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Chloride ions are responsible for triggering severe corrosion in the marine environment. Hence, there is a need to deploy corrosion resistant materials such as hexagonal boron nitride (h-BN) sheet to protect mechanical components operating under such harsh conditions. In this work, a first-principles approach was employed to investigate the effect of fluorine modification on the thermodynamic and kinetic behaviors of oxygen on different kinds of vacancy-defective hexagonal boron nitride (h -BN) in a Cl-containing marine environment. Geometrical and electronic structures were systematically analyzed along with adsorption and diffusion behaviors. The existence of a low energy barrier implies that there is a relatively attenuated ability to inhibit O diffusion for double vacancy V BN - h -BN sheet compared to single vacancy V B - h -BN and V N - h -BN sheets. Interestingly, the fluorine functionalization for three defective h -BN sheet is found to cause an increased energy barrier of O diffusion. The F @ Cl @ V N - h -BN sheet possesses the highest diffusion energy barrier, indicating a superior anti-oxidation property in the marine environment. This study provides some fundamental guidelines for realizing high-performance h -BN sheets for protecting equipment and components used in marine applications. [ABSTRACT FROM AUTHOR]

The Na 2 O-WO 3 binary system is an important chemical system with various applications, such as catalysts, energy and corrosion resistant materials. In this study, phase equilibria and liquidus temperatures in the Na 2 O-WO 3 binary system have been experimentally determined in air. The system was investigated at the temperature range from 550 to 830 °C using a high-temperature equilibration and quenching technique. The microstructure and compositions of the phases obtained in the quenched samples were then analyzed by an electron probe micro-analyzer (EPMA). Binary compounds Na 2 W 2 O 7 , Na 2 W 4 O 13 and Na 2 W 6 O 19 have been identified and the liquidus temperature temperatures in these primary phase fields were determined. Two peritectic points in the system were confirmed and compared with previous data. The present study provided useful thermodynamic data including liquidus and solid solutions. Accurate phase equilibria data will be used as the base for the development of thermodynamic modelling. [ABSTRACT FROM AUTHOR]

The growing need for more energy efficient systems has led to advent of hard and corrosion resistant materials which are difficult to machine with both conventional and non-conventional machining techniques. Although ECM offers athermal and force-free dissolution, the workpiece surface integrity in multicomponent materials is limited with ECM due to several multi-physical phenomena occurring on the surface like selective phase dissolution, passivation, pitting, particle breakout, etc. To tackle these challenges, aggressive acidic and basic reagents are added to the electrolytes. Although these reagents improve the machining performance, they are not sustainable for the environment and human life as they generate harmful waste which is difficult to dispose and recycle. Furthermore, the handling of these aggressive electrolytes requires specialized coatings, resins, filters, catalysts, etc. to protect the machine tools and equipment from damage. Hybrid laser-ECM (LECM) is a relatively novel drill-mill processing technique to process these advanced materials while using neutral electrolytes, thereby potentially reducing the negative impact of using acidic/basic reagents in electrolytes. Under controlled conditions and proper laser alignment, LECM can simultaneously apply laser and EC process energies in the same machining zone to provide synergistic benefits manifesting in terms of dominance of kinetics and thermodynamics over pure electrodynamics in ECM. This provides multi-fold benefits in improving passivation weakening and homogenize multiphase dissolution. Therefore, this study investigates for the first time the machining performance, removal behaviour, reaction products and power/resource consumption of LECM in neutral electrolyte in comparison to ECM in various neutral and basic electrolytes. The NbC–Ni cermet was used as the workpiece material, which is a cobalt-free alternative to conventional WC-Co. The results revealed that LECM in neutral NaNO 3 compared to ECM with NaOH addition not only provided better Sa (2.02 μm, 24% ↓), M.R.R. (153 μg/s, 31% ↑), aspect ratio (0.048, 14% ↑) and similar passivation weakening capability while maintaining a nearly neutral pH (8) of the reaction products, but also reduced electrolyte usage by 23.6% with a 16.4% increase in power consumption. These aspects make LECM a sustainable and cost-effective candidate for processing modern passivating multiphase materials like newer cermets, super alloys, high entropy alloys, etc. with nearly same performance as achieved by using ECM with acidic/basic electrolytes. Further fundamental and applied research is needed in LECM to meet the industrial specifications. [Display omitted] • LECM in neutral electrolyte provides sustainable, precise and productive machining comparable to ECM with aggressive electrolytes. • Machinability of NbC–Ni cermet is investigated as potential alternative to cermets with carcinogenic Co binder. • Material removal characteristics of NbC–Ni cermet with ECM/LECM are analysed. • Power and resource consumption, and environmental impact of LECM and ECM are reported. • LECM enhances processing benefits in sustainable way with marginal additional power consumption. [ABSTRACT FROM AUTHOR]

Nickel-titanium (NiTi) alloys are key in making medical implants due to their mechanical properties and biocompatibility, yet suffer from microbiologically influenced corrosion (MIC). This study isolated three samples of intestinal microbiotas from patient's stents to investigate their corrosion behavior on NiTi alloy. Using metagenomic analysis, corrosion electrochemistry, and morphology characterization, we found that different microbiota samples formed biofilms on NiTi alloy, causing varying degrees of pitting corrosion. The corrosion was linked to riboflavin-mediated MIC, with differences in riboflavin synthesis genes affecting corrosion rates. This research offers new insights into the MIC of NiTi alloys and helps develop more corrosion resistant materials. • Human intestinal microbiota significantly accelerates MIC of NiTi alloy. • Different human intestinal microbiota samples lead to distinct patterns of pitting corrosion and varying corrosion rates. • Riboflavin is identified as a facilitator of MIC by intestinal microbiota. [ABSTRACT FROM AUTHOR]

Hydrogen gas (H 2) is notified as a renewable energy carrier. It is wanted to discover a low-cost electrocatalyst for the hydrogen evolution reaction (HER) to substitute the high-cost Pt in electrolysis cell. Niobium electrocatalyst nominated to substitute noble materials for electrocatalytic H 2 production and its electrochemical manner was estimated in H 2 SO 4 acid of various concentrations utilizing a steady-state polarization and electrochemical impedance spectroscopy (EIS). The influences of acid concentration, cathodic potential and temperature on the H 2 creation were examined. The outcomes display that HER on Nb electrode proceeds by the Volmer-Heyrovsky mechanism. EIS tests, under open circuit and under cathodic polarization, were performed and the fitting has been done utilizing a suggested model for the electrode/electrolyte interface. Apparent activation energies (E a) were estimated to be ca. 10.5 kJ mol−1 for the HER on Nb. Thus, Nb is a good electrocatalyst for the cathodic H 2 manufacturing. • Nb is a low-cost electrocatalyst for the hydrogen evolution reaction (HER). • HER on Nb electrode proceeds by the Volmer-Heyrovsky mechanism. • Apparent activation energies (E a) are 10.5 kJ mol−1 for the HER on Nb. • Nb is a good electrocatalyst for the cathodic H 2 generation. • Nb is a corrosion resistant material in aggressive acid medium. [ABSTRACT FROM AUTHOR]

Proton exchange membrane fuel cells (PEMFCs) can experience reverse current during start-up and shutdown due to local fuel starvation, which also lead to carbon corrosion in the gas diffusion layer (GDL) and significantly reduce the durability of PEMFCs. However, the degeneration of the gas diffusion backing (GDB) is currently unclear. In this work, variety rule of structural and physical parameters are taken as object to investigate the performance degradation of GDB under different carbon corrosion potential. The experimental results indicate that the electrical conductivity experience the most significant decrease in particular at the corrosion potential changes from 0.7 V to 1.4 V. The oxidation of GDB significantly reduces the output power density, leading to a 30.85% decrease in the maximum output power density compared to the uncorroded state. The simulation results suggest that the impact of porosity degradation is relatively insignificant, whereas the electrical conductivity is the most pronounced for the decrease in durability. The findings indicated that the primary determinant of temperature distribution is the heat generated by electrochemical reactions dependent on electrical conductivity. For future technology of corrosion resistance for the GDB, it is necessary to develop carbon corrosion resistant materials and control strategy. • High reverse potentials decrease the fuel cells output performance. • Electrical conductivity has the most critical impact on the durability. • Thermal conductivity degenerate has little effect on temperature distribution. • Electrical conductivity degenerate decrease the oxidation reduction reaction. [ABSTRACT FROM AUTHOR]

