Corrosion Morphology Research Articles

Atmospheric Corrosion Behavior of Ni-advanced Weathering Steels in High-chloride Environment: Effect of Ni on Corrosion Morphology

Atmospheric Corrosion Behavior of Ni-advanced Weathering Steels in High-chloride Environment: Effect of Ni on Corrosion Morphology

Effect of the Sodium Silicate Inhibitor on the Corrosion Protection of AZ31 Magnesium Alloy

The effect of the sodium silicate inhibitor on the corrosion protection of the AZ31 magnesium alloy at room temperature was investigated. The results of electrochemical measurement and weight loss experiments showed that incorporating the sodium silicate significantly enhanced the anti-corrosion property of the AZ31 alloy. When the alloy was immersed in the corrosive solution with the 0.1 M sodium silicate, the corrosion rate of the AZ31 alloy declined to 0.014 mm·y−1, and the inhibition efficiency reached 99.1%. The observation of the corrosion morphology indicated that the magnesium silicate precipitated to cover the corroded area with a thickness of 105 μm, while the silicate ion adsorbed on the uncorroded area. The calculation results of the adsorption energy based on the molecular dynamics indicated that the physical adsorption occurred when the samples were immersed in a sodium silicate solution. Combined with the schematic diagram, the protective mechanism of the adsorption and precipitation after the addition of the sodium silicate inhibitor was investigated.

Localized corrosion behavior on a heterogeneous surface involving multicomponent reactive transport and morphology evolution

AbstractLocalized corrosion sometimes brings about unanticipated and catastrophic damages in petrochemical pipelines and pressure vessels. For localized corrosion modeling, multicomponent reactive transport and corrosion morphology evolution are two arduous problems that involve multi–physical‐(electro) chemical processes along with multi–temporal and spatial scales. In this study, the lattice Boltzmann method (LBM) is employed to shed some light on the evolution of localized corrosion on a heterogeneous surface focusing on the effects of electrolyte ohmic resistance and diffusion. The corrosion pit is always initiated at the junction of anode and cathode sites; however, quite different morphologies are prompted under ohmic control or ohmic‐diffusion control. Under ohmic control, the pit propagates along the interface of the anode and cathode. Under ohmic‐diffusion control, the pathway of reactive species is broadened, and the corrosion morphology is developed into a more regular shape, like a flattened semicircle in 2‐D modeling. This work presents the huge potential of LBM in long‐term corrosion modeling.

Variation of Corrosion Characteristics and Tensile Performances of WE43 Alloy Under Marine Atmospheric Environment.

This study aims to examine the variation in corrosion characteristics and tensile properties of WE43 magnesium alloy in an actual marine atmospheric environment by means of outdoor exposure tests. The macroscopic corrosion morphology, microstructure, and tensile properties were analyzed. The results indicated that WE43 alloy will corrode rapidly during exposure under marine atmospheric environmental conditions, resulting in a loose and porous Mg(OH)2 layer on the surface. The Mg matrix was mainly consumed as an anode, leading to the occurrence of corrosion pits. With the increase in exposure time, both the tensile strength and plasticity of WE43 alloy gradually deteriorated. After exposure for six months, the elongation and area reduction were significantly reduced, with a reduction ratio of more than 50%. After 18 months of exposure, the ultimate strength of the alloy decreased from 359 MPa to 300 MPa. According to an analysis of fractures in the alloy, the corrosion pits on the sample surface were the main reason for the decrease in tensile properties.

