Thickness Of Corrosion Layer Research Articles

Enhanced thermal stability and corrosion resistance of novel high-entropy spinels in cryolite-alumina molten salt applications

The development of spinel oxide materials with high thermal stability and corrosion resistance is essential for thermochemical reactions, particularly in aluminum electrolysis. This study presents the structural design of a family of high-entropy spinels (HESs) with a stable cubic spinel structure (<i>Fd3‾m</i>), specifically formulated as (Cr5/12 Mn5/12 Fe5/12 Co3/8 Y3/8)3O4, (Y = Ni, Cu, or Zn). Our results demonstrate that these high-entropy spinels significantly outperform conventional NiFe₂O₄, exhibiting superior corrosion resistance and thermal properties. Specifically, we observe lower high-temperature weight loss (0.24 %–0.74 % at 1000 °C), reduced thermal conductivity (1.810–2.258 W m−1 K−1 at room temperature), and lower thermal expansion coefficients (8.2 - 10.7 × 10−6 K−1 from 400 °C to 800 °C), while maintaining comparable specific heat capacities (0.51–0.55 J g−1 K−1). Corrosion testing at 800 °C for 20 h in a KF3-AlF3-Al2O3 molten salt environment shows a corrosion layer thickness of less than 150 μm, with minimal corrosion product formation. These findings not only advance our understanding of material properties under extreme conditions but also pave the way for the development of next-generation materials for thermochemical applications, specifically aimed at improving the efficiency of aluminum electrolysis.

High temperature corrosion behavior and mechanism of steel slag-based glass ceramic in the eutectic carbonates

Steel slag-based glass ceramic for thermal energy storage was first fabricated by quenching method, and then their high temperature corrosion behavior in the eutectic carbonates and related mechanism have been investigated using X-ray diffraction，Raman spectroscopy and scanning electron microscope techniques. The results show that holding time has a significant influence on the corrosion layer thickness at 800oC. As the holding time was extended, the thickness of the corrosion layer with obvious cracks tended to increase. Further EDS analyses disclosed that the divided corrosive layers along the extended directions of the cracks should be similar in both the compositions and microstructure. Based on these observations, the possible corrosion mechanism was discussed after defining phase structure of nonstoichiometric (Fe0.35Al0.20Mg0.44) Ca0.96(Fe0.08Si0.70Al0.20)2O6.12 as a combined system of CaMgSi2O6(Di)-CaFe3+AlSiO6(Es)-CaAl2Si2O8(An). Oxygen offered by the molten carbonates salt is regarded to play a critical role in the corrosion process. In an atmosphere rich in oxygen, both Na+ and K+ ions diffused into the diopside can replace Ca2+ and Mg2+, etc. resulting in polyhedral structural reorganization for electrical neutrality. On the other hand, the bonding stability of the cation-oxygen bonds in diopside was proved to be weaker than that in single oxides. These two aspects contribute to the continuous dissolution of Ca2+ and Mg2+, etc. in the molten carbonates salt.

Design of Near α-Ti Alloys with Optimized Mechanical and Corrosion Properties and Their Characterizations

The designed alloy Ti-10.56%Al-2.08%Zr-0.80%Sn-0.88%Mo-0.51%Si (mol%), modified alloy Ti-10.81%Al-4.80%Zr-1.23%Sn-0.76%Cu-0.35%Si (mol%) and reference alloy Ti-10.52%Al-2.07%Zr-1.1%Sn-0.2%Mo-0.76%Si (mol%) with the same bond order (Bot) value of 3.49 and different d-orbital energy level (Mdt) values of 2.43, 2.42 and 2.42 were proposed and their mechanical and corrosion properties were compared in the present study. The ultimate tensile strength (σUTS) and fracture strain (ɛf) values of the three near α-Ti alloys at both as-cast and solution-treated conditions were 989 and 1118 MPa and 11.6% and 3.4% for the designed alloy, 993 and 1354 MPa with 13.5% and 2.3% for the modified alloy and 991 and 1238 MPa with 12.7% and 3.1% for the reference alloy, respectively. The thickness of corrosion layers of the solution-treated designed, modified and reference near α-Ti alloys after immersion in hot salts for 28.8 ks were measured at 3.06, 3.68 and 4.89 µm. The comparable mechanical properties and improved hot salt corrosion resistance ability of designed and modified alloys compared to those of the reference alloy were obtained by considering their Bot and Mdt values; this might lead to the development of alternative near α-Ti alloys to conventional materials.

