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To enhance the performance of titanium plated coating on the surface of magnesium alloy AZ31, this study investigates the influence of N ion implantation dose on the structure, mechanical properties, and friction corrosion behavior of Ti film. The results reveal that N ion implantation leads to the formation of a new physical phase TiN and induces surface softening. However, with an increase in N ion implantation dose, microhardness of the Ti film increases due to the formation of TiN which enhances its hardness. Friction and wear experiments demonstrate that at maximum implantation dose, the coating exhibits minimal friction coefficient; however, an implantation dose of 5 × 10 ^15 ion cm ^−2 offers superior wear resistance. The electrochemical test results indicate the corrosion current density and self-corrosion potential of Ti coating decrease with the increase of implantation dose due to the formation of nitride and the presence of N element, and corrosion resistance of the modified coating has been significantly enhanced. The research results provide reference for improving the protection performance of Ti coating on magnesium alloy surface.

In this research, the electro-gas welding process was compared with a shielded metal arc welding process for welding steel A573 from a mechanical properties point of view. Visual and radiographic inspections confirmed the soundness of weldments produced by electro-gas welding and shielded metal arc welding techniques. Various assessments were performed, including hardness, tensile strength, V-notch impact toughness, macrostructure, microstructure, and electrochemical tests. The mechanical properties of the two welding processes were closely matched, with an average tensile strength of 590 MPa for electro-gas welding and 585 MPa for shielded metal arc welding. Furthermore, the influence of welding variables, such as groove design and heat input, on the welded joints’ quality, mechanical properties, and electrochemical behavior was thoroughly examined. Dilution estimates, particularly for the electro-gas welding process, were around 35%, and a significant similarity was observed between the chemical composition determined through dilution calculations and that obtained from chemical analysis using an arc spark emission spectrometer. Notably, the electro-gas welding process demonstrated exceptional productivity, surpassing the shielded metal arc welding process by more than elevenfold. The optimum welding parameters for the electro-gas welding process were identified to achieve superior mechanical properties, low corrosion rates, and reduced consumption of the welding electrodes. This included adopting a single V type and groove angle of 30° instead of 60°, resulting in a 23% reduction in economic costs. Selecting an appropriate heat input within the range of 12 to 14 kJ/mm further contributed to enhancing overall welding efficiency.

Coatings with different boron content were prepared by magnetic field-assisted Co-based laser metal deposition on 300 M ultra-high strength steel. The effects of boron content on the magnetic properties, mechanical properties, friction and wear properties, and corrosion resistance of the coating were investigated. The research results indicate that adding 6 wt% of boron to cobalt alloy in a 35 mT alternating magnetic field is beneficial for refining the microstructure, which can improve the mechanical properties of the coating. This research also discusses the effect of boron content on the wear and corrosion resistance of the coating. The results show that adding boron content enhances the magnetostrictive effect, and reduces the elastic modulus of the laser metal deposition coating while ensuring its hardness, thereby improving the wear and corrosion resistance of the laser metal deposition layer. The hardness of the coating can reach 1215 HV. The friction coefficient and corrosion current density of the coating are reduced by 26.9% and 60.2% respectively compared with the substrate. This work can help promote the application of laser metal deposition technology, reduce costs, and ensure performance.

Fe-based amorphous coatings hold immense potential for marine industries due to their remarkable properties, including high hardness, exceptional corrosion resistance, and outstanding wear resistance. However, their performance under thermal shock conditions, particularly in high-temperature applications, remains a topic requiring further investigation. In this work, a Fe-based amorphous coating with a composition of Fe _48 Mo _14 Cr _15 Y _2 C _15 B _6 was successfully developed using High-velocity oxygen fuel thermal spraying. To assess the thermal shock resistance of the amorphous coating, we subjected them to thermal cycles at 300 °C for 150 times, followed by cooling in two different mediums: saltwater quenching and air cooling. The results revealed that the coating maintained excellent contact with the substrate and preserved mainly amorphous structure both in the as-sprayed condition and after thermal shocks. Interestingly, the differential scanning calorimetry (DSC) results indicated that the air-cooled samples exhibited greater structural relaxation and crystallization compared to the brine-quenched samples. This microstructure changes in the air-cooled samples resulted in inferior mechanical properties, such as wear resistance and hardness, compared to the brine-quenched and as-sprayed samples.