Insights into the role of the Cr and rare element in improving the corrosion resistance of HRB400 rebars in simulated SO2-polluted marine environment

The present work aims to offer insights into the role of Cr and rare element (RE) in improving the corrosion resistance of HRB400 rebar in simulated concrete pore solution (SCPS) containing NaCl and NaHSO3. Electrochemical tests reveal that the increased SO2 concentration reduces the pitting potential and charge transfer resistance. However, the addition of Cr/RE significantly lowers the corrosion current density of HRB400, as confirmed by the corrosion morphology observed after immersion tests. Quantitative analysis of corrosion pits shows that SO2-induced corrosion tends to develop longitudinally, a tendency mitigated by the Cr/RE alloyed rebar. X-ray photoelectron spectroscopy (XPS) results confirm the presence of Cr and RE oxides in the oxide film and demonstrate that SO2 affects the Fe(II)/Fe(III) ratio. Cr and RE doping not only refines the microstructure and modifies inclusions but also enhances the protective properties of the oxide film on the rebar. Therefore, the combination of Cr and RE improves the durability of rebars in SO2-polluted marine environments.

Carbon dot aggregates: a new strategy to promote corrosion inhibition performance of carbon dots

The corrosion of metal not only produces serious economic losses and environmental pollution but also threatens equipment safety. Carbon dots (CDs) exhibit outstanding inhibition properties to availably retard the corrosion of metal. However, the present CDs-based corrosion inhibitors still fail to fully exert the environmentally friendly and low-cost merits of CDs. To address this issue, CD aggregates (CDAs) prepared by low-cost and eco-friendly CDs are developed as novel corrosion inhibitors for the first time, and their corrosion inhibition mechanism is disclosed. Specifically, CDAs with excellent long-term dispersion stability are synthesized by solvothermal treatment of CDs formed by citric acid and urea. CDAs at only 200 mg/L provide a corrosion inhibition effect of 90.38% for Q235 carbon steel in 1 mol/L HCl solution, approximately 1.53 times higher than that of CDs (59.21%). Moreover, the corrosion inhibition mechanism of CDAs is proposed through the analysis of adsorption isotherm, examination of corrosion morphologies, and theoretical calculations. That is, CDAs physically and chemically adsorb on the carbon steel surface, mainly hindering its anodic reaction, thus retarding the corrosion of carbon steel. This research firstly verifies the corrosion inhibition potential of green and low-cost CDAs and provides a novel strategy to promote the corrosion inhibition performance of CDs, promoting the progress of aggregate-based corrosion inhibitors.

High-Resolution In Situ Ultrasonic Imaging Platform for Studying Localized Corrosion Morphology

High-Resolution In Situ Ultrasonic Imaging Platform for Studying Localized Corrosion Morphology

Study on Corrosion Damage Behavior of 300M Ultra-high Strength Steel in Marine Atmospheric Environment

Abstract The marine atmospheric environment exposure test of 300M ultra-high strength steel was carried out at Hainan test station. The corrosion damage behavior of 300M ultra-high strength steel in marine atmospheric environment was studied by macroscopic and microscopic corrosion morphology, tensile properties and stress corrosion. The results show that the comprehensive corrosion behavior of 300M ultra-high strength steel occurred in the marine atmospheric environment. The color of the corrosion products changed from red to reddish brown, dark brown and black, and the maximum corrosion depth in the three years was 400μm. The corrosion had a significant effect on the tensile properties during the test. The tensile strength and elongation of 300M ultra-high strength steel decreased by 13.3 % and 81.8 %, respectively, which indicated that the effect of corrosion on the plasticity of the material was much greater than that on the tensile strength. Corrosion also caused a decrease in fracture toughness, and the fracture toughness of 300M ultra-high strength steel decreased by 26% in 2 years. The results of stress corrosion show that the crack propagation of 300M ultra-high strength steel is very rapid in the initial stage of marine atmospheric environment test, and the crack propagation length reaches 10.836mm in 7 days. The stress corrosion threshold KISCC of 300M ultra-high strength steel is 24.48MPa•m1/2, and the relative index of stress corrosion cracking sensitivity is 0.31, which indicates that 300M ultra-high strength steel is very sensitive to stress corrosion in marine atmospheric environment. The results show that 300M ultra-high strength steel has poor adaptability to the marine environment. Therefore, it is necessary to adopt excellent surface treatment process and spray aging resistant coating to effectively protect 300M ultra-high strength steel to ensure its long-term reliable use in the marine environment.