Mechanical properties and corrosion behavior in molten zinc of Mo–ZrO2 alloys

The effect of the ZrO2 doping amounts on the corrosion properties and mechanical properties of the molybdenum alloys in molten zinc was investigated. Among them, the Mo-1.5 wt% ZrO2 alloy has good corrosion resistance (at 460 °C) and excellent mechanical properties. Compared with that of pure molybdenum, the tensile strength of the Mo-1.5 wt%ZrO2 increased by 16.69% in the rotary forged state and 58.26% in the 1200 °C annealed states, and the compressive strength increased by 16.53% and 84.46%, respectively. At a corrosion temperature of 460 °C, a MoZn7 corrosion layer was formed, which isolates the molybdenum matrix from direct contact with the molten zinc. The distribution of ZrO2 particles in the corrosion layer, which changes the diffusion path of zinc and molybdenum atoms, thus slowing down the corrosion process. The thickness of the corrosion layer gradually decreases with increasing doping amount, where the corrosion layer thickness of the Mo-2.0 wt% ZrO2 is 45.21% lower than that of the pure molybdenum. At a corrosion temperature of 560 °C, the molybdenum matrix is exposed to molten zinc and the grains peel off. As the bond between Mo grains is better than the bond between Mo grains and zirconia, the grain spalling of the zirconia-doped molybdenum alloys is severer than that of pure molybdenum.

Nondestructive testing of corrosion thickness in coated steel structures with THz-TDS

The corrosion of steel plate structures usually occurs under the coating materials, and it is difficult to be accurately detected by the existing non-destructive testing (NDT) technologies. A novel non-contact terahertz time-domain spectroscopy (THz-TDS) is therefore proposed to measure the corrosion thickness under different coatings, which provides a method to quantify the corrosion degree of steel structures. In this study, the optical parameters of the corrosion products and the common coating materials (epoxy resin, rubber, and cement paste) are investigated by transmission THz-TDS, and the method of extracting the delay time difference in the reflection THz-TDS is proposed to measure the thickness of corrosion layer. The experiments show that the detection of the steel plate corrosion can be achieved from the reflected THz signal based on the peak number change and a significant attenuation of the signal peaks. Moreover, the reflected THz signal can measure the corrosion thickness with an accuracy of more than 90% and the minimum identification thickness is 40 μm. Besides, the thickness of the coating layer is simultaneously measured irrespective of the coating material types. It proves the applicability and accuracy of THz-TDS for NDT corrosion thickness of coated steel structures.

Terahertz Non-destructive testing and imaging of corrosion in coated steel plates

The corrosion will lead to the decrease of bearing capacity and durability of steel plate structures. Due to the limitations of the existing non-destructive testing (NDT) approaches, it is difficult to accurately evaluate the corrosion of steel plates, including the corrosion location, area, and thickness. In this paper, a method of extracting the delay time difference in the reflected terahertz (THz) signal is proposed to detect and image the corrosion in coated steel plates. The results from experiments and numerical modeling show that this THz method has a high measurement precision, and the thicknesses of coating and corrosion layers can be measured simultaneously. When the epoxy resin set as coating layer with a thickness of 1000 μm, the minimum thickness of corrosion layer that can be effectively detected in THz model is 25 μm, and the maximum thickness is 3700 μm. Meanwhile, the error percentage of the corrosion layer thickness in the range of 50 ∼ 3700 μm is less than 3%. In addition, a novel imaging technique to visualize the corrosion thickness of steel plates is developed by introducing the THz method. The three-dimensional (3-D) visual imaging directly describes the thickness and location distribution of the corrosion area while removing the effect of the coating layer. Those characteristic values, including the maximum, minimum, average, median, standard deviation, of the corrosion thickness, as well as the ratio of corrosion area/scanning area, can be extracted by this imaging method. In conclusion, the proposed THz technology can realize the NDT of the corrosion area, shape, and thickness, which serves as a guide to quantify the degree of corrosion for steel plate structures.

