Lower Corrosion Rate Research Articles

Electrochemical corrosion behavior of atmospheric-plasma-sprayed copper as a coating material for deep geological disposal canisters

Cu, which exhibits excellent corrosion resistance in underground environments, has been investigated as a canister material for use in the deep geological disposal of spent nuclear fuels. In this study, the technical viability of atmospheric plasma spraying for producing Cu-coated canisters was investigated. A high-purity Cu film (millimeter scale) was deposited onto a stainless-steel substrate using a plasma gun with a shroud structure. Potentiodynamic polarization studies revealed that the Cu film exhibited a sufficiently low corrosion rate in the groundwater electrolyte. In addition, no pitting corrosion was observed on the Cu film surface after accelerated corrosion studies. A prototype cylindrical Cu film was fabricated on a 1/20 scale on a stainless-steel tube to demonstrate the scalability of atmospheric plasma spraying in producing Cu-coated canisters.

The efficient solid electrochemical corrosion prelithiation of graphite and SiOx/C anodes for longer-lasting lithium ion batteries

In order to avoid side reactions with liquid electrolyte for the prelithiation method using metal lithium for the improvement of initial coulombic efficiency and prelithiation efficiency, we propose the solid electrochemical corrosion (SEC) of lithium replacing liquid electrolyte with solid electrolyte of lithium phosphorus oxynitride (LiPON) in previous works. However, the low prelithiation rate of solid electrochemical corrosion with LiPON interlayer between anode and lithium hinders its possible large-scale application. Here, an ultrathin film of Bi2O3 is introduced as the interface layer to improve the prelithiation rate of SEC, the prelithiation effects are investigated on both graphite and SiOx/C anodes by morphological, spectroscopic and electrochemical characterizations. The initial coulombic efficiencies of graphite and SiOx/C anodes can be respectively increased by about 5.1% and 9.7% after the prelithiation. The prelithiation efficiency values are as high as 79.3% for graphite and 86.7% for SiOx/C with SEC prelithiation. Our results demonstrate that SEC prelithiation with Bi2O3 interface layer could be applied to improve the capacity and cycling performance of lithium-ion batteries.

Study on corrosion induced RC beams using slag-based geopolymer aggregate concrete

The objective of this study is to assess the corrosion rate and potential level of reinforcing steel in geopolymer aggregate concrete. Geopolymer Aggregate Concrete (GPAC) is used as sustainable alternative material instead of natural aggregate. The alumino-silicate source materials, such as ground granulated blast furnace slag are combined with alkali activators such as sodium hydroxide and sodium silicate to create GPAC. In this work, concrete specimens made using GPAC and Ordinary Portland Cement (OPC) with natural aggregate were prepared and subjected to accelerated corrosion exposure. The rate of corrosion in GPAC and OPC concrete was assessed using artificially induced corrosion. The GPAC concrete specimen corrosion rate under accelerated conditions ranged from 1 to 2 mA, indicating a moderate to high rate of corrosion. The OPC concrete specimen corrosion rate between 1 and 2 mA, indicating extremely significant corrosion activity. When compared to OPC specimen, GPAC exhibits greater resistance to chloride-induced corrosion, with lower corrosion rates and mass loss percentages.

Exfoliated carbon nitrides for corrosion prevention in radiators: Temperature-dependent corrosion analysis

This article outlines the preparation and exfoliation of graphitic-carbon nitride (GCN) by thermal polymerization technique using urea proceeded by the hydrothermal approach for the application of corrosion resistance in radiators. The prepared sample was characterized by using various methods. X-ray powder diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR) confirmed the purity of GCN, and Surface morphology results revealed the formation of spherical-shaped GCN. Herein, graphitic carbon nitride (GCN) was synthesized to enhance its corrosion-resistance performance on mild steel (MS) under a seawater atmosphere. The corrosion behaviour of the graphitic-carbon nitride (GCN) synthesized by the hydrothermal method was examined by conducting electrochemical corrosion tests in a 3.5% NaCl medium under three different temperatures. The excellent temperature dependant electro-catalytic activity of the prepared GCN was analysed. The hydrothermal exfoliation process highly enhances the structural, optical, and electrochemical properties like corrosion resistance and stability of the prepared GCN. This study demonstrates that hydrothermally exfoliated GCN exhibits low corrosion rates and high electrochemical corrosion resistance, which could be a potential candidate for corrosion inhibitors in radiators.

