Main Corrosion Products Research Articles

Corrosion failure analysis of steel tubes operating in mining installations: Metallurgical, chemical and mechanical investigations

AbstractCorrosion of steel tubes represents a major challenge for various industries, leading to significant economic and environmental impacts, such as material losses, operational interruptions and safety risks. This study focuses on the metallurgical, chemical and mechanical characterization of corroded steel tubes operating in mining installations using metallographic analysis, X-ray diffraction (XRD), SEM-EDS studies, chemical analysis and micro-hardness measurements. The results reveal the existence of a considerable extent of corrosion, of which, the main corrosion products are magnetite – 72% and goethite – 18.1 associated with corrosion. The corroded tubes measured 0.128% carbon, against 0.23% in new tubes, indicating a loss in weight and mechanical strength properties. The observed tensile strength for the new tubes was 481 MPa while the same for the corroded tubes was to a large extent lower. Furthermore, metallographic examination indicates that indeed the structure is ferrite pearlite as to the composition. This study indicates that 304 L or 316 L stainless steels may be utilized which have better corrosion-protecting coatings thus prolonging service life and reducing maintenance activities.

Atmospheric corrosion of tin coating on T2 copper in Xiangtan, China

Atmospheric corrosion of tin coating on copper was explored to understand the differences in corrosion behavior between the skyward and earthward surfaces of the tin coating. Results show that average corrosion rate of the tin coating was 0.578 ± 0.051 and 1.137 ± 0.166 μm■y−1 after one year and two years of exposure in Xiangtan, China, respectively. Corrosion rate of the tin coating during the second year of exposure was higher than that during the first year. SnO2 was the main corrosion product of the tin coating. Localized corrosion vulneravbilty of the skyward surface was higher than that of the earthward surface during the first year of exposure, but it became lower than the latter during the second year. During the first year of exposure, icorr values of the skyward and earthward surfaces were relatively low, but they sharply increased during the second year of exposure.

Symbiosis of Sulfate-Reducing Bacteria and Total General Bacteria Affects Microbiologically Influenced Corrosion of Carbon Steel

The effects of the symbiosis of sulfate-reducing bacteria (SRB) and total general bacteria (TGB) on the microbiologically influenced corrosion (MIC) of carbon steel were investigated in this research. The SRB was the main corrosive bacterium, and TGB induced slightly general MIC. The symbiosis of SRB and TGB induced more severe MIC and pitting corrosion than SRB. The main corrosion products were FeS, Fe2O3, and FeOOH. The presence of TGB facilitates MIC and pitting corrosion by providing a locally anaerobic shelter for SRB. An MIC mechanism of the symbiosis of SRB and TGB was proposed.

Effects of Al2O3 micro/nanoparticles on the microstructure and corrosion behavior of W–Ni–Fe matrix through spark plasma sintering process

The purpose of this research is to examine the effect of Al2O3 micro/nanoparticles on the properties of the W–Ni–Fe matrix. The study involved analyzing the microstructure, hardness, density, and corrosion behavior of the W-4.9Ni-2.1Fe matrix with varying percentages of Al2O3 micro/nanoparticles (0.5, 1, and 1.5 wt%) that were sintered using the spark plasma method. The corrosion properties of different composites were studied using electrochemical impedance spectroscopy, Tafel polarization, and weight loss measurements. Furthermore, microstructural evaluations were carried out on samples before and after corrosion tests using optical and field emission scanning electron microscopy. The results indicated that a 1% increase in the percentage of Al2O3 nanoparticles led to approximately a 16% increase in the matrix hardness. This increase was attributed to the reduction in grain size and the distribution of pores in the nanocomposites. Tafel polarization measurements also showed that adding 1% Al2O3 nanoparticles resulted in an 83% improvement in the corrosion resistance of the W–Ni–Fe matrix in a 3.5 wt% NaCl solution. The improved corrosion resistance of the fabricated nanocomposites was attributed to the uniform distribution of Al2O3 nanoparticles in the matrix and reduction in the cathodic region. However, it was found that the formation of galvanic microcells was a critical cause of corrosion in micro-composites, leading to a reduction in corrosion resistance compared to the W–Ni–Fe matrix. Raman spectroscopy patterns indicated that Fe3O4, Fe(OH)2, NiO, and Ni(OH)2 were the main corrosion products.