Facile synthesis of ZnOHF/ZIF‐8 composite coating for corrosion protection of Zn–Cu–Ti alloy

ZnOHF/ZIF-8 (Zeolitic Imidazolate Frameworks-8) composite with a thickness of about 13.4 μm was coated on Zn–Cu–Ti alloy via hydrothermal route for the first time and its corrosion resistance performance was investigated in 3.5% NaCl solution. It is found that the Icorr of the composite-coated alloy (7.03 × 10–4 A/cm2) is lower than that of alloy substrate (12.47 × 10–4 A/cm2). Meanwhile, the composite-coated alloy shows a higher corrosion product resistance of 121.2 Ω cm2 in comparison with that of the alloy substrate (102.2 Ω cm2). Moreover, after 6 days of immersion, the composite-coated alloy exhibits a lower corrosion layer thickness. Its coating and corrosion layer is only about 42.5 μm, but for the alloy substrate this value is 67 μm. This work confirms the ZnOHF/ZIF-8 composite can be used as an effective anti-corrosion coating for Zn alloy.

Investigation of the corrosion of electro-less nickel-plated alloys in molten salt and its effect on phase change properties for energy storage applications

Interactions between electroless nickel plated Inconel 601, Monel 400, and stainless steel 316L alloys with two eutectic salts used as phase change materials, K2CO3 + Na2CO3 and NaCl + Na2CO3, were investigated at 720 °C (isothermal). The results of this study show that at these high temperatures, which is the target temperatures of the next generation of concentrated solar thermal power plants, these salt phase change materials are highly corrosive to stainless steel, whereas the Inconel 601, a high temperature nickel alloy, was resistant. Monel 400 experienced the most corrosion damage (500 µm thick corrosion layer) and resulted in the salts experiencing the greatest latent heat decrease by 18.1%, as confirmed by Differential Scanning Calorimetry (DSC). IN601 performed the best with an observed corrosion layer thickness of 107 µm, and resulted in one of the salts only decreasing in latent heat by 5.9%. IN601 with the nickel plating has shown improved corrosion resistance over uncoated samples. The thermophysical properties of the salt was measured before and after the exposure tests to demonstrate the significant effect corrosion has on the performance of the salts as a phase change material. Scanning Electron Microscopy (SEM) analysis showed that constituent elements have diffused from the alloy specimens, through the nickel plated layer and leached into the molten sat, which was characterized by Inductively Coupled Plasma- Optical Emission Spectroscopy (ICP-OES). A correlation was found between the corrosion of the specimens, the solubility of the alloying elements and a large decrease in the salt’s latent heat properties.

The cause of foaming in polishing porcelain stoneware tile residues during sintering: Interface corrosion of Silicate-SiC

The SiO2 layer preferentially generated on the surface of silicon carbide abrasives in Polishing Porcelain stoneware tile Residues (PPR) is corroded by silicate liquid during firing, resulting in continuous oxidation and foaming of silicon carbide, which makes the PPR difficult to be reused. The PPR is fired to form a silicate liquid that wraps micron silicon carbide in it. In this work, it is possible to study the corrosion of silicate to silicon carbide at high temperature by using two (Ceramic-SiC) and three (Ceramic-SiO2-SiC) layer structure model to simulate the corrosion of silicate to silicon carbide. The corrosion mechanism of SiC in PPR by silicate liquid during firing is revealed that the corrosion rate at its two sides (interfaces) determines the ultimate change in the thickness of the corrosion layer between the ceramic and the SiO2 layer. Importantly, the corrosion layer thickness with time on the silicate-SiO2 cross-section periodically presents wave-like changes, which can be attributed to the ionic migration between layers and the rate at which cations cross the corrosion layer when studying the three-layer model.

Corrosion behavior of ion-irradiated 12Cr2W2Mn F/M steel in liquid LBE

The corrosion characteristics of 12Cr2W2Mn Ferritic/martensitic (F/M) steel before and after Au-ions irradiation in static lead–bismuth eutectic (LBE) have been investigated at 400 °C for 100 h. The results show that the samples without irradiation have many unequal size Fe3O4 particles and little Cr-rich oxide after LBE corrosion test, and the thickness of corrosion layer is 4.4 μm. The irradiation samples display plenty compact triangular (Fe,Cr)3O4 and some Cr-rich oxide, and the thickness of corrosion layer is 4.4 μm with some cracks. Au-ions irradiation enahnced the LBE corrosion of F/M steel, which could be attributed to the irradiation defects provide diffusion path of O atoms in liquid LBE. A schematic model was presented to understand the effect of irradiation damage on LBE corrosion behavior of F/M steel.

