Removal Of Oxide Layer Research Articles

Features of the Application of Coatings Based on the ZrN System to Increase Resistance to Mechanical Wear and Corrosion of Titanium Alloy Products

The coatings of ZrN, (Zr,Ti)N, (Ti,Zr,Hf)N and (Ti,Zr,Nb)N deposited on the titanium alloy substrate were compared. The wear resistance in the pin-on-disk test together with the Al2O3 indenter and the corrosion resistance in 3.5% NaCl solution were studied. It was found that the (Zr,Nb,Ti)N coating has the best resistance to wear, but has low corrosion resistance. The (Ti,Zr,Hf)N coating, on the contrary, has the best corrosion resistance, but low resistance to wear. The ZrN coating has good corrosion resistance combined with good resistance to wear. This coating is best suited for use in friction conditions with a ceramic counterbody under the influence of seawater. An important resource for increasing the properties of coatings is increasing their adhesion to the substrate, which can be achieved in two combined ways: (1) complete removal of the original oxide layer from the surface of the substrate and (2) the use of optimal compositions of the adhesive sublayer, which have not only high adhesive properties in relation to both the substrate and the coating, but also high strength. While the introduction of Nb into the ZrN coating composition increases wear resistance and the introduction of Hf increases corrosion resistance, the ZrN coating without additives best resists wear and corrosion simultaneously.

Study of ultrasonic parameters for quality monitoring of plate heat exchanger

Abstract Heat exchangers are crucial heat transfer devices widely used in energy industries such as power generation, oil production, and engine cooling. The plate heat exchanger is one of the most economical and efficient types of exchangers. It transfers heat using metal plates and has a high heat transfer efficiency because the fluid is exposed to a higher plate surface area. However, due to the presence of dissolved or suspended particles in the heat-exchanging fluids, a layer of deposit (fouling layer) is formed on the heat exchanger plates. It results in reduced efficiency of the device. Thus, a common cleaning method, such as chemical-based or manual methods, is employed. However, it always poses a risk of over-cleaning or removal of the protective oxide layer. Thus, an efficient mechanism to monitor the onset of the fouling layer would greatly help to achieve increased efficiency and cost reduction in the cleaning of the plates. Recent advances show ultrasound as one of the promising non-destructive inspection techniques to monitor the growth of the fouling layer. However, the variation in heat-exchanging fluid temperature affects the investigated acoustical parameter measurement. Thus, this research aims to study the linear and nonlinear ultrasonic parameters incorporating temperature-dependent effects from the fluid to provide an accurate real-time monitoring tool. The nonlinear acoustics analysis is experimentally employed in the research using the Second harmonic generation method (SHGM). The proposed research will help design ultrasound-assisted plate heat exchangers for maximum heat transfer efficiency.

Balancing current density and electrolyte flow for improved zinc-air battery cyclability

Zinc-air batteries (ZABs), known for their high energy density and environmental friendliness, are emerging as promising solutions for sustainable energy storage. However, the irregular deposition of zinc on electrodes hinders the widespread utilization of rechargeable ZABs due to limited durability and stability. This study investigates the role of electrolyte flow in enhancing zinc electrodeposition and overall performance in zinc-air flow batteries (ZAFBs) at high current densities. We explore the interplay between current density, flow rate, and their influence on electrode surface morphology and the removal of the passivating zinc oxide layer to improve battery efficiency and lifespan. Using advanced in-situ synchrotron radiation x-ray tomography, we found that incorporating flowing electrolyte at specific current densities results in rounded dendrite tips, thinner and more uniform deposition layers, and improved zinc adhesion. Imaging and electrochemical analyses further reveal that flowing electrolyte enhances zinc morphology, reduces charge transfer resistance, diminishes passivation, and lowers galvanostatic charge/discharge polarization across various current densities, thereby improving battery cycling performance. Notably, the impact of flowing electrolyte is more pronounced at a moderate current density of 50 mA/cm2 compared to lower or higher currents. Our findings underscore the importance of electrolyte flow and current density management in developing high-performance ZAFBs, providing valuable insights for their future commercialization.

