Corrosion Mechanism of Alumina-magnesia Dry Materials for Smelting Manganese/chromium Steel in Coreless Medium Frequency Induction Furnaces

Alumina-magnesia dry materials are widely used in induction furnace linings, but they show different kinds of damage when melting different kinds of alloy steel. In this paper, the chemical composition, phase composition, and microstructure of the post-use dry materials for the working liners melting different kinds of steel were evaluated. Furthermore, the corrosion mechanism of the steel on the furnace lining materials was comprehensively analyzed. The findings reveal a significant ability of the Mn element in the molten steel to diffuse and penetrate into the refractories. Mn oxidizes to form MnO at the steel-refractory interface, and then forms a liquid phase with Al_(2)O_(3). The Cr element is dissolved into corundum and spinel of the refractories, resulting in lattice defects and structural damage of the materials. TiO2reacts with Al_(2)O_(3) to form Al_(2)TiO_(5), which plays a crucial role in preventing crack formation and propagation. Part of Ti4+dissolves into magnesia-alumina(MA), densifying the materials. TiO2also slows down the reaction between the Cr element and refractory components, further improving the corrosion resistance of the materials.

Corrosion mechanism associated with Mg_2Si and Si particles in Al-Mg-Si alloys

The electrochemical behaviors and coupling behaviors of the Mg2Si and Si phases with α（Al） were investigated, the corrosion morphologies of Al alloys containing Mg2Si and Si particles were observed, and the corrosion mechanism associated with them in Al-Mg-Si alloys was advanced. The results show that Si particle is always cathodic to the alloy base, Mg2Si is anodic to the alloy base and corrosion occurs on its surface at the beginning. However, during its corrosion process, the preferential dissolution of Mg and the enrichment of Si make Mg2Si transform to cathode from anode, leading to the anodic dissolution and corrosion of the alloy base at its adjacent periphery at a later stage. As the mole ratio of Mg to Si in an Al-Mg-Si alloy is less than 1.73, it contains Mg2Si and Si particles simultaneously in the grain boundary area, and corrosion initiates on the Mg2Si surface and the precipitate-free zone （PFZ） at the adjacent periphery of Si particle. As corrosion time is extended, Si particle leads to severe anodic dissolution and corrosion of the PFZ at its adjacent periphery, expedites the polarity transformation between Mg2Si and the PFZ and accelerates the corrosion of PFZ at the adjacent periphery of Mg2Si particle.

Study on Corrosion Mechanism Between MgO-CaO Refractories and Slag

Magnesiu-Calcia materials containing 22 -53 wt% CaO hare been investigated Jot refinery slag corrosion and penetration resistance by Scanning Electron Microscopy （ SEM） .nd XRD. The corrosion and penetration resistance of MgO-CaO materials is enhanced with the increase of CaO content in specimens. It can be explained that, with increase of CaO content, the specimens reacted will＋ slag form higher melting point minerals of C3S ant C2S, creating a dense surface layer, which stopped others from penetrating further. Thus , the corrosion and penetration resistame was improved. No matter what kinds of slag were chosen, the depth of penetration decreased will＋ increase of CaO con,tent.

Corrosion Mechanism of MgO-CaO Brick for AOD Furnace

Residual MgO-CaO brick after being used in AOD furnace was determined by OM, SEM and EDAX. Corrosion mechanism of MgO-CaO brick as furnace lining was studied. Results show that： The corrosion of MgO- CaO brick is mainly attributed to the solution and infiltration of silicate liquid phase. Transverse cracks between reacted zone and original zone are parallel to the working face, which is an important factor for deteriorating the corrosion of MgO-CaO bricks.

Corrosion Mechanisms of SEN Slagband Materials

Wear of a zirconia graphite slagband material by mold slag during casting of a TRIP steel grade was investigated on worn specimens with respect to corrosion and erosion. Corrosion dissolution of both the stabilizer oxide and the zirconia is decisive. Oxidation is dominating graphite wear whereas a possible dissolution in the liquid steel was not observed to play an important role here. The ratio of oxide corrosion to graphite oxidation decreases with decreasing vertical distance of the hot face to the steel bath. Unfortunately and contrary to other applications of carbon bonded refractories in steel industry graphite exhibits to be wetted by mold slag in the special case investigated here： it still acts as a refractive component but only partly as an infiltration inhibitor. Infiltration is followed by zirconia corrosion thus reducing erosion resistance, but nevertheless also gas phase transport of slag components may cause exsolution of the stabilizer oxide in un-infiltrated regions.

