Corrosion Products Research Articles

Galvanic corrosion of Q345 steel in seawater under varying dissolved oxygen conditions

The galvanic coupling corrosion behaviour of Q345 steel in seawater with different dissolved oxygen contents (DOC) was investigated in this paper by using self-designed detachable electrodes fabricated as chain electrodes, and by using immersion and electrochemical methods in combination with macroscopic and microscopic corrosion morphology. Compared with the corrosion of the chain electrode in the non-electrically connected state, in the electrically connected state, the corrosion current densities of the corresponding electrodes were smaller and the Rp values were larger when the DOC was 8.50, 7.50 and 5.50 mg L−1, indicating that the corrosion reaction was mainly a self-corrosion reaction when the DOC was 8.50, 7.50 and 5.50 mg L−1. When DOC is 9.50 and 6.50 mg L−1, the corrosion current density of the corresponding electrode was larger, the Rp value was smaller, the corrosion products on the surface of the electrode had a loose structure, the relative content of iron was higher, and the corrosion reaction was mainly galvanic coupling corrosion reaction.

The role of biotribocorrosion in the development and progression of clinical manifestations of pseudomembranous candidiasis

Objective. To establish the effect of biotribocorrosion on the development and chronic course of pseudomembranous candidiasis. Materials and methods. The study was conducted at the Department of Orthopedic Dentistry and Gnatology and at the Department of Propaedeutics of Orthopedic Dentistry of the Russian University of Medicine. The study involved 80 patients with pseudomembranous candidiasis using metal dentures and 40 patients with pseudomembranous candidiasis without metal-containing structures, who made up the control group. All participants in the study measured the difference in oral biopotentials, hydrogen index, and salivation rate. Results. In patients of the main group, the content of Fe, Cr, Ni, Ti, Si, K, Na in saliva was significantly increased (p < 0.05) compared with the control group. It was found that dissimilar metal alloys have different effects on the duration of use of dentures. In pseudomembranous candidiasis and the presence of metal-containing structures with signs of biotribocorrosion, a more pronounced electrochemical reaction of stainless steel coated with titanium nitride and uncoated significantly reduces the life of dentures (from 3 to 5 years), compared with CCC metal-ceramic prostheses (from 2 to 10 years) and Ni-Cr-Ni-Cr (from 5 to 8 years old). The greatest pH shift to the acidic side is observed with a combination of stainless steel and Ni-Cr prostheses (pH 5.5–6.0). In pseudomembranous candidiasis, patients using metal dentures have the highest potential differences between M-M. Conclusions. Due to tribocorrosion, corrosion products enter the oral fluid, under their influence, a decrease in pH occurs, provoking a weakening of the protective properties of saliva, a violation of metabolic processes and structural changes in the oral mucosa. Thus, there is a favorable environment for the growth of fungi of the genus Candida, inflammation of the oral mucosa occurs. Microbial flora and fungi that stimulate the development of the inflammatory process are localized in inflammatory areas.

THE ROLE OF INHIBITORS IN THE PROCESS OF FORMING A PROTECTIVE ANTI-CORROSION FILM ON THE STEEL SURFACE OF EQUIPMENT IN HEAT SUPPLY SYSTEMS

Known methods of combating internal corrosion of metal pipes in heat supply systems, by conducting anticorrosive water treatment, cannot maximize the effect of their corrosion protection. There is no universal method of anticorrosive water treatment, each method has its advantages and disadvantages, taking into account the condition of the pipes, the speed of the water supply, and the composition of the water. However, optimal inhibition of corrosion occurring on the inner surface of pipelines of heat supply equipment can be achieved by creating a protective film on the metal inner surface of the pipe using inhibitors. Corrosion products may interfere with the good adhesion of the resulting film to the surface. For more complete and effective inhibition of the surface and dosing of the inhibitor, preliminary chemically active cleaning of the surface with a solution of sulfuric acid, at its concentration of 3%, provided for washing solutions in a circulating mode for 3-5 hours, can contribute. The metal surface of the pipe cleaned by activation contributes to a stronger adhesion of the inhibitor to the surface and the creation of a film with high protective properties. To establish the quality of the obtained anticorrosive films, a JSM6490LV scanning electron microscope with INSAenergy dispersion microanalysis and HKL – Basic structural analysis systems with a useful magnification of 300.000 in combination with a high-performance Varian ProStar liquid chromatograph, an atomic adsorption spectrometer contrAA-300 with a plasma analyzer from 180 to 900 nm was used.The work is devoted to the selection of phosphate and high-modulus silicate inhibitors in order to form a protective film on the metal surface of the pipe to prevent the formation of scale deposits and protect against corrosion when the coolant passes through the pipe to the consumer.