Enhanced corrosion resistance of Zn–Cu–Ti alloy with addition of Cu–Ti amorphous ribbons in 3.5% NaCl solution

AbstractIn the present study, Zn–0.3Cu–0.3Ti alloy (sample I) was fabricated by a simple low‐temperature melting method using Cu–50Ti amorphous alloy ribbons for corrosion in 3.5% NaCl solution. As a comparison, crystalline Cu–50Ti master alloy was used to prepare Zn–0.3Cu–0.3Ti alloy (sample II). Sample I comprising Zn, TiZn3, and TiZn15 phases exhibits an equiaxed microstructure with subgrain structure. Large TiZn3 particles show cluster feature, whereas intermittent small TiZn15 particles exist at grain boundaries and subgrain boundaries. In sample II, the Zn matrix with typical dendritic microstructure is observed and no large particles are found. Compared with sample II, sample I shows lower weight gain and corrosion current density and a higher slope of cathode polarization curve. The weight gain for sample I is only 0.59 mg·cm−2, but for sample II, this value reaches 0.70 mg·cm−2. After 8 days of corrosion, corrosion products are mainly Zn5(OH)8Cl·H2O and ZnO, showing loose particle shape. As corrosion time increases from 2 days to 8 days, corrosion layer thickness increases from about 15 to 24 μm for sample 1.

High Temperature Corrosion Resistance in Molten Salts in Solar Power Concentration Plants: High Temperature Corrosión Monitoring in Dynamic and Static Conditions

The actual technology for solar power plants-CSP have termal storage system composed by molten salts. Molten salts technology means electrochemical electrolytes in contact with materials, and in this case high temperature molten salts. which are an ionic electrolyte. In order to follow up the evolution of the sal chemistry, i.e. concentrating the impurities such as chlorides and sulphates, and to monitor the corrosión rate and corrosión mechanism of structural materials, electrochemical sensors have been developed and patented. On the other hand, in order to check the reliabilify and performance of the sensors, static and dynamic test have been performed in a pilot plant.Moreover, his study assessed the behaviour of a constructive material in CSP plants, namely ferritic-martensitic steel, with molten NaNO3/KNO3 (60/40 wt%), also known as Solar Salt. To this end, EIS is presented as a suitable technique to evaluate and monitor the resistance of this material to Solar Salt at 580 °C. Tests were performed up to 1000 h and results were also supported by gravimetric and microstructural characterisation of the samples and chemical analysis of the salt. According to the EIS results, a diffusion-controlled reaction occurred during contact, which indicates that the corrosion process follows a porous layer mechanism. The results also indicated variations in corrosion layer thickness and instability of the salt during the whole test. The EIS results were also used for determining the corrosion rate, this being estimated at ~300 µm year−1. Results obtained by EIS were in line with the behaviour of P91 steel as measured by gravimetric, morphological and chemical analysis. Thus, the results confirm the suitability of EIS for monitoring corrosion processes in real-time of constructive materials in CSP plants.

Hot corrosion behavior of NdYbZr2O7 exposed to V2O5 and Na2SO4 + V2O5 molten salts

In order to evaluate the application prospects of NdYbZr2O7 as a novel TBC material, NdYbZr2O7 ceramic was synthesized via a solid-state reaction sintering method, and its hot corrosion behavior exposed to V2O5 and Na2SO4 + V2O5 molten salts at 900 °C, 1000 °C, and 1100 °C was comparatively investigated. For the V2O5 salt, the primary corrosion products were granular (Nd,Yb)VO4 as well as cube-like m-ZrO2. The corrosion layer consisted of two distinct layers, one of which was Zr-rich layer and another was V-rich layer. In the case of Na2SO4 + V2O5, NaVO3, as an intermediate product, played an important role in dissolving the NdYbZr2O7 ceramic. Herein, the (Nd,Yb)VO4 exhibited a rod/plate-like morphology, which could be attributed to the synergistic effect of low driving force and low nucleation rate. Since the molten salt infiltration rate was superior to the pore filling rate throughout the hot corrosion, the thickness of corrosion layer increased with the rise of temperature. The hot corrosion mechanisms of NdYbZr2O7 ceramic in various molten salts were discussed based on the phase diagram, Lewis acid-base rule and chemical thermodynamics. On this basis, the NdYbZr2O7 coating was prepared by atmospheric plasma spray (APS) and it exhibits a higher corrosion resistance compared to YSZ coating.

