Corrosion Products Research Articles

The clogging effect of nanoscale zero valent iron corrosion in bicarbonate anaerobic water on porous media: A real-time pore-scale visualization

The corrosion-induced permeability changes of nanoscale zero-valent iron (NZVI) are one of the crucial factors constraining the successful application of NZVI in the remediation of contaminated groundwater. It is of great significance to study the dynamic evolution of corrosion products of NZVI after NZVI is injected into porous media and its influence on pore plugging effect from the pore scale. Micro computed tomography (Micro-CT) imaging technology, mineralogical characterization and theoretical calculations were used to understand the details of NZVI corrosion plugging porous media at the pore scale. This study reveals the factors of NZVI corrosion plugging porous media, namely, gas production (H2) in the early and middle stages of corrosion (before 90 days) and solid phase changes (NZVI volume increase and migration) in the later stages (after 90 days). The permeability loss rate of the porous media was 66.8%, 87.3%, 79.4%, and 53.6% at the corrosion times of 30, 60, 90, and 120 days, respectively. After 90 d of corrosion, the particle size of NZVI increases by 7.9%, and the secondary minerals formed by corrosion are mainly Fe3O4/γ-Fe2O3 and FeOOH. In addition, this study also found that the migration of NZVI after 90 d was due to its corrosion reducing the magnetic attraction between particles, dissociating into smaller particles or agglomerates under the action of fluid dynamics, resulting in its redistribution in the porous medium and causing blockage. This study clarifies that NZVI corrosion plays a vital influence in affecting the permeability and clogging of porous media, providing valuable guidance for optimizing NZVI-based remediation technologies.

Creep stress induced pit-to-crack transition of Super304H in fireside corrosion

Parallel experiments on creep-rupture and corrosion of Super304H were conducted at 650 ℃ in a simulated ultra-supercritical fireside environment to study the impact of creep stress on fireside corrosion. The corrosion products, corrosion pits, grain structure and phase composition, and surface cracks of creep-corrosion and corrosion samples were compared. Results show that stresses not only affect the formation and growth of corrosion products, but also widen the recrystallization zone in corrosion affected area. A model of surface cracking from corrosion pits under the synergy of fireside corrosion and creep stress was proposed.

Study on the initial corrosion characteristics of weathering steel bridges with corrugated steel webs

In this study, the characteristics and influencing factors of the early corrosion evolution process of the weathering steel (WS) bridge in northwest China were examined, revealing the seldom-studied corrosion evolution law of the corrugated web of weathering steel. The corrosion losses and average corrosion thickness of WS bridge components were measured and evaluated. The results revealed that compared with traditional flat steel webs, the corrosion of corrugated steel webs was enhanced in the vertical direction and at the wave peak, and resulted in a more complex corrosion pattern. The trend of the rust layer on the inner and outer surfaces of the box girder is related to the stage characteristics of the corrosion products. The appearance of microscopic characteristics of the rust layer is periodic, with the rust layer thickness, colour, and particle size varying with the bridge’s location. The development of the corrosion pit followed a lognormal distribution, and the corrosion rate was balanced in the radial and depth directions. These results can serve as a basis for designers or inspectors to design WS bridge structures, select correct corrosion allowances, and improve corrosion monitoring and detection techniques.

Fluid depth-dependent biofilm characteristics and their influence on sulfate-reducing bacteria-induced corrosion of carbon steel

This study investigates the response of biofilm characteristics to variations in fluid depth and their influence on the corrosion behavior of carbon steel (C1020) under low-flow fluid conditions, utilizing Desulfovibrio vulgaris. The experiments were conducted in an anaerobic chamber at 30 °C, utilizing modified Baar's medium as the testing medium. The findings reveal that fluid depth significantly impacts biofilm-corrosion product composite formation, with deeper depths promoting thicker and more heterogeneous biofilm-corrosion product layer compared to shallower depths, where a thinner and more uniform biofilm-corrosion product layer is observed. Moreover, the characteristics of initially attached biofilms was verified as the primary factor affecting subsequent corrosion behavior during prolonged exposure. Corrosion analysis reveals that greater fluid depth leads to increased weight loss (91 ± 13.2 mg/cm2) and deeper pit depths (540 ± 69 μm), surpassing those observed in shallower test media (21 ± 2.3 mg/cm2 and 105 ± 17 μm) after 28 days of exposure. The corrosion products within the biofilm were predominantly FeS and Fe3(PO4)2·8H2O. A direct relationship was observed between the thickness of this biofilm-corrosion product layer and the progression of pit depth, suggesting a strong correlation between carbon steel corrosion and biofilm development in limited fluid depths (e.g., 5–15 mm). Furthermore, a significant association between the deepest pits (average) and the number of sessile cells within the biofilm underscores the pivotal role of sessile cell numbers in carbon steel corrosion.

