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Despite extensive research on the corrosion of the Fe-based amorphous alloy coatings (AACs) has been carried out, yet, regarding the corrosion morphology of the Fe-based AACs in NaOH solution, the current findings only indicate the existence of localized corrosion, without clarifying the occurrence and mechanism of pitting corrosion. This work investigated the corrosion behaviours of the Fe-based AACs in NaOH solutions through three-dimensional (3D) structure and morphology analysis cooperating with electrochemical testing. The work widens the pitting corrosion mechanism of the AACs. The results show that the Fe-based AACs in NaOH solution have an obvious secondary passivation phenomenon, and serious pitting corrosion occurs. As the concentrations of the NaOH solutions increase, the corrosion resistance of AACs gradually decreases. Additionally, the corrosion rates of the AACs are calculated directly based on the (pore) volume changes before and after corrosion treatments through X-ray micro-computed tomography (X-ray micro-CT) measurements, which provides a new method for the corrosion rate calculation.

This study investigated the corrosion behavior of TC18 titanium alloy with different initial microstructures in neutral salt spray environment by microstructural analysis, corrosion composition analysis, and electrochemical test in 3.5 wt% NaCl solution. In addition, the pitting mechanism of TC18 titanium alloy in salt spray corrosion was analyzed. Through SEM and Sensofar Neox 3D morphology observation, it was found that alloys with different microstructural morphologies exhibited different levels of corrosion resistance during the salt spray corrosion process, and that the pitting pit of TC18 titanium alloy with different initial microstructure tended to remain stable with increasing salt spray treatment time. The local dissolution of the passivation film was identified as the primary corrosion mechanism during the salt spray process of TC18 titanium alloy with different initial microstructures, as determined by XPS and EDS compositional analysis. The pitting corrosion resistance of TC18 titanium alloy can be effectively enhanced by its initial equiaxed microstructure, which has a smaller grain size, as evidenced by microstructural analysis, electrochemical impedance spectroscopy (EIS) results, and complementary evaluation analysis of Tafel polarization curves. Finally, a comprehensive discussion of the salt spray corrosion mechanism of TC18 titanium alloy is provided. This comprehensive study provides critical insights into the durability of marine equipment and the efficacy of preventive measures to mitigate the occurrence of pitting corrosion.

The effect of Ti and Y on the corrosion behavior of the FeCr alloy was investigated in a 3.5% NaCl solution. Ti was found to inhibit the formation of the σ phase, significantly reducing the presence of pitting in the material. In addition, Ti acted indirectly on the oxide layer, increasing the concentrations of Cr and Fe, consequently generating a probable enrichment of Cr2O3 and FeOOH, which enabled the formation of a more stable passive film resistant to attack by chloride ions. On the other hand, Y caused the precipitation of a phase identified as Fe17Y2, which was accompanied by an elongated σ phase, both located at the grain boundaries, besides the formation of Cr23C6 and Y2O3. Its addition resulted in an improvement in the corrosion resistance of the FeCr alloy by reducing the precipitation of the σ phase. However, its effect was much less important than that of Ti, since the results showed that the FeCrY alloy was still highly susceptible to localized forms of corrosion.

This study proposed a new insight to design the microstructure, improve the corrosion processes and ameliorate the corrosion resistance of Al-Mg-Si alloy through TCB seed alloy. The studied alloys were devised with great resistance to pitting corrosion by achieving the AlMnFeSi phase with smaller size and disperse distribution, the finer grain structure as well as higher density and more evenly aging precipitates. Taking the 6061-1TCB sample immersed for 72 h in the 3.5 % NaCl aqueous solution as an example, the depth of corrosion pits decreases from 20 μm to 4 μm as well as the percentage of pitting corrosion decreases from 6.6 % to 2.1 % compared with the 6061 alloy. The great intergranular resistance can be obtained by the more tortuous grain boundaries and higher percentage of low angle grain boundaries. Taking the 6061-1TCB sample as an example, the deepest position of intergranular corrosion decreases from 728 μm to 505 μm as well as the area percentage of detached grains decreases from 65 % to 22 % compared with the 6061 alloy. Based on the enhancement of pitting and intergranular corrosion resistance with TCB seed alloy, EXCO degree can also be improved from EA to PC level.

Nickel alloys are widely used in the oil and gas industry where high corrosion resistance in chloride water or in sour environments is required. When high mechanical properties are required in combination with high corrosion properties, alloy 718 (UNS N07718) is one of the preferred choices, although it still presents limitations in terms of corrosion resistance in some applications: despite offering outstanding resistance to localized corrosion, alloy 718 is not immune to it. Its high corrosion resistance is mainly due to its high nickel and chromium contents combined with additions of molybdenum and other noble elements. Metallic and non-metallic precipitates are formed during the manufacturing process and each is known to interact with the matrix and the oxide protective film, but there is a lack of studies on the mechanisms that occur during the initiation of localized corrosion in this alloy. In this work, we investigate the localized corrosion initiation process and follow up the first steps of corrosion attack in alloy 718 in a 1M NaCl solution through the combination of microscopy and electrochemical techniques. As a result of potential application in a brine electrolyte, we conclude that nitrides and carbides play an important role on the corrosion initiation.

The pitting mechanism of 7 series high-strength aluminum (Al) alloys (7xxx) is investigated experimentally and numerically (finite element method, FEM) by comparing the characteristics of passive films and pitting kinetics of two types of 7xxx Al alloys. The point defect model (PDM) is used to evaluate the passive film properties in the two varieties of 7xxx Al alloy, and the FEM is employed to calculate the point defect diffusion process in detail. The results reveal that the two 7xxx Al alloys exhibit various microstructures, particularly the 7xxx-1, characterized by a robust (111) fiber texture and a lower proportion of low-angle grain boundaries than the 7xxx-2. The diffusivity D of point defects in 7xxx-1 (3.85 × 10−18–52.74 × 10−18 cm2 s−1) is lower than that in 7xxx-2 (5.47 × 10−18–66.61 × 10−18 cm2 s−1) and the diffusion duration of 7xxx-1 is longer than 7xxx-2, which is closely associated with the rupture of passive film. Additionally, FEM proved that the initial shapes of pits dictate the progression of pitting, manifesting that the shallow dish shape grows laterally while the deep hole shape grows longitudinally.