CORROSION MECHANISM OF SnO2-BASED INERT ANODES

According to the extent of their damage in cryolite melts,the corrosion of SnO_(2)-based inert anodes can be divided into three types,slight corrosion,m&rked corrosion and catastrophic corrosion.The conditions under which these three types take place and their mechanisms are different.Our work shows that depletion of oxygen containing ions in melts,high density,electrolyte penetration into the electrode and intergranular corrosion contribute greatly to marked corrosion and catastrophic corrosion and that the reduction reaction by aluminium only attacks the electrode slightly.

Chemical Corrosion Mechanisms of Magnesite-chrome Bricks by Converter Slag

The corrosion resistance of four kinds magnesitechrome bricks against converter salg was investigated by static crucible slag tests. The microstructures of the asdelivered and tested refractories were analyzed by means of SEM and EDS. The results showed that： Different magnesite-chrome bricks have different slag resistances. Generally, the slag resiantance sequence is as follows： rebounded fused magnesite-chrome brick 〉 semi-reboun- ded magnesite-chrome brick 〉 direct-bonded magnesitechrome brick 〉 silicate bonded magnesite-chrome brick. Slag reacts with the periclase of magnesite-chrome refractories, which results in the dissoving of periclase in fayalite slag. However, the complex spinels have superior slag resistance.

Comparison of corrosion mechanisms of 510L low alloy steel treated by ACS and EPS techniques under various service environments

The corrosion mechanism of 510L low alloy steel treated by acid-cleaned surface(ACS)and eco-pickled surface(EPS)techniques in three simulated solutions(S0:atmospheric environment;S1:soil environment;S2:industrial environment)and the influence of interaction between different corrosive anions on corrosion were investigated.The results show that the total corrosion rates of samples in three simulated solutions were in order of S2>S0>S1,which is simultaneously correlated with initial corrosion dissolution processes as well as after the formation of corrosion products.HCO3−will inhibit the initial corrosion owing to the formation of films,whereas HSO3−will accelerate the dissolutions of the matrix based on the synergistic action of HSO3−and Cl−.On the other hand,there is no significant difference in corrosion rates between the samples treated by ACS and EPS techniques.The EPS technique that is safe,reusable and environmentally friendly can be further widely used in future work.

The corrosion characteristic and mechanism of Mg-5Y-1.5Nd-xZn-0.5Zr(x=0,2,4,6 wt.%)alloys in marine atmospheric environment

The microstructure and precipitated phases of as-cast Mg-5Y-1.5Nd-x Zn-0.5Zr(x=0,2,4,6 wt.%)alloys were investigated by optical microscopy,scanning electron microscopy,energy-dispersive spectrometry and X-ray Diffraction.The exposure corrosion experiment of these magnesium alloys was tested in South China Sea and KEXUE vessel atmospheric environment.The corrosion characteristic and mechanism of magnesium alloys of Mg-5Y-1.5Nd-x Zn-0.5Zr(x=0,2,4,6 wt.%)alloys were analyzed by weight loss rate,corrosion depth,corrosion products and corrosion morphologies.The electrochemical corrosion tests were also measured in the natural seawater.The comprehensive results showed that Mg-5Y-1.5Nd-4Zn-0.5Zr magnesium alloy existed the best corrosion resistance whether in the marine atmospheric environment and natural seawater environment.That depended on the microstructure,type and distribution of precipitated phases in Mg-5Y-1.5Nd-4Zn-0.5Zr magnesium alloy.Sufficient quantity anodic precipitated phases in the microstructure of Mg-5Y-1.5Nd-4Zn-0.5Zr alloy played the key role in the corrosion resistance.