Phase, Microstructure and Corrosion Behaviour of Al0.3FeCoNiCrx High-Entropy Alloys via Cr Addition.

The microstructure evolution of Al0.3FeCoNiCrx (x = 0, 0.3, 0.5, 1, 1.5) high-entropy alloys (HEAs) were studied using X-Ray diffraction technique and scanning electron microscope equipped with energy dispersive spectrometer. The short-term and long-term corrosion behaviours of these alloys in 3.5 wt.% NaCl solution were studied by electrochemical impedance spectroscopy, potentiodynamic polarisation measurement, immersion test and corrosion morphology analysis. The results show that all the designed HEAs present single-phase FCC structure, and the increase in Cr content changes the microstructural morphology from cellular to a typical dendritic-interdendritic state. Without the influence of phase transformation, the corrosion resistance of Al0.3FeCoNiCrx HEAs gradually increases with the increase in Cr content. Our designed alloys exhibit excellent corrosion resistance compared to the existing HEAs in the AlFeCoNiCr composition system.

Rapid α-Al2O3 Growth on an Iron Aluminide Coating at 600 °C in the Presence of O2, H2O, and KCl.

In this work, a slurry iron aluminide-coated ferritic steel SVM12 was subjected to a laboratory experiment mimicking superheater corrosion in a biomass-fired power boiler. The samples were exposed under model Cl-rich biomass conditions, in a KCl + O2 + H2O environment at 600 °C for 168, 2000, and 8000 h. The morphology of corrosion and the composition of the oxide scale and the coating were investigated by a combination of advanced analytical techniques such as FESEM/EDS, SEM/EBSD, and XRD. Even after short-term exposure, the coating developed a very fast-growing and up to 50 μm thick α-Al2O3 scale in contrast to the spontaneous formation of a protective, thin, dense, slow-growing, and very adhesive α-Al2O3 layer usually formed on metallic materials after high-temperature oxidation. In view of the literature on the formation of oxide scales on alloys and coatings, the formation of an α-Al2O3 scale at this relatively low temperature is very surprising in itself. The thick alumina scale was not protective as its formation resulted in fast degradation of the coating and rapid Fe2Al5 → FeAl phase transformation, which in turn generated porosity inside the coating. In all cases, the resulting thick Al2O3 scale was porous and consisted of both equiaxed α-Al2O3 grains and randomly oriented aggregated alumina whiskers. Potassium is concentrated in the outer part of the Al2O3 scale, while chlorine is concentrated close to the scale/aluminide interface. The unexpected formation of rapidly growing α-Al2O3 at relatively low temperature is attributed to the hydrolysis of aluminum chloride generated in the corrosion process.

Effect of quenching protocols on microstructure and corrosion morphology in a recycled Al–Mg–Si alloy: Tracing Cu impurities

In the present work, three different quenching protocols - water quenching (WQ), forced air quenching (FAQ) and air quenching (AQ) - were utilized to tailor the intragranular and intergranular preference of Cu impurities in a recycled AA6082 alloy. It is found that Cu tends to be incorporate in the precipitates at grain boundaries in the WQ-treated alloys. However, both AQ and FAQ protocols interestingly eliminate such intergranular Cu enrichment, consequently sequestering Cu solutes in (Mg, Si)-rich precipitates in grain interiors. As the quenching rates decrease, the FAQ- and AQ-treated alloys resultantly exhibit a positive shift in pitting potential, which is accompanied by a transition in corrosion morphology from boundary attack to pitting, with a notable reduction in corrosion depth.

