Oxidation Of Steel Research Articles

Electrochemical study and experimental simulation of the synergistic effect of a formulation based on Ficus pumila Linn. Leaves extract and zinc sulfate on the XC38 steel corrosion inhibition in NaCl solution

The inhibitive activity of a mixture of Ficus pumila Linn. leaves hydroalcoholic extracts (HEFP) and zinc ions against corrosion of XC38 steel in NaCl solution was investigated. Electrochemical measurements (potentiodynamic polarization and electrochemical impedance spectroscopy at and around the corrosion potential) and surface analysis (SEM/EDX) have shown that the presence of zinc ions considerably increases the inhibitive capacity of HEFP. However, appropriate concentrations of zinc ions (50 and 100 ppm) and of HEFP (200 ppm) are necessary to have an optimal inhibitive effect. The formation of organometallic complexes between zinc ions and some organic compounds of HEFP (polyphenols and carbohydrates) are the determining step of the synergistic inhibition. Since the main inhibitive agents in plant extracts are polyphenols, a simulation of this inhibitive character was electrochemically done with a mixture of flavonoid (quercetin), phenolic acid (gallic acid) and zinc ions in order to elucidate the inhibition mechanism. The obtained results showed that the electrochemical behavior of XC38 steel in the presence of this mixture is quite similar to that obtained in the presence of HEFP + Zn2+ formulation. The proposed inhibition mechanism, which explains the good inhibitive efficiency observed in presence of the HEFP + Zn2+ formulation, is based on concerted reactions between the steel oxidation products (Fe2+ and Fe3+), the zinc ions and the Iron(II) and Iron(III) complexing agents present in the extract.

Initial High-Temperature Oxidation Behavior of Fe–Mn Binaries in Air: The Kinetics and Mechanism of Oxidation

High-temperature oxidation of steels can be relatively fast when exposed to air. Consequently, elucidating the effect of different parameters on the oxidation mechanism and kinetics is challenging. In this study, short-time oxidation was investigated to determine the oxidation mechanism, the affecting parameters, and the linear-to-parabolic growth transition of different Fe–Mn alloys in various oxygen partial pressures (10–30 kPa) and gas flow rates (26.6 and 53.3 sccm) in a temperature range of 950–1150 °C. Oxidation kinetics was investigated using a thermogravimetric analyzer (TGA) under controlled atmosphere. Linear oxide growth was observed within the first 20 minutes of oxidation. The linear rate constant was significantly increased by increasing the oxygen partial pressure or the flow rate of the oxidizing gas. The morphology of the oxide layer was determined by scanning electron microscopy (SEM). The crystal structure of the oxides formed was followed by in-situ X-ray diffraction (XRD), confirming that the growing layer consists of wustite mainly, which upon slow cooling to room temperature, transformed into magnetite. Energy-dispersive X-ray spectroscopy (EDS) showed that the atomic ratio of Fe+Mn to O was ~ 1.03:1 in the oxide scale, corresponding to Fe(Mn)O formation. Based on the characterization and a model for linear growth kinetics, it is concluded that the oxidation rate is controlled by the diffusion of oxidizing molecules through the gas layer to the sample’s surface. The findings led to a better understanding of initial oxidation behavior and provided a pathway for improved insight into the high-temperature oxidation behavior for more complex alloys.

Selective Oxidation of a Medium-Mn Third Generation Advanced High Strength Steel during Austenitizing and Intercritical Annealing

The effect of the simulated continuous galvanizing line N2−5 vol% H2 process atmosphere oxygen partial pressure (pO2) on the external and internal selective oxidation of a prototype medium-Mn third generation (3G) advanced high strength steel was determined during a two-stage heat treatment cycle (i.e., austenitizing and intercritical annealing) which had previously yielded 3G properties. Thick external oxides (∼200 nm) were observed after the austenitizing heat treatment, regardless of the process atmosphere pO2 employed. An intermediate flash pickling step was successful in reducing the external oxide thickness significantly (to ∼30 nm) along with revealing some extruded metallic Fe nodules on the surface. The austenitizing heat treatment also resulted in a solute-depleted surface layer with a minimum thickness of 2 μm. This solute-depleted layer inhibited the formation of external oxides during intercritical annealing, resulting in a surface similar to that observed after flash pickling comprising a near-pure Fe surface with isolated, nodular external oxides. These surfaces are promising in terms of successful reactive wetting of this prototype medium-Mn steel during subsequent continuous hot-dip galvanizing.