• Mitigation of external and internal corrosion behaviour in high pressure high temperature (HPHT) oil wells based on material design and selection. • Main challenges associated with structural and stainless steels used in HPHT are sweet and sour corrosion. • Hydrogen ingress in HPHT results in embrittlement, stress induced corrosion cracking and corrosion fatigue leading to metal dissolution and final material breakdown in conventional dilute alloys. • Equiatomic and non-equiatomic complex concentrated alloys and coatings have better resistance to hydrogen embrittlement, stress corrosion cracking and corrosion fatigue than most conventional alloys in simulated HPHT environments. • Implications of potential applications of complex concentrated alloys such as cost and scalability issues are imminent. This review discusses potential applications of complex concentrated alloys (CCAs) for mitigating sweet and sour corrosion in high-pressure, high-temperature (HPHT) wells with concentrated chlorides, carbon dioxide and hydrogen sulphide. The harsh oil and gas environments lead to severe components failures through sour corrosion, sweet corrosion, hydrogen induced cracking, stress corrosion cracking and corrosion fatigue. Many of these failures are material driven. Hence the domain of complex concentrated alloys are being explored to reduce the severity of failures in the oil and gas industry, especially in HPHT zones. The CCAs possess high thermal stability, the balance of strength and ductility resulting from complex deformation mechanisms, and high creep resistance due to sluggish diffusion. These properties are driven by the design philosophy: high entropy and enthalpy of mixing, severe lattice distortion, sluggish diffusion, chemical ordering, and the cocktail effects. These effects allow for greater flexibility and many degrees of freedom which is absent in conventional one principal element-based materials. Most CCAs have shown excellent and superior mechanical and corrosion properties in some of the environments of currently used corrosion-resistant alloys in the oil and gas industry. This review highlights recent literature on potential high entropy alloy chemistries, microstructural features and their effects on mechanical and corrosion properties, and areas for future research directions. [ABSTRACT FROM AUTHOR]

Developing efficient microwave absorbing materials (MAMs) suitable for prolonged use in marine environments is of great importance. Laser cladding serves as one of the new techniques for the material of surface modification and microwave-absorbing materials in the 3D printing. However, it is usually challenging to prepare materials that combine desirable printability, corrosion resistance, and microwave absorption properties using this technology. To enhance the microwave absorption of laser-clad Ni-based alloys, the method of impedance modulation was employed by incorporating ceramic powders with varying AlN content. The results show that Ni/AlN/MWCNTs composite functional materials with core-shell heterostructures were prepared under optimized laser processing parameters. This unique core-shell structure optimizes impedance matching increased polarization loss and multiple scattering to boost microwave absorption. The optimized 20 wt% AlN content resulted in a minimum RL of − 13.24 dB at 13.86 GHz, in addition, electrochemical tests showed that AlN enhanced the resistance to the corrosion medium transfer during the corrosion process, and the corrosion resistance of the Ni/AlN/MWCNTs composites material (self-corrosion current density (8.52 × 10−8), the charge transfer resistance (1.55 × 10−5)). Therefore, this work provides innovative theoretical and practical insight for the design and manufacture of advanced microwave-absorbing materials for harsh environments by laser melting technology. [Display omitted] • The first application of laser cladding in the preparation of metal-based microwave-absorbing composite materials. • The coating design of the core-shell structure gives superior impedance matching and wave-absorbing capability. • Reveal the electromagnetic wave absorbing mechanism and corrosion resistance for the addition of AlN ceramics. • A new strategy for the regulation and the cladding of corrosion resistant wave-absorbing materials by in-situ deposition. [ABSTRACT FROM AUTHOR]

Cr 2 O 3 is the best-known corrosion resistant refractory materials under high temperature extremely harsh environment. However, the formation of toxic, carcinogenic & water-soluble Cr(VI) compounds during its application remained a major predicament. Here, we have introduced a facile route to fabricate the Al 2 O 3 -CaO-Cr 2 O 3 refractory castables to mitigate Cr(VI) using basic silica sol (pH∼9) via in-situ secondary phase modification. Basic silica sols 0.25, 0.49 and 0.98 wt% (CaO/SiO 2 ratio of 5.8, 2.9 and 1.45 respectively) were doped by keeping the castables properties reasonable. Addition of silica drastically reduces the mid-temperature (500–1100 °C) formation of Cr(VI) phase (CaCrO 4), while relatively higher temperature Cr(VI) phase (hauyne, Ca 4 Al 6 CrO 16) totally disappeared from 900 to 1300 °C. However, at 1300–1500 °C, silica addition promote the solid solution phase formation like Ca(Al,Cr) 12 O 19 and (Al,Cr) 2 O 3 where chromium exists as +3 oxidation state. Also, silica addition reduces the dimensional tolerance of the castables at a higher temperature associated with the secondary phases (dehydration of cement phases and expansive formation of CaAl 12 O 19). A comparable mechanical strength (up to 156 MPa) and a remarkable Cr(VI) reduction (up to 94%) could be achieved upon silica addition. Image 1 • Al 2 O 3 -CaO-Cr 2 O 3 castables were fabricated via doping SiO 2 sol to mitigate Cr(VI). • CaCr6+O 4 reduces drastically on SiO 2 addition, while Ca 4 Al 6 Cr6+O 16 doesn't form. • SiO 2 promotes the formation of Ca(Al,Cr3+) 12 O 19 & (Al,Cr3+) 2 O 3 at 1300–1500 °C. • SiO 2 reduces dimensional tolerance of the castables at the higher temperature. • A remarkable mechanical strength (∼156 MPa) & Cr(VI) reduction (∼94%) was achieved. [ABSTRACT FROM AUTHOR]

We describe new approaches based on compositional manipulation of the cementitious binder, and its geometrical arrangement, to mitigate steel corrosion in concrete, and a new ability to study corrosion processes from a fundamental point of view. First, we present a new approach to mitigate/delay corrosion initiation using calcium aluminate cement (CAC) and Ca(NO 3) 2 based functional coatings by replacing a fractional thickness of the ordinary portland cement (OPC) concrete cover. Second, within a related framework, we demonstrate how tailoring the binder chemistry to produce enhanced quantities of AFm phases is a significant means to immobilize Cl− ions while actively generating corrosion inhibiting species; thereby delaying corrosion initiation. Finally, we offer new insights from reactive force field molecular dynamics (ReaxFF-MD) simulations as a means to interrogate and explain electrochemical processes at the atomistic scale. We present examples of how atomistic simulations can uncover the origins of passivity and Cl− induced corrosion at a molecular level and how such understanding can accelerate the development of new corrosion resistant materials and mitigation strategies. [ABSTRACT FROM AUTHOR]

Abstract Engineering structures are often subjected to the conditions of cyclic-loading, which onsets material fatigue, detrimentally affecting the service-life and damage tolerance of components and joints. Carbon fibre reinforced plastics (CFRP) are high-strength, low-weight composites that are gaining ubiquity in place of metals and glass fibre reinforced plastics (GFRP) not only due to their outstanding strength-to-weight properties, but also because carbon fibres are relatively inert to environmental degradation and thus show potential as corrosion resistant materials. The effects of cyclic loading on the fatigue of CFRP are detailed in several papers. As such, collating research on CFRP fatigue into a single document is a worthwhile exercise, as it will benefit the engineering-readership interested in designing fatigue resistant structures and components using CFRP. This review article aims to provide the most relevant and up-to-date information on the fatigue of CFRP. The review focuses in particular on defining fatigue and the mechanics of cyclically-loaded composites, elucidating the fatigue response and fatigue properties of CFRP in different forms, discussing the importance of environmental factors on the fatigue performance and service-life, and summarising the different approaches taken to modelling fatigue in CFRP. [ABSTRACT FROM AUTHOR]