Microstructure of ternary Sn-Bi-xCu alloy on mechanical properties, current endurance and corrosion morphology via cycling corrosion test

Low melting temperature of Sn-58 wt.% Bi (SB) solders adding 0.5wt.% Cu (SB05C) and 1.7wt.% Cu (SB17C) concentrations were evaluated for the signal transmission in the 3D IC package. Microstructure combined with phase analysis and Pandat simulation were together with to explain the relationship among the mechanical property, electrical endurance and corrosion resistance. By Cu decoration, the presence Cu6Sn5 intermetallic compound (IMC) acts as heterogeneous nucleation sites to reduce surface free energy and generate fine Bi grain that resulted in higher hardness value. The power-law was used to explain the mechanism of interfacial IMC growth, both Cu6Sn5 and Cu3Sn formation were speculated to be volume diffusion control and surface reaction domination, respectively. The fracture morphology by shear testing indicates that earliest plastic deformation accompanied with brittle rupture were major factors due to the intergranular fracture and Cu6Sn5 compound induced bulk fracture. By cycling corrosion test (CCT), the lump shape of SnO2 by-product was found among solders at three cycling. After seven cycling, Sn phase has been completely corroded and Cu6Sn5 IMC began to be corroded forming circle shape of Cu2O but Bi phase still not be corroded among solders. In the electrical endurance, dense Cu6Sn5 dispersed in solder bulk and fine grain size were feasible to induce current crowding and joule heating, thus Cu deteriorated SB solders is easily failed.

Effect of ultrasonic impact treatment on surface residual stress, microstructure and electrochemical properties of the hot-rolled S355 steel

The effects of ultrasonic impact treatment (UIT) on the microstructure, corrosion resistance, and surface residual stress of hot-rolled S355 steel were investigated. In addition, the improving mechanism of the UIT induced corrosion resistance was discussed. The results show that the UIT can effectively improve the corrosion resistance of hot-rolled S355 steel, and corrosion current density reduction is demonstrated. Based on the corrosion morphology, it can be found that after the UIT the corrosion pits became shallower, the oxide layer becomes denser, and more flocculent structures appear on the surface as well as the appearance of dense irregular curved structures. Moreover, the residual tensile stress on the surface of the hot-rolled S355 steel is transformed into residual compressive stress after the UIT. The grains are refined, and the microhardness is increased, which implied that the significant plastic deformation has occurred on the surface of the hot-rolled S355 steel. The findings confirm that dense oxides could be generated on the surface of hot-rolled S355 steel treated by ultrasonic impact since the residual compressive stress is introduced, the plastic deformation is induced, and the grains are refined.

Microstructure and corrosion properties of CrMnFeCoNi high entropy alloy coating by temperature field-assisted laser cladding

The CrMnFeCoNi high entropy alloy coatings were prepared on the surface of Q345 steel using a temperature field-assisted laser cladding process, and the effects of the applied temperature field on the cladding coatings were studied. The microstructures and corrosion morphologies of the coatings were observed, and the elemental distribution, hardness, effective elastic modulus, electrochemical corrosion performance, and corrosion products of different coatings were analyzed. The results show that the porosity of the HEA coatings prepared with a temperature field is reduced to below 50 % of the initial level. The microstructure of the coating changed, with the nanoindentation hardness of the coating increasing by up to 0.55 GPa, enhancing the mechanical properties. Among all the coatings, the coating prepared at 250 °C temperature field exhibited the best corrosion resistance, with corrosion potential and current density of −0.27 V and 0.15 μA/cm2, respectively, improving the corrosion potential by 0.1 V and reducing the current density by 1.08 μA/cm2 compared to the sample prepared at room temperature. After incorporating the temperature field, the stability of the passive film on the coating during corrosion improved, and the nucleation rate of pitting decreased. Therefore, incorporating an appropriate temperature field during laser cladding can effectively enhance the overall performance of the CrMnFeCoNi HEA coating.