Corrosion assessment of promising hydrated salts as sorption materials for thermal energy storage systems

Salt hydrates are an appealing option to be used as sorption materials in thermal energy storage (TES). In this work, strontium bromide and magnesium sulphate have been selected as one of the most promising salt hydrates since they present high energy storage density (>130 kWh/m3) and efficiency (>20%). One of the main drawbacks of sorption materials rely on control the hydratation-dehydratation process but there are other parameters that can modify this behaviour as the corrosive potential of these salts in contact with the container material selected for the application. Hence, four different metal container materials, specifically stainless steel, copper, aluminium, and carbon steel have been tested in SrBr2·6H2O and MgSO4·7H2O hydrate salts, during 100 h at dehydratation conditions. After the gravimetric and micrograph analysis carried out via scanning electron microscopy (SEM) study, only carbon steel is not recommended for this application in contact with SrBr2·6H2O, obtaining a corrosion rate of 0.038 mm/year, with a metallographic corrosion layer thickness of 25.2 μm. Aluminium, copper and stainless steel showed a better corrosion resistance also in SrBr2·6H2O and MgSO4·7H2O with corrosion rates below 0.008 mm/year.

Innovative, DPN-Based Method for Analyzing the Early Stages of Mg Corrosion Under Natural Conditions

Mg and its alloys are highly prone to corrosion, which is an important consideration in many industries and applications. However, most available methods for studying the buildup of Mg corrosion layers as a function of time—an indirect measure of corrosion rate—are not sufficiently sensitive to monitor the early stages of the process. In this letter, a simple and innovative method is reported for monitoring changes in Mg corrosion layer thickness in various solutions, under close-to-natural conditions and starting from the first minutes of the process. Dip-pen nanolithography (DPN) was first used to pattern poly(methyl methacrylate) (PMMA) reference lines on the surface of the Mg alloy AE53, so as to indicate the initial conditions. Then, AFM was used—for the first time to the best of our knowledge—to measure the thickness of corrosion layers forming on three adjacent 100 µm × 100 µm surface areas at several time points (5–30 min) after immersion in solution. Test solutions included either saline or phosphate-buffered saline (PBS), in each case either with or without the addition of Fenton reagents, which are known to accelerate corrosion and are highly relevant for biological implants that employ Mg alloys as degradable substrates. In all tested solutions, the buildup of corrosion layers showed the expected dynamics—namely, an increase followed by a decrease and again an increase in layer thickness; however, the layers were considerably thicker in PBS than in saline, and in solutions with Fenton reagents than in those without them. These results demonstrate the unique advantage of the AFM instrument, as compared with other methods (such as SEM and potentiodynamic polarization), for measuring corrosion buildup, as the layer growth process can be accurately measured under natural conditions, in the presence of solutions, and from its very early stages. We report a simple and an innovative method for monitoring changes in corrosion layer thickness in various solutions, under close-to-natural conditions, starting from the first minutes of the process. We used dip-pen nanolithography by the NLP2000 to pattern reference lines on the surface of the Mg alloy AE53, which allowed us to accurately monitor the buildup of the corrosion layers using AFM at various time points after immersion in saline and PBS with or without the addition of Fenton reagents.