The corrosion characteristics and mechanism of directionally solidified Mg-3Zn-xCa alloys

An investigation into the corrosion characteristics and mechanism of directionally solidified(DSed) Mg-3Zn-xCa(x = 0, 0.2, 0.5,0.8 wt.%) alloys in 0.9 wt.% Na Cl solution is presented. The DSed microstructure consists of columnar dendrites and eutectics distributed in the interdendritic region. The primary dendritic arm spacing(PDAS) and the volume fraction(fv) of the secondary phases are under the significant impact of the content of Ca. The corrosion rates evaluated using electrochemical measurements and immersion tests are accelerated monotonously with the increase of Ca content in DSed alloys. The corrosion resistance of the DSed alloys is significantly affected by the corrosion products film(CPF) and the secondary phases. The corrosion products of DSed Mg-3Zn alloy contain Mg(OH)_(2) and ZnO. The existence of ZnO greatly enhances the corrosion resistance of DSed Mg-3Zn alloy. As for the DSed alloys containing Ca content, a relatively protective CPF without deep pits can form on the surface of DSed Mg-3Zn-0.2Ca specimen during the corrosion. The f_(v)of the secondary phases dominates the corrosion rate of the DSed Mg-Zn-Ca alloys. The corrosion of DSed Mg-3Zn-xCa alloys initiates as a result of microgalvanic coupling between the cathodes of secondary phases and α-Mg matrix anode. Then, the corrosion gradually extends longitudinally with the breakdown of CPF.

Superior corrosion resistance and corrosion mechanism of dual-main-phase (Ce_(15)Nd_(85))_(30)Fe_(bal)B_(1)M magnets in different solutions

The electrochemical corrosion behavior of both (Ce_(15)Nd_(85))_(30)Fe_(bal)B_(1)M sintered magnets prepared with dual-main-phase method and N45-type magnets was studied in 3.5 wt% NaCl,1.1 wt% NaH_(2)PO_(4),and 2.5 wt% NaOH solutions,respectively.The (Ce_(15)Nd_(85))_(30)Fe_(bal)B_(1)M sintered magnets perform superior corrosion resistance than N45-type magnets in the tested solutions.In general,two kinds of magnets exhibit the best corrosion resistance property in 2.5 wt% NaOH solution,while the worst in 3.5 wt% NaCl solution.Microstructures of samples before and after corrosion were investigated.With the addition of Ce by means of dual-main-phase method,which is conducive to facilitating low-temperature sintering and grain refinement,uniform grain size and(Nd,Ce)-rich phase distribution form,give rise to narrow and thin corrosion channels.Moreover,the corrosion rate of the(Nd,Ce)-rich phase is lower than that of Nd-rich one.Acco rdingly,corro sion re sistance of (Ce_(15)Nd_(85))_(30)Fe_(bal)B_(1)M sintered magnet is superior when compared with the commercial N45-type magnet which has comparable magnetic properties.

Corrosion mechanism of ceramic glaze from the Yangtze EstuaryⅡ

Ancient lead-glazed ceramics frequently corrode physically,chemically,and biologically when buried in soil,submerged in water,or exposed to air.In comparison to the other two environments,relatively little research has been conducted on how leadglazed ceramics deteriorate in the water environment.Four lead-glazed ceramic samples from the Yangtze EstuaryⅡwere examined for their micromorphology and structural composition using scanning electron microscopy-energy spectrum analysis,micro-area X-ray diffraction analysis,fluorescence microanalysis,and Fourier infrared spectroscopy analysis.The results demonstrate the formation of deposits of PbCO_(3),Pb(OH)Cl,and Cu FeS_(2)and corrosion pits and fractures on the glaze layer surfaces.According to the corrosion phenomenon,the lead glaze layers of ceramics mainly underwent chemical and microbial corrosion in water,and the corrosion process of the lead glaze was expounded and modeled.The research results deepen the understanding of the corrosion mechanism of lead-glazed ceramics,which is of great significance for the study of the conservation of lead-glazed ceramics and other types of ceramic relics and can also provide a reference for the long-term preservation of contemporary silicate products.