Influence of arc energy on the microstructure and corrosion behavior of ER2209 duplex stainless steel deposited on Q345B low-alloy steel by GMAW

In order to eliminate the complex effects of thermal cycling and the thermal effects of the next pass on multi-layer multi-pass welding of low-alloy steel and duplex stainless steel, ER2209 welding wire was single-layer single-pass deposited on the surface of Q345B hot-rolled plate by gas metal arc welding (GMAW). The microstructure and corrosion resistance of welded joints were studied by different arc energies. The results showed that the arc energy had a significant impact on the “tongue-shaped” morphology and the width of heat affect zone in the welded joint, which in turn affected the corrosion performance of the welded joints. Due to the least distribution of “tongue-shaped” morphology and minimum width of heat affected zone in the welded joint with arc energy of 0.645kJ/mm, it owned the best corrosion resistance. The weld metals of the welded joints were composed of ferrite and austenite phases. The ferrite phases were distributed along grain boundaries and intergranular. As the heat input increases, the distribution of ferrite phase along grain boundaries gradually decreased. The corrosion products and corrosion morphology of the welded joint were also investigated and the corrosion mechanism was discussed in detail. The research results of this article provide a theoretical basis for improving the corrosion performance of multi-layer multi-pass welded joints of low-alloy and duplex stainless dissimilar steels.

Investigation of the microstructural characteristics of laser-cladded Ti6Al4V titanium alloy and its corrosion behavior in simulated body fluid

Laser cladding technology has a wide range of potential industrial applications in the surface strengthening, repair and reuse of orthopedic implants. By employing this technique to conduct same-material surface restoration and enhancement on titanium alloys, it demonstrates significant developmental potential. However, the microstructure of laser additively manufactured titanium alloy differs significantly from that of traditional titanium alloys, which affects its corrosion resistance in human body fluids. To compare the corrosion resistance differences between the cladding layer and the substrate, this study investigates the microstructure of multi-pass laser cladding Ti6Al4V (TC4) titanium alloy and analyzes the corrosion morphology and corrosion products of the cladding layer in simulated body fluids (SBF). By comparing the electrochemical corrosion behavior of laser cladding with that of traditionally manufactured TC4, this research reveals the differences in corrosion resistance between the two titanium alloys. The research demonstrates that the microstructure of cladding primarily consists of prior-β grains and continuous grain boundary α phase, along with a complex basketweave structure composed of fine acicular α phase and lamellar α phase. Additionally, due to the complex thermal cycling process, the acicular α' colonies within the prior-β grains. These features enhance the cladding layer’s resistance to plastic deformation and increase microhardness, though with some uneven distribution. Interestingly, the TC4 cladding layer forms a porous passivation layer after corrosion, primarily composed of a TiO2 passivation film and deposits of hydroxyapatite and other phosphates. Due to the lower β-phase content, finer grains with higher energy states, and a greater proportion of high-angle grain boundaries (HAGBs) in the cladding layer, it exhibits higher electrochemical activity. As a result of these microstructural differences, the corrosion resistance of the TC4 cladding layer in SBF is inferior to that of TC4 manufactured using traditional techniques.

Insight into the effect of oxygen content on the corrosion behavior of X70 pipeline steel in a typical simulated soil solution by dissolution-diffusion-deposition model

In this work, traditional experimental methods were employed to investigate the effect of dissolved oxygen (DO) on the corrosion behavior of X70 pipeline steel in a low-temperature acidic-bentonite simulation soil solution. A novel model was utilized to describe the complex dissolution-diffusion-deposition process at the metal/solution interface. This model aims to enhance comprehension of the dynamics of the corrosion product layer of X70 pipeline steel under varying oxygen concentrations, as well as the effects of alloying elements (Fe, Cr and Cu) on the corrosion resistance. By integrating traditional experimental methods with calculation models, the results reveal a positive correlation between DO levels and the corrosion rate X70 pipeline steel. This relationship is attributed to the distinct characteristics of the corrosion product layers formed under different DO conditions. At low DO levels, the nucleation and growth rates of oxide/hydroxide are slower, leading to the formation of a denser, more protective corrosion product layer. Conversely, at high DO levels, the accelerated nucleation and growth rates produce larger oxide/hydroxide particles, resulting in a porous and less protective corrosion product layer. Furthermore, the variation in the protective qualities of the corrosion product layers under different DO conditions causes differences in corrosion morphology: X70 pipeline steel exhibits localized corrosion in low DO environments and more uniform corrosion under high DO conditions.