Thermodynamic Basis of Isothermal Carbothermic Reduction of Oxide in Liquid Steel for Simultaneous Analysis of Soluble/Insoluble Oxygen Contents in the Steel Specimens

Oxygen in liquid steel exists as soluble O (chemically dissolved in the steel matrix) and insoluble O (physically dispersed as the oxide inclusion). To measure the soluble O content ([S.O]) and the insoluble O content ([I.O]), both in the context of gas fusion analysis technique such as inert gas fusion infrared absorption method, it is necessary to melt the specimen under a C saturation condition in a “two-stage” isothermal heating mode. The first stage is carried out at a low temperature (TL), where only soluble O is extracted as CO(g). The second stage is subsequently carried out at a high temperature (TH), where the oxide inclusion is reduced by a carbothermic reaction. Therefore, it is necessary to identify the carbothermic reduction temperature of the oxide inclusion in the liquid steel at the C saturation (\( T_{{{\text{M}}_{x} {\text{O}}_{y} }}^{{{\text{Fe}}}} \)). A series of CALPHAD-type thermodynamic calculations were carried out to estimate the temperature of each oxide inclusion (Al2O3, FetO, SiO2, CaO, and MgO). It was found that the temperature depends on the metal content ([pct M]) and total pressure (P) inside the gas fusion chamber: increasing [pct M] or P increases \( T_{{{\text{M}}_{x} {\text{O}}_{y} }}^{{{\text{Fe}}}} \). The proposed method may be applied for the steel systems containing those inclusions except for FetO. In the case of Al2O3 inclusion containing steel ([pct Al] = 0.04), for example, \( T_{{{\text{Al}}_{2} {\text{O}}_{3} }}^{{{\text{Fe}}}} \), lies in the range of 1791 K (1518 °C) to 1838 K (1565 °C) depending on P inside the gas fusion chamber. Possible range of the \( T_{{{\text{M}}_{x} {\text{O}}_{y}}}^{{{\text{Fe}}}}\) is reported.

Carbonation and Corrosion Problems in Reinforced Concrete Structures

Reinforced concrete (RC) has been commonly used as a construction material for decades due to its high compressive strength and moderate tensile strength. However, these two properties of RC are frequently hampered by degradation. The main degradation processes in RC structures are carbonation and the corrosion of rebars. The scientific community is divided regarding the process by which carbonation causes structural damage. Some researchers suggest that carbonation weakens a structure and makes it prone to rebar corrosion, while others suggest that carbonation does not damage structures enough to cause rebar corrosion. This paper is a review of the research work carried out by different researchers on the carbonation and corrosion of RC structures. The process of carbonation and the factors that contribute to this process will be discussed, alongside recommendations for improving structures to decrease the carbonation process. The corrosion of rebars, damage to passive layers, volume expansion due to steel oxidation, and crack growth will also be discussed. Available protection methods for reducing carbonation, such as rebar structure coating, cathodic protection, and modifier implementation, will also be reviewed. The paper concludes by describing the most significant types of damage caused by carbonation, testing protocols, and mitigation against corrosion damage.