Diffusion Nitride Surface Layers on Aluminum Substrates Produced by Hybrid Method Using Gas Nitriding

While gas nitriding of steel is currently used in industry, nitriding of aluminum alloys remains an open challenge. The main obstacle is aluminum’s high susceptibility to passivation. The oxide film provides an effective barrier to nitrogen diffusion. Attempts to overcome this problem have mainly focused on glow discharge nitriding using cathode sputtering of an oxide layer. The produced AlN layers exhibit no diffusion zone and show limited performance properties. In this work, the effect of hybrid treatment aimed at producing diffusion layers of nitrides other than AlN on aluminum alloys was investigated on the model system of iron nitride–aluminum substrate. Hybrid treatment combines an electrochemical process involving the removal of the aluminum oxide layer from the substrate, its subsequent iron plating, and a further gas nitriding in high-purity ammonia. The obtained results prove that the hybrid treatment allows the production, at 530 °C/10 h, of diffusion layers of Fe3N iron nitrides on aluminum substrates with a nitrogen diffusion zone range in aluminum of ca. 12 µm. In alloys containing magnesium, its unfavorable effect on the nitrogen diffusion and the functional properties of the layers was observed. An interesting direction for further research is hybrid treatment of precipitation-hardened alloys without magnesium.

AN INVESTIGATION ON THE CAUSES OF CORROSION IN AISI 1009 STEEL PIPE OF THE FIRE LINE IN THE GAS REFINERY

In view of several reported cases of cracking in the piping of the fire extinguishing sector in the oil tanks, a detailed identification of the failure mechanisms was required for the safe continuation of gas processing. Therefore, this study investigated the damage of steel fire extinguishing pipes after a certain period of operation. Severe thinning of the wall thickness was observed in two parts of the pipe. Comprehensive analytical investigations, including optical microscope (OM), quantometer, XRD, FE-SEEM, EDS and microhardness were performed. In addition, the corrosion behavior of the material was investigated by polarization and EIS analysis and the most plausible reactions and corrosion mechanisms were elucidated. The corrosion products on the inside of the pipe included oxide compounds, while on the outside, it was mainly sulfides and oxides. A drastic and slight decrease in microhardness was observed near the inner and outer surfaces, respectively. Electrochemical tests proved the formation of a porous and non-protective layer of corrosion products. The corrosion resistance was found to be weak due to several factors: the nature of the AISI-1009 steel, several micropores, the periodic formation and removal of non-continuous oxide layers and the roughness that accelerated the strong thickness reduction.

Surface roughness effect on the triboelectric generation in p-Si with a native oxide layer

Triboelectric generation during the friction of the boron doped diamond probe on the p-doped silicon surface with a native oxide layer was studied. Triboelectric generation was detected at the probe loading force higher than 1 µN leading to the modification of the studied surface. Triboelectric current density reached value of 4·104 A/m2. Removal of the native oxide layer confirmed the tribo-tunneling mechanism of the electric current generation. Increase in the triboelectric current by the high loading force was explained by the increase in the contact area and the generation of the dangling bonds during the friction.

Computational modeling of a surfatron mode microwave plasma in NH3/N2 for remote radical generation in a silicon native oxide cleaning process

Plasma-produced NxHy radicals facilitate the removal of native oxide layers in a semiconductor wafer surface. A remote microwave excited plasma with a NH3–N2 feed gas is used commonly to produce the active radicals. We perform a three-dimensional modeling of a microwave excited plasma operating in a surfatron mode. The device consists of a rectangular waveguide intersecting a quartz tube through which the feed gas flows. We discuss the propagation of a polarized 2.45 GHz microwave from the waveguide into the quartz tube where power is deposited into the plasma. The plasma–wave interaction is found to be highly three dimensional, with a propagating surface mode of the wave established along the dielectric tube plasma interface. Significant heating occurs on the side of the tube that directly faces the incident wave. As the flow carries the plasma-produced species down the tube, species radial profiles become increasingly diffusion controlled and axisymmetric. The dominant radicals that exit the tube are H2 and NH2, with nearly complete conversion of the feed gases to product species. The gas temperature rises above this inlet feed gas temperature and increases with increasing wave power. However, the gas temperature increase is not consequential to the overall radical yield from the plasma. The parametric study with changing pressure and input power illustrates the role of specific chemical reactions in the overall remote plasma process.