Highlights • Complex structure with ultrafine-grained zone and coarse-grained zone was produced. • Ultrafine-grained zone produced by FSP exhibited high strength and low ductility. • Complex structure exhibited great mechanical properties and corrosion resistance. • The alleviation of strain concentration between PZ and BM led to improved ductility. Abstract A complex structure consisting of ultrafine-grained processed zone and coarse-grained base material zone was developed in this study, aiming at improving the yield strength of a high nitrogen stainless steel without sacrificing corrosion resistance and ductility. The ultrafine-grained processed zone was produced by friction stir processing, leading to ultra-high strength and great pitting corrosion resistance, but significantly reduced ductility; the coarse-grained zone exhibited excellent ductility but a very low yield strength. The enhancement and coordination between the processed zone and coarse-grained zone resulted in significantly improved yield strength and ductility of the complex structure. Thus, a combination of excellent mechanical properties and corrosion resistance was successfully achieved. [ABSTRACT FROM AUTHOR]

Abstract Surfaces of machine parts or tools are subjected to corrosive stresses or wear. To increase the wear resistance of surfaces, metal matrix composite (MMC) can be applied. For higher wear resistance, it is important to achieve a high particle content and a homogenous particle distribution. In this work, aluminium bronze substrate was reinforced by spherical fused tungsten carbides via laser melt injection. The laser power, travel speed and powder mass flow were varied. The influence of these process parameters on the hard particle content was investigated in single tracks. Furthermore, laser melting and laser melt injecting were compared. Laser melt injecting resulted in a significant increase in the track volume. Analytical calculation showed that the volume increase was higher than the volume of the injected particles. Single tracks composed of MMC could be produced without cracks and pores. Depending on the energy input per unit length, undesired melting of the particles was observed. The particle content was investigated via binary pictures from metallographic cross-sections using two different software packages. An approach to calculate the particle content as a function of the width, depth and height of laser melt injected tracks via circle segments is presented. [ABSTRACT FROM AUTHOR]

Abstract ZrO 2 films were prepared on 304 stainless steel by sol-gel method. The resistance of ZrO 2 films to high temperature and high humidity coal gas corrosion was studied. Experiments show that the film on the surface of the sample without vacuum treatment is ZrO 2 -Cr 2 O 3 -Fe 2 O 3 (ZrO 2 -passivation film) composite film. This film is effective against intergranular corrosion, however, as the corrosion humidity increases, sulfide corrosion occurs on the surface of the coated sample. The XPS test showed no change in the composition of the ZrO 2 film before and after etching. The sulfide of the sample is caused by Cr 2 O 3 -Fe 2 O 3. The high density ZrO 2 film is very resistant to high temperature coal-gas corrosion. Graphical abstract Image 1 Highlights • The stainless steel surface at the gap of the ZrO 2 film is passivated to form a ZrO 2 -Cr 2 O 3 -Fe 2 O 3 composite film. • The passivation film in ZrO 2 -Cr 2 O 3 -Fe 2 O 3 composite film provides a starting site for pitting corrosion. • ZrO 2 films was shown to provide good resistance to S penetration into the matrix at 600 °C. • Reducing the porosity of ZrO 2 film can improve its protective performance. [ABSTRACT FROM AUTHOR]

Abstract Ni-B/SiC micro- and nano-composite coatings were electrodeposited in a modified watts bath containing SiC micro- and nano-particles with the average size of 3 μm and 100 nm, respectively. The chemical composition, SiC content; X SiC (wt.%), morphology, surface roughness, thickness, hardness and corrosion resistance of the deposited coatings were studied as a function of the particle concentration in the deposition bath (C SiC = 2, 4, 6, 8 g/L) and deposition current density (i d = 0.5, 1, 2 and 3 A/dm2), using Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Inductively Coupled Plasma (ICP), X-Ray Diffraction (XRD), microhardness measurements and potentiodynamic polarization (PP) tastings, respectively. The results indicated that the SiC content and surface roughness (R a) of micro-composite coatings are increased with increasing both the C SiC and i d and reached to the maximum of X SiC = 14.8 wt% and R a = 4.58 μm at the C SiC = 8 g/L and i d = 3 A/dm2. While the SiC content and roughness of nano-composite coating are initially increased and then decreased with increasing both the C SiC and i d and the maximum of X SiC = 9.6 wt% and R a = 2.28 μm were obtained at the C SiC = 4 g/L and i d = 1 A/dm2. The thickness of both type of coatings increases almost linearly with i d and micro-composite coatings exhibit greater thickness values. The nano-composites exhibit higher hardness and corrosion resistance than micro-composites despite having lower SiC contents. The maximum hardness and minimum corrosion resistance were 1035 HV and 0.03 μA/cm2 for micro- and 889 HV and 0.38 μA/cm2 for nan-composite coatings, respectively. Highlights • Ni-B/SiC micro-/nano-composite coatings were electrodeposited using Watts bath. • SiC micro-/nano-particles improves Ni-B coatings hardness and corrosion resistance. • The highest hardness and corrosion resistance obtained at the maximum SiC content. • Nano-composite coatings show higher hardness & corrosion resistance than micro-ones. • SiC content of micro-composite coatings was higher than nano-composites coatings. [ABSTRACT FROM AUTHOR]

Highlights • A flexible, superhydrophobic and conductive nanofiber composite was prepared. • The nanofiber composite exhibited excellent durability and corrosion resistance. • The nanofiber composite could be used for wearable strain sensors. • The sensing performance could be maintained after cyclic abrasion and stretching. Abstract Conductive polymer composite based strain sensors have promising applications in the fields of artificial skin, wearable health-care device, etc. However, fabrication of strain sensors with good stretchability, anti-corrosion, excellent durability and reliability remains challenging. In this work, a superhydrophobic strain sensor based on conductive thermoplastic polyurethane/carbon nanotubes/polydimethylsiloxane (TPU/CNTs/PDMS) was prepared by ultrasonication induced CNTs decoration onto the electrospun TPU nanofiber surface, followed by the PDMS modification. Uniformly dispersed CNTs on the nanofiber surface with a hierarchical structure construct the conductive network. The PDMS layer with a low surface energy endows the nanofiber composite with superhydrophobicity thus anti-corrosion property. The introduction of CNTs/PDMS improves both the Young's modulus, tensile strength and the elongation at break. The superhydrophobicity and conductivity can be maintained after the cyclic stretching-releasing test, displaying excellent durability. When used as a wearable strain sensor, the nanofiber composite is capable of detecting body motion and could work even under harsh conditions (moisture, acid and alkaline environment), showing promising application in wearable electronics. [ABSTRACT FROM AUTHOR]

Abstract Magnesium (Mg) alloys are promising biodegradable metals for biomedical applications but limited by their too fast degradation rates. In this study, selective laser melting was used to fabricate three-dimensional honeycomb nanostructure-encapsulated Mg alloys, in which the honeycomb nanostructure was constructed by graphene oxide (GO) as a second phase and the grains of Mg alloys were encapsulated in the honeycomb unit. Results showed that GO distributed along the grain boundaries and gradually wrapped ɑ-Mg grains as GO content increasing. It was worth noting that a honeycomb nanostructure was formed with ɑ-Mg grains encapsulated in the honeycomb unit at a certain GO content (1.0 wt% in this study). As a result, the corrosion resistance and mechanical properties were both improved, which might be ascribed to the following mechanisms: (I) ɑ-Mg grains were refined due to the reduced connection and promoted nucleation by GO; (II) Benefiting from the outstanding anti-permeability of GO, the honeycomb nanostructure acted as a tight barrier to restrain the propagation of corrosion; (III) GO reinforced the corrosion layer to prevent it falling off the Mg matrix; (Ⅳ) The oxygen-containing groups on GO facilitated the deposition of bone-like apatite and further hindered the invasion of corrosive medium. These findings demonstrated the multiple defensive roles against corrosion in the honeycomb nanostructure-encapsulated Mg alloys and their great potential in biomedical applications. [ABSTRACT FROM AUTHOR]

