Corrosion Grooves Research Articles

Defending against fluorine corrosion: Insights from FeCoNiCrMo high-entropy alloy behavior in hydrofluoric acid solutions

The surging demand for advanced fluorine corrosion-resistant materials underscores their significance in ensuring operational safety and reliability across various industries. This study investigates the corrosion behavior of the FeCoNiCrMo high-entropy alloy (HEA) via a series of 28-day immersion tests in hydrofluoric acid (HF) solutions. The results demonstrate the FeCoNiCrMo HEA's superior corrosion-resistant performance in HF environments, exhibiting remarkably low corrosion rates of 0.179 mm/y, 0.276 mm/y, and 0.352 mm/y in 20 vol%, 30 vol%, and 40 vol% HF solutions, respectively. Comprehensive phase and microstructural characterizations were conducted on samples exposed to the 40 vol% HF solution to elucidate the corrosion mechanisms. The study revealed that localized pitting corrosion preferentially initiates within the interdendritic regions of the HEA matrix upon HF exposure. During the intermediate stage, micro-galvanic corrosion occurs between the dendritic arms and interdendritic regions, leading to the formation of a uniform and compact corrosion product film on the alloy surface. This film, enriched with Mo, Cr, and O, provides temporary protection. However, as corrosion progresses, the partial detachment of particulate corrosion products compromises the integrity of the film, resulting in increased dissolution within the interdendritic regions and the formation of irregular corrosion grooves in the later stage. These insights significantly enhance the understanding of the corrosion mechanisms of FeCoNiCrMo HEA in HF environments and provide valuable guidance for developing innovative protective materials designed for fluorine-rich engineering applications.

Effect of Boron on Stress Corrosion Resistance of S31254 Super‐Austenitic Stainless Steel After Cold Deformation

The effect of boron (B) on stress corrosion resistance of S31254 in the presence of residual stresses has been studied. The microstructure and corrosion resistance of S31254 containing B at different levels of cold deformation are analyzed in this study. In the results, it is shown that B favors the improvement of deformation uniformity of S31254. The grain boundary (GB) and slip bands have better corrosion resistance at 5% deformation, and the overall corrosion resistance is better than that of the undeformed state, with smaller passivation current density and narrower width of GB corrosion grooves, especially for the 40B samples. At 30% deformation, the overall corrosion resistance of 40B S31254 is better than 0B due to improved deformation uniformity.

Effect of Heat Treatments on the Corrosion Resistance of a High Strength Mg-Gd-Y-Zn-Zr Alloy.

Magnesium-rare earth (Mg-Re) alloys are very promising structural materials in lightweight industries, while the poor corrosion resistance limits their widespread application. In this work, to provide insights into the functions of precipitate characteristics on the corrosion behaviors of Mg-Re alloys, the influence of heat treatments on the corrosion behavior of Mg-11.46Gd-4.08Y-2.09Zn-0.56Zr alloy was investigated via an immersion test, electrochemical experiment and scanning electron microscope (SEM). The results showed that the corrosion rate of Mg-11.46Gd-4.08Y-2.09Zn-0.56Zr alloy specimens decreased by 17.58% and 20.44% after T5 and T6 heat treatment, respectively. In the heat-treated specimens, the corrosion did not extend further into the matrix but formed fine corrosion grooves along the extrusion direction. The improved homogeneity reduced the residual stress and the β’ precipitate introduced as a corrosion barrier after T5 and T6 heat treatment reduced the corrosion rate of the studied Mg alloy. In addition, the volume fraction of the long-period stacking-ordered (LPSO) phase decreased after heat treatment, which effectively reduced galvanic corrosion and enhanced the protective effect on the Mg matrix.

Susceptibility to intergranular corrosion in sensitized austenitic stainless steel characterized via crystallographic characteristics of grain boundaries

Failures caused by intergranular corrosion have often occurred in structures made of stainless steels, and it is necessary to establish a technique to evaluate the susceptibility to such corrosion. This study investigated the crystallographic characteristics of grain boundaries to evaluate the susceptibility. To measure the characteristics, microscopic analyses were performed by the techniques of electron backscattered diffraction and thermal etching with geometric measurements. Then, oxalic acid etching was conducted. The corrosion grooves became larger with increasing grain boundary energy, and as a result, it was found that the energy was the only variable able to characterize the susceptibility.