High-performance alloys such as super duplex stainless steels (SDSS) are of interest to the oil and gas industry, especially in deep and ultra-deep reservoirs where high pressures and highly corrosive environments are prevalent. SDSS have high nitrogen contents and pitting resistant equivalent number (PREN) values greater than 40, however, fusion welds of these alloys can exhibit unsuitable microstructures and defects that may result in failure during usage. Solid-state linear friction welding (LFW) offers an alternative for the effective joining of SDSS with a less detrimental effect on microstructure and properties. In this work, four LFW joints in UNS S32760 SDSS were produced and investigated by evaluating the process parameters required to achieve a high-quality joint with the desirable metallurgical, mechanical, and localized corrosion properties. These properties were assessed through metallography (optical microscopy and scanning electron microscopy), tensile and microhardness tests, and corrosion analysis according to the ASTM G48A standard. Results indicated that one specific combination of LFW parameters led to a defect-free joint, and that the mechanical properties of the weld in this case were comparable to those of the base material. Additionally, an adequate balance between ferrite and austenite phases was achieved throughout the microstructural gradients seen in the weld region. Microhardness values were below 350 HV, thus complying with the DNV–OS–F101 standard. Furthermore, no pitting corrosion was observed in this joint under the testing conditions suggested by ASTM G48A.

Corrosion poses significant safety and cost challenges in the aeronautic industry. Ultrasonic Lamb Waves (LW), emitted and received by a sparse array of piezoelectric elements (PZT), offer an efficient, cost-effective, and versatile solution for corrosion monitoring. This dataset corresponds to two experiments involving a LW solution based on a sparse PZT array and able to monitor corrosion pit growth on a 316L stainless steel plate during controlled corrosion. The corrosion pit size is electrochemically controlled by the imposed electrical potential and the injection of a corrosive NaCl solution through a capillary at the desired pit location. Simultaneously, the corrosion pit growth is monitored in-situ every 10 seconds using a sparse array of 4 PZTs bonded to the back of the steel plate. Two independent experiments were conducted to assess the repeatability of this approach. The collected dataset collected can facilitate the development of Structural Health Monitoring (SHM) algorithms and methodologies, provide data for waves/damage interaction modeling, and help bridging the gap between research and industry in this domain.

The chloride-induced stress corrosion cracking (CISCC) is one of the major integrity concerns in dry storage canisters made of austenitic stainless steels (ASSs). In this study, an advanced duplex stainless steel (DSS) with a composition of Fe–19Cr–4Ni-2.5Mo-4.5Mn (ADCS) was developed and its performance was compared with that of commercial ASS and DSS alloys. The chemical composition of ADCS was determined to obtain greater pitting and CISCC resistance as well as a proper combination of strength and ductility. Then, the thermomechanical processing (TMP) condition was applied, which resulted in higher strength than ASSs (304L SS and 316L SS) and better ductility than DSSs (2101 LDSS and 2205 DSS). The potentiodynamic polarization and electrochemical impedance spectra (EIS) results represented the better pitting corrosion resistance of ADCS compared to 304L SS and 316L SS by forming a better passive layer. The CISCC tests using four-point loaded specimens showed that cracks were initiated at 24 h for 304L SS and 144 h for 316L SS, while crack was not found until 1008 h for ADCS. Overall, the developed alloy, ADCS, showed better combination of CISCC resistance and mechanical properties as dry storage canister materials than commercial alloys.

Effects of Mo and C addition on the microstructural evolution and corrosion resistance in chloride solution of FeNiCrAl duplex alloy were investigated. The results showed that α phase stabilizing element Mo increased the α/γ volume ratio and γ phase stabilizing element C decreased its ratio in FeNiCrAl alloy, and the chemical composition of α and γ phases was changed by Mo and C addition, which affected the corrosion resistance of FeNiCrAl alloy. Pitting corrosion mainly occurred in α phase around NbC precipitated at α/γ interface due to the micro-galvanic corrosion (MGC) effect between α (anode), γ (cathode) and NbC (cathode) phases. The pitting corrosion resistance was improved by Mo and C addition, resulting from that Mo and C enhanced the passivity of passive films and decreased the MGC effect between α, γ and NbC phases.

The effect of sulfides on the pitting corrosion behavior and film chemistry of 70/30 copper-nickel alloys in aerated seawater was investigated. Sulfides in seawater prevent the formation of protective oxides on the surface of the alloy and alter the morphology and composition of the corrosion products. It results in the corrosion product film consisting of the double layer structure of the loose and porous sulfide-containing outer layer and the dense inner layer. This double-layer structure of the corrosion product film can't alleviate corrosion, but instead accelerates the development of pitting corrosion. The statistical analysis method is used to study the corrosion process of 70/30 copper-nickel alloy in sulfide-containing environment. This work records the trend of pitting corrosion towards the horizontal and longitudinal directions.

Pitting corrosion defect is a common defect in pipelines employed in the oil and gas industry. This paper explores the mechanical behavior and failure pressure (Pf) of the pipelines, and compares the traditional empirical methods used in oil and gas pipelines with pit arrangements including an isolated pit and pitting colony (three and five pits aligned in the longitudinal direction). This study is based on nonlinear finite element method (FEM) and 3-D pipeline models. Pf was predicted by FEM and traditional methods considering the interaction of pitting corrosion defects. The pipeline Pf values obtained by FEM and methods were compared to determine similarities in applications.

Steel wires are widely employed in structural engineering due to their robust strength. However, the emergence of pitting corrosion significantly impacts their capacity, fatigue performance, and mechanical traits, with no specific codes addressing this issue. To assess the load-bearing capacity of corroded steel wires, predict their remaining fatigue life, and analyze failure modes, a comprehensive physical test was conducted. Mechanical evaluations of corroded wires were followed by 3D scanning to analyze corrosion attributes and fracture surface morphology. Using fuzzy reliability theory, a model estimated wire capacity under varying corrosion degrees. Subsequent fatigue testing explored performance and developed a predictive residual life model. Investigation results revealed a rapid and gradual decrease in capacity's reliability coefficient. Corroded wire fracture morphologies were classified as typical and multi-source cracks, including subtypes like cracks expanding in the same plane and step-like fractures. All wire types exhibited a cracking threshold exceeding 5.6 MPa·m1/2, with fracture intensity declining as corrosion severity increased. Notably, the model better suited slightly corroded wires, showing up to 30.93 % relative error for severely corroded wires. Enhancing accuracy for the latter entails considering additional factors to refine the model.

