Main Corrosion Products Research Articles

Corrosion behavior of low-alloy steel in tidal zone: A simulated investigation

Corrosion behaviors of low-alloy steel were investigated in the simulated tidal zones using stereoscopic microscope, field emission scanning electron microscope, X-ray diffraction, open circuit potential, and electrochemical impedance spectroscopy. The result shows that the corrosion in various tidal zones is much more severe than that of the immersion (IM) zone, and more severe corrosion takes place in the low tide (LT) and middle tide (MT) zones compared with the high tide (HT) zone. In the present test-time scale, uniform corrosion predominantly occurs in the IM and LT zones, and non-uniform corrosion occurs in the MT and HT zones. The main corrosion products in the LT and MT zones are Fe3O4 while α-FeOOH dominates the composition of rust layers in the HT zone.

Water Corrosion of Tungsten Target for Accelerator-Driven Neutron Source.

The water corrosion of tungsten as a target material can affect the safe operation of accelerator-driven neutron source. This paper reported the corrosion behaviors of tungsten in ultrapure water and tap water for 7, 14, 21, 30 and 60 days. Moreover, ICP-MS, XRD, XPS, SEM-EDS and LSCM were used to analyze the components in solutions, crystalline structures, chemical compositions and surface morphologies. It was found that the dissolution of tungsten, due to corrosion, reached its maximum between 30 days and 60 days in both solutions. The cube-shape substance, CaWO4, was the main corrosion product after tungsten in tap water. The tungsten oxide was changed from WO3 to WO2 during the corrosion of tungsten in ultrapure water. Compared with tungsten in ultrapure water, tungsten in tap water had its surface completely destroyed, with a dense diamond shape. Therefore, based on the analysis from this study, the corrosion mechanisms of tungsten in ultrapure and tap water were revealed.

Corrosion behavior of WC–Co coating by plasma transferred arc on EH40 steel in low-temperature

Abstract To investigate the corrosion behavior of WC–Co composite coating, plasma transferred arc (PTA) welding was applied to prepare WC–Co coating on hull steel EH40 for achieving good metallurgical bonding. The phases of coatings were mainly composed of WC particles, solid solution γ-Co, Fe3Ni2, SiO2 and Mo2C. After electrochemical test, it can be concluded that Co-based coating with 45% WC content has better corrosion resistance in low temperature marine environment for obtaining denser oxide film. Through X-ray photo electron spectroscopy (XPS) analysis, the main corrosion products of immersion were Co(OH)2 and Co3O4. These corrosion products aggregate to form a stable corrosion product film, which plays some protective role for the coating. Hard particle WC is also partially oxidized to WO3. The pitting hole of 60% WC is the most serious. Pitting corrosion is easy to occur at the interface defects.

Fluorescent In Situ 3D Visualization of Dynamic Corrosion Processes of Magnesium Alloys.

Magnesium (Mg) alloys as implant materials with excellent biodegradation ability have promising clinical applications for tissue repair and restoration. Although the corrosion processes of Mg alloys in biophysiological media are closely related with their biodegradation ability, only limited methods have been developed for characterization of their corrosion processes, including electrochemical analysis, weight loss measurement, and hydrogen evolution analysis. Moreover, these methods suffer from drawbacks of poor spatiotemporal resolution, static observation, and tedious operation. To tackle these challenges, we herein developed a fluorescent probe PSPA for in situ 3D monitoring of the dynamic corrosion processes of Mg alloys on the basis of its selective turn-on detection ability toward magnesium hydroxide [Mg(OH)2], which is the main corrosion product of Mg alloys in biophysiological media. As far as we know, this is the first example of a fluorescent probe for the monitoring of corrosion processes of Mg alloys in biophysiological media. We believe this fluorescence analysis method with easy operation and high spatiotemporal resolution advantages will contribute greatly to the clinical applications of Mg alloy implants.