Cellular automata simulation on the corrosion behavior of Ni-base alloy in chloride molten salt

Chloride molten salt is required to study its corrosion behavior since it is recommended to be used as heat transfer and heat storage material in high-temperature thermal power generation system. In this paper, a simplify model was established by the reaction of diffusive corrosive gas and metal substrate in a chloride molten salt. A cellular automaton model based on the stochastic approach is adopted to simulate the uniform corrosion and the migration of metallic element. The corrosion behavior is also simulated considering the practical working condition, such as oxygen, moisture and so on. By comparing the simulation results with experimental data, it proves that the cellular automata simulation is an effective alternative method to describe the high-temperature corrosion process of molten salts. Simulation results of 25,000 time steps is taken as a comparison of the 21-day corrosion which reflects the Cr distribution, and the growth of corrosion layer with the migration of Cr element was reproduced. The change of corrosion layer thickness is similar to the mass loss. The simulation method provides insight on the distribution of corrosion products, corrosion kinetics and morphologies for the long-term application.

Effect of Temperature on the Corrosion Behavior of Biodegradable AZ31B Magnesium Alloy in Ringer’s Physiological Solution

In this work, the corrosion behaviors of the AZ31B alloy in Ringer’s solution at 20 °C and 37 °C were compared over four days to better understand the influence of temperature and immersion time on corrosion rate. The corrosion products on the surfaces of the AZ31B alloys were examined by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). Electrochemical impedance spectroscopy (EIS) provided information about the protective properties of the corrosion layers. A significant acceleration in corrosion rate with increasing temperature was measured using mass loss and evolved hydrogen methods. This temperature effect was directly related to the changes in chemical composition and thickness of the Al-rich corrosion layer formed on the surface of the AZ31B alloy. At 20 °C, the presence of a thick (micrometer scale) Al-rich corrosion layer on the surface reduced the corrosion rate in Ringer’s solution over time. At 37 °C, the incorporation of additional Mg and Al compounds containing Cl into the Al-rich corrosion layer was observed in the early stages of exposure to Ringer’s solution. At 37 °C, a significant decrease in the thickness of this corrosion layer was noted after four days.

Study on corrosion effect of high-performance concrete under the action of sulfate and chlorine

The thickness of corroded concrete layer and the compressive strength of prisms under the action of sulfate and chloride salt were investigated by ultrasonic test and compression test, respectively. The results show that under the single action of sulfate, the strength of concrete experienced two stages: a slow growth stage and a rapid descent stage. Correspondingly, under the combined action of sulfate and chloride, the concrete strength experienced another two stages: a slow growth stage and a slow degradation stage. The existence of chloride inhibited the corrosion damage of concrete in a certain extent. It was found that higher concentration of chlorine salt would lead to a stronger inhibition effect. A good consistency was observed among corrosion layer thickness, compressive strength and X-ray diffraction results. The inhabitation of chloride to the sulfate corrosion of concrete was proved.

Electrochemical impedance spectroscopy (EIS): An efficient technique for monitoring corrosion processes in molten salt environments in CSP applications

This study assessed the behaviour of a constructive material in CSP plants, namely ferritic-martensitic steel, with molten NaNO3/KNO3 (60/40 wt%), also known as Solar Salt. To this end, EIS is presented as a suitable technique to evaluate and monitor the resistance of this material to Solar Salt at 580 °C. Tests were performed up to 1000 h and results were also supported by gravimetric and microstructural characterisation of the samples and chemical analysis of the salt. According to the EIS results, a diffusion-controlled reaction occurred during contact, which indicates that the corrosion process follows a porous layer mechanism. The results also indicated variations in corrosion layer thickness and instability of the salt during the whole test. The EIS results were also used for determining the corrosion rate, this being estimated at ~300 µm year−1. Results obtained by EIS were in line with the behaviour of P91 steel as measured by gravimetric, morphological and chemical analysis. Thus, the results confirm the suitability of EIS for monitoring corrosion processes in real-time of constructive materials in CSP plants.

Initial formation of corrosion products on pure zinc in saline solution

Corrosion product formed on zinc sample during 2 weeks immersion in saline solution has been investigated. The corrosion layer morphology as well as its chemical composition, was analyzed using scanning electron microscopy (SEM), x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Electrochemical measurement was used to analyze the corrosion behavior. Zinc oxide, zinc hydroxide and zinc hydroxide chloride were formed on zinc surface in saline solution. The thickness of corrosion layer increased with the time increased. The pure Zn has an estimated corrosion rate of 0.063 mm y−1 after immersion for 336 h. Probable mechanisms of zinc corrosion products formation are presented.