Chemical aging of biochar-zero-valent iron composites in groundwater: Impact on Cd(II) and Cr(VI) co-removal

Biochar (BC), zero-valent iron (ZVI), and their composites are promising materials for use in permeable reactive barriers, although further research is needed to understand how their properties change during long-term aging in groundwater. In this study, BC, ZVI and their composites (4BC-1ZVI) were subjected to the chemical aging tests in five media (deionized water, NaCl, NaHCO3, CaCl2 and a mixture of CaCl2 and NaHCO3 solutions) for 20 days. After treatment, the microscopic analysis and performance tests for the co-removal of Cd(II) and Cr(VI) were carried out. The results indicated that the removal of Cd(II) by aged 4BC-1ZVI followed a pseudo-second-order model, whereas the removal of Cr(VI) was better fitted with a pseudo-first order model. The aging mechanism of 4BC-1ZVI was primarily governed by iron corrosion/passivation, the reduction of soluble components, and the formation of carbonate minerals. Less Fe3O4/ γ-Fe2O3 was formed during aging in deionized water, NaCl and CaCl2 solutions. The corrosion products, Fe3O4/ γ-Fe2O3, FeCO3 and α/γ-FeOOH, were observed after aging in NaHCO3 and a mixture of NaHCO3 and CaCl2 solutions. The decrease in the soluble components of biochar led to a decrease in cation exchange, while carbonate minerals contributed to Cd(II) precipitation. This work provides insights into the aging processes of BC-ZVI composites for long-term groundwater remediation applications.

Corrosion Inhibition of Carbon Steel in Neutral Chloride Solutions Using Salts of Primary Bile Acids.

Due to growing environmental concerns and regulatory pressures, the demand for environmentally friendly corrosion inhibitors has increased. Biosurfactants are biodegradable and have a low toxicity. However, very few studies have reported on their potential use as corrosion inhibitors. The present study reports the novel application of two bile salts (sodium cholate NaC and sodium chenodeoxycholate NaCDC) as environmentally friendly corrosion inhibitors for carbon steel in a neutral 20 mM NaCl solution. The results of potentiodynamic polarization and electrochemical impedance measurements showed that when added at a concentration of 5 mM, the corrosion inhibition efficiencies of NaC and NaCDC were about 60% and 85%, respectively. The poor inhibitory character of NaC was confirmed by XPS analysis, revealing the formation of oxidative corrosion products on the steel surface. For the steel sample immersed in the solution containing NaCDC, the XPS measurements showed clear evidence of the presence of an organic layer and a passive oxide film on the steel surface. While the steroidal skeleton of NaC is characterized by marked biplanarity (considering its hydrophobic and hydrophilic faces), NaCDC features a steroidal ring with a hydrophilic edge (it does not exhibit biplanarity). Thus, the self-assembly and adsorption behavior of these bile salts on the steel surface are different, leading in the case of NaCDC to form a densely packed protective organic layer.

Role of Mn in improving the corrosion resistance and cytocompatibility of antibacterial Mg-Ag-Mn alloy

To improve corrosion resistance and cytocompatibility of biodegradable Mg-Ag alloy, the non-toxic Mn was added to produce Mg-Ag-xMn (x=0, 0.5, 1, 2 and 3 wt%) alloys. It was revealed that Mg-Ag-2Mn alloy exhibits an optimized comprehensive property after post-casting heat treatment (PCHT). Microstructural factors for the improved performances are then determined. It is revealed that the addition of Mn promotes the precipitation of the Fe-containing α-Mn phase and alters the configuration of the corrosion product after PCHT, which enhances the corrosion resistance of the alloy and thus optimises the ionic release kinetics for improved biological performance.