Microstructure and corrosion characteristics of AA5083 alloy weld beads produced by GTAW and SpinArc-GMAW

In this study, bead-on-plate welding was performed on a sheet of AA5083 alloy using two distinct welding techniques: gas tungsten arc welding (GTAW) and SpinArc-gas metal arc welding (SA-GMAW). This study compares the microstructural, mechanical, and corrosion characteristics of processed weld beads. The microstructural features of the weld beads were characterized using optical microscope (OM), scanning electron microscope (SEM) and high-resolution transmission electron microscope (HR-TEM). The corrosion characteristics of weld beads were determined by potentiodynamic polarization method, and the corrosion morphology of the specimens were observed under SEM. In addition, a microhardness study was performed on the weld beads across the base metal (BM), heat affected zone (HAZ), and fusion zone (FZ). The findings indicate that the weld bead produced by GTAW exhibited superior corrosion resistance compared to the weld bead processed by SA-GMAW. The presence of porosities in the latter facilitated the corrosive medium to penetrate and break the passive layer easily that developed deeper corrosive pits. The presence of Fe and Mn rich intermetallics in FZ of GTAW processed weld bead assisted in better rate of corrosion observed at 0.1259 mm/yr. The hardness observed in the FZ of the SA-GMAW bead was found to be lower compared to the GTAW weld bead due to the presence of porosities and coarser grains.

Investigation of Factors Affecting Corrosion Mechanisms in Latent Heat Thermal Energy Storage Systems

Concentrated Solar Power (CSP) plants integrated with Latent Heat Thermal Energy Storage (LHTES) systems offer a promising solution for dispatchability, reliability, and economic concerns generally associated with renewable energy technologies. These systems, however, require an operational life of up to 30 years to compete with power plant systems operating on fossil fuels. This is a significant challenge due to the high temperatures and corrosive eutectic salts utilised in LHTES systems. Additionally, these systems and its subcomponents are expected to be under varying degrees of stress due to the diurnal cyclic temperature variations inherent in the plant’s operational cycle. Hence, it is crucial to understand the various factors that can affect the operational life of materials used in such applications and conduct thorough material compatibility studies to assess the combined impact of these operating conditions on corrosion mechanisms. This study presents a novel static immersion test approach using modified Compact Tension (CT) specimens manufactured from 316L to investigate the effects of Na2CO3:NaCl (59.45:40.55 wt.%) salt, elevated temperatures (700 ℃ for up to 1000 hours), and stress on corrosion induced in the alloy. The post-exposure results are characterised with Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) shows that corrosion mechanisms are significantly affected by factors such as high operating temperatures leading to changes in both corrosion morphology and rate, high stresses causing localised preferential corrosion, as well as corrosive salt and oxygen availability affecting the type of corrosion induced.

Chloride corrosion resistance of wet joints in manufactured sand reinforced concrete prepared in plateau environment

The durability of three types of wet joints in manufactured sand concrete prepared in simulated plateau environment was investigated. And the accelerated corrosion test on specimens in the chloride salt solution and the static tensile test on corroded steel bars in specimens were carried out by sequence. The durability of different types of specimens prepared in plateau environment was compared by analyzing the development of concrete cracks, the corrosion morphologies of internal steel bars, the degradation of mechanical properties of steel bars, and the concrete microstructure. The results demonstrate that the development of concrete cracks and the distribution of crack width are affected by wet joint. The nonlinearity of variation of average crack width with actual corrosion rate is enhanced by wet joint. The strength and elongation of steel bars in concrete decrease evidently by wet joint. The strength and elongation loss of steel bars after corrosion is effectively reduced by the punched treatment on joint interface. There is no clear superiority or inferiority pattern for the durability of wet joint specimens with untreated interface (UI) and chiseled interface (CI), and the durability of wet joint specimen with punched interface (PI) is better than that of UI and CI specimens.