The corrosion resistance of Cr reinforced HRB400 rebar in the marine environment was investigated. The addition of Cr increases the amount of Cr(OH)3 and α-FeOOH in the passivate film, resulting in a denser passivate film structure. This enhanced passivation film inhibits localized corrosion. The pitting potential and critical chloride concentration (CTL) of the steel increased with the increase in chromium content, indicating improved corrosion resistance of the steel. On the other hand, an increase in the concentration of Cl- in solution leads to a decrease in the pitting potential and resistance of the steel, which reduces the corrosion resistance. At higher Cl- concentrations, the Cl- ions form an electrochemical interface with the steel surface, resulting in a sharp decrease in the Rf value. In addition, the gradual decrease in solution pH leads to a decrease in the pitting potential and CTL of HRB400 and 1.5Cr steel. The corrosion resistance was also found to be reduced, pH reduction accelerated the intrusion of chloride ions, which led to a severe breakdown of the passivation film.

The pitting corrosion behaviors of high-strength metastable austenitic stainless steel (MASS) 14Cr10Mn with different cold rolling reductions (0 %, 10 % and 20 %) were investigated in simulated coastal atmospheric environments by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), electrochemical measurements and cyclic corrosion test. The cold rolling deformation noticeably increases the dislocation density in the steel. As the cold rolling reduction changes from 0 % to 20 %, the pitting potential and the polarization resistance decrease to some extent in 1 wt% NaCl solution. The cold rolling deformation increases the defect density and the contents of (Fe,Cr)-oxyhydroxides/hydroxides in the passive film on the specimen surface. After the wet-dry cyclic corrosion test, the corrosion pits initiate at the deformation band regions. The quantity, diameter and depth of the pits gradually increase with enlarging the cold rolling reduction.

Ferritic stainless steels have been utilized in marine atmosphere and are found to be susceptible to pitting corrosion in our field investigation. Alloying is an important to modify the passive film on the surface and improve the pitting corrosion resistance. Nevertheless, how the addition of titanium modifies the passive film and affects the pitting corrosion resistance of ferritic stainless steels remain controversial. This study has elucidated these topics through microstructure analysis and corrosion properties analysis. The results demonstrate that titanium addition increases the pitting potential almost linearly. Titanium forms TiO2 in the passive film and reduces defect density of the passive film. Moreover, titanium addition induces the precipitation of the Laves phase, which promotes micro-galvanic corrosion. For the titanium-alloyed ferritic stainless steels, pitting corrosion predominantly occurs in the ferrite phase adjacent to the Laves phase. The influence mechanism of titanium on the pitting corrosion of the ferritic stainless steel has been established, which takes micro-galvanic corrosion induced by titanium addition into account.

Early corrosion behavior of 35CrMo low-alloy steel for high-strength bolt in the simulated shallow seawater and deep-sea environment was studied using mass loss measurement, electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), Raman spectrometer, X-ray photoelectron spectrometer (XPS) and 3D microscope. The results show that the corrosion of 35CrMo steel initiates mainly at the steel matrix around the inclusions of CaO–MgO–Al2O3, (Ca, Mn)S and their mixed composite. The corrosion rate in the simulated deep-sea environment is lower than that in the shallow seawater, which is declined with immersion time. The corrosion products formed in the two environments are composed of γ-FeOOH, α-FeOOH, Fe3O4 and little Cr(III) oxide or/and hydroxide, but the rust layer produced in the deep-sea environment is thin and uniform. The steel has pits in a shallow dish shape and tends to develop uniform corrosion in the deep-sea environment.

Multiphase stainless steel is a kind of stainless steel that obtains good mechanical properties. Nevertheless, the passive and pitting behaviors of multiphase stainless steel remain inadequately elucidated. This study aims to investigate the passive and pitting behaviors of multiphase stainless steel by employing Auger electron spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy, and electrochemical techniques. The conclusions drawn from this research are as follows: The main constituents of the passive film on multiphase stainless steel comprise FeO, Fe2O3, Cr2O3, and Cr(OH)2. The passive film on the martensitic phase displays largest thicknesses. The Cr content in the passive film of the ferritic phase is highest. Particularly, the passive film on the (111) orientation of martensitic phase is thicker than that on the (001) and (101) orientations. Pitting corrosion in multiphase stainless steel primarily initiates at phase interfaces and subsequently extends into the ferritic phase.

The square wave polarisation technique and mathematical/electrochemical models were combined to investigate pitting corrosion of pipeline steel X100 under cathodic protection potential fluctuations with different duty cycles (δ). Mathematical equations were derived to describe the increased potential of the double-charge layer at the steel/solution interface, which increases density from 1100 mm−2 (δ = 10%) to over 6600 mm−2 (δ = 50%). However, an electrochemical model was developed to present the formation of an amorphous corrosion product layer, which reduces the number of local anodic corrosion areas and decreases pitting density when δ is higher than 50%.

The microstructure and corrosion performance of wrought, laser powder bed fusion (LPBF), and MoNi over-alloyed LPBF type 316L stainless steel is compared. Adding Mo and Ni to LPBF 316L stainless steel resulted in ẟ-ferrite. Potentio-dynamic polarisation was used to rank all microstructures, with LPBF + MoNi has more resistant than LPBF and wrought material. Bipolar electrochemistry was applied, with LPBF samples having the lowest critical pitting potential and highest pit growth kinetics. The best corrosion performance was for LPBF + MoNi stainless steel. Different pitting corrosion resistance as function of process directions were found. The tiny pores negatively impacted the pitting performance.