The role of electrode potential in CaCO3 scaling on steel surfaces under cathodic and corrosion conditions

The role of electrode potential in CaCO3 scaling behavior and kinetics on carbon steel and stainless steel surfaces is investigated through electrochemical tests, surface characterization, and numerical modeling. Under cathodic conditions, calcite is the dominant CaCO3 polymorph, its lateral growth on steel surfaces follows exponential kinetics. However, under gradually promoted corrosion conditions of carbon steel, the presence of corrosion products induces more aragonite deposition and inhibits the lateral growth of CaCO3 scale, gradually evolving from exponential to linear kinetics. This work provides further insight into how the cathodic and anodic reactions of steel corrosion respectively promote and inhibit CaCO3 scaling.

Corrosion behavior of 70/30 cupronickel in electrolytic seawater antifouling environment

Available chlorine is most commonly used in seawater cooling systems to eliminate biofouling. The corrosion behavior of 70/30 cupronickel alloy after exposure to seawater with different concentrations of available chlorine was studied by electrochemical and immersion tests. The electrochemical measurements show that 100 ppm available chlorine accelerates the corrosion of 70/30 cupronickel alloy in seawater. The corrosion rate of 70/30 cupronickel sample in seawater with 100 ppm available chlorine is 3–4 times higher than that in seawater with 0–10 ppm available chlorine. Scanning Kelvin probe (SKP) and scanning vibrating electrode technique (SVET) results demonstrate that the local electrochemical reaction of 70/30 cupronickel alloy is more active after soaking in seawater with 100 ppm available chlorine. Energy dispersive spectroscopy (EDS) results reveal that Cl element in the corrosion products is enriched after exposure to seawater with 100 ppm available chlorine. X-ray photoelectron spectroscopy (XPS) analysis demonstrates that the corrosion product of 70/30 cupronickel sample contains more Cu2(OH)3Cl after being immersed in seawater with 100 ppm available chlorine.

Study on corrosion behavior Ⅱ of hot-dipped Zn-6Al-3Mg alloy coating: Surface oxide layer and ternary eutectic corrosion

The oxide layer and ternary eutectic of Zn–6Al–3Mg alloy coating have an important effect on its corrosion behavior and corrosion resistance, but the influence of oxide layer on the corrosion behavior of the coating and the internal corrosion mechanism of ternary eutectic structure are still unclear. In this study, the oxide layer and ternary eutectic of the coating were characterized in detail, and the corrosion behavior of the oxide layer and ternary eutectic in the environment containing Cl were studied based on first principles of density functional theory. The results show that the surface oxide layer can initially prevent the erosion of Cl-, MgZn2 in ternary eutectic preferentially corrodes after the oxide layer dissolves, corrosion products are formed.

High-throughput screening of green amino acid and surfactant mixtures with high corrosion inhibition efficiency: Experimental and modelling perspectives

A high-throughput screening method is developed for rapid evaluation of corrosion inhibitors. By employing a fluorometric technique, this method quickly assesses the concentration of iron ions converted from corrosion products in the reaction pool to rapidly evaluate the corrosion inhibition performance of amino acid and surfactants. Utilizing this high-throughput screening platform, the corrosion inhibition effects of L-cysteine mixed with quaternary ammonium salts of different alkyl chain length were evaluated, and their optimal mixing ratios were determined. Through corrosion experiments and molecular simulations, the synergistic mechanisms of the inhibitor mixtures are revealed.