Stress corrosion behavior and microstructure analysis of Al-Zn-Mg-Cu alloys fabricated by CMT wire arc additive manufacturing with different post-treatments

In this study, Al-Zn-Mg-Cu alloys components were fabricated by cold metal transfer (CMT) wire arc additive manufacturing (WAAM), and the stress corrosion cracking (SCC) behavior of the alloys with different post-treatments was studied by combining in-situ electrochemical impedance spectroscopy (EIS) with slow strain rate tensile. The hot-rolling process was employed to close the internal pores of the WAAM products, following by single-stage aging (T6) to further improve the mechanical properties of the products. The elongation loss and SCC susceptibility index of T6 sample are 38.0% and 43.0%, respectively, which exceed those of the hot-rolled sample at 35.5% and 37.0%. Furthermore, the corrosion fracture of the T6 sample exhibits intensive secondary cracks, indicating an increased SCC susceptibility. The stress corrosion process is classified into four stages based on the trend of the EIS: (Ⅰ) Initial stage of corrosion; (Ⅱ) Corrosion products accumulation stage; (Ⅲ) Corrosion products coverage stage; (Ⅳ) Approaching fracture stage. The hot-rolled samples have reduced SCC susceptibility due to the presence of coarse grain boundary precipitates (GBPs) which can act as the irreversible traps to capture hydrogen. The ultimate tensile strength and elongation of T6 sample reached 568.3 ± 11.5MPa and 9.1 ± 0.7%, respectively. However, the small-sized GBPs and wider precipitates-free zone reduced its SCC resistance. This study found that the hot-rolling process can fully exploit the mechanical property potential of Al-Zn-Mg-Cu alloys and improve their SCC resistance, which is an important guiding significance for the practical application of WAAM technology in Al-Zn-Mg-Cu alloys.

Biochars-inlaided nano zero-valent iron reactors: A tool for visualized analysis of soil-nanomaterials micro-interfacial interaction in soil remediation process.

It is a great challenge to depict the evolution process of soil-nanomaterials micro-interfaces during soil remediation. A novel biochar loaded nano zero-valent iron (BC-nZVI) reactor with low density, high reactivity and suitable magnetism was prepared using the method we established. Fe0 nanoparticles (NPs) with the size <10nm uniformly embedded in a layer of porous carbon networks, which attached firmly in the pores and outer surface of biochars. The BC-nZVI reactors efficiently degraded and mineralized pentachlorophenol (PCP) in soil in a wide pH range within 72h at room temperature. BC-nZVI were easily collected from soil using sieving method or floating technology followed with magnetic separation. The evolution of interfacial properties of BC-nZVI was measured using XPS, Raman spectroscopy, XRD and SEM-EDS. Even supported by BCs, aggregation and oxidation of Fe NPs inevitably took place on the outer surface of BC-nZVI in PCP remediation process. For BC-nZVIFeSO4 prepared via traditional impregnation and carbothermal method, severe agglomeration and various aging products of Fe NPs were seen in the pores as well. Due to the protection of porous carbon networks, Fe NPs aggregation was greatly mitigated in the pores of BC-nZVI and the Fe2+/Fe3+ ratio on BC-nZVI surface was still as high as the fresh one. Meanwhile, about 10-20% of carbon matrix was oxidized and turned into amorphous carbon. The Fe NPs corrosion products, broken carbon phase, and K+ of BC-nZVI reactors were released into soil and had little effect or even enhanced the soil bacterial community diversity and biomass. However, the BC-nZVI itself showed certain adverse effect to soil microbes.