Release of nickel and chromium ions from stainless steel brackets as a result of long-term exposure to commonly used toothpaste

Background: Brackets in fixed orthodontic appliances are mostly made from metal or stainless steel. Maintaining oral hygiene by brushing the teeth with toothpaste during orthodontic treatment is important. One of the ingredients in toothpaste, sodium fluoride, can cause degradation of the stainless-steel surface, which has the potential to corrode or release metal elements. Purpose: the purpose of this study is to describe the Nickel and chromium ion release of stainless-steel brackets against toothpaste use in orthodontic treatment by means of narrative review. Review: The main corrosion products of stainless-steel brackets are nickel and chromium. Toothpaste detergents contain sodium lauryl sulfate, which can cause the release of nickel ions due to the presence of sodium ions, which can trigger redox reactions. In addition, the fluoride content will combine with hydrogen to produce hydrofluoric acid, which can damage the oxide layer on orthodontic wires, resulting in the release of metal ions such as nickel and chromium. The effects of the release of these ions can be carcinogenic, cause hypersensitivity reactions, and cause cytotoxicity. Corrosion causes the dissolution of filler metal, resulting in weakened bracket material and increased friction, leading to delayed tooth movement. Conclusion: Toothpaste can affect the release of nickel and chromium ions in stainless steel brackets in the presence of sodium and fluoride.

Effect of Molten Salts Composition on the Corrosion Behavior of Additively Manufactured 316L Stainless Steel for Concentrating Solar Power

The effects of different molten salts on the corrosion resistance of laser powder bed fusion (L-PBF) 316L stainless steel was evaluated at 650 and 700 °C. The samples were characterized via XRD and SEM/EDX after high-temperature corrosion tests to evaluate the corrosion damage to the L-PBF 316L stainless steel caused by the molten salts. The presence of the salts accelerated the corrosion process, the chloride-based salts being the most aggressive ones, followed by the carbonate-based and the nitrate/nitrite-based salts, respectively. The L-PBF 316L did not react strongly with the nitrate/nitrite-based salts, but some corrosion products not found in the samples tested in the absence of salts, such as NaFeO2, were formed. LiFeO2 and LiCrO2 were identified as the main corrosion products in the samples exposed to the carbonate-based molten salts, due to the high activity of Li ions. Their growth produced the depletion of Fe and Cr elements and the formation of vacancies that acted as diffusion paths on the surface of the steel. In the samples exposed to chloride-based molten salts, the attacked area was much deeper, and the corrosion process followed an active oxidation mechanism in which a chlorine cycle is assumed to have been involved.

Sulfide mediated zero valent iron for enhanced nickel removal under neutral condition: Reaction kinetic, mechanism, and stability

The application of sodium sulfide (Na2S) as sulfidation reagent of zero valent iron (ZVI) has been well studied, however, the effect of Na2S existence on ZVI reactivity remains obscure. In this study, Ni(II) removal performance, mechanism, and stability by ZVI with Na2S were investigated at neutral condition. The results showed that Ni(II) removal sharply increased from < 5–100% by ZVI within 60 min with the increase of Na2S concentration, but the subsequent Ni(II) release occurred. In addition to the slight Ni(II) removal by Na2S in aqueous phase, Ni(II) was mainly removed by the adsorption and reduction by Na2S mediated ZVI system. Characterization analysis indicated that Na2S could lead to the severe Fe0 corrosion and the main corrosion product on ZVI was lepidocrocite, which played the dominant role for Ni(II) immobilization. Meanwhile, the formation of iron sulfides on ZVI surface would enhance Ni(II) reduction and partially transform the adsorbed Ni(II) to NiS. Moreover, the higher ionic strength could further enhance the initial Ni(II) removal rate but the stability became poor. Regardless of the additive methods, the Ni(II) removal significantly enhanced in the system of ZVI and Na2S combination. Overall, this work reveals the sulfide mediated Fe0 corrosion and provides a potential method for enhancing the reactivity of ZVI in the treatment of Ni(II) pollution.