Abstract Application of deep holes is extensively found in the oil and gas industry to manufacture downhole equipment. These deep holes are fabricated in drill collars to deploy delicate sensors downhole for obtaining vital information like temperature, pressure and other geo-physical data from the bottom of the hole. High temperature and corrosion resistant materials like Inconel 718 is often used for drill collars to shield these sensitive communication equipment from the hostile downhole environment. Gundrilling is an established hole making method known for drilling precise and high aspect-ratio (AR>10) holes in conventional materials such as steels, cast iron and aluminium alloys etc. However, gundrilling of Inconel 718 offers unprecedented challenges like excessive tool wear, hole straightness deviation due to poor thermal conductivity and work-hardening tendency of the alloy. Moreover, as the drilling depth increases the deviation is further exacerbated due to the low rigidity of long gundrill shafts. The present study in the Phase 1 introduces a dynamic model using multispan Euler-Bernoulli beam theory to evaluate the effectiveness of coolant pressure and rotation speed during deep hole fabrication in Inconel 718. In addition, experimental investigations have been conducted to validate the model by studying the effects of coolant pressure and rotation speed on straightness of the fabricated holes. It was found that the straightness deviation was 0.37 mm corresponding to 137.89 bar and 1600 rpm coolant pressure and rotation speed respectively. In Phase 2, a non-contacting EDM process was used to fabricate a straight guide hole followed by conventional gundrilling (CG) with optimum pressure (137.89 bar) and speed (1600 rpm) obtained from the Phase 1 trials. The experimental results revealed that the thrust force reduced drastically from 800 N (CG) to 250 N (EDMG). Moreover, a significant improvement in both rake wear and flank wear was also observed. Finally, a straightness deviation of 0.19 mm was recorded for a maximum drilling depth of 350 mm which is 48.65% lesser than CG. From the study, it was found that this novel EDMG process improved the drilling capability of Inconel 718 by reducing the thrust force generated, enhancing tool life and minimizing the straightness deviation. Highlights • A novel sequential electrical discharge machining and gundrilling (EDMG) process has been proposed for drilling deep holes in difficult-to-cut materials like Inconel 718. • A significant improvement was observed both in rake and flank wear of the tool. • Gun drill dynamic behaviour model has been proposed and validated to identify optimum drilling parameters. • A drastic reduction in thrust force was obtained during EDMG when compared to conventional gundrilling (CG). • An improvement of 48.65 % was achieved in hole straightness deviation after EDMG when compared to CG. [ABSTRACT FROM AUTHOR]

Abstract Electroless Ni plating is commonly used as a coating of machined parts because of its superior corrosion resistance. The ITER Blanket Remote Handling System will use electroless Ni plating but will be operated in a γ-ray radiation environment, for which corrosion resistance—essential for the remote maintenance of ITER in-vessel components—has never before been demonstrated. This paper presents irradiation tests of electroless Ni plating carried out under dry or humid conditions. Corrosion resistance of electroless Ni plating was markedly affected in humid environments, however, in dry environments radiation resistance was verified. From surface analyses we can infer that radiolysis-enhanced corrosion was most likely caused by hydroxyl radicals produced from the interaction of water vapor and γ-rays in humid environments. [ABSTRACT FROM AUTHOR]

Abstract In this research, a new method to identify the corrosion types (generalized, mixed, localized, and the passivation situation) is proposed. The proposed method is based on the electrochemical noise analysis using the Stockwell transform and Shannon energy. To develop the experimental analysis, the 6061-T6 aluminum was exposed to three different corrosive media: 15% H 2 SO 4 , 3.5% NaCl and diH 2 O. The experimental results using the Stockwell transform presented a better classification than the performed by Wavelet transform. Highlights • Corrosion type identification using the Stockwell transform • Corrosion type identification using the Shannon energy • Comparison between the proposed methodology and the Wavelet transform technique [ABSTRACT FROM AUTHOR]

Abstract When transmitting highly corrosive offshore hydrocarbons, one economical approach is lining internally a thin corrosion resistance alloy (CRA) layer within an ordinary carbon steel pipe. Most commonly the liner is mechanically bonded to the outer pipe by mechanical expansion. The lined pipe is expected to make optimize usage of the two types of materials, providing significant corrosion and structural resistance. This study investigates full history interaction behaviors between the outer pipe and liner and the structural behaviors of the lined pipe under axial compression, through finite element analysis (FEA). Comprehensive finite element (FE) models are developed, where the manufacturing process, the non-linear material properties of stainless steel and the interactions between the constituent components are considered. The numerically determined failure modes, load-deformation histories and ultimate strengths are compared with those from tests. The interaction stress and axial loading histories of the specimen under axial compressions are studied, where the internal content pressure and external hydrostatic pressures are considered simultaneously. Confinement factor is suggested to ensure the structural reliability of the liner in engineering practice. Parametric studies are conducted to study the effects of the outer pipe strength, liner strength, outer pipe thickness and liner thickness on the structural behaviors of the axially loaded lined pipes. Highlights • FE models of lined pipe incorporating manufacture induced residual hoop stress and nonlinear material property are developed. • The interaction behaviors of lined pipe are analyzed. Confinement factor is suggested to ensure liner fails after outer pipe. • The parametric studies are carried out on the lined pipe. [ABSTRACT FROM AUTHOR]

Abstract The Mg-4Ag and Mg-5Gd binary alloys' degradation and corrosion properties were studied under in-vitro conditions (in a SBF solution of pH 7.4 at 37 °C) by using various analytical techniques and time-frame windows (up to 3 vs. 28 days), and compared with the pure Mg alloy. Different kinetics and mechanisms of the alloys' degradation were identified, influencing their corrosion rates' dynamics. The Electrochemical Impedance Spectroscopy (EIS) measurements, being performed for up to 3 days, revealed that the corrosion of all three alloys are under a kinetic-controlled mechanism, among which only pure Mg and Mg-4Ag show a repassivation ability in this time-frame. However, the corrosion rates of binary alloys after 28 days of incubation reaching a value of around 0.33 mm/y and a release of 64 mg/L Mg2+ ions, that was accompanied by a pH change up to 8.3, an be lower compared to the pure Mg alloy (0.62 mm/y, 117 mg/L of Mg2+, pH of 9.0). While thick and homogenous layers of differently-shaped and chemically secondary-phased Mg(OH) 2 products were identified on both binary alloys, MgO products and an apatite structure are formed on the pure Mg alloy surface. The Mg-4Ag alloy seems to be biomedically the most appropriate regarding the in-vitro degradation process. Highlights • The corrosion of all Mg alloys follows kinetic-controlled mechanism. • Only pure Mg and Mg-4Ag show a repassivation ability during 3 days. • The corrosion rate of binary alloys in SBF after 28 days is 50% lower. • Thick & homogenous layers of differently-shaped Mg(OH) 2 are formed on binary alloys. • MgO products and an apatite structure are formed on pure Mg alloy surface. [ABSTRACT FROM AUTHOR]