Evolution of Non-Metallic Inclusions in 27SiMn Steel

To study the evolution of non-metallic inclusions in 27SiMn steel, the 27SiMn steel produced using the LD-LF-CCM process was sampled in various stages in a steel factory. The evolutionary behavior of inclusion in various processes was systematically analyzed by scanning electron microscopy (SEM-EDS), and the total oxygen content and nitrogen content in 27SiMn steel were measured at various production steps. On the basis of the calcium treatment for 27SiMn steel, the equilibrium reactions for Ca-Al were calculated according to the thermodynamic equilibrium model. The results showed that the types of inclusions at the start of LF stations are mainly Al2O3-FeO and MnS-Al2O3. Before calcium treatment, the inclusions are mostly calcium aluminate and CaO-MgO-Al2O3. Compared with the process after soft blowing, the number density of inclusions in tundish increased by 77.88%, possibly due to secondary oxidation. From the soft blowing process to the continuous casting round billet, the inclusions translate into spherical CaO-MgO-Al2O3-SiO2, and a large number of CaS were observed. One part of the CaS precipitated separately, the other part was semi-wrapped with the composite inclusions. At the same time, calcium treatment increases the number density, mean diameter, and the area fraction of inclusions. The mass fraction of T.O. (total oxygen content) increased significantly after soft blowing, and the N content increased greatly from station to tundish. The change trend of N content in steel was basically consistent with that of T.O. content. It was necessary to prevent the secondary oxidation of molten steel during calcium treatment and the casting process. When the liquidus temperature of liquid steel is 1873 K, w[Al] = 0.022%, and w[Ca] in steel is controlled between 1.085 × 10−6 and 4.986 × 10−6, the Al2O3 inclusion degeneration effect is good.

Exposure of Stainless Steel 316 to Subcritical, Transition, and Near-Supercritical Water

This work investigates the oxidation of austenitic stainless steel 316 at temperatures close to the critical point of water: subcritical water at 330°C and 27 MPa, the transition between subcritical and supercritical water at 374°C and 27 MPa, and supercritical water (SCW) at 380°C and 27 MPa. The surfaces of the samples were characterized using x-ray diffraction, Raman spectroscopy, scanning electron microscopy, and x-ray photoelectron spectroscopy before and after exposure. Magnetite (Fe3O4) was found to be present on all surfaces of all samples. The samples exposed to subcritical water also showed the presence of a nickel-iron chromium mixed spinel Ni(Fe2-xCrx)O4. The oxide morphology was observed to vary based on exposure temperature; an increased nucleation and growth rate, and an increased generation of Fe2+ was observed on samples exposed to the transition region and SCW.

Effect of Shot Peening on the Surface Oxidation of P92 Steel in the Steam Environment at 600 °C

Abstract The effect of shot peening on oxidation behavior of P92 steel was investigated under the steam environment of 600 °C. Evolution of microstructure, hardness and residual stress under different air pressure of shot peening were discussed. On the shot peened surface, a stable hematite outer layer was detected by using scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and X-ray diffraction (XRD) analysis. The increased oxidation resistance of hematite layer was ascribed to the increased outward diffusion of Cr and the decreased inward diffusion of oxygen. In addition, the role of residual stress in the oxygen diffusion was discussed.

The effect of dissolved oxygen on the oxidation of an austenitic steel in supercritical water

ABSTRACT The oxidation experiments of austenitic steel TP347HFG were carried out at 620°C under 25 MPa in supercritical water with the dissolved oxygen content of 0–2000 ppb. The oxidation rate of TP347HFG increased with the rise in dissolved oxygen content. A double-layered oxide scale composed of a Fe-rich outer layer and a Cr-rich inner layer developed on the TP347HFG steel surface. Haematite was detected in supercritical water with 2000 ppb dissolved oxygen while absent in deaerated supercritical water. The content of dissolved oxygen has a great impact on the formation and distribution of Cr2O3. A thicker and continuous Cr2O3 were observed in the grain boundary near the interface of oxide and the substrate in deaerated supercritical water. The Cr evaporation may be responsible for the oxidation resistance of TP347HFG steel in supercritical water with different dissolved oxygen content. The influence mechanisms of dissolved oxygen on oxidation rate and oxides composition were discussed in this paper.