Effect of Temperature and NaClO on the Corrosion Behavior of Copper in Synthetic Tap Water

The corrosion behavior of copper was investigated in synthetic tap water with and without sodium hypochlorite (NaClO) at different temperatures during immersion for 70 d by using scanning electron microscopy (SEM), X-ray diffraction (XRD), and electrochemical measurement techniques. The weight loss corrosion rate and pit depth of copper first increase and then decrease with the change in solution temperature from 25 to 80 °C. This is mainly related to the corrosion products formed on the copper surface. The main corrosion products change from Cu2O and Cu2(OH)2CO3 to CuO with the increase in solution temperature. The presence of 3 ppm NaClO slightly increases the weight loss corrosion rate and pit depth of copper under all temperatures except for 50 °C and reduces the temperature of the maximum corrosion rate from 50 to 40 °C. Free chlorine reduction accelerates the cathodic reaction of the corrosion process.

Grain boundary infiltration and corrosion mechanism of CMAS attack on M-YTaO4 thermal barrier coating ceramics at 1300 °C

M-YTaO4 is one of the most promising candidates for the next-generation thermal barrier coatings. However, the CMAS-induced degradation of M-YTaO4 is still in dispute. This work comprehensively investigates the CMAS corrosion of M-YTaO4 at 1300 °C which provides new insights into the corrosion mechanism. CMAS attacks M-YTaO4 forming a thick recession layer and the main corrosion product is accurately confirmed to be (Ca2-xYx)(Ta2-y-zMgyAlz)O7 solid solution. The recession layer presented a small difference in Young's modulus with M-YTaO4. No delamination cracking occurred during the thermal cycling process indicating good reliability. In addition, grain boundary infiltration of CMAS is first revealed in M-YTaO4. The results have corrected the misjudgment of the corrosion mechanism and CMAS infiltration process in previous studies which provides guidelines for the design of M-YTaO4 thermal barrier coatings.

Microstructure evolution and corrosion behavior of TIG welded joint of a new Mg[sbnd]Gd[sbnd]Nd[sbnd]Zn[sbnd]Zr alloy during post-weld heat treatment

The corrosion behavior of the tungsten inert gas (TIG) welded Mg3Nd3Gd0.2Zn0.5Zr alloy with different post-weld heat treatments was systematically investigated. The results show that the corrosion resistance of the sand-cast base material (BM) was inferior to that of the fusion zone (FZ), which was attributed to the larger grain size and exacerbated galvanic corrosion caused by coarser Mg3(Nd, Gd) eutectic phases and numerous β precipitates. It is found that post-weld solid-solution (T4) treatment could significantly enhance the corrosion resistance of the joint due to the dissolution of the cathodic second phases and the denser protective film abundant in RE oxides generated in corrosive solution. The precipitation of nanosized phases and ZnZr clusters would slightly increase the susceptibility to localized corrosion of the peak-aged (T6) joint. As the main corrosion products, MgO and Mg(OH)2 are distributed throughout the whole corrosion film, while RE oxides and RE hydroxides are mainly distributed in the inner layer, which can be explained by inward oxidation and replacement reactions between RE elements and MgO/Mg(OH)2. Based on the composition and structure of the corrosion product film, a physical model has been proposed for depicting the microstructure evolution associated with the corresponding corrosion behavior of the joints. This work could promote the applications of welded MgRE alloy joint in some corrosion environments.