An overview of modern ways of cleaning from rust and preservation of iron historical artefacts

This overview focused on the recent advances in rust cleaning and conservation of iron-based historical artefacts. Archaeological iron artefacts undergo various forms of corrosion, including soil and atmospheric. In general the main corrosion products are goethite α-FeO​​(OH), acaganeite β-FeO (OH), lepidocrocite γ-FeO (OH), magnetite Fe3O4, siderite FeCO3, vivanite Fe3(PO4)2 ∙ 8H2O, etc. A number factors contribute to the process corrosion, but Cl- anion embedded in the crystal lattice of acagenite is crucial. It has been considered corrosion product removers from the artefact surface, and found out that all of them should contain inhibitors slowing down the interaction of the artefact iron core with acids. Organic acids, in particular citric, maleic and acetic acids are considered to be non-aggressive and environmental-friendly. After removing corrosion product layer, iron historical heritages are affected by atmospheric corrosion thus stabilizing substances and protective coatings must be applied. The most common protectors are tannin-iron complex compounds, which provide an anti-corrosion coatings and prevent further destruction of artefacts. Preservation of iron-based historical artefacts with synthetic polymer waxes, resins and synthetic polymers is thought to be promising.

Corrosion Behavior of an Mg2Sn Alloy.

In the present work, the corrosion behavior of the Mg2Sn alloy (Mg66.7Sn33.3, concentration in at.%) has been studied. The alloy was prepared from high purity Sn and Mg lumps by induction melting in argon. The alloy was composed of intermetallic Mg2Sn with a small amount of Mg2Sn + (Sn) eutectic. The corrosion behavior was studied by hydrogen evolution, immersion, and potentiodynamic experiments. Three aqueous solutions of NaCl (3.5 wt.%), NaOH (0.1 wt.%) and HCl (0.1 wt.%) were chosen as corrosion media. The alloy was found to be cathodic with respect to metallic Mg and anodic with respect to Sn. The corrosion potentials of the Mg2Sn alloy were −1380, −1498 and −1361 mV vs. sat. Ag/AgCl in HCl, NaCl and NaOH solutions, respectively. The highest corrosion rate of the alloy, 92 mmpy, was found in aqueous HCl. The high corrosion rate was accompanied by massive hydrogen evolution on the alloy’s surface. The corrosion rate was found to decrease sharply with increasing pH of the electrolyte. In the NaOH electrolyte, a passivation of the alloy was observed. The corrosion of the alloy involved a simultaneous oxidation of Mg and Sn. The main corrosion products on the alloy surface were MgSn(OH)6 and Mg(OH)2. The corrosion mechanism is discussed and implications for practical applications of the alloy are provided.

The role of temperature in thaumasite formation under the immersion of magnesium sulfate solution

To clarify the role of temperature in thaumasite formation of cement mortar under magnesium sulfate solution at two different temperatures, the corrosion products and microstructure of cement-based materials with different amounts and particle sizes of limestone powder were quantitatively analysed by Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, scanning electron microscopy and energy-dispersive spectroscopy. At 5°C, the main corrosion products of cement mortar were gypsum and thaumasite. At 20°C, the main corrosion products of cement mortar were gypsum and ettringite. When the temperature increased from 5°C to 20°C, the contents of ettringite, thaumasite and gypsum changed from 0.3, 12.3 and 64.6% to 4.6, 0 and 57.0%, respectively. The formation of thaumasite was the combination of direct reaction with ettringite transformation. The incorporation of limestone powder accelerated the corrosion of mortars, and the change coefficient of compressive strength of mortars decreased from 100% to 47.3% when its content increased from 0% to 30%. Low temperature and incorporation of finer limestone powder enhanced the corrosion of magnesium sulfate solution.