Biocompatibility is a critical aspect of the use of materials in the human body. The use of base metal alloys in dentistry is primarily regulated by health and safety standards set by regulatory authorities in various countries. The porcelain-fused-to-metal (PFM) process applied to Ni-Cr dental alloys can alter their properties, particularly in terms of corrosion and surface characteristics. This study aimed to assess the effect of the heat processing used for dental porcelain firing on these properties. The two casted alloys: Ceramic N and Ivoclar Vivadent 4all, used in the study were characterized by analyzing the microstructure by scanning electron microscopy (SEM), composition with energy dispersive x-ray spectroscopy (EDS), hardness, surface profile and electrochemical corrosion resistance (E _corr , j _corr , polarization curve, E _br and electrochemical impedance spectroscopy (EIS) results), as well as ions release before and after the simulated porcelain firing. Based on the conducted research the following conclusions can be drawn: Analyzes of the material characteristics before and after the simulation showed that the discussed process, although it does not cause the formation of chemical impurities on the surface of the alloys, results in changes in the chemical composition and structure of surface oxides, increases roughness and reduces hardness. The results of the corrosion examinations showed a deterioration in anti-corrosion properties after the simulation. The statistically significant decrease in corrosion resistance may result from the increased heterogeneity of the surface oxide layers and partial changes in their composition.

Traditional corrosion inhibitors have been frequently used for metal protection against strong acids. However, most of them are hazardous compounds with high costs. Therefore, due to the strict environmentally friendly regulations, green and low-cost compounds from renewable sources have gained high consideration in recent applications. In the present study, the Arachis hypogaea shell extract, commonly called groundnut, a cost-effective was selected to inhibit API X 65 pipeline steel corrosion in 1 mol·L ^−1 H _2 SO _4 solution. The Arachis hypogaea shell composition was examined by FTIR analysis. The Arachis hypogaea shell on pipeline steel in H _2 SO _4 solutions was studied via gravimetric, potentiodynamic polarization, and surface analysis (SEM and EDX). Electron donor atoms present in the Arachis hypogaea shell extract molecules is responsible for its adsorption on the surface of the metal. Experimental study shows that with increasing Arachis hypogaea shell concentrations, the inhibition tendency increased and reached 98.84% at 4 g L ^−1 after 24 h. Arachis hypogaea shell extract behaved as mixed-type inhibitor, and the surface coverage fits the Langmuir isotherm, signifying that the steel surface was covered by a monolayer of inhibitor molecules without intermolecular interactions. SEM analysis shows that Arachis hypogaea molecule adsorption on the metal surface reduced considerably its dissolution rate resulting in a smooth and clean surface with few damaged areas. The use of water for extraction of Arachis hypogaea shell exhibiting inhibition efficiency, non-toxic, and cost-effective than other green inhibitors, proposes the Arachis hypogaea shell as an excellent green inhibitor for API X 65 steel corrosion in 1 mol·L ^−1 H _2 SO _4 solution.

In this study, the effect of corrosion and wear behaviour of Cr-Mn steel on fine grains were investigated. The sample were solution annealed (SA) for 1 h at 1050 °C and then cold rolled (CW) to 30%. Further the cold rolled sample were thermally aged (CW + TA) 900 °C for four hours. The findings showed that under the 10 N applied load, wear resistance increased with an increase in hardness and martensite fraction of the cold worked (CW) samples. However, the Cr-Mn steel had the superior wear resistance after thermal ageing (TA). In microstructural examination deformation bands can also be visible in cold work samples. The analysis implies that the γ -phase is apparent across all peaks within the spectra of SA samples. In instances involving 30% cold work, prominent α ′ martensite peaks were observed, accompanied by minimal ε -martensite peaks. Electrochemical impedance spectroscopy (EIS) analysis discloses a reduction in impedance and a concurrent increase in the defect density of the passive film. The CW+TA structure with good inclusive performances created an early constant hardened layer, which didn’t delaminate and peel off prematurely, thereby effectively increasing the wear resistance, according to analysis of the wear mechanism. The results also concluded that the corrosion resistance of CW sample decreases due to SIM formation, however CW+TA sample provide better corrosion resistance due to smaller and refined grain size.