High-temperature oxidation behaviour of nanostructure surface layered austenitic stainless steel

The present study investigates the high-temperature oxidation behaviour of nanostructure surface layered AISI 304L stainless steel. A severely deformed layer of ∼300 μm thickness, consisting of nanoscale grains (∼40 nm size) in the topmost region, is successfully developed using the surface mechanical attrition treatment (SMAT) process. The SMATed layer is substantially stable up to 700 °C; however, the surface hardness is reduced by ∼37% at 800 °C for 25 h oxidation duration. Glow discharge optical emission spectroscopy and X-ray photoelectron spectroscopy analysis revealed the considerable difference in the chemistry and elemental distribution across the oxide scale of SMATed and non-SMATed specimens. Adherent, denser, and thinner scale, dominated by nanocrystals of Cr- and Mn-rich oxides, is formed on the SMATed steel. However, the Fe-oxide dominated scale containing micro-crystals is found on the non-SMATed specimens, which shows noticeable exfoliation. A high density of grain boundaries and lattice defects in the SMATed layer display admirable reactive diffusion properties of Cr and Mn during oxidation of steel, instigating the formation of a protective oxide scale. The SMATed specimens exhibit multiple zones in the oxide scale: (i) Cr/Mn depleted outer layer, (ii) Cr-/Mn-rich inner layer, and (iii) gradually decreasing Cr/Mn region.

Effect of arsenic on the high temperature oxidation and hot shortness behaviour of copper-bearing steel

To understand the disadvantages caused by As in Cu-bearing steels during hot working processes, high temperature oxidation and surface hot shortness characteristics were systematically investigated using thermogravimetry (TG), optical microscopy (OM), scanning electron microscopy (SEM) and Gleeble-3800 thermal/mechanical simulation system. Analyses of TG curves and the oxide scale morphologies showed that the oxidation kinetics for all steels obeyed the initial linear oxidation law and the later parabolic oxidation law at 950–1050 °C, while the kinetics presented two different stages of the linear oxidation law at 1100 and 1150 °C due to oxide scale separation. Increasing the As content from 0 to 0.15 wt.% decreased the oxidation activation energy and accelerated the oxidation degree of Cu-bearing steel. Cu + As enrichment indicated that an increase in As content induced the precipitation of a more hazardous Cu-rich liquid phase along grain boundaries by decreasing the solubility of Cu in austenite and the melting point of the Cu phase at 1050 °C. Furthermore, the degree of Cu + As enrichment became more serious with an increase in the oxidation temperature from 1000 to 1050 °C, and then decreased because of occlusion and faster back diffusion of Cu + As into the matrix at 1100 and 1150 °C. The hot compression results agreed well with the enrichment behaviour of Cu + As obtained from investigations of isothermal oxidation.

BEHAVIORS OF OXIDATION AND DECARBURIZATION ON SURFACE OF HIGH-CARBON STEEL WIRE RODS

The quality of high-carbon wire rods is subject to high requirements in terms of the size of the decarbonized layer, the amount and composition of the scale formed by the interaction of the oxidizing furnace atmosphere with the surface of steel. In this connection, studies of the kinetics of high-temperature oxidation of high-carbon steel are of great practical importance, both in the development of new and adjustment of existing modes of heat treatment of steel. The results of experimental studies of hightemperature oxidation and decarburization of the surface of high-carbon steel grade 80P on the synchronous thermal analysis device STA 449 F3 Jupiter presented. Temperature intervals of intensification of scale formation and decarburization of the surface in various media (weakly oxidizing and oxidizing) have been established. Phase transformations in high-carbon steel grade 80P have been studied by differential scanning calorimetry and the temperatures of the beginning and end of the formation of homogeneous austenite during heating have been established. It was noted that in the range of heating temperatures of steel 720‒950°C, along with phase transformations, the intensification of the processes of scale formation and depletion of the surface layers with carbon begins. The exponential dependence of steel loss on the heating temperature of the sample was obtained by thermogravimetric analysis. It was shown that the oxidation rate of the surface increases by 3 times with an increase in the temperature of the workpiece from 900 to 1000°C, and up to 1200°C ‒ by 8 times. It was noted that the temperature at which the oxidation rate of steel is minimal in the temperature range from 900 to 1000 °C is about 929 °C, in the range of 1100‒1250°C ‒ 1157°C. The obtained results can be used to select the main technological parameters of the heat treatment mode of wire rods made of 80P steel, which ensure the formation of a minimum amount of easily removed scale on the metal surface.