Enhanced corrosion resistance of harmonic structured β-type Ti-25Nb-25Zr alloy in aerated Fusayama-Meyer’s simulated saliva solution

In this study, the microstructure of the β-type Ti-25Nb-25Zr alloy is modified to a bimodal harmonic design, exhibiting fine and coarse grains of ∼3 μm and ∼70 μm, respectively. The high-angle grain boundary density of the harmonic Ti-25Nb-25Zr alloy increases nearly fourfold over its coarse-grained counterpart. Both the harmonic and course-grained Ti-25Nb-25Zr alloys show excellent passivation and corrosion resistance when studied electrochemically in Fusayama-Meyer’s simulated saliva solution. The harmonic structure in the Ti-25Nb-25Zr further improves corrosion resistance, almost six times the coarse-grained counterpart. The improved corrosion resistance is attributed to the excessive high-angle grain boundary, which binds the corrosion product to the substrate, restricting further corrosion.

Advanced corrosion resistance and mechanistic insights of electroless Ni-P-PTFE coatings on L245NS substrate in H2S-saturated environments

The extraction and transportation of oil and gas pose significant challenges due to corrosive environments, particularly hydrogen sulfide (H2S) exposure. This study investigates the use of polytetrafluoroethylene (PTFE) to enhance the corrosion resistance of nickel‑phosphorus (NiP) coatings in H2S-rich environments. Electroless deposition was employed to prepare Ni-P/PTFE coatings, which were then subjected to simulated H2S corrosion tests. Results indicate that the incorporation of PTFE led to a more uniform NiP coating with reduced porosity, significantly improving corrosion resistance. The coatings exhibited enhanced protective performance by stabilizing corrosion product layers and preventing the formation of corrosion channels. Ni-P-PTFE coatings overcame the existing research challenge of NiP coatings' corrosion in H2S environments, showing no penetration of the corrosive medium into the substrate after 720 h of immersion. The corrosion rate of the coating is only 0.0261 mm/year, only 4.27 % of the corrosion rate of the L245NS substrate in the early stage of corrosion. Moreover, after characterization by SEM, XRD and XPS, it was found that the presence of PTFE altered the corrosion mechanism, promoting the formation of stable nickel sulfide and oxide layers on the surface. This study sheds light on the mechanisms underlying PTFE-enhanced corrosion resistance in NiP coatings, offering promising implications for extending the lifespan of equipment in the oil and gas industry.

Defending against fluorine corrosion: Insights from FeCoNiCrMo high-entropy alloy behavior in hydrofluoric acid solutions

The surging demand for advanced fluorine corrosion-resistant materials underscores their significance in ensuring operational safety and reliability across various industries. This study investigates the corrosion behavior of the FeCoNiCrMo high-entropy alloy (HEA) via a series of 28-day immersion tests in hydrofluoric acid (HF) solutions. The results demonstrate the FeCoNiCrMo HEA's superior corrosion-resistant performance in HF environments, exhibiting remarkably low corrosion rates of 0.179 mm/y, 0.276 mm/y, and 0.352 mm/y in 20 vol%, 30 vol%, and 40 vol% HF solutions, respectively. Comprehensive phase and microstructural characterizations were conducted on samples exposed to the 40 vol% HF solution to elucidate the corrosion mechanisms. The study revealed that localized pitting corrosion preferentially initiates within the interdendritic regions of the HEA matrix upon HF exposure. During the intermediate stage, micro-galvanic corrosion occurs between the dendritic arms and interdendritic regions, leading to the formation of a uniform and compact corrosion product film on the alloy surface. This film, enriched with Mo, Cr, and O, provides temporary protection. However, as corrosion progresses, the partial detachment of particulate corrosion products compromises the integrity of the film, resulting in increased dissolution within the interdendritic regions and the formation of irregular corrosion grooves in the later stage. These insights significantly enhance the understanding of the corrosion mechanisms of FeCoNiCrMo HEA in HF environments and provide valuable guidance for developing innovative protective materials designed for fluorine-rich engineering applications.