Effect of nitrate-carbonate molten salt flow rate for the 347H corrosion behavior

Molten salts have been widely adopted for solar thermal power stations because of their superior thermophysical properties. However, the corrosive effect on the metal material with molten salt is an important factor for the long-term operation of CSP systems. For the study of the corrosive influence on metallic materials of molten salts in dynamic conditions, the corrosion performance of the 347H sample in molten salts at different flow rates was analyzed by using nitrate-carbonate molten salt as the base salt. The findings revealed a higher corrosion rate of the 347H samples under dynamic conditions, compared to static conditions. Moreover, as the flow velocity for the molten salt increases, 347H sample corrosion rates increase. The morphological analysis of the 347H sample revealed that, under molten salt static conditions, a dense corrosion layer was mainly formed in the 347H sample, while, under molten salt dynamic conditions, a grooved structure was observed in the 347H sample. The main corrosion products of 347H samples in different flow rates are composed of Fe2O3, Fe3O4, NiFe2O4 and NaFeO2. Therefore, for changing the molten salt flow rate, the sample’s corrosion morphology changes but does not affect the sample’s corrosion product type.

Effect of tissue fixatives on the corrosion of biomedical magnesium alloys

In this work, the corrosion behavior of pure Mg, Mg3Ag, Mg6Ag, and MgZnYNd alloys in different fixatives (ethyl alcohol (EA), 85 % ethyl alcohol (85 % EA), 10 % neutral buffered formalin (10 % NBF), 4 % glutaric dialdehyde (4 % GD), and 4 % paraformaldehyde (4 % PFA)) was investigated to provide a valuable reference for the selection of fixatives during the histological evaluation of Mg implants. Through the hydrogen evolution test, pH test, and corrosion morphology and product characterization, it was found that corrosion proceeded slowest in the EA and 85 % EA groups, slightly faster in 4 % GD, faster in 10 % NBF, and fastest in 4 % PFA. After corrosion, the EA group surface remained unchanged, while the 85%EA group surface developed minor cracks and warping. The 4%GD fixative formed a dense needle-like protective layer on the Mg substrate. The 10%NBF group initially grew a uniform layer, but later developed irregular pits due to accelerated corrosion. In contrast, the 4%PFA solution caused more severe corrosion attributed to chloride ions. The main corrosion products in the EA and 85%EA groups were MgO and Mg(OH)2, while the other fixatives containing diverse ions also yielded phosphates like Mg3(PO4)2 and MgHPO4. In 4 % PFA, AgCl formed on the surface of Mg6Ag alloy after corrosion. Therefore, to minimize Mg alloy corrosion without compromising staining quality, EA or 85 % EA is recommended, while 4 % PFA is not recommended due to its significant impact.

Corrosion Behavior of 30 ppi TAD3D/5A05Al Composite in Neutral Salt Spray Corrosion

This study created ceramic preforms with a 3D network structure (TAD3D) by using treated aluminum dross (TAD) and kaolin slurry, with 30 ppi polyurethane foam as a template via the sacrificial template method. TAD3D/5A05Al composites were then produced via pressureless infiltration of 5A05Al aluminum alloy into TAD3D. The corrosion behavior and resistance of TAD3D/5A05Al in salt spray were assessed via neutral salt spray corrosion (NSS), scanning electron microscopy (SEM), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) tests. The results showed that after 24 to 360 h of NSS corrosion, the corrosion of the 5A05 matrix was primarily pitting, with pits expanding and deepening over time, and showing a tendency to interconnect. The main corrosion products were MgAl2O4, Al(OH)3, and Al2O3. As corrosion progressed, these products increased and filled cracks, pits, and grooves at the composite interface on the material’s surface. Corrosion products transferred to the grooves at the composite interface and grew on the ceramic surface. Corrosion products on the ceramic framework and the Al matrix can form a continuous passivation film covering the composite surface. PDP and EIS results indicated that the composite’s corrosion resistance decreased by 240 h but increased after that time. After 240 h, the surface passivation film can weaken corrosion effects and enhance the composite’s resistance, although it remained weaker than that of the uncorroded samples. Additionally, grooves at the composite interface deepened over time, with loosely structured corrosion products inside, potentially leading to severe localized corrosion.