Combustion enhancement of boron-containing fuel-rich mixture by steam reforming in a supersonic flow

In this paper, a novel experimental investigation was conducted to enhance the combustion of boron-containing fuel-rich mixture by steam reforming in a supersonic flow. The ground direct-connected experiments were designed to simulate a flight condition at Mach number 5.9 and an altitude of 25 km. The operating characteristics and performance evaluation of the scramjet combustor were analyzed and discussed. The experimental results demonstrate that steam reforming can enhance the combustion of boron-containing fuel-rich mixtures in the supersonic flow. The performance of the combustor is firstly enhanced and then weakened with the increase of the steam-fuel ratio. The optimal steam-fuel ratio is approximately 0.189, which maximizes performance. At this steam-fuel ratio, combustion efficiency reaches 0.451, which is 9.9 % and 7.4 % higher than steam-fuel ratios of 0 and 0.395, respectively. The possible mechanism of steam reforming promoting boron combustion in the supersonic mainstream is explained. Steam accelerates the removal of the liquid oxide layer surrounding the boron particle, then combines with oxygen to produce hydrogen with good ignition-combustion characteristics and a new oxide layer. The cycle continues until the boron burns out. These conclusions can promote an understanding of enhancing the combustion of boron-containing fuel-rich mixture by steam reforming in the supersonic flow.

Electron knock-on damage effects on electron magnetic chiral dichroism of magnetic metals using cobalt as a model

Electron magnetic chiral dichroism (EMCD) is a high-resolution technique currently in development for quantitative magnetic measurements using transmitted electrons. However, the inevitable electron damage to materials can be a significant yet easily overlooked factor affecting the quantification accuracy. This work experimentally investigated the electron knock-on damage effects on EMCD of magnetic metals using metallic cobalt as a model. Three issues are involved in the metal-surface damage process. It was revealed that under sustained electron irradiation during spectra acquisition, gradual removal of the thin surface oxidation layer, rather than a simple continuous thickness reduction that changes the diffraction and plural scattering conditions, can lead to notable residual nonmagnetic components in EMCD spectra and may make the quantified result of the orbital-to-spin moment ratio remarkably higher than the actual value. It was, thus, proposed to pay great attention to the surface oxidation and to minimize the effect of the oxidation layer by performing electron irradiation on the target area prior to EMCD experiments. A further experiment was additionally proposed to quantify the impact of thickness reduction on the magnetic components of momentum-resolved electron energy-loss spectra and the EMCD quantification. This study advances the application of EMCD in magnetic metals.

Wet chemical poly-Si(n) wrap-around removal for TOPCon solar cells

This work gives an overview on different technological solutions for polysilicon removal in industrial tunnel oxide passivated contact (i-TOPCon) n-type silicon solar cell fabrication. The removal of parasitically deposited poly-Si layers on the front and the edges is a mandatory requirement for a low reverse bias junction leakage current (Irev). A polysilicon removal study on wafer level shows (i) that the efficient removal of the surface oxide layer before poly-Si etching is crucial to achieve short etching times and (ii) that an additive in the KOH solution enhances etching selectivity between poly-Si and silicon oxide surfaces. To evaluate the impact on device level, TOPCon cells have been fabricated in parallel using in-situ n-doped PECVD and LPCVD layers, as well as ex-situ LPCVD poly-Si layers, with another variation of poly-Si removal processes, namely wet chemical inline, wet chemical batch cluster and atmospheric dry etching (ADE). Our results show that a two-minute inline polysilicon removal in hot KOH meets the Irev qualification in case of as deposited in-situ doped layers, whereas for ex-situ doped layers a batch process with a five-minute KOH etching time is needed. LPCVD poly-Si cells show efficiencies above 23%, PECVD poly-Si cells with a batch cluster poly-Si removal process up to 23.4%.

Finite Modeling and Simulation of the Effects of Neutral Electrolytic Pickling Process Parameters on EN 1.4404 Steel Strips

Surface treatment via neutral electrolytic pickling (NEP) aims to remove oxide layers and scaling from stainless steel. The objective of this study was to investigate the factors that affect the energy efficiency of the process. This study developed a COMSOL Multiphysics model for the distribution of current across a bipolar steel strip by controlling the following parameters: Na2SO4 concentration, temperature, electrode-to-strip distance, and inter-electrode distance. Full factorial measurements of the electrolyte’s conductivity as well as the steel strip’s and the electrode’s polarization were conducted to provide data for the NEP model. Galvanostatic pulse measurements were performed to calculate transient times during pickling. According to the model, an applied voltage of less than 11 V was insufficient to polarize the steel strip to the potentials needed on both the anodic and cathodic sides. A higher voltage of 11–15 V resulted in anodic current densities of 600–1600 A m−2 and cathodic current densities of 700–2000 A m−2 on the steel strip. These current densities are within the range of previous experimental studies and industrial practices. The model showed that when a steel strip acts as a bipolar electrode, the current’s efficiency decreases, as only a fraction of the strip facing the anodes or cathodes is polarized sufficiently. The galvanostatic tests showed that anodic polarization of the steel strip is easier than cathodic polarization. The slow polarization in the cathodic direction can be improved by using a higher current density. The time needed to polarize stainless steel indicates that the strip’s velocity should be less than 1 m s−1 to give enough time for polarizing the steel strip.