A case study: anti-corrosion performances of plasma sprayed AT13 coatings on CrZrCu thin wall cylinder with adjusted parameters for controlling deformation

PurposeThis paper aims to control the deformation of a thin wall CrZrCu cylinder components (wall thickness 5 mm, diameter 400 mm) during thermal spray alumina-titania (AT13) coating by adjusting the spray parameters without deteriorating its quality evidently.Design/methodology/approachThe deformation was controlled by lowering the temperature of the component in the way of adjusting the spray parameters. The main parameters adjust included extending the spraying distance, from normally 120 mm to 140 mm, decreasing plasma power from 50to 42 kW. An alumina-titanium (AT13) ceramic coating was chosen for protecting the substrate from corrosion. Microscopic morphology and phase analysis, insulation resistance testing, neutral salt test and electrochemical method were used to analyze the anti-corrosion and insulation performances of the coating.FindingsThe results indicate that, after adjusting the spraying parameters, the coating has a relatively high porosity, with an average value of 8.96 ± 0.77%. The bonding strength of the coating is relatively low, with an average value of 17.69 ± 0.85 MPa. However, after sealing, the polarization resistance of the coating in seawater can be maintained above 6.25 × 106 Ω.cm2 for an extended period. The coating has a high resistance (=1.1 M Ω), and there is no apparent galvanic corrosion when contacted with TC4 alloy. Additionally, analysis of corrosion products on the sample surface reveals that the samples with sprayed alumina-titanium ceramic show no copper corrosion products on the surface, and the coating remains intact, effectively isolating the corrosive medium.Originality/valueBy adjusting the spraying parameters, the deformation of the cylinder thin-walled component can be effectively controlled, making the φ 400 × 392 mm (thickness 5 mm) CrZrCu cylinder com-ponent with a maximum diameter deformation of only 0.14 mm. The satisfactory corrosion performances can be achieved under adjusting spraying parameters, which can guarantee the application of ceramic coating for weapon launching system of naval ships.

Коррозионные характеристики композитов БрАМц9-2/06Х18Н9Т, полученных двухпроволочным электронно-лучевым аддитивным производством

Introduction. The development of novel materials based on copper alloys and stainless steel, as well as the determination of the optimal parameters for its processing make it possible to expand the area of its implementation, increase efficiency and service life of tools and constructions. The load-bearing parts of marine equipment (bearing constructions, piston cylinders, pumps, valves, gears, rotary instruments, etc.), made of austenitic steels or aluminum bronze, are in direct contact with sea water, so the problem of increasing its corrosion resistance in the presence of strong oxidizing agents (Cl-, F- anions) is relevant. One of the advanced and actively researched methods for producing copper/steel composites is additive manufacturing that allow fabricating complex parts through layer-by-layer growth. In particular, the synthesis of composites based on aluminum bronze and steel can be realized by wire-feed electron beam additive manufacturing. In order to implement composite materials produced via additive technologies in a humid (marine) climate, it is necessary to ensure not only high strength, but also corrosion properties. The purpose of this work is to study the corrosion resistance of composites, based on aluminum bronze CuAl9Mn2 and stainless steel ER 321 produced by dual-wire-feed electron beam additive manufacturing. Research methods. Examination of the surface of CuAl9Mn2/ER 321 composites before and after corrosion tests was carried out by methods of voltammetry and electrochemical impedance spectroscopy using a potentiostat-galvanostat. Results and discussion. Using a complex of electrochemical methods, it is revealed that the developed composites with a volume fraction of steel ≥ 25% demonstrate a significant decrease in anodic current densities and a simultaneous increase in charge transfer resistance. Composites with a steel content of 75 vol. % are characterized by the highest corrosion properties in 3.5 wt. % NaCl solution, which is referred to a reduction in corrosion rate by 9.5 times compared to aluminum bronze. It is shown that the main processes occurring on the surface of the composites (CuAl9Mn2 + ER 321) are anodic oxidation of copper and iron, leading to the formation of corrosion products – Cu2O and FeCl2.