Few work have been performed regarding the quantitative characterization of three-dimensional (3D) pitting corrosion process directly, although the corrosion behaviors and the passivation film stability of metals in various solutions have been studied heavily. The reported work quantitatively characterized the 3D pitting corrosion of the Fe-based amorphous alloy coating (Fe-based AAC) via X-ray micro-computed tomography (X-ray micro-CT) and further elucidated the mechanism of its pitting corrosion. Moreover, the microstructure and electrochemical performance of the Fe-based AAC have also been explored. The results showed that the targeted thermal sprayed Fe43Cr20Mo10W4C15B6Y2 coating was prone to be corroded with the increase of the hydrogen ion concentration, i.e. higher hydrogen ion concentration leads to poorer corrosion performance of the Fe-based AAC. The X-ray micro-CT results revealed that the pits in the Fe-based AAC initially nucleated below the pitting potential, and they also generated in the over-passivation stage. Furthermore, it was found that the corrosive medium does not penetrate into the coating/substrate interface, and the deduced corrosion mechanism from the findings was also discussed.

Fe–20Mn–11.5Al–1.4C–5Cr (wt%) lightweight stainless steel (LWSS) was found to have equivalent or better resistance to pitting corrosion than Fe–11Cr (wt%) stainless steel (SS). The desirable resistance to pitting corrosion of the LWSS alloy was attributed to the formation of protective passive film. On LWSS, an (Al,Fe,Cr)-oxide was formed, and on SS, a (Fe,Cr)-oxide was formed. The passive film of LWSS had a higher Cr + Al content than that of SS. In addition, compared to the passive film of SS, the passive film of LWSS was found to be thick and the concentration of point defects was also low.

Corrosion-resistant materials with good mechanical properties are an endless goal to develop reliable structural materials. Multiple strengthening mechanisms stemming from diverse microstructural factors have been developed, while the effect of microstructural factors on corrosion properties in high-entropy alloys has not been clearly defined yet. Herein, the corrosion behaviors of CoCrFeNiMo medium-entropy alloys with different annealing times are investigated. The influences of microstructures are summarized as follows: alloyed Mo accelerates repassivation, Mo-rich precipitates form micro-galvanic couples, and unrecrystallized microstructures induce pitting corrosion. Regarding mechanical properties, the alloyed Mo, Mo-rich precipitates, and unrecrystallized region with profuse dislocations lead significant solid solution strengthening, precipitation strengthening, and dislocation strengthening, respectively. Particularly, the sample annealed for 60 min possesses dissolved Mo in the matrix, fine precipitates, wide recrystallized regions, and low dislocation density, resulting in a wide passivation range of 1.512 V and high yield strength × fracture strain of 220.3 MPa simultaneously. The sample annealed for 60 min reveals a synergistic combination of diverse microstructural factors affecting corrosion and mechanical properties.

The interfacial microstructures and corrosion behavior of tungsten heavy alloy/superalloy dissimilar joints brazed with various Cu–Ti based multicomponent amorphous alloys were investigated by time-varying chemical bath immersion tests and electrochemical measurements. The longitudinal analysis of corrosion behavior differences in different regions of dissimilar joints was conducted, and the horizontal analysis of the influence of compositional variation in filler materials on corrosion behavior was investigated. Importantly, the brazed joint with CuTiNiZrV filler material (CT3 joint) exhibited the noblest Ecorr (−0.911 VSCE) and the highest charge transfer resistance (1610.5 Ω cm2). From the compositional and microstructural effects on the corrosion resistance, the enhancing anti-corrosion performance was mainly attributed to the tailoring of the microstructures and corrosion potential of the brazing seam, and the formation of protective compact oxide film (Fe2O3-NiO-CoO-VO).

pitting corrosion is an important factor, which leads to stress concentration. A sharp stress concentration will have a big impact on the fatigue life of 7075- T651 aluminum alloy. Most of the studies have been conducted to investigate its fatigue performance and proposed some estimated models. However, these models only considered the influence of the depth, the length, and the width of pits on the fatigue life and neglected their coupling effects. In order to predict the fatigue life of 7075- T651 aluminum alloy accurately. First, some numerical models were established to explore the stress concentration factor (SCF) affected by pit sizes. Second, some data driven models were proposed to investigate it. The SCF was regarded as the output and the length, the width, and the depth of pits were acted as the inputs. Third, the fatigue performance of the aluminum alloy 7075-T651 was explored, based on the fracture mechanics theory. The results indicate that the neural network optimized by the sparrow search algorithm not only has a relatively small error but also has stronger robustness, which can predict the SCF well. In addition, the SCF increases, as the length and the width of the pits increase, and decreases, as the pit depth increases. The pit depth can be treated as an important factor to influence the fatigue life of 7075- T651 aluminum alloy.

AISI316L stainless steel components produced via additive manufacturing techniques have quickly found new applications across several industrial sectors. However, parts manufactured through this method generally exhibit poor surface quality and performance in the as-built state. This work addresses the influence of laser polishing and water jet assisted recirculating shot peening on the surface quality, microstructure and electrochemical properties of AISI316L samples produced by the laser powder bed fusion method. To do so, surface roughness analysis, residual stress measurement, scanning electron microscope and electron backscatter diffraction analysis were employed along with electrochemical tests, including cyclic potentiodynamic polarization, electrochemical impedance spectroscopy and Mott-Schottky analysis. Laser polished samples exhibited a smooth surface with high tensile residual stress on the surface, which led to the reduction of pitting potential and formation of passive layers, including more crystal defects. Microscopical analysis evidenced that the higher density of lattice defects and local microstrain on the surface of the shot peened samples promoted surface hardness and induced compressive residual stress. Therfore, the shot peened samples exhibited a wider passive range in cyclic potentiodynamic polarization measurements, higher polarization resistance in electrochemical impedance spectroscopy measurements, and less defective passive film in Mott-Schottky analysis. Moreover, it was calculated that the passive film thickness of the shot peened sample was slightly larger than the other samples. Low surface roughness, high crystal defect density, and compressive residual stresses enhanced the passive layer's resistance to defect transport, lowered the point defect concentration in the passive film, and improved the pitting resistance of the samples.

