that the concentration of Cu2+ was 0.133 mg/L after 7 days of co-culture, and the CCK-8 results proved that Cu2+ had no cytotoxicity to RAW264.7 at this concentration. Then, we studied the effects of Ti-5Cu alloy on macrophage polarization; it was shown that the Ti-5Cu alloy is more prone to modulate the RAW264.7 polarization towards the M2 phenotype and the conditioned medium derived from Ti-5Cu alloy significantly promoted the proliferation and osteogenic differentiation of MC3T3-E1 cells. However, when the expression of Oncostatin M (OSM) gene of RAW264.7 was knocked down, the osteogenic differentiation of MC3T3-E1 cells was decreased. This suggests that the OSM secreted by RAW264.7 co-cultured with Ti-5Cu alloy could accelerate the osteogenic differentiation of MC3T3-E1 cells by acting on OSMR/gp130 receptors.

Accelerated biocorrosion of stainless steel in marine water via extracellular electron transfer encoding gene phzH of Pseudomonas aeruginosa.

Microbiologically influenced corrosion (MIC) constantly occurs in water/wastewater systems, especially in marine water. MIC contributes to billions of dollars in damage to marine industry each year, yet the physiological mechanisms behind this process remain poorly understood. Pseudomonas aeruginosa is a representative marine electro-active bacterium, which has been confirmed to cause severe MIC on carbon steel through extracellular electron transfer (EET). However, little is known about how P. aeruginosa causes corrosion on stainless steel. In this study, the corrosivity of wild-type strain, phzH knockout, phzH complemented, and phzH overexpression P. aeruginosa mutants were evaluated to explore the underlying MIC mechanism. We found the accelerated MIC on 2205 duplex stainless steel (DSS) was due to the secretion of phenazine-1-carboxamide (PCN), which was regulated by the phzH gene. Surface analysis, Mott-Schottky test and H2O2 measurement results showed that PCN damaged the passive film by forming H2O2 to oxidize chromium oxide to soluble hexavalent chromium, leading to more severe pitting corrosion. The normalized corrosion rate per cell followed the same order as the general corrosion rate obtained under each experimental condition, eliminating the influence of the total amount of sessile cells on corrosion. These findings provide new insight and are meaningful for the investigation of MIC mechanisms on stainless steel. The understanding of MIC can improve the sustainability and resilience of infrastructure, leading to huge environmental and economic benefits.

Direct microbial electron uptake as a mechanism for stainless steel corrosion in aerobic environments.

Shewanella oneidensis MR-1 is an attractive model microbe for elucidating the biofilm-metal interactions that contribute to the billions of dollars in corrosion damage to industrial applications each year. Multiple mechanisms for S. oneidensis-enhanced corrosion have been proposed, but none of these mechanisms have previously been rigorously investigated with methods that rule out alternative routes for electron transfer. We found that S. oneidensis grown under aerobic conditions formed thick biofilms (∼50 µm) on stainless steel coupons, accelerating corrosion over sterile controls. H2 and flavins were ruled out as intermediary electron carriers because stainless steel did not reduce riboflavin and previous studies have demonstrated stainless does not generate H2. Strain ∆mtrCBA, in which the genes for the most abundant porin-cytochrome conduit in S. oneidensis were deleted, corroded stainless steel substantially less than wild-type in aerobic cultures. Wild-type biofilms readily reduced nitrate with stainless steel as the sole electron donor under anaerobic conditions, but strain ∆mtrCBA did not. These results demonstrate that S. oneidensis can directly consume electrons from iron-containing metals and illustrate how direct metal-to-microbe electron transfer can be an important route for corrosion, even in aerobic environments.

Mitigation of carbon steel biocorrosion using a green biocide enhanced by a nature-mimicking anti-biofilm peptide in a flow loop.