Comparative Research on Fatigue Performance of High-Strength Bainitic Steel with or without Corrosion

High-strength bainitic steels have acquired a promising place among steels due to their wide applications in engineering structures. It is, therefore, worthwhile to investigate their fatigue performance in different environments. When fatigue is atmospheric, lattice strength of weaker zones including granular bainite, phase boundary and MA constituents determines the nucleation life of fatigue. The deflected microstructural short cracks enhance the early propagation life of fatigue. In lath bainite, fine ferrite laths, high-density dislocations within the grains, small grain size and high proportion of HAGBs inhibit the crack growth process to improve propagation life of fatigue. The fracture reveals transgranular mode for propagation of fatigue. The pre-corrosion strategy is adopted before investigating corrosion fatigue process, so that there is an adequate corrosion effect on samples. The pre-corrosion time is determined to be 3 days through the analysis of electrochemical parameters, viz. corrosion potential and current. For overall fatigue life, corrosion grooves have significant deterioration effect. The transgranular and intergranular features are observed in fracture at initial stage of crack growth. Only transgranular features are found at middle and final stages.

Evaluation of the alkali and oxidation resistance of PBO fibers

Poly( p-phenylene benzobisoxazole) (PBO) fiber, well-known for its super high strength, is a novel fiber with excellent heat resistance and flame retardancy. However, chemical stability appears to be one of its few weaknesses. In this study, PBO fibers were treated with sodium hydroxide (NaOH) and potassium permanganate (KMnO4) solutions under various conditions. Scanning electron microscopy, optical microscopy, tensile testing, Fourier-transform infrared spectroscopy, differential scanning calorimetry (DSC), and thermogravimetric analysis were employed to characterize the variations of its structure and properties. The results show that many longitudinal corrosion grooves appeared on the surface of PBO fibers treated with KMnO4, while only subtle microcracks occurred after treatment with NaOH. The breaking tenacity of the fiber decreased from 38.13 cN dtex−1 to 2.76 cN dtex−1 after treatment with KMnO4 for 6 h, while it remained at a higher level (27.67cN dtex−1) when treated with NaOH. After treatment with KMnO4 solution, a more obvious absorption peak appeared in the vicinity of 1448.3 cm−1, inferring an occurrence of chemical changes for oxazole ring. Moreover, the remaining mass and initial degradation temperature are significantly improved, also indicating that the cyclic or cross-linked structure is rebuilt. Furthermore, the cyclization or cross-linking of macromolecules destroyed the highly ordered structure of PBO fibers, demonstrated by acromion melting peaks at low temperature in the DSC curves. However, the aggregation and chemical structures of PBO fibers have no obvious changes after treatment with NaOH.

Process mineralogy of refractory gold ore in thiosulfate solutions

A mineralogical characterization was carried out in samples of refractory gold ore with 59 g/ton, according to fire assays, which were taken from a previous leaching process with ammonium thiosulfate. The potential window used to evaluate the cathodic and anodic processes was chosen knowing that gold and copper reduction, and thiosulfate and Cu(I) species oxidation occurs in it. The leaching process consisted of a pretreatment of the mineral (in ammonium hydroxide and copper sulfate during 12 h with and without air bubbling) followed by leaching (in ammonium thiosulfate solution and EDTA at a pH ∼ 10 during 24 h with mechanical stirring at a rate of 250 rpm) which rendered a gold-release of 81.57%. When oxidants and stabilizers like Cu(II), NH3 and EDTA are present in thiosulfate based leaching solutions, the chemistry turns complex, and the partial reduction of copper, and redissolution of gold may occur. This fact and the low gold concentration make the electrowinning process especially difficult. Characterization techniques such as polarized light microscopy, X-Ray Diffraction, Rietveld quantification, and Automated Digital Imaging System, were chosen to track the process mineralogy of the sample, and the results prior to the leaching revealed association, size, and shape of each mineral occurrence; it was found that the mineral composition was pyrite crystals, exhibiting subhedral and inequigranular morphology (75%); galena crystals (10%); sphalerite (1.8%); chalcopyrite and arsenopyrite crystals (<3%); and free gold (<1%). The rest of the sample was comprised of aluminosilicate phases such as quartz and muscovite. After the leaching process, the main feature found was some accumulation of individual pyrite grains with corrosion grooves, and decrease in the particle size; on the other hand, the dissolution of the accompanying phases, with respect to the galvanic interactions, evidenced the next sequence of dissolution: I/E = pyrite > galena > M3 > sphalerite. Rietveld quantification suggested changes in the ratio of the main phases: pyrite decreased from 75.6% up to 65.7%; quartz increased from 21.1% up to 31.3%; galena decreased from 10.4% up to 7.6%; sphalerite decreased from 1.8% up to 1.1%. It is worth saying that the presence of precipitated amorphous phases was not observed.