Mathematical modeling of selective dissolution of AISI 304 steel in circulating chloride-containing waters during operation of heat exchangers

Purpose. Investigation of the effect of chloride-containing medium, chemical composition and structural heterogeneity of AiSi304 steel on selective dissolution of metals ΔCr, ΔNi and ΔFe from stable pits.
 Research methods. X-ray structural analysis, optical microscopy, energy dispersive microanalysis, analysis of the developed linear regression mathematical models of the second order for corrosion losses of metals from pits.
 Results. Based on the analysis of the developed linear regression mathematical models of the second order for corrosion losses of metals from pits, it was found that ΔFe from pits on the surface of AISI 304 steel in model circulating water with pH = 4...8 and chloride concentration of 300 and 600 mg / l decrease with an increase in it. the amount of oxides (1.98...3.95 microns), the average diameter of the austenite grain and increase when the average distance between the oxides and the volume of b- ferite in steel increases. It is proved that ΔNi from pits decreases with an increase in the amount of oxides in steel (1.98...3.95 μm), the volume of b- ferite and a decrease in the average diameter of austenite grain.
 It was determined that ΔCr of steel from pits mainly depends on the concentration of chlorides in the model circulating water, the amount of oxides (1.98 ... 3.95 μm), the average diameter of the austetin grain and the volume of b-ferite. It is hypothesized that this is due to the intensity of adsorption of chlorine ions on imperfections in the structure of AISI304 steel near these oxides at the intersection with the grain boundaries of austenite, where pits nucleate and grow.
 Scientific novelty. It was established for the first time that the coefficient of selective dissolution of Cr from pits on the surface of AISI 304 (ZCr ) steel in the circulating waters of the river decreases with an increase in the volume of b-ferite in the steel, the average diameter of austenite grain and a decrease in the amount of oxides. This can facilitate the transition of metastable pits to stable ones. Moreover, this process is autocatalytic; therefore, it does not depend on the parameters of the model circulating water.
 Statement of tasks. Based on the established features of selective dissolution of ΔCr, ΔNi and ΔFe from pits on the surface of AISI304 steel, to study the effect of its plastic defermation on pitting resistance in chloride-containing model circulating waters.
 Practical value. The developed mathematical models are used to assess the pitting resistance of AISI304 steel in model circulating waters, depending on its parameters and the environment where heat exchangers made of this steel operate.

Oxidation and wear behavior of high-speed steel and semi-high-speed steel used in hot strip mill

Oxidation and wear behavior of high-speed steel and semi-high-speed steel used in hot strip mill

Different Setup of Capacitive Coupling Protection System on Mild Steel

A Capacitive Coupling Corrosion Protection (CCCP) technology based on coupler pads was investigated. The layout of the coupler pads on the mild steel surface was studied to get the best outdoor corrosion protection. A square wave of current/voltage is supplied to the steel surface for 72 hours via a copper coupler pad in three arrangements, i.e., single, double-sided, and opposite configurations. The efficiency of the CCCP configuration was assessed by measuring electrical current consumption, weight loss, and post-experimental surface morphology observations. It is found that the current consumption of 600 μA/cm2 in the double-sided configuration is practically stable. The lowest weight loss and clean surface morphology also prove that the double-sided configuration can improve the corrosion protection of mild steel. It was discovered that by employing more coupling pads on both sides of the metal sheet, the excessive positive charge capable of producing oxidation of mild steel could be easily discharged.