Biocorrosion, also called microbiologically influenced corrosion (MIC), is a common operational threat to many industrial processes. It threatens carbon steel, stainless steel and many other metals. In the bioprocessing industry, reactor vessels in biomass processing and bioleaching are prone to MIC. MIC is caused by biofilms. The formation and morphology of biofilms can be impacted by fluid flow. Fluid velocity affects biocide distribution and MIC. Thus, assessing the efficacy of a biocide for the mitigation of MIC under flow condition is desired before a field trial. In this work, a benchtop closed flow loop bioreactor design was used to investigate the biocide mitigation of MIC of C1018 carbon steel at 25 °C for 7 days using enriched artificial seawater. An oilfield biofilm consortium was analyzed using metagenomics. The biofilm consortium was grown anaerobically in the flow loop which had a holding vessel for the culture medium and a chamber to hold C1018 carbon steel coupons. Peptide A (codename) was a chemically synthesized cyclic 14-mer (cys-ser-val-pro-tyr-asp-tyr-asn-trp-tyr-ser-asn-trp-cys) with its core 12-mer sequence originated from a biofilm dispersing protein secreted by a sea anemone which possesses a biofilm-free exterior. It was used as a biocide enhancer. The combination of 50 ppm (w/w) THPS (tetrakis hydroxymethyl phosphonium sulfate) biocide + 100 nM (180 ppb by mass) Peptide A resulted in extra 1-log reduction in the sulfate reducing bacteria (SRB) sessile cell count and the acid producing bacteria (APB) sessile cell count compared to 50 ppm THPS alone treatment. Furthermore, with the enhancement of 100 nM Peptide A, extra 44% reduction in weight loss and 36% abatement in corrosion pit depth were achieved compared to 50 ppm THPS alone treatment.

Corrosion behavior of high nitrogen nickel-free austenitic stainless steel in the presence of artificial saliva and Streptococcus mutans.

High nitrogen nickel-free austenitic stainless steels (HNSs) have great potentials to be used in dentistry owing to its exceptional mechanical properties, high corrosion resistance, and biocompatibility. In this study, HNSs with nitrogen of 0.88 wt% and 1.08 wt% displayed much lower maximum pit depths than 316L stainless steel (SS) after 21 d of immersion in abiotic artificial saliva (2.2 µm and 1.7 µm vs. 4.5 µm). Microbiologically influenced corrosion (MIC) evaluations revealed that Streptococcus mutans biofilms led to much severer corrosion of 316L SS than HNSs. Corrosion current densities of HNSs were two orders of magnitude lower than that of 316L SS after incubation of 7 d (37.5 nA/cm2 and 29.9 nA/cm2 vs. 5.63 µA/cm2). The pitting potentials of HNSs were at least 550 mV higher than that of 316L SS in the presence of S. mutans, confirming the better MIC resistance of HNSs. Cytotoxicity assay confirmed that HNSs were not toxic to MC3T3-E1 cells and allowed better sessile cell growth on them than on 316L SS. It can be concluded that HNSs are more suitable dental materials than the conventional 316L SS.

Stainless steel corrosion via direct iron-to-microbe electron transfer by Geobacter species.

Microbial corrosion of iron-based materials is a substantial economic problem. A mechanistic understanding is required to develop mitigation strategies, but previous mechanistic studies have been limited to investigations with relatively pure Fe(0), which is not a common structural material. We report here that the mechanism for microbial corrosion of stainless steel, the metal of choice for many actual applications, can be significantly different from that for Fe(0). Although H2 is often an intermediary electron carrier between the metal and microbes during Fe(0) corrosion, we found that H2 is not abiotically produced from stainless steel, making this corrosion mechanism unlikely. Geobacter sulfurreducens and Geobacter metallireducens, electrotrophs that are known to directly accept electrons from other microbes or electrodes, extracted electrons from stainless steel via direct iron-to-microbe electron transfer. Genetic modification to prevent H2 consumption did not negatively impact on stainless steel corrosion. Corrosion was inhibited when genes for outer-surface cytochromes that are key electrical contacts were deleted. These results indicate that a common model of microbial Fe(0) corrosion by hydrogenase-positive microbes, in which H2 serves as an intermediary electron carrier between the metal surface and the microbe, may not apply to the microbial corrosion of stainless steel. However, direct iron-to-microbe electron transfer is a feasible route for stainless steel corrosion.

Responses of soil microbiome to steel corrosion.