Tribo-corrosive wear behaviour of squeeze-casted Mg/TiN/hBN composite under different ageing temperature

The combined and individual effects of adding hard TiN ceramic particles and soft hBN solid lubricant particulates on AZ91D magnesium alloy were studied by analysing the tribocorrosion behaviour under various ageing conditions. The proposed materials were fabricated through the Stir-Ultrasonication-Squeeze casting technique and T6 heat treated at various ageing temperatures (170, 200, 230, and 260 °C). The tribocorrosion test results revealed that the ‘AHTT’ hybrid composite had a high corrosion potential (Ecorr) of − 1.38 V, low corrosion current density (Icorr) of 1.82 × 10−6 A cm−2 and low corrosion rate of 0.049 mm/yr. at 200 °C due to grain strengthening, formation of protective tribo-films and H3BO3 precipitates reduce the oxidation reaction during wear and corrosion. At a temperature of 200 °C, the nyquist plot reveals the presence of capacitive loops at both high and medium frequencies, which can be attributed to the formation of a thick tribo film layer that functions as a protective barrier. Furthermore, the stable reprecipitated secondary β-Mg17Al12 acts as a cathode, effectively restricting the formation of Mg+ ions.

Surface and corrosion properties of corn cob and egg shell particles reinforced AA3104-H19 composite via stir casting process

Aluminium alloys have been the most commonly used materials in the automotive and marine industries. However, depreciation in strength due to contact with environmental contaminants occurs over time. Hence, this study examined the effect of corn cob (CC) and egg shell (ES) particles on the corrosion, hardness and microstructure properties of AA3104-H19 composite. The corrosion experiment was conducted in 3.65 wt% NaCl solution. The microstructure of the material was examined with a scanning electron microscope (SEM) and X-ray diffractometer (XRD). The hardness was measured using a simple Brinell hardness tester loading. The control sample (AA3104-H19 alloy) exhibited the highest corrosion rate (CR) and corrosion current density (jcorr) of 0.0914 mm/year and 7.867 μA/cm2, respectively, Al90%-CC10%-ES0% sample exhibited the lowest CR and jcorr of 0.0135 mm/year and 1.16 μA/cm2, respectively. More so, the control sample exhibited a Brinell hardness of 96.3 kgf/mm2, while the Al90%-CC0%-ES10% sample exhibited an improved Brinell hardness of 99.6 kgf/mm2. The low corrosion rate of Al90%-CC10%-ES0% and high Brinell hardness Al90%-CC0%-ES10% of samples indicated that the samples exhibited superior corrosion resistance and enhanced resistance to indentation, respectively, relative to the other test samples. The SEM images revealed that the reinforced samples exhibited more uniform morphology than the control sample. The presence of AlSiO2 as indicated by the XRD results could have enhanced the corrosion rate of the material. The ESD revealed elements such as Ca, Mg, Si, Al and C, which are beneficial to the surface and corrosion properties of the material.

Evaluation of Physiochemical and Biological Properties of Biofunctionalized Mg-Based Implants Obtained via Large-Scale PEO Process for Dentistry Applications.