Lightweight 3rd generation Al–Cu–Li alloy AA2050 was severely deformed via Multi Axial Forging (MAF) at 170 °C followed by artificial aging at 150 °C. Effect of MAF and post MAF aging on microstructure and precipitation was investigated using transmission electron microscopy (TEM). Formation of deformation bands and large dislocation cells were evident on MAF processed samples. Post MAF peak aging resulted in the distribution of fine T _1 precipitates in grain interiors with reduction in grain boundary precipitation. Bulk texture studies reveal the formation of strong Goss and S texture components upon MAF processing. Further, low temperature artificial aging doesn’t exhibit significant changes in texture characteristics, either in terms of texture intensities or texture components. Polarization studies showed that peak aged samples exhibited better corrosion resistance compared to un-aged samples. Overall, 12 pass MAF processed and peak aged samples showed higher corrosion resistance. Further, corrosion surface morphologies examination revealed the change in corrosion mechanisms with thermomechanical treatments. Improved corrosion resistance after MAF and peak aging widens the requirements in aerospace and aircraft applications for such engineering alloys.

The Al-Zn sacrificial anodes are widely used for cathodic protection in marine steel structures. This study evaluates the impact of bismuth addition on the electrochemical properties of the Al-Zn sacrificial anode in artificial seawater. The microstructure analysis confirms the presence of uniformly distributed intermetallic β -AlFeSi and spherical Bi within the α -Al matrix. The open circuit potential (OCP) comparison between Al-Zn-Bi and carbon steel reveals a potential difference of approximately 400 mV, indicating sufficient cathodic protection for the steel. Electrochemical impedance measurements indicate the initial hindered dissolution of the anode due to surface film formation, which later dissociates due to the aggressive attack of Cl ^− species in the electrolyte. The sufficiently negative surface potential (−0.875 V _vs. Ag/AgCl ) observed at 10 mA cm ^−2 demonstrates the suitability of anode for fulfilling the cathodic protection criteria of steel structures.

Understanding of the relationship between microstructural change and corrosion behavior is essential for achieving the optimum benefit of strengthening precipitates in providing high strength without sacrificing the corrosion resistance of 7000 series aluminum alloys. This work aims at revealing the relationship between the microstructural rearrangement and corrosion behavior of a 7075 series aluminum alloy as a result of annealing at the temperature range of 300 °C–600 °C. Microstructural observation indicated a gradual dissolution of Cu in the solid solution matrix with increasing annealing temperature. At 600 °C, a formation of segregated Al _2 Cu phase occurred along the grain boundaries. After subjected to corrosion tests, exfoliation corrosion was observed on the as-received specimen, as well as on the specimens annealed at 300, 400 and 500 °C, whilst an intergranular corrosion occurred on that annealed at 600 °C. The corrosion resistance was higher on the specimen annealed at 500 °C compared those annealed at other temperatures, as the result of Cu enrichment the solid solution matrix.

The prevalence of catastrophic structural member failure caused by steel corrosion in civil infrastructure underscores the importance of reducing reinforcement corrosion to enhance overall infrastructure costs, reliability, and sustainable development. The present research investigates the potential of corrosion inhibitors to enhance the durability and strength of concrete structures, with a focus on their long-term effectiveness in resisting corrosion in reinforced concrete structures. Multiple approaches such as inhibitors, repairing processes, and coatings have been explored to prevent concrete corrosion damage, with an emphasis on concrete corrosion performance in coastal and corrosive situations. This study investigates the effect of six different corrosion inhibitors (zinc oxide, magnesium oxide, urea, sodium nitrate, sodium molybdate, and diethyl ether) on the compressive strength and durability of concrete samples. The compressive strength is assessed using both destructive (28 days cube compressive strength) and non-destructive (Ultrasonic Pulse Velocity) test methods, while concrete durability is evaluated using the rapid chloride permeability test (RCPT). The compressive strength of the admixture incorporated samples are found to be higher than the control sample by almost 50% and above with excellent concrete quality. The RCPT values of inhibitor-incorporated samples are moderate and low with control samples having high permeability even in adverse conditions of freezing, thawing, and deicing. The samples incorporated with inhibitors also show less negative half-cell potential which is 1.43 times less than that of the control sample indicating the lesser probability of occurrence of corrosion. SEM imaging is also conducted to analyze the microstructure of each mix. The findings of this study highlight the importance of inhibitors in enhancing the durability of reinforced concrete structures.