Feasibility evaluation of a Zn-Cu alloy for intrauterine devices: In vitro and in vivo studies

The comprehensively adopted copper-containing intrauterine devices (Cu-IUDs) present typical adverse effects such as bleeding and pain at the initial stage of post-implantation. The replacement of Cu material is demanded. Zinc and its alloys, the emerging biodegradable materials, exhibited contraceptive effects since 1969. In this work, we evaluated the feasibility of bulk Zn alloys as IUD active material. Using pure Cu and pure Zn as control groups, we investigated the contraceptive performance of Zn-0.5Cu and Zn-1Cu alloys via in vitro and in vivo tests. The results showed that the main corrosion product of Zn-Cu alloys is ZnO from both in vitro and in vivo studies. CaZn2(PO4)2·2H2O is formed atop after long-term immersion in simulated uterine fluid, whereas CaCO3 is generally formed atop after implantation in the rat uterine environment. The cytocompatibility of the Zn-1Cu alloy was significantly higher than that of the pure Zn and pure Cu to the human endometrial epithelial cell lines. Furthermore, the in vivo results showed that the Zn-1Cu alloy presented much improved histocompatibility, least damage and the fastest recovery on endometrium structure in comparison to pure Zn, Zn-0.5Cu and pure Cu. The systematic and comparing studies suggest that Zn-1Cu alloy can be considered as a possible candidate for IUD with great biochemical and biocompatible properties as well as high contraceptive effectiveness. Statement of significanceThe existing adverse effects with the intrinsic properties of copper materials for copper-containing intrauterine devices (Cu-IUD) are of concerns in their employment. Such as burst release of cupric ions (Cu2+) at the initial stage of the Cu-IUD. Zinc and its alloys which have been emerging as a potential biodegradable material exhibited contraceptive effects since 1969. In this study, Zn-1Cu alloys displayed significantly improved biocompatibility with human uterus cells and a decreased inflammatory response within the uterus. Therefore, high antifertility efficacy of the Zn-1Cu alloy was well maintained, while the adverse effects are significantly eased, suggesting that the Zn-1Cu alloy is promising for IUD.

Microbiologically influenced corrosion of Cu by marine ammonifying Alcaligenes aquatilis bacterium

In this work, we studied the microbiologically influenced corrosion mechanism of Cu by marine ammonifying bacterium Alcaligenes aquatilis. Through immersion experiments, we found that A. aquatilis could accelerate the corrosion rate of copper, resulting in the development of pits. In the presence of A. aquatilis, the morphology and composition of the corrosion products differed from the abiotic samples, and we found that Cu2O was the main corrosion product. By analyzing the biotic medium and experimental NH3 addition, we verified that NH3 was the main component that intensified copper corrosion. Furthermore, we found that NH3 played a catalytic role in the corrosion of Cu in the presence of A. aquatilis.

Micro‐Raman spectroscopy and complementary techniques for the study of iron weapons from Motya and Lilybaeum (Sicily, Italy): Corrosion patterns in lagoon‐like and calcarenitic hypogea environments

AbstractMicro‐Raman spectroscopy (μ‐RS) has been used to characterize mineralogical phases of corroded iron materials, buried in lagoon‐like and calcarenitic hypogea environments. A set of samples from the Phoenician site of Motya (8th–6th centuries BC, Sicily) and from the Punic Necropolis of Lilybaeum (4th century BC, Sicily) were analyzed combining μ‐RS with scanning electron microscopy‐energy‐dispersive X‐ray spectroscopy (SEM‐EDS) and high‐resolution field emission scanning electron microscopy (HR‐FESEM). Micro‐Raman results revealed the presence of magnetite, goethite, lepidocrocite, and hematite as the main corrosion products and soil minerals as quartz, calcite, barite, actinolite, microcline, zircon, and Ti‐oxides. SEM and HR‐FESEM allowed exploring micro‐ and sub‐micrometer structures of iron oxy‐hydroxides though sections from rim to core. The different corrosion models suggest polymorphic inter‐conversions among iron oxy‐hydroxides and dissolution‐re‐precipitation reactions. In addition, the occurrence of magnetite and metal core that survived in armors buried in the hypogea site of Lilybaeum indicates more stable environmental conditions than those of Motya.