The X90 pipeline steel pipe is expected to become the standard steel in future pipeline construction due to its high transmission efficiency and lower cost. However, little study has been conducted on corrosion on-line monitoring of X90 steel. To investigate the pitting development of X90 steel, a combined electrochemical device and acoustic emission (AE) system was set up in this work. The results reveal that the pitting process can be divided into three stages: activation response and passive film rupture, and corrosion pit propagation, and pitting reaction. In addition, the corrosion rate of metal is quite high during the activation reaction and passivation film rupture stage, and the characteristic parameters of the AE signal are very large. In the frequency domain, the frequency range is mostly centered between 100 and 200 kHz, with a peak frequency of about 150 kHz. The corrosion pit propagation stage is the transition stage from metal oxidation to metal pitting reaction. The activity of the signal is low, and the characteristic signal is diminished, and the frequency domain characteristics are comparable to the preceding stage. The signal activity rises, the total signal intensity increases, and several signals exceeding 55 dB arise during the pitting response stage.

The effect of alloying elements in dispersion-strengthened-high-strength (DSHS) steel on the pitting corrosion in the marine atmospheric environment was investigated. The results showed that Cr, Ni and Mo showed a degree of bias in the rust layer with increasing exposure time, repairing defects in the rust layer and spreading to the interior of the rust layer. The generation of the protective product α-FeOOH was promoted, slowing down the corrosion reaction. The alloying elements made the rust layer cation-selective and the enhanced protective effect of the rust layer inhibits the vertical development of pitting corrosion at 25 °C. However, the vertical development of pitting corrosion in the late stages of corrosion at 65 °C with 3.5 wt.% NaCl was slightly increased.

In this paper the negative effects of the chloride ions attack in reinforced concrete (RC) elements have been studied. For this the vertical and horizontal chloride diffusivity has been treated by several models to identify the more relevant factor affecting the chloride concentration. The pitting corrosion has been treated to define the resistance losses of the shear forces and bending moments. An alternative deterministic/probabilistic procedure, by a direct and systematic new model, has been proposed to estimate the total time of service life for RC elements at the design phase. Several detailing configurations of steel bars in a RC beam, water/cement ratio and level of aggressiveness have been analysed to compare the model predictions. In this sense, this paper should provide useful results for analysts in terms of probability of failure for resistance losses and time of corrosion initiation. The goal is not only to provide practical results but also to evaluate the issue in a more modern risk analysis throughout the proposed prediction model.

The deep-sea field exposure experiment of 5A06 aluminum alloy was carried out successfully in the South China Sea with the sea depths of 1200 m, 2000 m, and 3000 m for one year. Corrosion morphologies show that pitting corrosion and crevice corrosion as the main corrosion types occur on the specimen surface, and that the crevice corrosion makes more contributions. The corrosion data results show that average corrosion rate, maximum pitting depth and corrosion area ratio reduce with the sea depth increasing and that the highest values are 13.8 μm a−1, 87.2 μm and 18.32% for 1200 m specimen. XPS results show that the oxygen content decreases with the sea depth increasing while the magnesium content increases. Comparing with 1200 m specimen, 2000 m and 3000 m specimens display higher ratios of Al2O3: Al(OH)3 and MgO: Mg(OH)2, which may be ascribed to the slightly higher oxygen concentration. Mott–Schottky results show that donor densities and acceptor densities are 1.14 × 1024 cm−3 and 9.16 × 1023 cm−3 for 1200 m, 2.82 × 1023 cm−3 and 2.10 × 1023 cm−3 for 1200 m, and 3.11 × 1023 cm−3 and 4.05 × 1023 cm−3 for 3000 m, respectively.

The effect of NaClO solution on pitting behavior of 304 stainless steel was investigated by electrochemical tests and composition analysis. The results show that the open circuit potential (OCP) shifts to the positive direction with the increase of [ClO−], indicating that the passivation film formed on the sample surface is faster, but, has no effect on pitting potential (Eb) in the first stage (< 24 h). After 24 h immersion, the pitting occurs because Cl− is detected in the wake of the decomposition of ClO− for its thermodynamics instability. In the later stage, the [Cl−] increases with the increase of [ClO−], correspondingly resulting in lower pitting resistance. X-ray photoelectron spectroscopy (XPS) reveals that the Cr/Fe atomic ratio in the passivation film decreases with the increase of [ClO−], because Cr(III) is oxidized to Cr(VI) and dissolves in the solution, which further weakens the pitting resistance of 304 stainless steel. The electrochemical impedance spectroscopy (EIS), combined with the Mott-Schottky analysis (MSA) was employed to verify the properties of the passivation film related to pitting.

The formation mechanism of MnS inclusions during heat treatment and its effect on the pitting behavior of laser powder bed fusion (L-PBF)-fabricated 316L stainless steel (SS) were investigated. MnS inclusions precipitated at the grain boundaries of the samples, and the spherical oxide particles can become nucleation sites. The quantity and size of the MnS inclusions increased with prolonged heating. Compared with the as-received sample, the pitting of heat-treated L-PBF-fabricated 316L SS samples was mainly induced by the newly generated MnS inclusions rather than the fabricated gas pores and extended along the grain boundaries; this caused the dramatic pitting resistance deterioration.

The third-generation alloy, AA2198-T8, is highly recommended for the aerospace industry. However, it has come under scrutiny due to its high cost. This study aims to decrease the cost of manufacturing through a hybrid design that uses AA2198-T8 alloys for the crucial parts and AA2024-T3 alloys for the remaining structure. The two main techniques for joining AA2024-T3 to AA2198-T8 are reversed double-sided friction stir welding (DS-FSW) and traditional single-sided friction welding (SS-FSW). They were carried out under unaltered tool rotation speed followed by five different welding speeds. The mechanical properties of the joints were explored, and the maximum joining efficiency of the welding process was 96% for reversed DS-FSW at 102 mm/min welding speed. The hybrid joint was tested for compliance with ASTM G34 standards to examine the welding joint's exfoliation corrosion (EXCO) for eight exposure times. The findings showed that joint efficiency decreased relative to as-welded joints, and mechanical property deterioration increased with EXCO exposure duration, reaching 40% for specimens exposed for 120 h to the corroding solution. It has been noted that morphology and grain size changes significantly impact EXCO.