An increasing number of tooth replacement procedures ending with implant failure generates a great need for the delivery of novel biomedical solutions with appropriate mechanical characteristics that would mimic natural tissue and undergo biodegradation. This phenomenon constitutes a significant difficulty for scientists, since currently applied biomaterials dedicated for this purpose are based on stainless steel, Ti, and Ti and CoCr alloys. One of the most promising raw materials is magnesium, which has been proven to promote bone regeneration and accelerate the tissue healing process. Nevertheless, its high reactivity with body fluid components is associated with fast and difficult-to-control biocorrosion, which strongly limits the application of Mg implants as medical devices. The achievement of appropriate functionality, both physiochemical and biological, to enable the commercial use of Mg biomaterials is possible only after their superficial modification. Therefore, the obtainment of uniform, reproducible coatings increasing resistance to the aqueous environment of the human body combined with a nanostructured surface that enhances implant-cell behaviors is an extremely important issue. Herein, we present a successful strategy for the modification of Mg implants via the PEO process, resulting in the obtainment of biomaterials with lower corrosion rates and superior biological properties, such as the promotion of extracellular matrix formation and a positive impact on the proliferation of MG-63 cells. The implants were investigated regarding their chemical composition using the FT-IR and XRD methods, which revealed that MgO layer formation, as well as the incorporation of electrolyte components such as fluorine and silica, were responsible for the increased microhardness of the samples. An extensive study of the biomaterials' morphology confirmed that successful surface modification led to a microporous structure suitable for the attachment and proliferation of cells. The three-layer nature of the newly-formed coatings, typical for PEO modification, was confirmed via cross-section analysis. A biocorrosion and biodegradation study proved that applied modification increased their resistance to body fluids. The cell culture study performed herein confirmed that the correct adjustment of modification parameters results in a lack of cytotoxicity of the magnesium implants, cell proliferation enhancement, and improvement in extracellular matrix formation.

Corrosion inhibition capabilities of aluminium thin films on AZ31 magnesium alloy

Al coating of varying thicknesses in the 50 to 200 nm range was coated on AZ31 Mg alloys to improve its corrosion capabilities. The thermal evaporation method is used for coating AZ31 Mg alloys. GIXRD, SEM, AFM and XEDS studied the structure, microstructure, and chemical analysis. GIXRD studies showed an amorphous thin film on the surface. AFM showed that the surface roughness increases with the coating thickness. Corrosion studies were done by electrochemical analysis in 3.5 wt-% NaCl environment. The Al coating has improved the corrosion resistance of the AZ31 alloy to the best with the lowest corrosion rate 0.07 mmpy, with the corrosion current density and corrosion potential of 0.32 × 10−5 A/cm2 and −1.17 V, respectively.

Synthesis of hexagonal boron nitride nanocoatings for corrosion prevention of iron substrates

Iron and its alloys have applications in diverse fields such as civil infrastructure, aerospace, and defense. Corrosion of these alloys in saline environments is a significant concern that causes huge environmental losses. The current study explores pulsed laser deposition technique to synthesize hexagonal boron nitride (hBN) films as protective coatings, directly on iron (Fe), to mitigate the corrosion. Microstructural, mechanical, wetting, and corrosion properties of hBN-coated Fe substrates were investigated at different deposition temperatures (25–800 °C) and varying thicknesses (35–115 nm). Raman spectra and transmission electron microscopy confirmed the presence of hBN in as-deposited films. Crystallinity and surface roughness of hBN coatings increased as deposition temperature increased. Electrochemical studies performed in 3.5 wt% NaCl solution showed that the 115 nm thick hBN coatings deposited at 600 °C resulted in lower corrosion rates and has ~6-fold higher corrosion resistance than bare Fe. Also, the corrosion rates decreased with an increase in hBN coating thickness. Overall results suggest that hBN nanocoatings reduced the corrosion activity and can potentially serve as a corrosion-resistant barrier coatings in saline environments.

Influence of roughness on the early corrosion of API steels by atomic force microscopy (AFM): A real-time assessment

Roughness surface significantly affects the corrosion process of steels. However, this relationship in early stages at the local level has not been well studied. The mechanisms associated with the beginning of corrosion are thus not well known. Likewise, the lateral distribution of roughness is rarely considered, which can lead to inaccurate representations of surface features. Herein, the effect of roughness on the deterioration of carbon steels was locally studied by means of a fluid cell (FC) coupled to an atomic force microscope (AFM). The steel studied was prepared using grit papers with different abrasive particle sizes (#600, #1500, #2000) and exposed to artificial seawater for 4 h. A power spectral density (PSD) approach, which considered lateral distribution of surface roughness, was used to compare with traditional statistical roughness parameters. According to the roughness evolution, the corrosion susceptibility was #600 > #1500 > #2000, indicating greater corrosion resistance for smoother surfaces. The calculus carried out for estimating the corrosion rate as function roughness variation dictates that there may be up to three stages in the onset of corrosion. The first and third stages show a low corrosion rate (considerably less than 4 ×10−6 A/cm2), while the middle stage reflects an accelerated corrosion rate (up to 5.3 ×10−5 A/cm2 for #600 at 2 h). These results were in concordance with conventional electrochemical impedance spectroscopy tests. This method is proposed as a preventive strategy for the assessment of pipeline materials integrity which are used for transporting petroleum industry products.