Corrosion behavior of HRB400 and HRB400M steel bars in concrete under DC interference

The influence of direct current interference on the corrosion behavior of HRB400 and HRB400M steel bars in simulated concrete solution was studied using methods such as weight loss experiment, electrochemical experiment, surface technology and product analysis. The research results showed that with the increase of DC interference voltage, the corrosion rates of HRB400 and HRB400M steel bars would increase. The corrosion resistance of HRB400M steel bars was better than HRB400 steel bars under the experimental conditions. In addition, direct current interference could cause damage to the corrosion product layer on the surface of HRB400 steel bars and HRB400M steel bars. And the corrosion form and corrosion product types of HRB400 and HRB400M steel bars would be affected by direct current interference. The main corrosion products of HRB400 steel bars included γ-FeOOH and Fe2O3 when it was not interfered by DC. When DC interference was applied, the main corrosion products included Fe3O4 and Fe2O3. The corrosion products on the surface of HRB400M steel bars were mainly Fe3O4 and Fe2O3, and the types of products increased to form Cr2O3 and MnFe2O4.

Improving mild steel corrosion resistance in tap water: Influence of water flow and supply rates

The mild steel corrosion has been studied in hot tap water (50 °C) using linear polarization technique in the laboratory set-up that models water circulating system. The influence of water flow rate (0.15–0.45 m/s) and water supply rate (0–70 % of system volume per hour) on corrosion kinetics have been investigated. The corrosion products, formed on the surface of the steel corrosion probes, have been analyzed with XRD. It has been found, that in condition of low water flow rate (0.15 m/s) and in the absence of water supply the corrosion rate is high (0.29 mm/year) due to low blocking abilities of the surface deposits. Amorphous Fe(OH)3 is the main corrosion product to be detected on the surface. The increase in water flow rate above 0.15 m/s and water supply rate above 30 % of system volume per hour leads to the 1.6 times corrosion rate reduction (to 0.18 mm/year) due to the formation of dense surface layer of calcium carbonate and iron oxyhydroxides. The results obtained can be utilized to improve the corrosion performance of hot water supply systems.

Reactive Transport Modelling of the Long-Term Interaction between Carbon Steel and MX-80 Bentonite at 25 °C

The geological disposal in deep bedrock repositories is the preferred option for the management of high-level radioactive waste (HLW). In some of these concepts, carbon steel is considered as a potential canister material and bentonites are planned as backfill material to protect metallic waste containers. Therefore, a 1D radial reactive transport model has been developed in order to better understand the processes occurring during the long-term iron-bentonite interaction. The numerical model accounts for diffusion, aqueous complexation reactions, mineral dissolution/precipitation and cation exchange at a constant temperature of 25 °C under anoxic conditions. Our results suggest that Fe is sorbed at the montmorillonite surface via cation exchange in the short-term, and it is consumed by formation of the secondary phases in the long-term. The numerical model predicts precipitation of nontronite, magnetite and greenalite as corrosion products. Calcite precipitates due to cation exchange in the short-term and due to montmorillonite dissolution in the long-term. Results further reveal a significant increase in pH in the long-term, while dissolution/precipitation reactions result in limited variations of the porosity. A sensitivity analysis has also been performed to test the effect of selected parameters, such as corrosion rate, diffusion coefficient and composition of the bentonite porewater, on the corrosion processes. Overall, outcomes suggest that the predicted main corrosion products in the long-term are Fe-silicate minerals, such phases thus should deserve further attention as a chemical barrier in the diffusion of radionuclides to the repository far field.