Abstract Unlike aluminium oxide surface layers, magnesium oxide layers obtained by anodising processes exhibit some drawbacks, especially chemical instability in the presence of humidity, resulting in susceptibility to cracking and spalling. This work was dedicated to the development of a new hybrid method allowing us to produce composite aluminium oxide surface layers on magnesium alloys to ensure better performance properties than those achieved by magnesium oxide layers produced by commercial anodising. Composite aluminium oxide layers were produced on magnesium AZ91D alloy using a three stage hybrid method: magnetron sputtering deposition of an aluminium coating, followed by anodising in classical or plasma electrolytic oxidation (PEO) variant, combined with final tightening of the layer by hydrothermal treatment. The structure and the properties of the composite oxide layers were characterised. The investigations proved that the hybrid method using classical anodising is a promising method to improve the corrosion resistance of the AZ91D alloy much more efficiently than commercial anodising, but at the cost of decreased wear resistance. Based on preliminary investigation, a modified variant of the hybrid method using PEO treatment was found to result in both high wear and corrosion resistant composite aluminium oxide layers on AZ91D alloy, making it a prospective solution. Highlights • Corrosion resistant composite Al oxide layers were produced on AZ91D Mg alloy. • a hybrid treatment was developed to produce composite Al oxide layers. • The hybrid treatment combines PVD, anodising or PEO with final sealing. • Only the composite Al oxide layers produced using PEO exhibit high wear resistance. • The composite layers obtained by PEO are an alternative for AZ91D alloy anodising. [ABSTRACT FROM AUTHOR]

Abstract In the present paper, we study the enhancement of the adhesion between the titania doped hydroxyapatite coating and the Ti6Al4V alloy substrate by the addition of three different biocompatible carbides. The coatings were prepared by the magnetron sputtering technique. The addition of interlayer preserved the crystalline structure of hydroxyapatite. The morphology of the coating is influenced by the interlayer composition. The adhesion of the coatings was significantly improved by the interlayer, independent of it's composition. The best adhesion was found for the coatings with NbC interlayer, which also showed the best corrosion resistance in simulated body fluid at 37 °C, due to its flat surface grown without any distinct features. As expected, the results of the in vitro biological tests were almost similar for all coatings comprising an adhesion layer, as the same titania doped hydroxyapatite layer was on top. The experimental results revealed that the adhesion between Ti6Al4V and titania doped hydroxyapatite was improved by a hard metal carbide interlayer, without affecting the required biomedical properties such as good corrosion resistance, high proliferation level of osteoblast cells, and good gene expression levels. [ABSTRACT FROM AUTHOR]

Abstract In this study, the microstructure of a hot spray formed Al-Zn-Mg-Cu alloy was observed, and the effects of ageing treatment parameters on the precipitation, the mechanical properties and corrosion behavior of the alloy were investigated. The as-deposited Al-Zn-Mg-Cu alloy had a fine equiaxed grain structure with low level of segregation and porosity. After hot extrusion and solution treatment, most of the coarse phases were dissolved, providing a favorable condition for subsequent ageing strengthening. The alloy was subjected to three different ageing treatments: peak-aging, over-aging, and non-isothermal retrogression and re-ageing (NRRA). Results showed that the alloy in peak-ageing condition possessed much better mechanical properties, but poorer corrosion resistance than that in the over-ageing condition. After NRRA treatment, however, great comprehensive performance was achieved for the alloy. In NRRA condition, the optimum combination of the size and number of strengthening phases was responsible for the high mechanical properties, whilst the separated grain boundary precipitates (GBPs) and the higher Cu content of the GBPs contributed to the better corrosion resistance. [ABSTRACT FROM AUTHOR]

Abstract In recent years, research is focused on the development of rare earth zirconates based thermal barrier coatings (TBC). In the present study, bilayered 8 wt% yttria stabilized zirconia (YSZ)/gadolinium zirconate (GZO) TBC system has been developed by atmospheric plasma spraying (APS) process from powders prepared by a single step co-precipitation technique. Hot corrosion behavior of all the coatings are tested in fused Na 2 SO 4 + V 2 O 5 mixture at the concentration of approximately 25 mg/cm2 at 910 °C for 30 h. Formation of gadolinium vanadate (GdVO 4) is observed to be the corrosion product in YSZ/GZO bilayer coatings from Energy Dispersive X-ray analysis (EDAX) and is further confirmed by X-ray diffractometry (XRD) analysis. FESEM cross-section analysis of the YSZ/GZO bilayer coating after corrosion test affirms the effectiveness of the bilayer design in preventing the penetration of corrosive salts to the YSZ layer. Also, YSZ/GZO bilayer TBC exhibited a higher thermal cyclic life (300 cycles) than the single layer 8YSZ (175 cycles) coatings at 1100 °C. Highlights • Plasma spray grade GZO powder by single step co-precipitation process • Bilayered YSZ/GZO plasma sprayed coating from synthesized powders • Improved hot corrosion and thermal cycling for YSZ/GZO • Bilayer design reduces phase transformation of zirconia during hot corrosion. [ABSTRACT FROM AUTHOR]

Abstract The amount of residual contact stress between an inner corrosion-resistant alloy pipe and its external carbon steel counterpart is the main challenge when manufacturing lined pipes. This study outlines the experimental and numerical evaluation of the manufacturing parameters of mechanically bonded double-walled pipes, produced by the thermo hydraulic shrink fit process. The measurements indicate that the gripping force between the outer 4-inch carbon steel and inner 3-inch stainless steel pipes was 33.94 MPa when processed at 350 °C with a hydraulic pressure of 30 MPa. The experimental results correlate with those of finite element method simulations for gripping force. The magnitudes of the measured gripping forces in the experiment are sufficiently high for most scenarios. The cross-sections of the final lined pipes were inspected for possible defects with the most common being the lamination-type defect for this production process. Highlights • Production Process of Double-Wall CRA Pipe by using the Thermo Hydraulic Shrink Fit (THSF) Process. • Experimentally and Numerically Investigating the Amount of Gripping Force. • Discussing the production Challenges and Possible Manufacturing Defects. • Comparison of the FEM Results With Theoretical Models in Literature. [ABSTRACT FROM AUTHOR]

Abstract Antithermal grain boundary migration is an interesting phenomenon that has been recently discovered. These grain boundaries behave opposite to what is expected of thermally activated grain boundary migration; the antithermal grain boundaries exhibit mobility that decreases with increasing temperature. Two recent studies have provided insight into important behaviors correlated with antithermal migration. O'Brien and Foiles (J Mater. Sci. Vol. 51, p. 6607–6623, 2016) demonstrated that the high mobility exhibited by an antithermal Σ7 grain boundary is enabled by ordered atomic motions. Ulomek and Mohles (Acta Mater. Vol. 103, p. 424–432, 2016) demonstrated that the thermal migration of a different Σ7 grain boundary exhibited a two-step migration process. In this work, we demonstrate that the antithermal temperature dependence exhibited by these types of grain boundaries is caused by a combination of these two discoveries. Specifically, ordered atomic motions about Coincidence Site Lattice atoms (atoms common to the lattices on either side of the grain boundary), seen by O'Brien and Foiles, are interrupted by additional thermal energy at higher temperature. This is the source of the two-step process seen by Ulomek and Mohles. This two-step process is akin to stick-slip behaviors observed in shear coupled grain boundary migration. As temperature is increased, the duration of the stagnant portion increases and the mobility decreases. This behavior is demonstrated through molecular dynamics simulations in nickel bicrystals over temperatures ranging from 100 to 1400 K for Σ7 and Σ9 grain boundaries. For these Σ7 and Σ9 grain boundaries, those that have ordered atomic mechanisms are almost exclusively antithermal, while those that do not have ordered atomic mechanisms are thermally activated. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Annealing Ni−Mo alloy coating at 200 and 400 °C increases the deposit hardness. • Ni−Mo coatings heated at 400 and 600 °C become brittle. • Heating Ni−Mo deposit at 400 °C significantly improves its corrosion resistance. • Annealing Ni−Mo deposit affects thickness and composition of passive film. Abstract Ni−26 wt% Mo alloy coatings were annealed for 1 h in an air atmosphere at temperatures of 200, 400 and 600 °C. The influence of heat treatment on the structure and the mechanical and corrosion properties was investigated. It was found that the coating microhardness increased significantly after annealing at 200 and 400 °C. The results of the scratch test revealed that. Ni−Mo alloys heated at higher temperatures (400 and 600 °C) were characterized by lower adhesion and more brittle nature in comparison to the as−deposited coating and the coating heated at 200 °C. Annealing at 400 °C led to a significant improvement of corrosion resistance of the coating. This was the consequence of an increase in the thickness of an oxide layer formed on the coating surface. When exposed to a corrosive solution, the protective ability of the oxide layer deteriorated, which was followed by a systematic drop of polarization, charge transfer, and pore resistance. XPS analysis revealed that the surface layer of the as−deposited coating and the coating heated at 200 °C was mainly composed of NiOOH and Ni(OH) 2 and contained higher amounts of Mo in comparison to the deposit bulk. The surface layer of coatings heated at higher temperatures was composed of NiO and contained only small amounts of Mo. [ABSTRACT FROM AUTHOR]