Study on the microstructure of air reactive brazing joint between Al2O3 ceramic and Q235 steel

Q235 steel /Al2O3 ceramics were brazed with Ag-CuO filler metal at 1050°C and held for 15min in air. When brazing Q235 steel and Al2O3 ceramics directly, it was found that serious oxidation occurred on the steel side during the brazing process. Although the joining was realized, a loose oxide film was formed on the surface of the base steel, which affected the mechanical properties of joints. When Q235 steel with aluminized surface was adopted to braze with Al2O3 ceramics, a Al2O3 layer formed on the surface of Q235 steel successfully avoided the oxidation of Q235 steel, and a compact and defection-free joint was obtained. The typical organization of joint was Al2O3/ CuAl2O4/ CuO/ Ag/ CuO/ CuAl2O4 /Al2O3/ FeAl/ FeAl2/ Fe.

High-Temperature Oxidation of Steels in Direct-Fired CO2 Power Cycle Environments

Future direct-fired supercritical CO2 power cycles require steels resistant to oxidation/corrosion in high-temperature CO2 environments containing various impurities. Herein we studied the oxidation behavior of 14 candidate steels in a simulated direct-fired CO2 power cycle environment consisting of 95% CO2, 4% H2O, 1% O2 with/without 0.1% SO2 at 1 atm and 550 °C, 600 °C, 650 °C for up to 2500 h. Steels with ≥ 11.5 wt% Cr exhibited at least partial coverage by Cr-rich oxide scales leading to a significant decrease in the oxidation rates in both gases. While SO2 had little effect on low-Cr steels that formed Fe-rich oxides, it generally worsened performance of high-Cr (> 11.5 wt%) steels by hindering the establishment of a protective Cr-rich oxide. This effect was most pronounced at the lowest temperature of 550 °C, which was attributed to strong preferential adsorption of sulfur-containing species within the oxide at relatively low temperatures.

Use of licorice plant extract for controlling corrosion of steel rebar in chloride-polluted concrete pore solution

The possibility of using licorice extract as a green inhibitor for steel reinforcements in chloride-contaminated simulated concrete pore solution was explored in this study. Different licorice amounts were added to alkaline solutions and then 1% NaCl was also added. Electrochemical studies, up to 24 h, and surface analysis (X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy) were performed. Results demonstrated the inhibition effectiveness of the plant extract on steel rebar corrosion, regardless of the concentration, being detected an inhibition efficiency higher than 80 % with electrochemical techniques for 0.1% licorice extract, which showed the most effective performance. Surface analysis methods confirmed the presence of licorice on the surface, through the deposition of organic molecules present in the plant extract on the surface oxide/hydroxide. DFT calculations confirmed that compounds present in licorice can be chemically adsorbed on steel oxide surface.

Surface Structure Analysis of Initial High-Temperature Oxidation of SS441 Stainless Steel.

Chromia-forming ferritic stainless steel (FSS) is a highly promising interconnect material for application in solid oxide fuel cells. In this study, initial oxidation of chromium oxides was performed at 500–800 °C to understand the evolution of materials at an early stage. The structural variations in oxide scales were analyzed through scanning electron microscopy, energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), X-ray diffractometry (XRD), laser confocal microscopy (LSCM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Surface electrochemical properties were investigated through electrochemical impedance spectroscopy to understand how the heat treatment temperature affected surface impedance. Treatment temperatures higher than 700 °C facilitate the diffusion of Cr and Mn, thus allowing ferritic spinels to form on the surface and leading to high electrical conductivity.

Improved Oxidation and Hot Corrosion Resistance of 1Cr11Ni2W2MoV Stainless Steel at 650 °C by a Novel Glass-Ceramic Coating

A novel glass-ceramic coating was applied onto the 1Cr11Ni2W2MoV stainless steel. The oxidation and corrosion behaviors of coated and uncoated steels were comparatively investigated in air and in the presence of NaCl + Na2SO4 eutectic deposits at 650 °C, respectively. Protective scales formed on the surface of stainless steel prevented the severe oxidation of the alloy. Catastrophic hot corrosion occurred on the steel when a salt film was attached, producing loose iron oxide layers and internal corrosion zone. The glass-ceramic coating acted as a barrier that effectively hindered the invasion of corrosive species during the oxidation and hot corrosion tests.