Improving corrosion resistance of copper-nickel alloys by the microalloying-facilitated formation of protective corrosion product films

Improving corrosion resistance of copper-nickel alloys by the microalloying-facilitated formation of protective corrosion product films

Research on Source Term Calculation of Corrosion Products under Fusion Reactor Pulse Condition

Research on Source Term Calculation of Corrosion Products under Fusion Reactor Pulse Condition

Effect of temperature gradient on the formed corrosion products films of 70/30 Cu-Ni alloy immersed in 3.5% NaCl solution

Effect of temperature gradient on the formed corrosion products films of 70/30 Cu-Ni alloy immersed in 3.5% NaCl solution

Corrosion Behaviour of Cu-Plate Current Collector under Ex-situ Cyclic Stability Testing for Energy Storage Application

This study compares the corrosion behaviour of a copper plate current collector subjected to an ex-situ cyclic stability test in a 6M KOH and a 6M Na2SO4 electrolyte solution for an electrochemical supercapacitor cell. Through experimental analysis, the change in microstructures resulting from the corrosion behaviour of the copper plate current collector samples are examined by employing various analytical techniques, including microscopy, spectroscopy, and surface roughness analyzer. The corrosion behaviour was studied by employing potentiodynamic polarization and electrochemical impedance spectroscopy analyses. The copper plate current collector samples analysed in 6M KOH and 6M Na2SO4 electrolyte solution showed uniform and localized corrosion product formation, respectively. The CU-72HRS sample recorded a corrosion potential of -608.6mV, -628.87mV, and -89.5mV, -87.588mV using both Tafel and resistance polarization data fitting analysis, respectively, for both 6M KOH and 6M Na2SO4 electrolyte solution using a scan rate of 5mV/s at a voltage window of -1 to 1V. Comparing the microstructural changes under various cyclic conditions provides valuable insights into the durability and reliability of copper plates as current collectors in energy storage systems. The results of this study help improve our understanding of the supercapacitor cell performance in ex-situ cyclic stability tests, assisting in the development of more efficient and durable energy storage technologies.

Corrosion of Sewage Pumps in Acidic Environments: A Comprehensive Study in Libya

Purpose: this article aims to investigate the corrosion behavior of nodular cast iron, a common material used in sewage pump systems. When exposed to acidic conditions. By understanding the underlying mechanisms. Methodology: the experimental strategy used to accomplish this aim was as follows: 1- Immersion test: samples of nodular cast iron were immersed in an acidic medium for 30, 60, 90 days. 2-Electrochemical tests: electrochemical techniques were used to assess the corrosion rate and mechanism. 3-Surface analysis: to describe the corrosion products and surface morphology, surface analysis methods such energy- dispersive X- ray spectroscopy (EDX) and scanning electron microscopy (SEM) were used. Findings: pitting corrosion: nodular cast iron exhibited a high susceptibility to pitting corrosion, leading to localized metal loss. Unstable oxide layer: the formation of an unstable oxide layer on the metal surface contributed to the initiation and propagation of corrosion. Uniform corrosion: in addition to pitting, uniform corrosion was also observed, resulting from the dissolution of the metal in the acidic medium. Implications: improved material selection: careful material selection to ensure the long-term durability of pump components. Effective corrosion mitigation strategies: such as protective coatings and cathodic protection. Enhanced wastewater management.

Characterization of passive layer formation kinetics of Zn5Al hot-dip galvanized coatings using gel electrolytes

Purpose The formation of a natural passive layer on hot-dip galvanized coatings increases their corrosion resistance. Although the basic mechanisms of passive layer formation are known, the quantitative determination of the evolution of its passive character, in particular its surface resistivity, and its development under atmospheric weathering remains largely unexplored for zinc-5% aluminum (Zn5Al) coatings. Design/methodology/approach Zn5Al-galvanized test sheets were exposed to atmospheric weathering for four weeks during summer and winter, and the development of polarization resistance measured using a gel-type electrolyte over these periods. Further investigation included stripping away the formed passive layer midway through the exposure period and electrochemical characterization of the passive layer that re-formed after under continue weathering. Findings The results showed a steadily increasing resistivity of the corrosion product (passive) layer over the course of the weathering period; this was confirmed by supplementary macroscopic and microscopic analyses. Exposure conditions affected the speed of development. Polarization resistance values were higher by approximately 50 kΩcm2 during the winter compared to summer. Upon interruption of exposure and removal of the passive layer, it rebuilt up much more rapidly after exposure resumed in comparison with the initial layer. Originality/value The use of gel electrolyte for determining the polarization resistance of a metal surface is a novel and useful method. To the best of the authors’ knowledge, this study has, for the first time, established the suitability of this electrochemical test method for quantifying the coating resistance of Zn5Al galvanized steel after calibrating the measurement parameters.