Highlights • Mg-2Zn-0.6Zr-xNd alloys were designed to obtain different second phases. • Nd-containing T phases acted as micro-anodes in galvanic corrosion. • Corrosion mechanism during degradation process in SBF was discussed. Abstract A complete understanding of the role of Mg-Zn-Nd (T) phase in surface micro-galvanic corrosion of Mg alloys has not been fully developed. Therefore, the microstructure evolution and corrosion behavior in simulated body fluid (SBF) of Mg-2Zn-0.6Zr-xNd alloys (x = 0, 0.2, 0.6 and 1 wt%) were investigated. It was found that the MgZn phase in Mg-2Zn-0.6Zr alloy changed to Mg 60 Zn 32 Nd 8 (T 2) and Mg 35 Zn 40 Nd 25 (T 3) phases after adding 0.2–1 wt% Nd. With the formation of T phases, the grain size increased first and then decreased. By using scanning kelvin probe force microscopy (SKPFM), the Volta potentials of second phases relative to Mg matrix were measured. T 2 and T 3 phases with a relative Volta potential of about −400 mV acted as micro-anodes, so that they were corroded preferentially during the corrosion process. Because of the appropriate amount of anodic T phases and their discontinuous distribution, the alloy with 0.2 wt% Nd addition showed a uniform surface corrosion characteristic and exhibit the best corrosion resistance. [ABSTRACT FROM AUTHOR]

Highlights • Covalently-jointed core-shell structure SiO 2 @PANI sol was synthesized by using GPTMS. • SiO 2 @PANI/VTMS sol was prepared by in situ embedding SiO 2 @PANI particles with VTMS. • The sol could form hydrophobic coatings on the surface of Mg-Li alloy directly. • The coatings have better corrosion resistance performance for the active Mg-Li alloy. • Protection is due to the synergistic effect of hydrophobicity, barrier and passivation. Abstract A new method was developed in this paper to obtain self-film-forming polyaniline (PANI) grafting SiO 2 (SiO 2 @PANI) sol which could form hydrophobic coatings on the surface of magnesium-lithium (Mg-Li) alloy directly for the purpose of anticorrosion. Firstly, covalently-jointed SiO 2 @PANI sol with core-shell structure was synthesized with (3-glycidoxypropyl)-trimethoxylsilane (GPTMS) modified SiO 2 as core and PANI as shell, and then SiO 2 @PANI/VTMS sol was prepared after embedded SiO 2 @PANI with vinyl trimethoxysilane (VTMS). The structure and morphology of SiO 2 @PANI particle were characterized by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The hydrophobic and anticorrosion properties of SiO 2 @PANI/VTMS coating on Mg-Li alloy were evaluated by contact angle, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves. The results showed that aniline is polymerizing on the surface of SiO 2 preferentially through the reaction between the epoxide group in GPTMS and amino group in aniline. The obtained SiO 2 @PANI sol dispersed stably in ethanol and supplied well microroughness to coatings, and subsequently enhanced hydrophobic properties of SiO 2 @PANI/VTMS coatings along with low surface energy supplied by VTMS. The hydrophobic angle of SiO 2 @PANI/VTMS coatings is high up to 133.8°. Consequently, the coatings have better corrosion resistance performance for the active Mg-Li alloy. Its impedance value is 5 × 104 Ω·cm2, and corrosion current density is merely 6.7 × 10−7 A·cm−2. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A new biocompatible sintered Zr-Ti-Nb alloy was processed by High Pressure Torsion (HPT) for the first time. • HPT provides a significant reduction in both the total porosity and size the pores of the alloy. • HPT eliminates the chemical heterogeneity of the alloy. • The phase composition of the alloy is stable with respect to the HPT treatment. Abstract The effects of High Pressure Torsion (HPT) deformation on the microstructure and mechanical properties of a corrosion-resistant, low modulus Zr-Ti-Nb alloy, obtained by vacuum sintering of cold pressed powder are studied. It is shown that HPT treatment leads to the following effects: elimination of the residual chemical heterogeneity of the alloy, significant reduction of the porosity of the material and the pore size and improvement of mechanical properties. The phase composition of the alloy does not change during processing. The results show the potential of the HPT method for the production of alloys with a favorable combination of properties. [ABSTRACT FROM AUTHOR]

Abstract 304 stainless steel is widely used in many industrial fields, however, poor wear resistance of H 2 S limited its applications. In this study, novel composites coatings were deposited onto stainless steel surface by a liquid nitrocarburization technique. XRD, EMPA, SEM were conducted to investigate the surface modification of 304 Austenitic Stainless Steel after liquid nitrocarburization for 8 h at 703 K (430 °C). Wear test results showed that the wear resistance of nitrocarburized 304 stainless steel was increased in comparison with the non-nitrocarburized one. The corrosion potential was investigated by standard saturated hydrogen sulfide gas. And the results indicated that the austenite transformed into the S phase after forming supersaturated solid solution of N on the surface and kept intact after corrosion test. The corrosion current density was clearly reduced. Low diffusion coefficient of hydrogen atoms in S-phase reduced the possibility of environmental cracking of H 2 S and improved the H 2 S corrosion resistance of after liquid nitrocarburization. [ABSTRACT FROM AUTHOR]

Highlights • Fatigue loading tests on corroded RC beams are performed. • Load-deflection, fatigue crack of concrete, and failure modes are discussed. • A developed flexural stiffness deterioration model under fatigue is proposed. • Theoretical predictions agree well with the experimental observations. Abstract Corrosion of reinforcing bars accelerates the fatigue damage accumulation and significantly reduces the fatigue life of aging reinforced concrete (RC) bridges. This paper experimentally investigates the effects of corrosion on the fatigue behavior of reinforced concrete beams. An accelerated corrosion test is conducted in the laboratory conditions to obtain various corroded beam specimens. The initial crack width and the crack distribution are discussed. Based on the fatigue loading test, the load-deflection, fatigue crack propagation of concrete, fatigue life and the failure modes of RC beams after different fatigue cycles are investigated. Following that, a developed flexural stiffness calculation model for the corroded beams after fatigue is proposed. This model includes the effects of fatigue, corrosion-induced cracking and fatigue modulus degradation of concrete and other influential factors. The proposed method is validated with the experimental observations from various corroded RC beams of the current paper and available in open literature. [ABSTRACT FROM AUTHOR]

Selective laser melting (SLM) method has a great potential for fabricating injection mold with complex structure. In this study, two S136 mold steel pre-alloy powders with trace element difference were fabricated by SLM, and then comparison of samples on microstructure, mechanical and corrosion resistant property was investigated. Results showed that the sample fabricated with a higher Si+Mn content exhibited the lower mechanical properties, such as micro-hardness of 48.73 HRC, ultimate tensile strength of 1186.7 MPa and elongation of 10.6% due to a few of pores observed on the cross surface. For the SLM sample produced by another powder with a lower Si+Mn content, it showed equiaxed grains and cellular dendrite grains coexisted and exhibited the superior mechanical properties (50.31 HRC, 1467.9 MPa and 11.1%) combined with well corrosion resistance. Then the injection mold insert with conformal cooling channel was successfully processed by this powder. The cooling time was reduced by 30% during the injection cycle. Therefore, it can be seen that trace element differences have an important effect on the SLM S136 mold steel. The results suggest that it is essential for successful fabricating components with a suitable composition of alloy during SLM process. [ABSTRACT FROM AUTHOR]