An effective pore sealing post-treatment was applied on a micro-arc oxidation (MAO) layer coated on AZ91 Mg alloy using a new organic-inorganic sealant fabricated by mixing cement particles in paraffin wax. The corrosion behavior of the untreated alloy, the coatings before and after sealing treatment was comparably investigated in 3.5% NaCl solution by immersion tests and electrochemical measurements. Results show that the pores of the MAO coating are successfully sealed and the resultant surface is smooth and hydrophobic. The sealed coating provides excellent corrosion protection for Mg alloys by remarkably delaying the initiation of pitting corrosion. Moreover, the sealed MAO coating reveals an improvement in corrosion resistance compared with the unsealed coating. Such improvement is related to the hydrophobic surface and a new layer formed by the combination of ionic species originating from decomposed coating materials and cement particles in the electrolyte. The new layer along with the decomposed MAO coating develops a two-layer structure which postpones the initiation of pitting corrosion. In addition, the corrosion products that remain in pits also contribute to the smallest corrosion rate for the sealed coating. The sealing treatment using the sealant presented herein provides an effective way to modify porous coatings to enhance the corrosion resistance performance of magnesium alloys.

Carbon steel remains the most commonly used material in CO2 – containing oilfield, and other energy applications. Pitting corrosion is a prominent form of corrosion attack on carbon steel, and linked to the formation of non – protective iron carbonate (FeCO3) films and/or their breakdown. The conditions for local breakdown of FeCO3, and other fundamental aspects of pitting corrosion are still not clearly understood; particularly in relation to the evolution of the local chemistry within active pits. Local distribution of corrosion activities/species is likely to influence FeCO3 formation; evolution and properties to support and/or impede pit propagation. This study investigates the local corrosion environment within an artificially machined pits to understand the local pitting corrosion behaviour. It focuses on the local evolution of FeCO3 and pitting corrosion. Pits with specific geometry on X65 carbon steel samples are exposed to two different environments: pH of 4 and 5.9 for 168 h. Tests were performed at atmospheric pressure and 60 °C in 1 M NaCl solution. Linear polarization technique was implemented in combination with a suite of post-experiment surface analysis: Scanning Electron Microscopy, X-ray diffraction, 3D-profilometry and Raman spectroscopy for assessing overall corrosion rate, localised corrosion products and pitting characteristics. Results show that at both pH levels, more crystalline FeCO3 was formed within the pits than at the top surfaces. The size and compactness of FeCO3 decrease from the base of the pits towards the top surfaces, which correlates with the extent of pitting corrosion within the pit and the spatial variation in the local chemistry.

Ti-15-3 titanium alloy has been widely used as a connecting material for aerospace structural parts. However, the non-uniform pitting caused by salt spray corrosion and the limitations of the conventional electrochemical techniques in predicting localized corrosion seriously prevent the practical application of Ti-15-3 alloy. Herein, the electrochemical noise based on discrete wavelet transform and Hilbert-Huang transform is employed for studying pitting corrosion of both the untreated and polished Ti-15-3 alloy under different neutral salt spray time. Combining with the further analysis of the electrochemical impedance spectroscopy, a complementary evaluation is used to analyze the effect of surface roughness on pitting corrosion behaviors of Ti-15-3 alloy systematically. It is found that pitting forms of both surface roughness electrodes exposed to different salt spray time are successfully distinguished, and the polished Ti-15-3 alloy shows better corrosion resistance. Microstructural characterization confirms the inferences from electrochemical noise analyses, the results indicate that the smooth surface of the polished Ti-15-3 alloy is less vulnerable to the coexistence of metastable pitting and the growth of stable pitting, and effectively improves the resistance to pitting corrosion of Ti-15-3 alloy. Furthermore, a possible mechanism for the triggering of pitting corrosion of Ti-15-3 alloy with different roughness in salt spray environment is proposed. This work will provide significant insights for rational design of Ti-15-3 alloy used in the tropical ocean facilities to avoid the attack of pitting corrosion.

The correlation between (Ca, Mg, Al)-Ox-Sy inclusions and localised marine corrosion of EH36 steels was investigated. According to their ability to induce localised corrosion, the inclusions were categorised as ‘active’ or ‘inactive’, and the main difference between them was the ratio of CaO/Al2O3. The residual stress at the active inclusion/matrix interface was higher than the yield strength of the steel; therefore, a local plastic deformation region was preferentially formed, triggering localised corrosion initiation. Moreover, the occluded cell accelerated the localised corrosion propagation, and finally the dissolution of the inclusions and the matrix resulted in a stable pit.

The atmospheric corrosion behavior and mechanism of the 7A85 aluminum alloy exposed to the Qingdao industrial-marine atmospheric environment for five years was investigated using the weight-loss method, mechanical property analysis, morphology observations, scanning Kelvin probe force microscopy, and corrosion product analysis. The results showed that the mechanical properties of the exposed 7A85 Al alloy deteriorated considerably, which was mainly induced by pitting corrosion and intergranular corrosion. Al2CuMg and Al7Cu2Fe intermetallic particles were the main precipitates in the 7A85 Al alloy, and the particles not only induced a defective film but also acted as cathode phases in the precipitate–matrix galvanic corrosion couple, which led to pitting corrosion initiation during atmospheric corrosion in Qingdao. Moreover, intergranular corrosion initiated and then propagated owing to micro-galvanic corrosion along the grain boundaries.

A new type of pitting corrosion in copper, namely “moundless” corrosion, has recently been reported in Japan. This type of pitting corrosion has some unique morphological features that differ from ordinary types of pitting corrosion, such as type I or type II. Firstly, this type of pitting corrosion has no mound of corrosion products that cover the mouth of the pit. In addition, a glassy verdigris exists around the pit. Furthermore, the pit measures

Pitting corrosion would pose difficulty for the cleaning of equipment used in food processing, even when using the Cleaning in Place (CIP) process. It tends to occur at a location requiring welding. In general, Gas Tungsten Arc Welding (GTAW) is the most applicable process for food and drug equipment. To improve the properties of the weldment, filler metals are commonly used. However, the use of thin-sheet stainless steel in the application of filler metals would be difficult in food processing. In this research, the weld metal properties would be improved only by using N2 mixing to the backing gas during welding. Experiments were conducted using various mixtures of N2 on 1.5, 2.0, and 3.0 mm thicknesses of 304 stainless steel. The roots of weld metal taken from the samples were evaluated for corrosion properties in 3.5%NaCl from the polarization curves. The results showed the improvement of pitting corrosion from 379 mV to 757 mV, while the general corrosion rate decreased from 0.00477 mm/y to 0.00099 mm/y with 100%Ar and 100%N2, respectively. Both Nitrogen content and solidification rate together affected the solidification modes and ferrite contents that would affect the corrosion properties. At least 15%N2 mixing would be sufficient for weld metal property improvement. Due to the decrease of ferrite content from N2 addition, solidification cracking susceptibility test by fishbone test was acceptable with no cracking observed, showing the potential to recommend N2 mixtures for actual production.