Corrosion and Formation of Surface Films on AZ31 Mg Alloy in Aqueous Solution Containing Sulfate Ions with Different pHs

This study aims to clarify how a solution’s pH can influence the corrosion and formation of surface films on the AZ31 Mg alloy in aqueous solutions containing sulfate ions. The corrosion and surface film formation behaviors were examined using in situ observation, open-circuit potential (OCP) transient, weight change measurement and electrochemical impedance spectroscopy (EIS). The morphologies of the surface films were analyzed via metal/insulator/metal (MIM) coloring and FESEM. The findings show that at pH 2, severe corrosion occurred together with rapid hydrogen evolution and formation of a highly porous surface film with numerous cracks. However, at pH 3, the corrosion rate dropped significantly and remarkably low corrosion rates were observed at pH 4 and 10. At pH 11 and 12, weight gains were noticed, suggesting the growth of surface films on the AZ31 Mg alloy. Flake-like films formed at pH 12, while needle-like structures were present between pH 3 and 11. Impedance measurements revealed increased impedance at higher pH of sulfate-ion-containing solutions. Higher impedance was related to the formation of denser surface films on the AZ31 Mg alloy. In addition, the films displayed metal/insulator/metal (MIM) colors via Au coating above pH 4, indicating uniform film thickness despite the presence of needle-like or flake-like structures.

Effect of microwave melting and subsequent rolling on the corrosion behavior and electrochemical properties of an aluminum anode using response surface methodology

To obtain aluminum-air batteries with a high anodic efficiency and low corrosion rate, it is necessary to study the methods by which their aluminum alloy anodes are prepared. Here, the performance of an aluminum alloy anode was optimized by microwave melting and rolling. The aluminum anode showed the best performance under a 1000 W microwave power, two passes, and 40% reduction degree (sample denoted 1000W-2–40%). Under these conditions, the grain size of the Al–Zn–Bi–Pb anode was uniform, and no intergranular corrosion was observed. The corrosion resistance was high, and the anodic efficiency reached 72.72%. Finally, by observing the microstructure of an aluminum anode obtained under 1000 W microwave treatment, the corrosion mechanism was analyzed. The activity of the rolled aluminum anode was improved due to the existence of ZnAl2O4 phase. However, in 1000W-1–30%, 1000W-2–20%, and 1000W-3–30% samples, fine grains precipitated at high-angle grain boundaries. The grain orientation was mainly (110), which led to the intergranular corrosion of a large area of the anode, which made it unsuitable for use in aluminum-air batteries.

Mechanical and corrosion properties of Ti–29Nb–13Ta-4.6Zr alloy prepared by cryomilling and spark plasma sintering

In the present study, Ti–29Nb–13Ta-4.6Zr alloys were prepared by cryomilling and spark plasma sintering. Experimental results show that the as-sintered alloys have a fine-grain structured β phase and a small amount of α phase. By optimizing the sintering temperature to 1050 °C, Ti–29Nb–13Ta-4.6Zr alloy with a compression yield strength of 972 ± 18 MPa and an ultimate compression stress of 2071 ± 27 MPa, as well as an ultimate tensile strength of 1034 ± 19 MPa and a plastic strain of 8.7 ± 0.3%, together with a low Young's modulus of 74 ± 2 GPa can be obtained. Additionally, the as-sintered alloys also show preferable corrosion resistance with a low corrosion rate of ∼0.71 μm/year in Ringer's solution.