Abstract Corrosion studies in molten fluoride and chloride salts were surveyed, and key data were aggregated into a single dataset. Studies were graphed by salt purity, temperature, sample material, container material, and experimental method (loop, capsule, crucible). To elucidate and quantify the factors that affect corrosion in molten salts, a data analysis using a newly-defined corrosion resistance score and a correlation analysis using techniques borrowed from machine learning were performed. It is shown that salt purity had the strongest correlation with corrosion rates in molten chlorides and fluorides. Data analysis across varied works was inconsistent due to the lack of standardization among molten salt corrosion studies. Highlights • Corrosion studies in fluoride and chloride salts from 1960 to 2016 are aggregated into a single dataset. • Corrosion testing techniques and reviewed. • Attributes of each study are processed and graphed to elucidate how they affect corrosion rates. • A data analysis is performed to show how important factors correlate with corrosion in molten salts. [ABSTRACT FROM AUTHOR]

• Purpose of the current article is to describe casing and tubing pipelines' corrosion failures and their control. • CO 2 and H 2 S cause sweet and sour corrosion and enormously contribute to internal pipeline failure (≈ 60%). • The use of corrosion inhibitors is the most cost-effective way to prevent casing and tubing corrosion. • Mechanism of sweet and sour corrosion and formation of corrosion products depends upon various parameters. • The main input parameters are pH, temperature, P CO2 , P H2S , etc. Casing and tubing for oil and gas wells are frequently made of steel alloys. Many corrosive gases, organic acids, salts, and other contaminants are present in the fluids of oil and gas wells, which hurt their productivity, efficiency, and continuous production. The common corrosive species include carbon dioxide (CO 2), hydrogen sulfide (H 2 S), water (H 2 O), organic acids (HCOOH, CH 3 COOH etc.) and salts (NaCl, CaCl 2 , MgCl 2 , NH 4 Cl etc.) that can cause the corrosion of metals at any stage of production, purification, storage and transportation processes. The purpose of the current article is to cover the corrosion of oil and gas well casing and tubing and corrosion mitigation techniques. Numerous factors influence the corrosion rate in these wells, and various management techniques and procedures have been implemented to address corrosion-related problems in oil and gas wells. Corrosion-resistant materials are one of the most popular and frequently used techniques. To prevent internal pipeline corrosion, anti-corrosive and wear-resistance coatings are also utilized. Another frequent method against corrosion is using scavengers, primarily for H 2 S and O 2 , to lessen the corrosivity of the well fluids. The most popular H 2 S-scavenging technique uses alkaline solutions and activated carbon. Triazine and aldehydes are the most common and efficient non-generative H 2 S scavengers. The use of corrosion inhibitors is one of the most practical and cost-effective ways to prevent corrosion in well casing and tubing. The corrosion inhibitors adsorb at the point where corrosive fluids and internal pipelines interface, preventing the corrosive attack. [Display omitted] [ABSTRACT FROM AUTHOR]

Highlights • Ni alloyed with metals in groups ≤ 6 bind atomic O stronger than alloy groups ≥ 7. • Atomic C binds stronger to the (100) than (111) facet of Ni-based alloy surfaces. • Alloying of Ni surfaces has little effect on CO binding. • CO dissociation is more favorable than the Boudouard reaction on Ni-based alloys. Abstract Oxidation and corrosion of nickel and Ni-based alloys are a problem for many industrial applications, such as power plants that use supercritical CO 2 as the working fluid. In supercritical CO 2 environments, CO 2 dissociates on the surface forming adsorbed CO and O, which can oxidize the surface. The adsorbed CO can further breakdown via direct CO dissociation or via the Boudouard reaction to form adsorbed C, which can in turn carburize the surface. Understanding how the adsorbed species interact with different Ni-based alloys can help guide the design of future alloys. The interactions of adsorbed O, C, and CO on the (100) and (111) facets of pure Ni and Ni individually alloyed with Al, Co, Cr, Cu, Fe, Mn, Mo, Nb, Ti, V, and W are examined using density functional theory. We find that the binding of CO is energetically similar across all alloy surfaces and both facets, while O binding varies strongly with different metals added to nickel and C binding varies between the different facets but only slightly for different metals alloyed to nickel. The binding of O is weaker on pure Ni and Ni alloyed with Cu, Co, Fe, Al, or Mn and stronger on Ni alloyed with Nb, Cr, Mo, Ti, V, or W, while the binding of C is weaker on the (111) facet than the (100) facet. The difference in the binding energies of the adsorbates across the different alloy surfaces is due mainly to the ensemble effect, rather than the ligand effect. The thermodynamics of CO breakdown are also studied and we find that the breakdown of CO via direct CO dissociation is endothermic on the (111) facet and exothermic on the (100) facet, with the alloy surfaces that bind O strongly having the most exothermic reaction energies. The breakdown of CO via the Boudouard reaction has similar reaction energies across the different alloy surfaces of a single facet and is endothermic on both facets, with the (111) facet being most endothermic. This comprehensive study presents a summary of the current literature as well as a well-rounded view of the products of CO 2 breakdown on Ni surfaces alloyed with the most common alloying elements used in industrial applications. Graphical abstract Image, graphical abstract [ABSTRACT FROM AUTHOR]

Highlights • Sulphuric acid corrosion behavior of alkali activated fly ash/slag cements is studied. • Pure fly ash-based sample maintains the highest compressive strength during acid corrosion. • Sulphuric acid attack leads to a total porosity increase regardless of the compact level of binder. • Loss of aluminum from binder during acid attack decreases as slag content increases. Abstract In the present work alkali-activated fly ash/slag cements (AACs) are synthesized and exposed to sulphuric acid (pH = 1.0) to investigate their anti-corrosion properties. The mineralogical compositions, pore structure and microstructure of different layers of the corroded samples are examined, along with the compressive strength change. The results show that with fly ash/slag ratio varying from 100/0 to 0/100, the compressive strengths of all of the samples decrease during acid attack; the most anti-corrosion mixture is found in the pure fly ash binder, which retains 83.5% strength after 28 days of exposure. Gypsum is only observed in the surface layer (0–5 mm) of samples. In terms of pore structure, the acid attack results in higher porosities in the corroded layers than their corresponding uncorroded layers. The samples with slag addition show a notably pore structure change. The sulphuric acid attack on the AACs binders has certainly led to the increase of porosity, regardless of the compact level of AACs (slag addition leads to compacter microstructure). The Al/Si atomic ratios in the corroded layer decrease after acid attack, and the reduction ratios become smaller as slag content increases, suggesting a dense matrix is advantage to impede the loss of aluminum from gel structures. [ABSTRACT FROM AUTHOR]

Abstract Fiber reinforced polymer (FRP) composites are commonly used in the chemical industry for storage tanks and pipelines, since most metallic alloys suffer from corrosion and result in costly maintenance and safety hazards. E-glass fiber is commonly used because of its low cost, but it is extremely susceptible to rapid degradation in low-pH environments. C-glass is an acid-resistant substitute, and while not as durable as carbon, it is much cheaper. Nevertheless, durable fibers are not the only key aspect of designing corrosion-resistant composites, as various degradation mechanisms must be considered. In this study, plain-weave laminates of C-glass and amine-cured epoxy are exposed to water and sulfuric acid solutions, and the relationship between diffusion kinetics and strength-loss is discussed. Results show that both solutions attack the fiber surface to some degree, but more importantly sulfuric acid increases the saturation uptake of water in the material, causing high swelling stresses that significantly reduce mechanical properties. [ABSTRACT FROM AUTHOR]