Corrosion behavior of as-weld CLAM steel after laser shock peening process and tempering in static molten lithium lead

China low activation martensitic steel was welded by gas tungsten arc welding, after that laser shock peening and tempering treatment are applied to as-weld material, its compatibility with molten lithium lead are studied. Tempering treatment weight loss is 1.32 mg/cm2 compared to LSP is 1.91 mg/cm2 after 3000 h. Tempered martensite is more excellent than coarse martensite, as-weld surface corrosion grooves are serious. Passivation layers protect the internal metal from destroy in molten metal and it firstly appeared in defective areas during LSP process. Main elements markedly reduced through dissolving into molten metal, microstructure and phase transformation took place along the whole corrosion surface.

Mineralogía del proceso de lixiviación de oro en minerales refractarios con soluciones de tiosulfato

La mineralogía de procesos es una herramienta que ofrece información de gran utilidad para la modificación de procesos de obtención de oro para mejorar su eficiencia. El objetivo de este trabajo fue evaluar la mineralogía y la oxidación del mineral en el proceso de lixiviación de oro a partir de muestras de mineral aurífero refractario con soluciones de tiosulfato mediante técnicas analíticas como la Microscopía Óptica de Luz Plana Polarizada (MOLPP), Tratamiento Digital de Imágenes TDI, Microscopía Electrónica de Barrido (SEM/EDS) y Difracción de Rayos X (DRX). La caracterización mineralógica previa al proceso de lixiviación reveló asociación, tamaño y forma de ocurrencia de cada una de las fases minerales, encontrándose que el mineral empleado estaba compuesto principalmente por pirita en cristales inequigranulares y subhedrales (58% de la muestra); cristales de galena (15% de la muestra); cristales de esfalerita, calcopirita y arsenopirita (7% de la muestra);menos del 1% de oro libre y fases de aluminosilicatos (19% de la muestra). Ensayos al fuego mostraron 59 g/ton de oro y 70 g/ton de plata. Luego del proceso de lixiviación se encontró acumulación de granos individuales de pirita con surcos de corrosión, disminución de su tamaño de partícula, así como la disolución de las fases acompañantes:esfalerita, calcopirita, galena y arsenopirita. No se observó la presencia de cobre precipitado. Fue necesario realizar un pretratamiento oxidante del mineral, seguido por una lixiviación se logró una liberación de oro hasta del 82%. La caracterización mineralógica permitió definir condiciones adecuadas para la recuperación de oro.

Correlation Between Microstructure and Corrosion Behavior of Two 90Cu10Ni Alloy Tubes

Two kinds of 90Cu10Ni tubes with different service lives (more than 3 years and only 1 year, respectively) under identical working conditions were studied by an immersion test in a 3.5 wt% NaCl solution and the electron backscattered diffraction (EBSD) technique. The morphology after immersion showed severer corrosion attack at the grain boundaries of the tube with shorter service life compared with the tube with longer service life. The grain boundary characterization distributions (GBCDs) of the two tubes obtained by EBSD revealed more Σ3 boundaries and twins, and larger random boundary meshes in the tube with longer service life. A short immersion test in a modified Livingston’s solution was conducted to evaluate the tendency to corrosion attack of different types of the grain boundaries. SEM and AFM were used to characterize the corrosion morphologies of the boundaries. A strong correlation between varying depths of corrosion grooves and types of the grain boundaries was obtained. The influence of deviation angle of low Σ boundaries on corrosion resistance of the grain boundaries was also discussed. It is concluded that a special “grain boundary engineering” (GBE) treatment has been performed on the tube with longer service life. It is proposed that the optimized GBCD is responsible for the better service performance of the tube.