INFLUENCE OF NI AS MINORITY ALLOYING ELEMENT ON THE CORROSION BEHAVIOR OF AMORPHOUS AL-CU-MG ALLOYS IN CHLORIDE SOLUTION

The influence of nickel as minority alloying element on the corrosion behavior of amorphous alloys (Al74Cu16Mg10)99Ni, (Al74Cu16Mg10)98Ni2 and (Al74Cu16Mg10)97Ni3 was investigated. The amorphous alloys were obtained as ribbons by Chill Block Melt Spinning (CBMS). The amorphous structure of the alloys was proven by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The corrosion rate was calculated gravimetric using continuous immersion tests for 360 hours in 3.5% NaCl solution at a temperature of 25oC. The lowest corrosion rate was found in the alloy containing 3 at. % Ni. The chemical composition of the accumulated corrosion products was studied using XRD.The influence of nickel on the local corrosion resistance of the amorphous ribbons of (Al74Cu16Mg10)100-хNiх x = 0, 1, 2, 3% alloys was investigated electrochemically in a solution of 3.5% NaCl at 25°C. Pitting potential (Epitt) and repassivation potential (Erp) were determined. It was found that most resistant to pitting corrosion was the (Al74Cu16Mg10)97Ni3 alloy, which showed the noblest pitting potential (Epitt -0.332 V) and repassivation potential (Erp -0.530 V).All obtained corrosion test results of the nickel-containing amorphous alloys were compared to the base amorphous Al74Cu16Mg10 alloy.

Enhanced corrosion performance of low‐cost titanium alloys in a simulated diabetic environment

AbstractDue to their excellent biocompatibility, titanium alloys are the preferred materials for manufacturing bioimplants. Low‐cost titanium alloys have been developed as cheaper and less toxic alternatives for Ti–6Al–4V in the biomedical industry, but their suitability for diabetes patients is yet to be evaluated. With the growing number of diabetes patients globally, this research investigated the corrosion performance of low‐cost Ti–3Fe, Ti–4.5Al–1V–3Fe, and Ti–6Al–1V–3Fe alloys in 0.9 wt.% sodium chloride solution and glucose‐containing Hanks balanced salt solution (HBSS) compared with Ti–6Al–4V. Glucose was added to simulate the body fluids of patients with prediabetic and diabetic conditions. Open circuit potential and potentiodynamic polarization tests were performed. The results reveal that Ti–4.5Al–1V–3Fe and Ti–6Al–1V–3Fe alloys show superior corrosion resistance compared with the other alloys in the glucose‐containing solutions, as they had the lowest corrosion rate and higher corrosion potential. Consequently, these alloys hold promise as effective implants, particularly for people living with diabetes.

Study on Degradation Law and the Equivalent Thickness Model of Steel Subjected to Sulfate Corrosion.

In order to study the variation of mechanical properties of steel under acid rain corrosion conditions in northern China, monotonic tensile tests were conducted on Q235 steel with a thickness of 3.0 mm and 4.5 mm using a method of artificially prepared simulated acid rain solution for indoor accelerated corrosion. The results show that the failure mode of corroded steel standard tensile coupon includes normal fault and oblique fault. The failure patterns of the test specimen show that the thickness of the steel and corrosion rate affected the corrosion resistance. Larger thicknesses and lower corrosion rates will delay the failure mode of corrosion on steel. The strength reduction factor (Ru), deformability reduction factor (Rd) and energy absorption reduction factor (Re) decrease linearly with the increasing corrosion rate from 0% to 30%. The results are interpreted also from the microstructural point of view. The number, size, and distribution of the pits are random when the steel is subjected to sulfate corrosion. The higher the corrosion rate, the clearer, denser, and more hemispherical the corrosion pits. The microstructure of steel tensile fracture can be divided into intergranular fracture and cleavage fracture. As the corrosion rate increases, the dimples at the tensile fracture gradually disappear and the cleavage surface gradually increases. An equivalent thickness reduction model is proposed based on Faraday's law and the meso-damage theory.