Influence of trace Sc on microstructure and corrosion behavior of Mg-0.5Zn alloys

Purpose This paper aims to explore the impact of Sc element on the microstructure and corrosion properties of Mg-0.5Zn alloy. Design/methodology/approach Three kinds of Mg-0.5Zn-xSc (x = 0.1, 0.3 and 0.5 Wt.%) alloys were obtained, and the microstructure and corrosion properties were both analyzed. Findings As the Sc concentration increases, the corrosion resistance of the alloys initially improves and subsequently deteriorates. The trace addition of Sc can effectively reduce the grain size of Mg-Zn-Sc alloys and enhance the density of the corrosion products film. Consequently, an appropriate amount of Sc can reduce the corrosion rate of Mg-0.5Zn alloy. Originality/value However, the addition of Sc also introduces the second phase particles in the alloy, leading to galvanic corrosion, which adversely affects the corrosion resistance of Mg-0.5Zn alloy. Therefore, the amount of Sc added should be carefully controlled.

ИССЛЕДОВАНИЕ НАБОРА ПРОЧНОСТИ ТЯЖЕЛОГО БЕТОНА В АГРЕССИВНОЙ СРЕДЕ. С ИСПОЛЬЗОВАНИЕМ СУЛЬФАТОСТОЙКОГО ЦЕМЕНТА

Experimental data are presented on changes in the compressive strength of heavy concrete using sulfate-resistant cement, Crimean aggregates and additives based on polycarboxylate ethers when kept in an aggressive environment - liquid from water treatment facilities in an urban-type settlement Gvardeiskoe, Simferopol district, Republic of Crimea. Compositions of heavy concrete have been developed using hyperplasticizing (polycarboxylate) additives that are capable of increasing their physical and mechanical characteristics over time when operating in aggressive environments. It is relevant to further develop the theoretical and experimental foundations for the production of cement concrete using the latest generation of superplasticizing additives based on polycarboxylates for wastewater treatment and recreational facilities. The durability of cement concrete is a key issue when using it in wastewater treatment and recreational facilities. Cement concrete can be susceptible to sulfate corrosion. Sulfates have a complex mechanism of action on the chemically active component of concrete - cement stone. Sulfates have a complex mechanism of action on the chemically active component of concrete - cement stone. The corrosive effect can increase or decrease depending on the concentration of aggressive components, with varying levels of exposure to salt solutions on the concrete structure, periodic drying, and partial immersion. This is due to the fact that the chemical processes of interaction between an aggressive environment and cement stone in concrete are influenced by physical processes of mass transfer of soluble components and crystallization of corrosion products or soluble components, which can accelerate or inhibit chemical processes. The parameters of the strength characteristics of the optimized compositions at different periods of strength gain have been established, and the average density and water resistance of the optimized concrete compositions have been established.

Improving high temperature corrosion resistance of Cr3C2–25NiCr coating by incorporating nano yttria-stablized zirconia

The hot corrosion behavior of Cr3C2–25NiCr composite coatings reinforced with nano yttria stabilized zirconia (YSZ) was evaluated under actual boiler conditions in a thermal power plant at 850 °C with cyclic thermal loading. The nano YSZ content was varied between 5 and 10 wt%, and the coatings were applied using the high-velocity oxy-fuel (HVOF) method. A comparative analysis of the impact of varying nano YSZ content on hot corrosion performance was conducted through weight change measurements, while corrosion products were characterized using X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, and cross-sectional analysis. Results indicated that increasing nano YSZ content improved the corrosion resistance of the coatings at high temperatures in the boiler environment, with lower weight gain and the formation of protective oxide scales. Higher nano YSZ content in the coating matrix led to a decrease in corrosion rates during the hot corrosion tests. The corrosion rates for the 5 wt% and 10 wt% YSZ–Cr3C2–25NiCr coated specimens were 4.82 mpy and 3.45 mpy, respectively, reflecting reductions in corrosion rates of 80.79% and 89.26%. The addition of YSZ significantly decreased the corrosion rate, with further reductions observed as the YSZ content in the Cr3C2–25NiCr coating increased. XRD analysis confirmed the presence of Ni, Cr2O3, Cr3C2 and ZrO2–Y2O3 phases, indicating that YSZ particles remained in the coating matrix after exposure.