Zr-based conversion film fabricated on cold rolled steel by separately providing zirconium and fluorine ions: Performance and mechanism study

Controlling the concentrations of Zr4+ and F− in traditional Zirconium (Zr)-based film-formation solution is challenging due to their dependence on the hydrolytic equilibrium of H2ZrF6. In this study, Zr-based films were prepared on cold rolled steel surface through the film-formation solution prepared by mixing Zr(NO3)4 and different amount of HF. The electrochemical results demonstrated that the Zr-based film prepared by Zr(NO3)4 and HF exhibited superior corrosion resistance compared to H2ZrF6. Under optimal film formation conditions, the protective efficiency of the prepared film reached 74.4 % which was higher than that of film fabricated in H2ZrF6. The electrochemical results concurrently demonstrated the self-reinforcing anti-corrosion performance of the prepared films. Scanning electron microscopy revealed that the Zr film, prepared in Zr(NO3)4 and HF, exhibited excellent corrosion resistance attributed to its high film density. The X-ray photoelectron spectroscopy and energy dispersive spectroscopic results indicated the presence of a fluoride layer on the surface of the Zr film. The F− ions can chelate with the corrosion products and selectively deposit onto the damaged areas of the film, thereby effectively contributing to the repair of the film layer. The results of density functional theory calculations demonstrated that Zr4+ readily forms Zr(OH)4 rather than ZrF62−. The present study offers an enhanced approach for regulating the properties of films prepared via H2ZrF6 by separately providing zirconium and fluorine ions.

The electrochemical corrosion behavior and antibacterial properties of Cu-xFe alloy

Copper-based alloys have garnered significant attention for their potential in antimicrobial applications aimed at mitigating medical-related infections. Nonetheless, the alloying elements in conventional copper alloys frequently exhibit biotoxicity. This study explored the corrosion behavior, antimicrobial activity, and ion release of Cu–Fe alloys with varying iron contents and aging treatment. The results indicate that increasing the iron content in Cu–Fe alloys and applying appropriate aging treatment can enhance both the antibacterial efficiency and corrosion rate. Transmission electron microscopy (TEM) observations revealed a corrosion mechanism in which dispersed iron phases act as nucleation sites. These nanoscale precipitates increase the Cu/Fe interfacial area, thereby promoting ion release at the interface. Furthermore, in-situ scanning electron microscopy (SEM) revealed that corrosion products are more likely to detach in iron-rich segregated areas, which effectively promotes the sustained release of copper ions.

Effect of flavin adenine dinucleotide (FAD) on Desulfovibrio desulfuricans corrosion of pipeline welded joint

The impact of Flavin adenine dinucleotide (FAD) on sulfate-reducing bacteria (SRB) corrosion of a pipeline welded joint (WJ) was investigated under anaerobic condition in this paper. The results showed that the thickness of the corrosion product on heat affected zone (HAZ) was lower than that on base metal (BM) and welded zone (WZ), and the FAD addition enhanced the development of the protruding microbial tubercles on the WJ. The local corrosion degrees of the BM and WZ coupons were significantly higher than that of the HAZ coupon. Besides, the FAD addition simultaneously promoted local corrosion of all three zones of the WJ in the SRB inoculated environment, and the promotion role was much more pronounced on the WZ coupons. The selective promotion effect of FAD on SRB corrosion in the WJ was attributed to the special structure of the WZ, the selected SRB attachment and the FAD/FADH2 redox feedback cycle.

Assessing the effect of different biodiesels on corrosion of nickel alloy

This investigation explores the corrosion behaviour of Ni alloy (UNS718), which is a potential material for storing biodiesel and making engine components. The study also examines the connection between Ni alloy corrosion and biodiesel degradation. Immersion tests were conducted using in-house biodiesels to evaluate the corrosion rates of Used Cooking Oil (UCOB), Karanja oil (KOB), and Jatropha oil (JOB) biodiesels on Ni alloy (UNS718). The results highlighted the role of corrosion product morphology and the formation of corrosion-driven pitting, cracks, etc., on Ni alloy when exposed to different biodiesels such as KOB, JOB, and UCOB. The study utilized gravimetric techniques to measure the corrosion rate and advanced analytical tools such as FESEM, EDS, XPS, NMR and XRF. It revealed decreased corrosion rates of Ni alloys with prolonged biodiesel immersion. For example, after 2160 h, Jatropha biodiesel exhibited a corrosion rate of 0.000699 mm/year, while the corrosion rates of Ni alloy exposed to UCOB and KOB were 0.001398 mm/year and 0.001048 mm/year, respectively. The study also suggests a detailed mechanism of Ni alloy corrosion when exposed to different biodiesels such as Karanja, Jatropha, and Used Cooking Oil.