(Invited, Digital Presentation) Low-Temperature Direct Bonding of Wide-Bandgap Semiconductor Substrates

Low-temperature direct bonding technique of semiconductor substrates has been developed to integrate dissimilar materials (e.g. Si, Ge, III-V) regardless of lattice and thermal expansion mismatches. Among the direct bonding techniques, a hydrophilic bonding method, which initiates a dehydration reaction between OH-terminated substrates, is commonly used because wafer-scale bonding can be fabricated under atmospheric conditions. Recently, our research group achieved direct bonding of wide-gap materials, including SiC, GaN, β-Ga2O3, and diamond substrates, by using this bonding method.The hydrophilic bonding of Si wafers has been practically applied for the fabrication of silicon-on-insulator substrates. In the bonding process, the Si substrates are typically irradiated with reactive ion etching using oxygen plasma, which efficiently generates OH groups on the surface. By contacting the substrates under atmospheric conditions, the activated surfaces can adhere to each other by hydrogen bonds across the OH groups. The annealing at ~200 °C causes the dehydration reaction and forms atomic bonds between the substrates, as shown in the following equation.Si-OH + HO-Si → Si-O-Si +H2OThe bonding process generates a sub-10-nm-thick SiOx layer at the bonding interface, which limits thermal and electrical conductance between the bonding substrates.Our research group demonstrated that the diamond substrates can be bonded with other semiconductor substrates (e.g. Si, InP, β-Ga2O3) by the hydrophilic bonding method. The pre-bonding treatment using oxygen plasma is not suitable for the diamond surface because it is easily etched by the strong oxidizing treatment. Meanwhile, the mild oxidizing treatment using H2SO4/H2O2 (i.e. piranha solution) and NH3/H2O2 (i.e. SC1) mixtures enables OH termination of the diamond substrate without a significant increase in the surface roughness. Figure A shows the photograph of the diamond substrate bonded on the Si substrate. At the Si/diamond and InP/diamond bonding interfaces, ~3-nm-thick SiOx and InPOx layers were observed by an electron microscope, respectively, as displayed in Figure B. These oxide layers were formed by the oxidizing treatment at the pre-bonding step.However, when β-Ga2O3 and diamond substrates were bonded, such an oxide intermediate layer was not observed at the bonding interface. This is because diamond never develops the oxide layer and β-Ga2O3 is an oxide material. As shown in Figure C, we achieved the direct bonding of monocrystalline β-Ga2O3 and diamond substrates with an amorphous intermediate layer thinner than 1 nm. As the intermediate layer was atomically thin, efficient electrical and thermal conductance across β-Ga2O3/diamond substrates was possible, as plotted in Figure D.Qiushi Kang et al. demonstrated that the hydrophilic bonding of the SiC substrate is possible by using oxygen plasma. This treatment develops the ~4-nm-thick SiOx layer on the SiC substrate, which possibly became a thermal and electrical barrier at the bonding interface. However, our research group revealed that the SiC substrate dipped into HF acid can form direct bonding with an atomically thin intermediate layer. It is known that the SiC surface is OH terminated after the removal of the native oxide layer by HF acid, unlike the Si substrate. We revealed that the HF-dipped SiC substrate can form direct bonding with the O2-plasma-activated β-Ga2O3 substrate through an intermediate layer as thin as 1 nm. as displayed in Figure E.About the GaN substrate, we have demonstrated that hydrophilic bonding with the Si substrate is possible using oxygen and nitrogen plasma activations. In addition, the GaN substrate dipped into H2SO4/H2O2 and NH3/H2O2 mixtures can also form direct bonding. The thickness of the GaOx layer at the GaN/Si bonding interface was approximately 1 nm.We believe the low-temperature direct bonding technique will contribute to future wide-bandgap semiconductor devices because it is possible to achieve efficient electrical and thermal conduction across dissimilar materials. Figure 1