Preparation of Cu/CuO@Stearic acid layer with superhydrophobicity to provide multiple barriers for corrosion protection of carbon steel

Carbon steel is a widely used metallic material. It is prone to corrosion. In this study, we designed and fabricated a superhydrophobic layer with corrosion resistance for protection of carbon steel substrate. Multiple layers were formed that acted as barriers to protect the substrate from corrosion. This superhydrophobic layer reduced the contact area between the substrate and the corrosive medium owing to the superhydrophobicity. The experimental results showed that a copper layer uniformly covered the carbon steel substrate, and the outer surface of the copper layer was converted into copper oxide, which had a multi-scale structure. The Cu/CuO double layer was modified with stearic acid (SA) to form a Cu/CuO@SA superhydrophobic layer. The superhydrophobic layer exhibited a high water contact angle (up to 160°) and a low sliding angle (<3°). The superhydrophobic layer also exhibited repulsive effect to salt, acidic and alkaline solutions. Atmospheric stability test and UV irradiation test were conducted and the results indicated that the superhydrophobic layer was stable throughout the test period. The corrosion potential of the superhydrophobic sample was −0.18 V and the corrosion current density was 7.72 × 10−7 A cm−2, which was one order of magnitude lower than that of the carbon steel substrate. These results indicate that the superhydrophobic sample had a low corrosion tendency and corrosion rate. The polarization resistance and impedance modulus of the superhydrophobic sample were two orders of magnitude higher than the bare steel sample, indicating corrosion resistance and effective protection to the carbon steel substrate.

Effect of Sealing Treatment on Corrosion Resistance of Arc-Sprayed Zn and Zn85-Al15 Coatings

This study investigated the corrosion morphology of arc-sprayed Zn and Zn85-Al15 coatings with and without sealing treatment under simulated defect conditions. The hole sealing treatment was carried out by Conventional Impregnation Sealing (CIS). The performance of two coatings was assessed by employing morphological analysis, chemical composition, and electrochemical studies. The results showed that the corrosion performance of two coatings with sealing treatments was better than that of the un-sealing coating. Through the double protection of coating and sealing treatment, the defect-free material has excellent anti-corrosion performance in the salt spray experiment. In the simulated defect environment, the Zn-Al coating has better corrosion resistance, and the corrosion products are denser and more stable near the defects, which reduces the overall corrosion rate of the coating. The electrochemical experiment results demonstrated that the Zn-Al coating exhibited a three times lower corrosion rate compared to the Zn coating in the immersion experiment, and the corrosion rate did not change with the thickness of the coating. The average adhesion values of the two different methods (chilled iron and alumina) were similar (~8 MPa), but after the salt spray test, the adhesion strength increased. The corrosion mechanisms of Zn coating and Zn-Al coating are analyzed and compared. In general, it was indicated that the Zn85/Al15 coating prepared by sealing treatment has better corrosion resistance than the matrix steel. This study can provide some reference for corrosion behavior in defect environments.

Microstructure and mechanical properties of biodegradable Zn-2Cu-0.1Ti alloy for orthopedic applications

Bioresorbable implants are intended to be biocompatible, mechanically stable, and to corrode gradually in response to an appropriate host response. In this work, a Zn-2Cu-0.1Ti (ZCT) alloy was fabricated by a combination of casting and hot-rolling. X-ray diffraction analysis revealed the presence of both TiZn16 phase and a CuZn4 phase in the alloy. ZCT showed an extraordinary increase in yield strength compared with the unalloyed Zn to 248 MPa (from 100 MPa) and a similar elongation to failure (33–34%). The alloy also possesses a relatively low corrosion rate when immersed in simulated body fluid. The 50 % extract of ZCT alloy exhibits excellent biocompatibility for MC3T3-E1 cells. These results indicate that the ZCT alloy has potential for clinical applications.

Duplex corrosion mechanisms correlated to α/γ phase selection in containerlessly processed Fe-Cr-Ni-Mo alloy

The α/γ phase selection mechanism and corrosion resistance of Fe-21%Cr-12%Ni-5%Mo alloy were investigated by both individual electromagnetic levitation (EML) and EML coupled with falling quench (EML+FQ) techniques. The decomposition of primary δ phase could be partially or completely suppressed in two containerless processing. Both selective and pitting corrosion behaviors were discovered in alloy, which were related to the crystalline orientations and solute distributions of constituent phases. The anti-corrosion property of EML+FQ processed alloy was significantly enhanced with higher corrosion potential of 0 VSCE, lower corrosion current density of 4.1 × 10−7 A/cm2 and lower corrosion rate decreasing over one order of magnitude.