The effect of copper and molybdenum on pitting corrosion and stress corrosion cracking behavior of ultra-pure ferritic stainless steels

The work addresses the influence of Cu and Mo additions on corrosion resistance of ferritic stainless steels in chloride media. According to the results, 0.5% Cu addition and the precipitation of ε-Cu phases decreased the pitting corrosion resistance in chloride media. The addition of both Cu and Mo to 19% Cr ferritic stainless steels causes SCC and the susceptibility to SCC increases with the aging treatment. The SCC initiated from pitting of ε-Cu phases and was mostly intergranular. The selective dissolution and repassivation of Mo promoted the second corrosion grooves parallel to stress.

Corrosion of steel reinforcement in concrete of different compressive strengths

Corrosion of steel bars embedded in concrete having compressive strengths of 20, 30 and 46 MPa was investigated. Reinforced concrete specimens were immersed in a 3% NaCl solution by weight for 1, 7 and 15 days. In order to accelerate the chemical reactions, an external current of 0.4 A was applied using portable power supply. Corrosion rate was measured by retrieving electrochemical information of polarization technique. Pull-out tests of reinforced concrete specimens were then conducted to assess the corroded steel/concrete bond characteristics. Experimental results showed that corrosion rate of steel bars and bond strength between corroded steel/concrete were dependent on concrete strength and accelerated corrosion period. As concrete strength increased from 20 to 46 MPa, corrosion rate of embedded steel decreased. First day of corrosion acceleration caused a slight increase in steel/concrete bond strength, whereas sever corrosion after 7 and 15 days of corrosion acceleration significantly reduced steel/concrete bond strength. Visual and metallographic observation of steel bars removed from concrete samples after testing revealed that the severity of corrosion reactions and reduction of steel bar diameter increased as the corrosion acceleration period increased. Presence of localized corrosion pits as well as severe corrosion grooves of steel bars was confirmed after 7 and 15 days of corrosion acceleration, respectively.

Failure investigation of Muntz tubesheet and Ti tubes of surface condenser

Failure investigation was carried out on corroded Muntz tubesheet and Ti tubes of a surface condenser. The Muntz metal was found to have suffered from corrosion grooves and micropits, which were crystallographic in nature. X-ray mapping revealed the occurrence of dezincification. The Ti tube ends suffered from separation and cracking of the deformed grains in addition to shallow localized attack. Corrosion of the Muntz metal was attributed to coupling with Ti, while corrosion of Ti was due to formation of Ti-hydride as a result of the utilization of sacrificial Al anodes in the waterbox. Seasonal variations in seawater temperature and proximity of Ti tube ends to waterbox anodes may have aided hydriding of the Ti tubes. Recommendations were given to discontinue the application of sacrificial cathodic protection and to epoxy coat the cast iron waterbox and the Muntz tubesheets.

Groove dimensioning using remote field eddy current inspection

The remote field eddy current technique is used for dimensioning the grooves that may occur in the ferromagnetic pipes. We propose a method to estimate the depth and the length of corrosion grooves from measurement of a pick-up coil signal phase at different positions close to the defect. Groove dimensioning requires the knowledge of the physical relation between measurements and defect dimensions; therefore finite-element calculations are performed to design parametric algebraic functions for modeling the physical phenomena. Different models are possible; the choice of this algebraic function is discussed from identification criteria. By means of new measurement formalism and two previously defined measurement relations, estimates of groove sizes may be given. In the first approach, algebraic function parameters and groove dimensions are linked through a polynomial function; this approach is proved to be better than a second one which tries to take advantage of more physical considerations.

H2SO4-NaCl溶液中における310鋼のき裂進展速度と溶解速度の関係

Relationship between crack propagation rate and dissolution rate of type 310 stainless steel was studied to clarify the effect of the lattice defects on crack initiation and crack propagation in H2SO4-NaCl solutions.Stress corrosion morphology changed in order of general corrosion, localized corrosion, stress corrosion cracking with increasing NaCl concentration. Stress corrosion cracking was observed at the potential range of active region on an anodic polarization curve. Dissolution rates of prestrained specimens were increased with increasing the dislocation density. Optical micrograph showed the formation of corrosion grooves and dissolution rates of these corrosion grooves are close to the crack propagation rates under low initial stress intensity. Transmission electron microscopic observation showed the existence of bundle structure that is high dislocation density region like a plane. As the dissolution rate was accelerated with increasing the dislocation density, this corrosion grooves might be formed by the preferential dissolution of bundle structure.From these results, it is thought that the crack initiation and the propagation are accelerated with preferential dissolution of bundle structure.