An overview of the synthesis of silicon carbide–boron carbide composite powders

Abstract Recently, silicon carbide–boron carbide composite ceramics have attracted more and more attention. The most important achievements of the silicon carbide–boron carbide composite ceramics should be applied in terms of mechanical, physical, and chemical for use in various advanced industries, such as armor plates, nozzles, abrasive tools, mechanical seals, etc. To prepare silicon carbide–boron carbide composite ceramics with good performance, the synthesis of silicon carbide–boron carbide composite powders is the basis. The synthesis approaches of silicon carbide–boron carbide composite powders are systematically summarized in this review, including ball milling, high-energy ball milling, self-propagating high-temperature synthesis (SHS), and sol–gel. Particularly, nanosized silicon carbide–boron carbide composite powders can be in situ synthesized by high-energy ball milling, SHS, or sol–gel. When commercial silicon carbide and/or boron carbide powders are used as raw materials to synthesize silicon carbide–boron carbide composite powders, the pretreatment of acid etching can significantly remove oxide layers existing on the surfaces of initial powders.

Zero-Dimensional Ignition Model of Boron Agglomerates.

Boron primarily exists in the form of agglomerates in ramjet combustion chambers. However, the model used to predict the ignition time of boron agglomerates is usually based on the single-particle assumption, resulting in inaccurate predictions. This study aims to develop a numerical model that can accurately describe the ignition of boron agglomerates. The model is based on the ignition model of a single particle boron proposed by the group of Kuo. Thiele modulus and effectiveness factor are introduced to represent the diffusion resistance of reaction gases in the pores of boron agglomerates. The model includes the necessary physical processes to accurately predict the ignition time. The rates of evaporation and heterogeneous reactions involved in the oxide layer removal process are corrected based on the fact that the diffusion rate of (BO)n in the liquid oxide layer equals to its consumption rate at the oxide-air interface. To evaluate the accuracy of the model, the obtained results for ignition time are compared with experimental data, showing reasonable consistency between them. The model is then applied to investigate the ignition characteristics of boron agglomerates. Parameters, such as initial average pore diameter, oxide layer thicknesses, initial particle diameter, O2 concentration, H2O concentration, and environmental pressure, are studied for their effects on the ignition time. In summary, the boron ignition model established in this study is a powerful tool to investigate the ignition mechanisms and characteristics of boron agglomerates. It can be further coupled with flow analysis for the detailed simulation of turbulent combustion in ramjet combustors.

Effect of pressure on sintering of TiC-Fe-Cr-Mo cermets under vacuum conditions

TiC-Fe-Cr3C2-Mo and TiC-Fe-Cr3C2-Mo2C powder mixtures have been consolidated by liquid phase sintering under different vacuum conditions. Densification is improved by reducing the pressure of the furnace chamber from 10−2 to 10−5 mbar. This is due to a more efficient carbothermal reduction of powder oxides, which enhances the diffusion phenomena needed for good wetting of ceramic grains by the liquid phase. Cermets based on fine Mo2C powders exhibit higher densities than those based on coarse Mo additions. This is associated to higher C losses after sintering suggesting that diffusion kinetics and removal of oxide layers from starting powders are key for successful liquid phase sintering of TiC-Fe-Cr-Mo cermets. Ar injection in the sintering chamber at 1300 °C, used for avoiding the evaporation of the binder phase, leads to residual porosity due to Ar entrapment in pores open to the sintering atmosphere. Compositional gradients found at the surface of cermets sintered at 10−2 mbar are not present at 10−5 mbar. This is likely associated to the slight surface oxidation once the close porosity state is reached. The hardness of TiC-Fe-Cr-Mo cermets can be modified by applying standard heat treatments, leading to values in the range of those used for certain hot rolling applications.

Study of the radioactivity inventory deposited in the reactor coolant system during the decommissioning of Kori Unit 1

The Kori Unit 1, a first nuclear power plant (NPP) in South Korea stopped operation permanently on June 18, 2017 after 40 years of operation. Before the main decommissioning activities begin, full-system chemical decontamination operation (FSCDO) of the primary systems is planned to secure the safety of workers and minimize the quantity of radioactive waste. In this study, the radioactive inventory at the time of decommissioning of Kori Unit 1 was investigated. The CRUDTRAN code was used to make predictions by using the actual operation and maintenance history and design data of Kori Unit 1. Regarding the steam generator (SG), the prediction results obtained using the CRUDTRAN code were 17–30% higher or more conservative than the direct measurement results obtained using survey meters. By applying the oxide layer removal ratio (OLRR; obtained through a chemical decontamination field test using the contaminated specimen) to the oxidation/deoxidation process during FSCDO, the removal rate of radioactive inventory could be predicted. As an actual decommissioning work proceeds, the detailed data of radioactive elements in RCS systems can be obtained through sampling and chemical analysis. Those data will be much valuable for both the operation and future decommissioning of current NPPs.