Atmospheric Corrosion of Different Steel Types in Urban and Marine Exposure.

The aim of the present work is to study the atmospheric corrosion behavior of metals exposed to both urban (Milan, IT-Lombardia) and marine (Bonassola, IT-Liguria) atmospheres in Italy. A number of coupons (100 × 150 mm) of carbon steel (CS), hot-dip galvanized steel (GS) and different grades of stainless steel (SS) were exposed. At fixed periods of time, samples were characterized by means of Linear Polarization Resistance (LPR), mass loss tests and corrosion product analysis. The corrosion rate on carbon steel exposed to an urban atmosphere, obtained by means of mass loss tests and LPR, are in good agreement with the value estimated by the dose-response function according to the ISO 9223 standard. The yielded results can be classified in corrosivity class C2 of the same ISO 9223. Similar measurements on galvanized steel exhibited a coherent average corrosion rate. Higher corrosion rates were measured for samples exposed to a marine atmosphere for both materials, with values belonging to exposure classes C4-C5 for both materials. Stainless steel samples exhibited only superficial staining in the case of marine exposure, even after just a few months.

A Review of Additive Manufacturing of Biodegradable Fe and Zn Alloys for Medical Implants Using Laser Powder Bed Fusion (LPBF).

This review explores the advancements in additive manufacturing (AM) of biodegradable iron (Fe) and zinc (Zn) alloys, focusing on their potential for medical implants, particularly in vascular and bone applications. Fe alloys are noted for their superior mechanical properties and biocompatibility but exhibit a slow corrosion rate, limiting their biodegradability. Strategies such as alloying with manganese (Mn) and optimizing microstructure via laser powder bed fusion (LPBF) have been employed to increase Fe's corrosion rate and mechanical performance. Zn alloys, characterized by moderate biodegradation rates and biocompatible corrosion products, address the limitations of Fe, though their mechanical properties require improvement through alloying and microstructural refinement. LPBF has enabled the fabrication of dense and porous structures for both materials, with energy density optimization playing a critical role in achieving defect-free parts. Fe alloys exhibit higher strength and hardness, while Zn alloys offer better corrosion control and biocompatibility. In vitro and in vivo studies demonstrate promising outcomes for both materials, with Fe alloys excelling in load-bearing applications and Zn alloys in controlled degradation and vascular applications. Despite these advancements, challenges such as localized corrosion, cytotoxicity, and long-term performance require further investigation to fully harness the potential of AM-fabricated Fe and Zn biodegradable implants.

Bottom of Line Corrosion Mechanism in Marginal Sour Environment Wet Gas Pipelines

Internal pipeline corrosion is a well-recognized issue in the oil and gas industry, especially in multiphase flow systems, such as wet gas transportation pipelines that contain mixed phases. Internal corrosion typically manifests as either top-of-the-line corrosion (TLC) or bottom-of-the-line corrosion (BLC). While corrosion mechanisms in sweet environments (dominated by CO₂) are relatively well-understood, those in sour environments (dominated by H₂S) remain less thoroughly examined. In sour environments, the primary corrosion product is iron sulfide (FeS), while in sweet environments, iron carbonate (FeCO₃) tends to form. In marginally sour conditions, FeS layers are often non-uniform, promoting localized corrosion and pitting because low concentration of H2S. It is hypothesizes that higher concentrations of H₂S reduce both the pitting rate and depth.The objective of this research is to investigate the corrosion rate, surface profile, and morphology in a marginal sour environment, using profilometry analysis (ASTM G46) to assess pitting. The experiments were conducted in a glass cell setup simulating pipeline conditions with 3 wt% brine solution and 1000 ppm acetic acid. Corrosion behavior was assessed at H₂S concentrations of 0 ppm, 30 ppm, and 80 ppm using weight loss analysis, surface morphology, and profilometry measurements. Results indicate that increasing H₂S concentration decreases the pitting rate, supporting the study’s hypothesis.