High temperature corrosion behavior of 430 ferrite stainless steel in a molten sulfur environment

Abstract AISI type 430 stainless steel is a common current collector in sodium sulfur batteries. The corrosion behavior of stainless steel 430 (SS430) was investigated in this article in a sulfur environment at 350 °C using the gravimetric method. The corrosion mechanism and the characteristics of vulcanization films were studied by diffraction X-ray (XRD) and scanning electron microscopy (SEM), and resistance was tested by a four-probe tester. The results showed that the intensive vulcanization of SS430 took place at a corrosion time above 24 h. The dynamic vulcanization of SS430 first increased to a maximum point of 0.6532 mm × a-1 after 120 h in a 350 °C molten sulfur environment and then decreased. Block resistance reached 0.6058 mΩ after 120 h. The main corrosion product of SS430 was FeS2 within 48 h and its microstructure was porous. The Cr6S7 was observed again after 72 h. A dense Cr2S3 and FeS2 coating formed after 120 h, which protected the SS430 and reduced corrosion.

Failure analysis on aluminum alloy drill pipe with pits and parallel transverse cracks

In recent years, aluminum alloy drill pipe are used more and more frequently in the exploration and development of the deep wells, ultra-deep wells and sour gas wells due to the high strength, light weight and corrosion resistance to H2S and CO2. However, the pitting and fracture failure sometimes occurred, resulting in giant economic losses and fatal disaster. In this study, the failure analysis of aluminum alloy drill pipe was addressed and the formation cause of the pits and parallel transvers cracks was investigated. Results show that the chemical composition and the regular mechanical properties (including tensile and impact properties) meet ISO 15546:2011 standard requirements. But the tensile strength of samples immersed in the mud environment is lower than that of ISO 15546:2011 standard requirements. Metallographic analysis results show intermittent ribbon Al6(MnFe) solid solution, S (CuMgAl2) phase and AlFeSi phase distributed on α solid solution. The failure cause of aluminum alloy drill pipe is mainly attributed to the brittleness sensitivity of intermittent banded second phase and inclusions to corrosive media from mud environment. Cracks and pits are prone to generate here. XRD and EDS analysis results of corrosion products and the pits bottom show that the main corrosion products are Al2O3, Al2S3, AlPO4, BaSO4 and CaCl5. S and Cl are from environment media. The microscopic morphology analysis results of the tensile and impact specimens fracture show that the fracture is the brittle fracture caused by the environmental medium.

IMPROVING MILD STEEL CORROSION RESISTANCE IN TAP WATER: INFLUENCE OF WATER FLOW AND SUPPLY RATES

The mild steel corrosion has been studied in hot tap water (50 °C) using linear polarization technique in the laboratory set-up that models water circulating system. The influence of water flow rate (0.15-0.45 m/s) and water supply rate (0-70 % of system volume per hour) on corrosion kinetics have been investigated. The corrosion products, formed on the surface of the steel corrosion probes, have been analysed with X-Ray Diffraction (XRD). It has been found, that in condition of low water flow rate (0.15 m/s) and in the absence of water supply the corrosion rate is high (0.29 mm/year) due to low blocking abilities of the surface deposits. Amorphous Fe(OH)3 is the main corrosion product to be detected on the surface. The increase in water flow rate above 0.15 m/s and water supply rate above 30 % of system volume per hour leads to the 1.6 times corrosion rate reduction (to 0.18 mm/year) due to the formation of dense surface layer of calcium carbonate and iron oxyhydroxides. The results obtained can be utilized to improve the corrosion performance of hot water supply systems.