Understanding on corrosion mechanism of oxidized AZW800 alloy in 3.5 wt% NaCl solution

Magnesium alloys are more widely used at higher temperatures. However, it is not well known whether oxide layer, produced at high temperature, could show corrosion protection. Thus, the corrosion behaviors of oxidized AZW800 alloy were investigated by hydrogen evolution and electrochemical measurements to evaluate effect of oxide layer on corrosion resistance. The results showed that corrosion of removed oxide layer AZW800 alloy showed characteristic of localized corrosion, leaving randomly bulky pits. While reserved oxide layer AZW800 alloy exhibited a relatively uniform corrosion. The results indicated that oxide layer could hinder corrosion of oxidized AZW800 alloy in the initial period of immersion. While subsequently, aggravated corrosion would occur owing to defects of oxide layer and less protective products film. Besides, present of oxide layer eliminated micro-galvanic couple on alloy surface. The synergistic effect of elimination of micro-galvanic couple on alloy surface and alkalization effect transforms localized corrosion into relatively uniform corrosion of alloys.

UV and aging effect on the degradation of PEDOT:PSS/nSi films for Hybrid Silicon solar cells

Poly(3,4-ethylene-dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is one of the most successful conductive polymers, key component in different organic-based devices including silicon Hybrid Solar Cells (HSCs). However, there is limited information so far about the stability of this polymer under operation scenarios similar to those employed during performance, including UV irradiation or storage time. In this work, PEDOT:PSS thin layers have been spin coated onto silicon substrates, and their stability has been analysed under different conditions. Firstly, the influence under laser irradiation has been studied by Raman spectroscopy using both an UV-laser of 325 nm and a VIS-laser of 633 nm, with variable irradiation intensities and exposure time. Secondly, the effect of the removal of the native silicon oxide layer on the silicon substrate on the stability and passivation performance of the PEDOT:PSS has been analysed. Lastly, and closely related to its application in HSCs, the photoluminescence recombination has been analysed over storage time for 2 months to evaluate their real implementation as long-lasting solar cells.

Separation of tungsten and cobalt from cemented tungsten carbide by rapid breakdown anodization

Cemented tungsten carbide (WC-Co) has been used as an important industrial material and secondary resource of tungsten (W) and cobalt (Co). The recycling methodology of WC-Co scraps has drawn much attention because the recovery of strategic metals such as W and Co are critical. Here, rapid breakdown anodization (RBA) was applied for the first time to the conversion of WC-Co into high-purity hydrated tungsten oxide (WO3-H2O) up to 99.99 wt% and pure Co metal up to 90.43 wt% by using WC-Co as a sacrificial anode. Effective cobalt leaching was achieved in acidic aqueous solution without encountering anodic passivation issue due to the successful removal of tungsten oxidation layer during the electro-dissolution of WC-Co. Based on the particle formation mechanism of RBA, a two-stage reaction was confirmed, including electrochemical dissolution and chemical precipitation. The high purity of recovered WO3-H2O powders was realized by using high current density and high electrolyte concentration. We demonstrate that RBA is a new pathway for effective and environmentally-friendly WC-Co recycling with a significantly simplified process compared to conventional hydrometallurgical methods.

Corrosion Behavior of EN18 Steel and Copper in the Sulfuric Acid Medium for As-Bought and Annealed Materials

EN18 steel and copper are used as materials for oil and gas industries for chemical storage, which come in contact with the sulfuric acid medium during the pickling process. In such instances cleaning of impurities and oxide layer removal, leads to excessive corrosion. Thus, the improvement in the microstructure through annealing treatment and its effect on the corrosion behavior of EN18 steel and copper are studied by immersing in 0.5 M H2SO4 for as-bought and 0.5, 0.25, 0.1 M H2SO4 medium solutions after annealing treatment. The metal specimens were heated to 900 °C for EN18 steel and 600 °C for copper and then both were furnace cooled and the change in the microstructure of annealed and as-received metal specimens was analyzed using Scanning Electron microscopy (SEM). The Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic polarization (PDP) measurement showed that there is a decrease in the corrosion rate for both metals after annealing treatment. The effect of corrosion rate at the temperature range of 30-50 °C was analyzed and activation parameters were described using Arrhenius and transition state theories. Suitable corrosion mechanisms for both steel and copper in the H2SO4 medium have been discussed.