New Problems of Boiler Corrosion after Coupling Combustion of Coal and Biomass and Anti-Corrosion Technologies

This study explores the corrosion issues arising from the coupled combustion of coal and biomass and proposes potential solutions.Biomass,as a renewable energy source,offers advantages in energy-saving and carbon reduction.However,the corrosive effects of alkali metal compounds,sulfur(S)and chlorine(Cl)elements in the ash after combustion cannot be underestimated due to the high volatile content of biomass fuels.We investigate the corrosion mechanisms,as well as the transfer of Cl and alkali metal elements during this process.Comparative corrosion analyses are conducted among coal-fired boilers,pure biomass boilers and boilers with coupled combustion.Various biomass types in co-firing are studied to understand different corrosion outcomes.The main factors influencing corrosion include the physicochemical properties of biomass feedstock,furnace temperature and heating surface materials,with the chemical composition and ash content of biomass playing a dominant role.Currently,the methods used for anti-corrosion include water washing pretreatment of biomass feedstock,application of novel alloys and coatings and the development of additives to inhibit fouling,ash deposition and corrosion.Efficient inhibitors are economical and easy to produce.Additionally,biomass can be converted into biomass gasification gas,although challenges related to tar still need to be addressed.

Experimental Study on Corrosion of Stainless Steel in Low Temperature Multi effect Seawater Desalination

Starting from the corrosion mechanism,this paper analyzes the characteristics of various types of stainless steel and selects the best performance composite plate composite plate stainless steel.Analyze and select the most suitable corrosion detection method based on specific practical multi working conditions,discuss the interference factors that affect metal corrosion during experimental simulation,and the advantages of newly developed sheet metal.The new development of composite board panels,with the substrate and composite materials applying their respective capabilities for MED,will bring breakthrough progress to the scientific research and engineering applica-tion of composite boards.

Effect of extrusion on corrosion behavior and corrosion mechanism of Mg-Y alloy

The influences of the hot extrusion process on the microstructure, corrosion behavior and corrosion mechanism for Mg-Y magnesium alloy were studied by means of the microstructure observation, weight loss test, electrochemical test and corrosion morphology test. The results showed that with increasing of the extrusion ratio, the shear flow line on the vertical section of the extruded alloy increased, the shear bands parallel lines became more clearly visible, and a large number of fine equiaxed grains distributed in parallel with the flow lines. The open circuit potential had a certain degree of improvement after extrusion, the open circuit potential increased with increment of extrusion ratio, and the corrosion potential of the vertical section was higher than that of the same alloy in the same compression ratio. The shift rate of the corrosion potential relatively became larger with increasing of the extrusion ratio, and the cathode corrosion current corresponding to the branch migration shifted to the positive direction. The high frequency capacitive arc increased with increment of the extrusion ratio, and the radius of capacitive arc of the vertical section was slightly larger than that of the transverse section. The corrosion morphologies of Mg-0.25 Y alloy were uniform corrosion, and the corrosion morphologies of Mg-（2.5, 5, 8 and 15） were the pitting corrosion and the small range, deep depth localized corrosion.

Corrosion behaviors and mechanism of electroless Ni-Cu-P/n-TiN composite coating

In the present investigation, electroless Ni-Cu-P/n-TiN composite coating was prepared using alkaline citrate-based bath. X-ray diffraction （XRD）, scanning electron microscopy（SEM）, energy-dispersive spectroscopy（EDS）, electrochemical measurements, weight loss tests and Raman spectrometer were used to character the properties of the coating. As the Cu content increased from 7.3 wt% to 24.8 wt%, the corrosion current density of the Ni-Cu-P/n-TiN coating decreased from 10.80 to 4.34 ~tA. And the inclusion of Cu in NiP alloy resulted in refinement and less porosity in microstructure. The addition of TiN resulted in a slight decline in anti-corrosion property of the coating. As the mass loss test showed, Ni-24.8%Cu-P exhibited perfect corrosion resistance. Studies by Raman spectroscopy on coatings proved that Cu（II）3（PO4）（OH）3, Cu（OH）2 and CuO were examined while no compound of nickel was found, and Cu exhibited preferred corrosion in saline solution, providing cathodic protection to Ni alloy.