The pitting corrosion of an aluminum alloy AA1050 after being processed by continuous closed die forging (CCDF) was evaluated by cyclic potentiodynamic polarization (CPP). Microstructure evolution, mechanical and corrosion behaviors were studied as a function of the total strain imposed. The CCDF process was carried out at 0, 16 and 24 passes with loading times of 10 and 15 s. The electron backscatter diffraction (EBSD) analysis revealed a grain refinement of 0.78 µm after 24 passes, which promoted an increment in the yield strength (YS), ultimate tensile strength (UTS) and vickers hardness (HV) by a factor of 9, 3 and 2 respectively; but the uniform strain and strain to rupture decreased by 93% and 72% respectively. Resistance to corrosion after 16 and 24 passes was compared with the reference material (0 passes), using CPP in a Na2S04 0.1 mol/l +100 mg/l of NaCl electrolyte. Results showed that the specimens with 24 passes decreased its corrosion rate one order of magnitude. In addition, specimens with very fine grain sizes have shown nobler pitting potential and lower pitting volume fraction than coarse grain specimens.

This study presents a combined electrochemical and X-ray photoelectron spectroscopy (XPS) surface analytical investigation on the natural passivation process and its effect on Cl− induced corrosion resistance of traditional carbon steel, ferritic and austenitic stainless steels (SSs) (i.e. HRB400 steel, 430 and 304 SSs) in simulated concrete pore solution (SPS). It was found that a complete and more compact passive film with a stratified structure could be naturally formed on the tested steel surfaces after different immersion time. The chemical composition of the passive film and its corrosion resistance strongly depended on the alloying element and natural passivation time. For HRB400 steel, the outer layer of natural passive film was mainly composed of Fe3+ species and the inner layer was predominated by Fe2+ ones, while the outer layer of natural passive film formed on SSs surface consisted of Fe and Cr oxides and hydroxides, enriched in Fe3+ species, and an inner layer was made of mixed Fe2+ and Cr3+ oxides (enriched in Fe2+ species). The natural pre-passivation could effectively improve the Cl− induced corrosion resistance of three steels. Compared with HRB400 steel, both austenitic and ferritic SSs exhibited the better corrosion resistance due to the formation of Cr-enriched passive film, of which, 304 SS had the highest pitting corrosion resistance.

The effect of multi-pass MAG welding transfer modes on the sigma phase precipitation and corrosion performance of AISI 316L thick plate were investigated. The evolution of the microstructure was examined by optical and electron microscopy as well as ferritscope measurements and energy dispersive X-ray spectrometry. An electrochemical microcell was then used to characterize the electrochemical behaviour of the different weld regions. The fusion line was the most critical zone for pitting corrosion for all welding procedures, due to the sigma phase precipitation, alloy elements partitioning and galvanic coupling between base metal and weld metal. It was observed the formation of sigma phase after short-circuiting or spray-arc modes, with no evidence of it to the pulsed-arc, which obtained the best corrosion resistance performance. The results evidenced the selective corrosion around sigma phase due to the depletion in Cr and Mo, with subsequent pitting nucleation. A strong correlation between the MAG welding transfer modes and the sigma phase morphology was observed. The influence of weld parameters on microstructure evolution and corrosion resistance performance was discussed. The corrosion resistance performance of the MAG welding procedures was ranked as: pulsed-arc > short-circuit > spray-arc.

The aim of this study is to investigate the effects of seawater retention inside subsea oil and gas pipelines on the corrosion of several corrosion resistant alloys commonly used in seawater. Pitting corrosion, crevice corrosion, and electrochemical test samples were immersed in coastal waters at the depth of about 170 m in South China Sea (western Pacific Ocean). Assessments of the pitting and crevice corrosion for different alloys were carried out through electrochemical measurements and surface characterizations. The results showed that, the order of the pitting corrosion resistance of five alloys in marine environment was: 825 Ni-based alloy ∼ 2507 super duplex stainless steel > 2205 duplex stainless steel ∼ 317L ∼ 316L, while the crevice corrosion resistance was: 825 Ni-based alloy ∼ 2507 super duplex stainless steel > 2205 duplex stainless steel > 317L > 316L. The pitting initiations of 2205 duplex stainless steel, 2507 super duplex stainless steel, and 825 Ni-based alloy were later than those of 316L and 317L stainless steels. After the exposure for 592 d, the passivation for 316L, 317L and 2205 stainless steels were completely broken down while 2507 super duplex stainless steel and 825 Ni-based alloy still had a wide and stable passive zone. In crevice corrosion samples, the most severe corrosion was observed in the crevice edge area. A boat shaped corrosion pit was found in the inner coverage area far from the edge of crevice, which was probably related to the distribution of microorganisms in this area.

In this present work, solutions are sought regarding the problems of dissimilar welding of austenitic stainless steel for industrial fabrication work. There is support for the popular 200 grade stainless steel as a low-cost alternate to for 300 series grade in developing countries in Southeast Asia, especially Thailand, Vietnam, Myanmar, Laos and Cambodia. This study evaluates the microstructure, mechanical properties and pitting corrosion of dissimilar welding of the alternative low cost stainless steel grades 204Cu and 304 employing a GTA welding process by using different filler metals, namely 309L and 316L. It was found that for both weld metals and both filler metals the melting area in 204Cu BM side was larger than the 304 BM side. The delta-ferrite content in the weld metal of 309L was lower than 316L, HAZ and PMZ on the 204Cu side was wider than the 304 side of both welded metals. For the mechanical properties, the hardness volume of the welded metal of the 309L was higher than the 316L. Hardness adjacent to the fusion line of the 304 side was lower than the 204Cu side of both the filler metals. The tensile strength of the welded metal of 316L was more than the 309L and both welded metals ductile fractured in the welded zone (close to the 304 BM side). The pitting corrosion resistance of the welded metal for 309L was higher than for 316L and both welded metals initiated pitting at the boundary between the austenite phase and the delta-ferrite phase.