Delamination of thermally sprayed ZnAl15/organic duplex coating systems on structural steel for offshore wind applications

Duplex coating systems incorporating both thermally sprayed metal (TSM) and organic coatings have demonstrated excellent corrosion protection performance in highly corrosive offshore applications. However, the present work showed extensive delamination of organic coatings from the TSM (ZnAl15) layer during ISO 12944-9 cyclic ageing test. A positive correlation was uncovered between cathode-to-anode ratio and the extent of the delamination, which was further verified by delamination measurement on samples with varying artificial scribes. A depletion of aluminum at the tip of propagating cracks in the TSM layer was detected by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), suggesting the occurrence of local acidification driven by hydrolysis of Al3+. X-ray diffraction (XRD) analysis confirmed ZnO, Zn5(OH)8Cl2·H2O, and AlO(OH) as the main corrosion products in the artificial scribe. Careful considerations and supplementary real-field assessment were recommended when employing ISO 12944-9 cyclic ageing test for a robust anticorrosive performance evaluation of this type of duplex coating system.

Mott–Schottky Analysis of Historical and Archaeological Copper–based Objects

AbstractThe application of Mott–Schottky (M−S) analysis of impedance data to sub–micro samples extracted from the corrosion patina of copper, bronze, and brass archaeological artifacts attached to graphite electrodes is described. The corresponding theoretical approach is developed to account for the contribution of the composition and structure of the corrosion patina and the effect of the bare graphite substrate. Experimental data in contact with 0.10 M Na2SO4 aqueous solution at pH 6.28 are consistent with the p‐type semiconducting nature of the main copper corrosion products, cuprite, and tenorite. The values of the apparent flat band potential and the slope of the M−S plots allow archaeological samples to be grouped according to their M−S parameters (slopes and intercepts). Assuming equivalent conditions of corrosion, the resulting grouping is judged to be dependent on the composition, and/or method of manufacture, and/or age. Studied samples include Renaissance statues from the Hofkirche in Innsbruck and a variety of objects from museums and Archaeological Heritage Office (soprintendenza) in Austria (Bad Aussee, Johanneum Graz, and the Tyrolean State Museums), and Italy (Genoa and San Remo), dating from the Bronze Age to the 18th century. Complementary data are provided by voltammetry of immobilized particles.

Study on corrosion law of coiled tubing in high CO2 gas field

The corrosion rates of CT80 grade coiled tubing steel (CT80) and 2205 duplex stainless steel (2205DSS), as well as other attachments, were determined using the weight loss method in a high-temperature and high-pressure autoclave to simulate operational corrosion conditions. The rates were compared with the predicted rates based on BP (backpropagation) neural network optimized by genetic algorithm, in response to the severe corrosion issue encountered during coiled tubing operations in high CO2 gas fields in Sichuan, China. In the gas phase, the results revealed that with the increase of the temperature and the CO2 partial pressure in the high CO2 gas field, the corrosion rate of CT80 gradually increases, while the rate of 2205DSS remains relatively stable and lower than that of CT80. In the liquid phase, the corrosion rate of CT80 exhibits an initial increase followed by a subsequent decrease with increasing temperature and partial pressure, while the 2205DSS corrosion rate remains slightly low and fairly stable. Furthermore, the XRD results of the corrosion product in the liquid phase revealed a higher corrosion rate on CT80 due to its loose and porous film structure, with FeCO3 and Fe2O3 being the main corrosion products. In contrast, 2205DSS exhibited only slight corrosion, characterized by a denser corrosion product film primarily composed of Cr2O3. The average error between the measured values and model calculated values is ∼15%, indicating that 2205DSS exhibited better wear resistance, making it suitable for application in the high CO2 gas field.