Microstructure and properties of biodegradable co-continuous (HA+β-TCP)/Zn–3Sn composite fabricated by vacuum casting-infiltration technique

The co-continuous (HA+β-TCP)/Zn–3Sn composite was fabricated via vacuum casting-infiltration method. The microstructure, mechanical properties, corrosion behaviors, and hemolysis ratio of the composite were studied by scanning electron microscope, X-ray diffractometer, mechanical testing, electrochemical test, immersion test, and ultraviolet spectrophotometry. The results indicate that Zn–3Sn alloy infiltrated into porous HA+β-TCP scaffold, which resulted in the formation of a compact (HA+β-TCP)/Zn–3Sn co-continuous composite, without any reaction layer between the Zn–3Sn alloy and the HA+β-TCP scaffold. The compressive strength of the composite was equal to about 3/4 that of Zn–3Sn alloy bulk. The corrosion rate of composite in simulated body fluid solution was slightly higher than that of Zn–3Sn alloy bulk. The main corrosion product on the composite surface was Zn(OH)2. The hemolysis rate of the composite was lower than that of Zn–3Sn alloy bulk and exhibited superior blood compatibility.

The Effect of Sn Addition on Zn-Al-Mg Alloy; Part II: Corrosion Behaviour.

Corrosion behaviour of Sn (0.0, 0.5, 1.0, 2.0 and 3.0 wt.%)-doped Zn 1.6 wt.% Al 1.6 wt.% Mg alloys exposed to salt spray testing was investigated. Intergranular corrosion was observed for all alloys in both as-cast and annealed states. However, due to microstructure spheroidisation in the annealed samples, potential intergranular corrosion paths are significantly reduced. Samples with 0.5 wt.% of Sn showed the best corrosion properties. The main corrosion products identified by XRD analysis for all samples were simonkolleite and hydrozincite. Occasionally, ZnO and AlO were identified in limited amounts.

Evaluation of the Protection Ability of a Magnesium Hydroxide Coating against the Bio-Corrosion of Concrete Sewer Pipes, by Using Short and Long Duration Accelerated Acid Spraying Tests.

The Microbiologically Induced Corrosion (MIC) of concrete sewer pipes is a commonly known problem that can lead to the destruction of the system, creating multiple public health issues and the need for costly repair investments. The present study focuses on the development of a magnesium hydroxide coating, with optimized properties to protect concrete against MIC. The anti-corrosion properties of the respective coating were evaluated by using short and long duration accelerated sulfuric acid spraying tests. The coating presented satisfying adhesion ability, based on pull-off and Scanning Electron Microscopy (SEM) analysis measurements. The surface pH of the coated concrete was maintained at the alkaline region (i.e., >8.0) throughout the duration of all acid spraying tests. The consumption of the coating, due to the reaction (neutralization) with sulfuric acid, was confirmed by the respective mass and thickness measurements. The protection ability of this coating was also evaluated by recording the formation of gypsum (i.e., the main corrosion product of concrete) during the performed tests, by X-ray Diffraction (XRD) analysis and by the Attenuated Total Reflectance (ATR) measurements. Finally, a long duration acid spraying test was additionally used to evaluate the behavior of the coating, simulating better the conditions existing in a real sewer pipe, and the obtained results showed that this coating is capable of offering prolonged protection to the concrete substrate.

Controlling Atmospheric Corrosion of Weathering Steel Using Anodic Polarization Protection Technique

The atmospheric corrosion of weathering steels varies as a function of geographic zone, season, and other environmental variables related to that region which the experiments have been done. Meanwhile, rusting is a continuous process, and it is the main corrosion product of atmospheric corrosion. The current study investigates the effects of rust on weathering steel in the localized region of Digha, a sea resort of West Bengal, India. The investigations have been performed by purposely accelerating the rusting of weathering steel in a laboratory within one week in order to simulate approximately 18 months of actual rusting that can be achieved at field exposure. Anodic polarization of weathering steel comparable to potentiostatic passivation is obtained by shorting weathering steel with nobler metals, such as copper or graphite. The effect of rust formation on corrosion resistance after being immersed in 0.01 M KCl solutions for polished and unpolished samples has been investigated using electrochemical techniques, such as potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The rusted surfaces’ morphology and composition were characterized using field emission scanning electron microscope (FE-SEM) and energy dispersive X-ray analysis (EDX). Based on the obtained results, it is concluded that the progressive rusting of weathering steel leads to a decrease in corrosion rate.