Corrosion behavior and mechanism of the automotive hot-dip galvanized steel with alkaline mud adhesion

The corrosion behavior and mechanism of hot-dip galvanized steel and interstitial-free （IF） substrate with alkaline mud adhesion were investigated by scanning electron microscopy （SEM）, X-ray diffraction （XRD）, electrochemical impedance spectroscopy （EIS）, and linear polarization. The results show that non-uniform corrosion occurs on the galvanized steel and IF substrate during 250 h with the mud adhesion. The corrosion products on the galvanized steel are very loose and porous, which are mainly ZnO, Zn5（OH）8C12·H2O and Zn（OH）2, and Fe-Zn alloy layer with a lower corrosion rate is exposed on the galvanized steel surface; however, the corrosion products on IF substrate are considerably harder and denser, whose compositions of rust are mainly FeOOH and Fe3O4, and several pits appear on their surface. The results of continuous EIS and linear polarization measurements exhibit a corrosion mechanism, that is, under activation control, the charge transfer resistances present different tendencies between the galvanized steel and IF substrate; in addition, the evolution of linear polarization resistances is similar to that of charge transfer resistances. The higher contents of dissolved oxygen and Cl^- ions in the mud play an important role in accelerating the corrosion.

Mechanism of liquid zinc corrosion on metals

Two kinds of materials, soluble and insoluble in liquid zinc, such as Fe and FeB, are separately dealt with.A new theory is presented for insoluble materials. Based on the theory, the surface defects of insoluble materials are themain reason that the matcrials are correded.

Study of corrosion mechanism of dawsonite led by CO_(2)partial pressure

The stability of dawsonite is an important factor affecting the feasibility evaluation of CO_(2)geological storage.In this paper,a series of experiments on the interaction of CO_(2)-water-dawsonite-bearing sandstone were carried out under different CO_(2)pressures.Considering the dissolution morphology and element composition of dawsonite after the experiment and the fluid evolution in equilibrium with dawsonite,the corrosion mechanism of dawsonite led by CO_(2)partial pressure was discussed.The CO_(2)fugacity of the vapor phase in the system was calculated using the Peng-Robinson equation of state combined with the van der Waals 1-fluid mixing rule.The experimental results indicated that the thermodynamic stability of dawsonite increased with the increase of CO_(2)partial pressure and decreased with the increase of temperature.The temperature at which dawsonite dissolution occurred was higher at higher f_(CO_(2)).There were two different ways to reduce dawsonite’s stability:the transformation of constituent elements and crystal structure damage.Dawsonite undergoes component element transformation and crystal structure damage under different CO_(2)pressures with certain temperature limits.Based on the comparison of the corrosion temperature of dawsonite,three corrosion evolution models of dawsonite under low,medium,and high CO_(2)pressures were summarized.Under conditions of medium and low CO_(2)pressure,as the temperature continued to increase and exceeded its stability limit,the dawsonite crystal structure was corroded first.Then the constituent elements of dawsonite dissolved,and the transformation of dawsonite to gibbsite began.At high CO_(2)pressure,the constituent elements of dawsonite dissolved first with the increase of temperature,forming gibbsite,followed by the corrosion of crystalline structure.

The Mechanism and Influencing Factors of Corrosion in a Gas Heating-Furnace

Natural gas should be heated and throttled for the purpose of purification and transportation at the first gas production factory of the Changqing field. The safe use and heat-transfer efficiency of a heating-furnace affect the safe and smooth production of natural gas directly. At gas collecting stations now, no measures of anticorrosion have been adopted in heating furnaces which erode and scale badly. In order to solve the corrosive problem of heating-furnaces, prolong operating life of heating-furnaces, assure safe and smooth production of natural gas, the mechanism and influencing factors of corrosion of the heating-furnace were analyzed and some corresponding measures were brought forward based on a field investigation of usage behavior and present operational status of heating-furnaces at the first gas production factory. The results show that the corrosive ion and soluble CO2 and O2 in water erode metal badly at the condition of being heated. Corrosion of a heating-furnace are mostly oxygen corrosion, corrosive ion corrosion, acid corrosion, iron encrustation corrosion, dry and wet interface corrosion, caustic corrosion, etc; The influencing factors of corrosion mainly include soluble O2 and CO2 in water, pH value, heat loading, corrosive ion, soluble solid （salinity） and non-flowing character of water, etc.