The role of heat treatments, non-metallic aluminium oxide inclusions, and microstructure on the corrosion resistance of an API 5L X42 steel was examined in a 0.1 M chloride environment (pH ∼ 7). Energy Disperse Spectrometry analysis found aluminium oxide inclusions on as-rolled, annealed, normalised, quenched, and quenched plus tempered samples. Heat treatments changed the percentage of aluminium oxide inclusions in X42 steel. Annealed, normalised, quenched, and quenched plus tempered samples reached mean values of 0.15, 0.15, 0.12 and 0.07 percent respectively, whereas, rolled samples reached a mean value of 0.85 percent. It was found that the percentage of aluminium oxides did not affect the corrosion rate but promoted pitting corrosion. The average corrosion rate showed the following order in millimetres per year: as-rolled (0.067)

2205 DSS is an excellent corrosion-resistant engineering metal material, but it is still threatened by microbiological corrosion. The addition of copper elements is a new approach to improving the resistance of 2205 DSS to microbiological corrosion. In this study, 2205-Cu DSS was compared with 2205 DSS to study its antimicrobial properties and resistance to microbiological corrosion in the presence of the electroactive bacterium Shewanella algae. The results showed that compared to 2205 DSS, the biofilm thickness and the number of live bacteria on the surface of 2205-Cu DSS were significantly reduced, demonstrating excellent antimicrobial properties against S. algae. Electrochemical tests and surface morphology characterization results showed that the corrosion rate and pitting of 2205-Cu DSS by S. algae were lower than that of 2205 DSS, indicating better resistance to microbiological corrosion. The good antimicrobial properties and resistance to microbiological corrosion exhibited by 2205-Cu DSS are attributed to the contact antimicrobial properties of copper elements in the 2205-Cu DSS matrix and the release of copper ions for antimicrobial effects. This study provides a new strategy for combating microbiological corrosion., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Introduction: Primary Ewing Sarcoma of Bone is a malignancy whose treatment requires both systemic chemotherapy and local control through surgical resection and/or radiation. Ewing Sarcoma of the pelvis has been noted to confer a worse prognosis relative to other anatomic sites of Ewing Sarcoma. This study explores the presenting features, treatment modalities for local control, and overall survival of primary Ewing sarcoma of the pelvis in comparison to other commonly affected anatomic sites. Methods: The National Cancer Institute Surveillance, Epidemiology, and End-Results (SEER) database was used to identify cases of pelvic Ewing sarcoma diagnosed between years 2004 and 2015. Demographic variables including sex, race, and age at diagnosis were described for each case, as well as therapeutic modalities including surgery and radiation. Bone-specific Collaborative Staging variables, including tumor size, tumor extension, and metastasis at diagnosis, were described for the same cohort. Univariate and multivariate assessments were performed for statistical comparison between presenting factors, treatment modalities, and between anatomic locations of presentation. Results: Within the database, 296 patients with Ewing sarcoma of the pelvic bones were available for review, which represented 25.7% of the 1152 cases surveyed across all anatomic sites. In the subset of patients with Ewing Sarcoma of the pelvis, 63.5% were male; the median age of diagnosis was 17 years; extra-compartmental tumor extension was noted in 82.1%; average tumor size was 9.7 cm; and metastasis at diagnosis was noted in 46.1% of the cohort. Only 28.6% of the pelvis sarcoma patients received surgical resection as part or all of their local control treatment, while 67.6% received some form of radiation therapy. When compared to the presenting features of Ewing Sarcoma from other anatomic sites, patients with pelvic tumors had larger tumors at time of diagnosis, higher rates of metastatic disease, and were less likely to undergo surgical intervention. The 2-, 5-, and 10-year overall survival rates for the patients presenting with Ewing Sarcoma of the pelvis was 70.3%, 49.7%, and 41.9%, respectively, which were significantly lower across all time-points than any other anatomic site. Discussion and Conclusion: Ewing Sarcoma of the pelvis is an aggressive malignancy that presents with relatively large tumors and a high rate of metastatic dissemination. Surgical intervention is less frequent when Ewing Sarcoma presents in the pelvis than when it presents in other anatomic locations. These factors may contribute to the worse overall survival of Ewing Sarcoma when compared to the same diagnosis originating in other anatomic sites. Prospective, randomized study is required to determine the true causal effects of these factors on survival.

The effects of additive manufacturing (AM) and post-AM heat treatment on microstructural characteristics and pitting corrosion of 2205 duplex stainless steel were studied and benchmarked against its conventionally hot-rolled counterpart. The rapid solidification and possible loss of N associated with AM resulted in a non-equilibrium microstructure dominated by δ-ferrite with a minor fraction of austenite and abundant Cr2N precipitation. Atom probe tomography revealed that no depletion of Cr occurs around intragranular Cr2N. A deduction in Cr was observed adjacent to intergranular Cr2N particles, however, Cr content in these regions remained above the critical value of 13 wt%. Post-AM heat treatment was effective in restoring the duplex microstructure while dissolving the Cr2N precipitates. Although the pitting resistance in the as-built AM specimen was lower than that of its hot-rolled counterpart, it was fully recovered after post-AM heat treatment.

In this study (Part II), the empirical formulation of corrosion model of a ship’s ballast tank was developed to predict nonlinear time-dependent corrosion wastage based on the advanced data processing technique proposed by Part I. The detail on how to propose generalised mathematical formulation of corrosion model was precisely documented in the previous paper (Part I). The statistical scatter of corrosion data at any exposure time was investigated by the refined method and formulated based on a 2-parameter Weibull distribution which selected the best fit PDF. Throughout the nine (9) steps, empirical formulation of the ship’s seawater ballast tank was successfully proposed and four (4) key step results were also obtained. The proposed method in Part I was verified and confirmed by this application of seawater ballast tank, thus making it possible to predict accurate behaviours of nonlinear time-dependent corrosion. Developed procedures and obtained corrosion damage model for ship’s seawater ballast tank can be used for development of engineering software.