A Parametric Estimation Approach for Groove Dimensioning Using Remote Field Eddy Current Inspection

The remote field eddy current technique is used for dimensioning grooves that may occur in ferromagnetic pipes. We propose a method to estimate the depth and the length of corrosion grooves from the measurement of a pick-up coil signal phase at different positions close to the defect. Groove dimensioning needs the knowledge of the physical relation between measurements and defect dimensions; therefore, finite-element calculations are performed to obtain a parametric algebraic function of the physical phenomena. The parameters of this model function are obtained by an optimization technique. By means of this model and a previously defined general approach, an estimate of groove size may be given. In this approach, algebraic function parameters and groove dimensions are linked through a polynomial function. To validate this estimation procedure, a statistical study has been performed. The approach is proved to be suitable for real measurements.

A Parametric Estimation Approach for Groove Dimensioning Using Remote Field Eddy Current Inspection

The remote field eddy current technique is used for dimensioning grooves that may occur in ferromagnetic pipes. We propose a method to estimate the depth and the length of corrosion grooves from the measurement of a pick-up coil signal phase at different positions close to the defect. Groove dimensioning needs the knowledge of the physical relation between measurements and defect dimensions; therefore, finite-element calculations are performed to obtain a parametric algebraic function of the physical phenomena. The parameters of this model function are obtained by an optimization technique. By means of this model and a previously defined general approach, an estimate of groove size may be given. In this approach, algebraic function parameters and groove dimensions are linked through a polynomial function. To validate this estimation procedure, a statistical study has been performed. The approach is proved to be suitable for real measurements.

ＡＥ検出によるＺｎ‐Ｎｉ合金めっき皮膜の引張破断強度評価

According to our previous work on the corrosion behavior of zinc-nickel alloy electroplated steel sheets in aqueous solutions, corrosion induces the formation of grooves that reach to the underlying steel. The corrosion grooves, which are thought to be caused by corrosion cracking, may cause deteriorating in corrosion resistance.In the present study, a method for measuring the fracture strength of zinc-nickel alloy electroplating films was established as a part of fundamental study toward improving corrosion resistance through suppression of corrosion groove formation. Fracture strength was determined by detection of acoustic emissions generated by film cracking during tensile testing of specimens. The fracture strength of zinc-nickel alloy films varied depending on plating current density.

Field and laboratory study of cavitation corrosion of nickel aluminium bronze in sea water

AbstractA case study of a nickel aluminium bronze vertical type pump that failed during service in sea water and a laboratory investigation of the cavitation corrosion behaviour of the cast alloy are reported. The failure of the pump was found to result essentially from cavitation damage and erosion corrosion grooves. Other factors such as sulphide attack and preferential phase corrosion played a secondary role. The preferential attack occurred at the boundaries between the copper rich α-phase and the intermetallic K precipitates. It had an average depth of penetration ranging from 17 to 48 μm. In laboratory tests, the presence of cavitation was found to shift the free corrosion potential of the material in the active direction by 65 mV: It also increased the cathodic and anodic currents during polarisation by an order of magnitude. The rate of mass loss in the presence of cavitation was found to be 186 times that under quiescent condition. Cathodic protection reduced the rate by 47% with respect to that ...

Intergranular corrosion of copper and α-Cu-Al alloy bicrystals

Abstract Intergranular corrosion in copper bicrystals with symmetrical [110] tilt boundaries and in Cu-9 at.% Al alloy bicrystals with symmetrical [110] and [100] tilt boundaries was investigated by examining the depths of corrosion grooves developed at the boundaries after an immersion test in acid solutions (modified Livingston's etchants) usually used to reveal lattice dislocations. On the plot of depth of penetration against misorientation, cusps (sharp minima) were observed at misorientations of 38·9°, Σ = 9 (221), 70·5°, Σ = 3 (111) and 129·5°, Σ = 11 (113) in the [110] tilt boundaries of copper and Cu–9 at.% Al alloy, and at those of 22·6°, Σ = 13a (015), 36·9°, Σ = 5 (013), 43·6°, Σ = 29a (025), 53·1°, Σ = 5 (012) and 67·4°, Σ = 13a (023) in the [100] tilt boundary of Cu–9 at.% Al alloy. The misorientation dependences of the penetration depth were compared with those of grain-boundary energies in copper and aluminium reported in the literature.