The process of microbiologically influenced corrosion (MIC) in soils has received widespread attention. Herein, long-term outdoor soil burial experiments were conducted to elucidate the community composition and functional interaction of soil microorganisms associated with metal corrosion. The results indicated that iron-oxidizing (e.g., Gallionella), nitrifying (e.g., Nitrospira), and denitrifying (e.g., Hydrogenophaga) microorganisms were significantly enriched in response to metal corrosion and were positively correlated with the metal mass loss. Corrosion process may promote the preferential growth of the abundant microbes. The functional annotation revealed that the metabolic processes of nitrogen cycling and electron transfer pathways were strengthened, and also that the corrosion of metals in soil was closely associated with the biogeochemical cycling of iron and nitrogen elements and extracellular electron transfer. Niche disturbance of microbial communities induced by the buried metals facilitated the synergetic effect of the major MIC participants. The co-occurrence network analysis suggested possible niche correlations among corrosion related bioindicators.

Microbiologically influenced corrosion of 304 stainless steel by nitrate reducing Bacillus cereus in simulated Beijing soil solution.

In this work, microbiologically influenced corrosion (MIC) of 304 stainless steel (SS) caused by Bacillus cereus was investigated by electrochemical measurements and surface analyses in simulated Beijing soil solution under aerobic condition. The nitrate-reducing bacterium (NRB), B. cereus, was isolated from Beijing soil and identified using 16S rDNA. Confocal laser scanning microscopy (CLSM) images showed that the largest pit depths on 304 SS with and without B. cereus after 14 days of incubation were 7.17 and 4.59 µm, respectively, indicating that pitting corrosion was accelerated by B. cereus. X-ray photoelectron spectroscopy (XPS) and energy dispersive spectrometry (EDS) results revealed that B. cereus and its metabolic products were detrimental to the integrity of the passive film on 304 SS. The electrochemical results showed that B. cereus significantly reduced the corrosion resistance of 304 SS and accelerated the anodic dissolution reaction, thereby speeding up the corrosion process.

Accelerated Corrosion of 316L Stainless Steel Caused by Shewanella algae Biofilms.

In the marine environment, microbiologically influenced corrosion (MIC) is a major problematic issue, which leads to severe damage to metals and alloys. The prerequisite to mitigate this worldwide problem is to investigate the mechanisms of marine-corroding microbes. Therefore, the corrosion behavior of 316L stainless steel in the presence of marine Shewanella algae was investigated by means of electrochemical measurements and surface analysis. The results revealed that S. algae is capable of forming a dense and thick biofilm on the surfaces of 316L SS coupons after 7 days of incubation, which reached about a thickness of 40.4 µm. According to electrochemical results, the S. algae biofilm also induced the corrosion of 316L SS coupons. The accelerated corrosion of 316L SS coupons was in the form of pits, which was formed underneath the biofilms. The largest pit depth after 14 days of incubation time reached 9.8 µm, which was 6.7 times higher than the one immersed in abiotic medium (1.45 µm). This is the first study demonstrating the MIC of 316L SS due to the S. algae biofilm.

Salvia officinalis extract mitigates the microbiologically influenced corrosion of 304L stainless steel by Pseudomonas aeruginosa biofilm.

The mitigation of microbiologically influenced corrosion (MIC) of 304L stainless steel (SS) against Pseudomonas aeruginosa by a Salvia officinalis extract was investigated using electrochemical and surface analysis techniques. The extract was characterized by HPLC-Q-TOF-MS and its antibiofilm property was evaluated. The data revealed the presence of well-known antimicrobial and anticorrosion compounds in the extract. The S. officinalis extract was found effective in preventing biofilm formation and inhibiting mature biofilm. Electrochemical results indicated that P. aeruginosa accelerated the MIC of 304L SS, while the extract was found to prevent the MIC with an inhibition efficiency of 97.5 ±â€¯1.5%. This was attributed to the formation of a protective film by the adsorption of some compounds from the extract on the 304L SS surface.

Severe microbiologically influenced corrosion of S32654 super austenitic stainless steel by acid producing bacterium Acidithiobacillus caldus SM-1.

Microbiologically influenced corrosion (MIC) of S32654 (654SMO) super austenitic stainless steel (SASS) by acid producing bacterium (APB), Acidithiobacillus caldus SM-1, a strain of sulfur-oxidizing bacteria (SOB) used in biohydrometallurgy field, was investigated using electrochemical measurements and surface characterizations during a 14-day immersion test. The results indicated that S32654 SASS was susceptible to MIC by APB, and A. caldus SM-1 was capable of producing an aggressive acidic environment underneath the biofilm, resulting in the dissolution of the passive film and severe pitting attacks against S32654 SASS, which is commonly regarded as a corrosion resistant material.