Carbon-based material is commonly used for anodes in MFCs, but its low conductivity often limits anodic performance. Application of corrosion-resistive current collector to carbon-based anode can be a promising strategy for increasing the anodic performance. In this study, it was hypothesized increasing metal current collector improved anodic performance. Two different carbon-felt anodes with titanium wires (CF-W) or stainless steel mesh (CF-M) as a current collector were tested in a single chamber MFC. In the short-term tests such as polarization and impedance tests, CF-M with the larger current collector area (21.7 cm 2 ) had 33% higher maximum power (2311 mW/m 2 ), 81% lower anodic resistance (3 Ω), and 92% lower anodic impedance (1.1 Ω). However, in the long-term tests, CF-W with the smaller current collector area (0.6 cm 2 ) showed higher performance in power and current generation, COD removal, and CE (51%, 10%, 11%, and 5% higher, respectively) and produced 41% higher net current in cyclic voltagramm (20.0 mA vs. 14.2 mA). This result shows that larger current collector is advantageous in short-term performance and disadvantageous in long-term performance, because the larger current collector is good for current collection, but interferes with mass transfer and microbial growth. [ABSTRACT FROM AUTHOR]

Abstract Additive manufacturing has emerged in recent years as one of the most in-demand technology for manufacturing of prototypes and components with complex geometries. Its application in biomedicine shows a big productive potential concerning customized implants with optimized geometries, reducing risks of rejection and achieving better ergonomic results. However, Ti-6Al-4V ELI pieces produced by Direct Metal Laser Sintering (DMLS) need a post heat treatment in order to reach optimum mechanical properties as well as to release internal stresses resulted from the manufacturing process. This study aims at analyzing the change of microstructure in DMLS samples by effect of heat treatments and its influence in the corrosion behavior and in the anodizing process. The surfaces were analyzed by 3D confocal profilometry, scanning electron microscopy and energy dispersive X-ray spectroscopy. DMLS samples showed different microstructures after heat treatments in the range from 650 to 1050 °C. The main difference in the microstructures is the nucleation and growth of β phase, which could have a detrimental effect on its corrosion behavior. The corrosion behavior was studied by cyclic potentiodynamic polarization in phosphate buffered saline solution at 37 °C. After anodizing, an oxide film was grown on the material surface, composed of a barrier and a nanoporous layer doped with F ions. The passive current density was reduced by approximately two orders of magnitude for all conditions, despite morphological differences on the layers. This is not only an improvement of the corrosion resistance but also a decrease in the ion release into bloodstream. Graphical abstract Image 1 Highlights • Microstructures containing β phase displayed pitting potential. • Microstructures affects the morphologies of the anodized oxide layers. • Despite morphological differences, anodizing was successful for all conditions. • Anodic layers reduced current density by two orders of magnitude for all conditions. [ABSTRACT FROM AUTHOR]

Abstract Third party threats from accidentally dropped objects could cause external impact loading that may potentially affect the integrity and safety of a subsea pipeline system. These incidents may occur during installation, construction and operation phases of the project. To evaluate the structural integrity of carbon steel (CS) subsea pipelines due to dropped objects events, risk assessment is conducted following the procedure detailed in DNV-RP-F107, which gives a closed-form formula for predicting the impact-energy capacity of the CS pipeline and assumes an acceptance criterion of limiting the dent-depth ratio to 5% of pipe diameter for a no-leakage condition. In the case of CS pipelines mechanically-lined with corrosion resistant alloy (CRA), the applicability of the impact-energy formula and the acceptance criterion is, however, largely unknown considering that CRA-lined pipes involve additional modes of failure in the form of liner separation and its potential for subsequent fatigue failure during operation. This paper discusses finite element modelling undertaken to evaluate the structural response of a CRA-lined pipeline subjected to external impact loads. Results confirm that liner separation is of minor importance and the use of the established acceptance criterion derived for plain carbon steel pipes can be justified to apply to CRA-lined pipelines. Highlights • FE analysis shows pipelines mechanically-lined with CRA respond to impact loads in same manner as plain steel pipes. • The results reveal that backing steel pipe dominates the response. • The FE analysis verifies that 5% OD dent depth is acceptable for a CRA-lined pipe. • In terms of predicting impact-energy capacity, the simplified equation in DNV-RP-F107 may be used for CRA-lined pipe. [ABSTRACT FROM AUTHOR]

An alloying element of Sn-1.0Ag-based solder alloy can provide a great opportunity to improve their solder properties and increase its capacity for corrosion resistance. We have developed Sn-1.0Ag-xCe solder alloys consisting of a range of cerium contents from 0 to 0.5 wt% in the production of the refinement and continuation of the precipitates, as well as the reduction in grain size of the alloy microstructures. An increase of cerium addition supported on corrosion resistance exhibited relatively improved pitting potential, film and charge transfer resistances which particularly promoted the formation of passive film, resulting in an improvement of pitting resistance. [ABSTRACT FROM AUTHOR]

Effect of the concentration of Cr 3+ in molten LiF-NaF-KF salt on the corrosion of SiC was investigated. Results reveal that increasing initial concentrations of Cr 3+ in salt can enhance both the loss of Si and the deposition of Cr on SiC, which results in the weight change of SiC from loss to gain. The corrosion of SiC in molten LiF-NaF-KF salt with Cr 3+ should be attributed to the oxides in SiC, the oxygen-containing impurities and Cr 3+ in salt. The oxygen-containing impurities in salt react with SiC to form oxides that can be corroded by fluoride salt. The Cr 3+ in salt can react with SiC and the oxides (SiO x ). [ABSTRACT FROM AUTHOR]

The corrosion resistance of a stoichiometric NiAl 2 O 4 spinel was studied. NiAl 2 O 4 spinel samples were exposed to either CaO, Fe 2 O 3 , MgO, V 2 O 5 or synthetic slags at 1450 °C for 6 h. Two different synthetic slags were used, one containing high amount of Fe 2 O 3 , SiO 2 and MgO and other with high amount of CaO and Al 2 O 3 . In most the cases, NiAl 2 O 4 spinel was not chemically stable and, depending on the nature of the corrosive agent, several corrosion products were formed. The higher reactivity was observed for the system where a synthetic slag with high content of Ca and Al was used. Using the corrosion results and thermodynamic equilibrium calculations (FactSage 6.2) it was possible to elucidate the corrosion mechanisms. [ABSTRACT FROM AUTHOR]

High strain rate rolling (HSRR) and artificial aging are conducted to improve mechanical properties and bio-corrosion resistance of Mg-4Zn alloy by modifying grain size and precipitates. The under-aged state is the most corrosion resistant among four states in single and double aging. Bio-corrosion resistance of the as-rolled alloy can be improved by double aging of 70 °C × 10 h + 160 °C × 2 h, resulting from stress relief and uniformly distributed nano-scale G.P. zones and β 1 ′ precipitates. [ABSTRACT FROM AUTHOR]

Alloy 718 is a Ni-based superalloy commonly used for parts of aircraft engines and power plants where very high demands on high-temperature yield strength, creep and corrosion resistance must be met. Polycrystalline parts such as turbine discs are industrially manufactured via hot-forging followed by solution annealing and dual ageing to form nanoscale γ′ and γ" precipitates. However, through the alternative process of ‘direct ageing’, increased yield strength contributions of ∼10% can be achieved while maintaining sufficient creep resistance. In addition to this so-called ‘direct ageing effect’, the omission of solution annealing between forging and ageing is economically attractive. Therefore, to date, direct ageing is widely implemented in the production of forged aerospace parts. However, the detailed mechanisms behind the direct ageing effect yet remain unclear. We present a correlative microscopy approach to identify the detailed microstructural evolution during conventional versus direct ageing. Our results confirm higher dislocation densities, lower δ-phase volume fractions and the absence of selected γ-matrix grain growth, as suggested in previous research. However, a key finding reported here via the use of atom probe microscopy is a remarkable structuring within and between the nanoscale γ′ and γ" precipitation. Not only do we find an increase in both the volume fraction and size of the γ" precipitates after direct ageing, we report a prevalence of stacked co-precipitation in various sequences depending on the nucleation condition. The findings are summarized in a microstructural model for conventional and direct ageing. [ABSTRACT FROM AUTHOR]