The corrosion resistance of white ultra-high performance concrete under the coupling environment of acid rain and carbonization.

Acid rain and carbonization are two primary types of environmental corrosion that threaten the health of urban concrete structures over time. However, the coupling effects of acid rain and carbonization on concrete deterioration have been rarely reported. In this paper, four coupling regimes were designed using accelerated simulation experiments to investigate the deterioration properties of white ultra-high performance concrete (WUHPC). The results showed that under acid rain corrosion, the WUHPC surface was covered with white crystals before peeling off after 7 days, resulting first in an increase, followed by a rapid decrease in weight and strength, and the erosion depth linearly increased at a rate of 33.0 μm per day. Meanwhile, negligible changes occurred with only carbonization. However, under coupling corrosion, the deterioration worsened after environmental alternation. The strength of WUHPC with acid rain after carbonization decreased by 27.7%, reaching a minimum of 72.0 MPa. The erosion depth growth under acid rain followed by carbonization was 20.0 μm per day, which was much faster than that (3.9 μm per day) of single carbonization. The major corrosion products under acid rain were gypsum crystal, and the crystal shrank with time, leaving more voids and a weakened bonding strength. The calcium carbonate sediment generated during carbonization blocked the pores on the surface, hindered the diffusion of acid solution, and partly consumed acid ions via dissolution, resulting in facilitated acid rain corrosion. Once carbonate was consumed in a short time, more capillary pores were unblocked to promote further acid rain corrosion.

Comparison of Corrosion Behavior of Two Stainless Steels for Medical Applications

Various materials are used in medicine and the main requirement is their biocompatibility, including corrosion resistance. In addition to destroying materials, the products released during corrosion can cause adverse reactions in the human body. Corrosion testing of any material proposed for biomaterials should therefore be conducted in a model or controlled environment similar to that of the human body. In this work, the results obtained in the study of high nitrogen stainless steel (HNS) as a material for the fabrication of implants are presented and compared with the results for classical Cr-Ni stainless steel, in analogous environments and conditions. The tests were carried out in Ringer’s and Hartmann’s solutions, at specified concentrations, temperatures and pH values. A three-electrode glass cell was used under open air conditions. The following electrochemical methods were used: open circuit potential (OCP) – time measurement, cyclic potentiodynamic and potentiostatic polarizations. By means of light and scanning electron microscopy, surface changes were determined after exposing the steel specimens to the experimental media. The surface of the samples was also examined by EDX analysis to determine the nature of the corrosion products formed. From the results obtained, it was found that HNS-steel has higher resistance than Cr-Ni-steel in the model solutions studied.

EIS Method to Study the Corrosion Resistance of Three Arc Spraying Composite Coatings in 3.5% NaCl Solution

To determine the sealing system of arc-spraying aluminum coating for steel structures in high humidity and harsh environments, electrochemical impedance spectroscopy (EIS) was used to study the corrosion resistance and matrix protection of three arc-sprayed aluminum /organic composite coatings in 3.5% NaCl solution. The results indicated that during the 660-day soaking experiment, the coating capacitance of the epoxy-sealing paint system was consistently lower than that of the phosphating primer system and the nano-sealing primer system. The coating resistance showed a decreasing-increasing-decreasing trend but remained above the level of 105 Ω· cm2, and it was higher than the other two systems. The coating reaction resistance remained above 107 Ω· cm2 throughout the entire experimental period, and in the later stage of the experiment, it was 2-3 orders of magnitude higher than the other two systems. It showed that the epoxy sealer system has better shielding performance and corrosion resistance. The protective process of arc-spraying composite coating on the substrate can be divided into four stages: water penetration of organic sealing coating, contact of aluminum coating with medium, formation of shielding layer by corrosion products of aluminum coating, and penetration of corrosion products of aluminum coating to seal pores of organic sealing coating.