Corrosion effect of Bacillus cereus on X80 pipeline steel in a Beijing soil environment.

The corrosion of X80 pipeline steel in the presence of Bacillus cereus (B. cereus) was studied through electrochemical and surface analyses and live/dead staining. Scanning electron microscopy and live/dead straining results showed that a number of B. cereus adhered to the X80 steel. Electrochemical impedance spectroscopy showed that B. cereus could accelerate the corrosion of X80 steel. In addition, surface morphology observations indicated that B. cereus could accelerate pitting corrosion in X80 steel. The depth of the largest pits due to B. cereus was approximately 11.23µm. Many pits were found on the U-shaped bents and cracks formed under stress after 60days of immersion in the presence of B. cereus. These indicate that pitting corrosion can be accelerated by B. cereus. X-ray photoelectron spectroscopy results revealed that NH4+ existed on the surface of X80 steel. B. cereus is a type of nitrate-reducing bacteria and hence the corrosion mechanism of B. cereus may involve nitrate reduction on the X80 steel.

Anaerobic Corrosion of 304 Stainless Steel Caused by the Pseudomonas aeruginosa Biofilm.

Pseudomonas aeruginosa is a ubiquitous bacterium capable of forming problematic biofilms in many environments. They cause biocorrosion of medical implants and industrial equipment and infrastructure. Aerobic corrosion of P. aeruginosa against stainless steels has been reported by some researchers while there is a lack of reports on anaerobic P. aeruginosa corrosion in the literature. In this work, the corrosion by a wild-type P. aeruginosa (strain PAO1) biofilm against 304 stainless steel (304 SS) was investigated under strictly anaerobic condition for up to 14 days. The anaerobic corrosion of 304 SS by P. aeruginosa was reported for the first time. Results showed that the average sessile cell counts on 304 SS coupons after 7- and 14-day incubations were 4.8 × 107 and 6.2 × 107 cells/cm2, respectively. Scanning electron microscopy and confocal laser scanning microscopy corroborated the sessile cell counts. The X-ray diffraction analysis identified the corrosion product as iron nitride, confirming that the corrosion was caused by the nitrate reducing biofilm. The largest pit depths on 304 SS surfaces after the 7- and 14-day incubations with P. aeruginosa were 3.9 and 7.4 µm, respectively. Electrochemical tests corroborated the pitting data.

Relationship between Microstructure and Corrosion Behavior of Martensitic High Nitrogen Stainless Steel 30Cr15Mo1N at Different Austenitizing Temperatures.

The relationship between microstructure and corrosion behavior of martensitic high nitrogen stainless steel 30Cr15Mo1N at different austenitizing temperatures was investigated by microscopy observation, electrochemical measurement, X-ray photoelectron spectroscopy analysis and immersion testing. The results indicated that finer Cr-rich M2N dispersed more homogeneously than coarse M23C6, and the fractions of M23C6 and M2N both decreased with increasing austenitizing temperature. The Cr-depleted zone around M23C6 was wider and its minimum Cr concentration was lower than M2N. The metastable pits initiated preferentially around coarse M23C6 which induced severer Cr-depletion, and the pit growth followed the power law. The increasing of austenitizing temperature induced fewer metastable pit initiation sites, more uniform element distribution and higher contents of Cr, Mo and N in the matrix. In addition, the passive film thickened and Cr2O3, Cr3+ and CrN enriched with increasing austenitizing temperature, which enhanced the stability of the passive film and repassivation ability of pits. Therefore, as austenitizing temperature increased, the metastable and stable pitting potentials increased and pit growth rate decreased, revealing less susceptible metastable pit initiation, larger repassivation tendency and higher corrosion resistance. The determining factor of pitting potentials could be divided into three stages: dissolution of M23C6 (below 1000 °C), dissolution of M2N (from 1000 to 1050 °C) and existence of a few undissolved precipitates and non-metallic inclusions (above 1050 °C).