Multi-ion erosion test and molecular dynamics simulation of carbon nanotube concrete under stray current and salt brine environment

This study considers the superior mechanical properties of carbon nanotube concrete (CNC) and conducts corrosion tests over varying durations to investigate key aspects such as corrosion depth, strength loss, ion migration patterns, and microscopic morphological changes in CNC under the influence of stray current in a salt brine environment. Through compressive strength test, chloride ion color test, ion content titration test, microscopic detection test and molecular dynamics simulation, the results show that in an environment where multiple erosive ions coexist, sulfate ions are the most erosive ions to CNC, and are easily combined with calcium ions. The electric field speeds up the transmission of ions, especially chloride ions. Carbon nanotube has a certain adsorption effect on sulfate ions. The main corrosion products are ettringite, gypsum and magnesium hydroxide. Among them, ettringite and gypsum mainly cause expansion and corrosion.

Failure analysis of the end surface of the burner nozzle made of UMCo50 material in long-term high temperature oxygen-enriched sulfur-chlorine environment

As the core device of coal water slurry gasification technology, the failure of the burner nozzle will bring serious technical and safety problems. The purpose of this paper is to determine the mechanism of burner failure based on the characteristics of corrosion products and cracks. The results showed that the Cr2O3 oxide film on the surface of UMCo50 was damaged under the effect of mechanical erosion, high temperature and stress, and the corrosive elements S and Cl in the combustion chamber made it further cracked and peeled off. Therefore, the matrix was corroded and cracks occurred. During the crack propagation process, more M23C6 carbides were precipitated at the grain boundary, it caused Cr-depleted at the grain boundary, which reduced the corrosion resistance of the matrix near the grain boundary. The exfoliation of carbides distributed along the grain boundary also accelerated crack propagation. Through XPS and XRD analysis, it was found that the main corrosion products on the crack surface of the failed parts were: Cr2O3, CoCr2O4, CoO, Fe2O3, FeS. According to the causes of failure analysis, the corresponding improvement measures are put forward.

Corrosion behavior of Al/Mg/Al multilayered composite elaborated by accumulated roll bonding

The corrosion behavior of an Al1050/AZ31/Al1050 multilayered hybrid composite fabricated by the accumulated roll bonding (ARB) technique up to six cycles in a 3.5 wt.% NaCl solution was studied through potentio- dynamic polarizationtests (PDP), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM−EDS), Raman spectroscopy and X-ray diffraction (XRD). In order to deeply apprehend the corrosion resistance and corrosion products of the Al1050/AZ31/Al1050 multilayered hybrid composite, almost similar investigation was performed on the Al1050/Al1050/Al1050 multilayered sample elaborated by ARB up to one cycle. Potentiodynamic polarization plots and electrochemical impedance spectroscopy show that the corrosion rate is strongly affected by the ARB strain level. A higher corrosion rate and reduced polarization resistance are evidenced compared to the Al1050/Al1050/Al1050 multilayered sample.The AZ31 layers seem to dominate the corrosion process. Raman and XRD analyses confirm the presence of the main corrosion product of Mg(OH)2 and the absence of any chloride such as (Mg(OH)2)·MgCl2.

Impact of sulfoaluminate cement modification on corrosion resistance of reactive powder concrete subjected to ammonium sulfate-rich sewer environment

Using sulfoaluminate cement (CSA) to partially replace Portland cement (PC) was effective in improving the early strength and eliminating the autogenous shrinkage of UHPC at ambient temperatures. However, the sulfate resistance of PC-CSA blended UHPC has not yet been well understood. This study investigates the effects of adding CSA on the corrosion resistance of reactive powder concrete (RPC) exposed to an ammonium-magnesium sulfate solution. The results showed that the main corrosion products generated in the RPC were gypsum, ettringite, and thaumasite. The addition of 8 wt% CSA significantly improved the corrosion resistance of RPC owing to reaction between CH, ye'elimite, and gypsum that created ettringite, which refined the pore structure and improved the aggregate-paste interface bonding. Specifically, incorporating 8 wt% CSA caused a 13.28% reduction in the porosity of RPC pastes after corrosion. In contrast, excessive adding CSA produced massive gypsum crystals and led to the separation of pastes from aggregates, reducing the corrosion resistance of RPC. At last, CSA modification can be considered as a low-carbon method for the design of RPC materials applied in ammonium sulfate-rich sewage environments.