This study was conducted to investigate the effect of the ultrasonic field on the preparation of amorphous/crystalline Fe-based coatings. For this purpose, Fe _86.3 Si _5.9 B _3.2 Cr _4.6 (wt%) powder was deposited on GTD-111 superalloy substrate with and without ultrasonic field by selective laser melting method. After coating, the corrosion behavior, microstructure, and hardness of the amorphous coating were investigated. The results showed that in conditions without ultrasonic vibration, the growth of grains starts in columnar form. At the same time, the use of an ultrasonic field inhibits columnar growth and creates equiaxed grains. In addition, the ultrasonic field increased the amorphous phase by 34.5%. This is attributed to the increased solidification rate caused by the cavitation effect. The experimental results of corrosion show that the self-corrosion current density of 6.83×10 ^−7 A⋅cm ^2 is obtained due to the refinement of the microstructure and the increase of the amorphous phase. The wear results showed that the increase in the amorphous phase, as well as the decrease in the grain size, reduction in the grain ratio, and the increase in the tendency to equiaxed grains when using the ultrasonic field, reduce the coefficient of friction by 97%.

The incorporation of inorganic nanofillers into polymeric matrices represents an effective strategy for the development of smart coatings for corrosion protection of metallic substrates. In this work, wet-jet milling exfoliation was used to massively produce few-layer hexagonal boron nitride ( h -BN) flakes as a corrosion-protection pigment in polyisobutylene (PIB)-based composite coatings for marine applications. This approach represents an innovative advance in the application of two-dimensional (2D) material-based composites as corrosion protection systems at the industrial scale. Although rarely used as an organic coating, PIB was selected as a ground-breaking polymeric matrix for our h -BN-based composite coating thanks to its excellent barrier properties. The optimization of the coating indicates that 5 wt.% is the most effective h -BN content, yielding a corrosion rate of the protected structural steel as low as 7.4 × 10 ^−6 mm yr ^−1 . The 2D morphology and hydrophobicity of the h -BN flakes, together with the capability of PIB to act as a physical barrier against corrosive species, are the main reasons behind the excellent anticorrosion performance of our composite coating.

Magnesium implants that are biocompatible and biodegradable are important for orthopaedic applications. Mg-based alloys and their corrosion behavior have been studied in vitro and in a few in vivo studies. However, depending on the composition and microstructure, Mg-based alloys display varied biocompatibility, degradability, biocompatibility, and bioactivity. As a result, there is a critical need to create safe and cost-effective magnesium alloys for orthopaedic applications. The current investigation examined cytotoxicity, hemocompatibility, in vitro corrosion, and biomineralization of pure Mg, Mg Ni/Ti, and Mg 0.4Ce/ZnO2 nanocomposites to establish its suitability as a biodegradable material. The biodegradation behaviour of pure Mg and its nanocomposites were investigated using a phosphate buffer solution. The Cytotoxicity of pure Mg and its nanocomposites were assessed using MG 63 cells in MTT (3-(4, 5-dimethyl-2-thiazolyl)−2,5 diphenyltetrazolium bromide) assays after 24 h. Biomineralization by MG 63 cells on pure Mg and its nanocomposites were analyzed using Alizarin red staining. The in vitro corrosion findings indicate more localized corrosion with rapid degradation on the surface of pure Mg and its nanocomposites. Pure Mg and its nanocomposites exhibited high hemolysis. The results of cytotoxicity showed high cell viability in pure Mg compared to its nanocomposites. According to the Alizarin red staining results, calcium was found to be deposited on the surface of Mg nanocomposites, and no calcium deposits on the pure Mg surface. The results of in vitro studies revealed that pure Mg and its nanocomposites responded differently in different tests. From these results, comparing Mg nanocomposites could be a more effective strategy to address the current challenges in orthopaedic implant applications.

The corrosion mechanism of the low carbon low alloy steel with Al _2 O _3 particles and rare Earth (RE) oxide particles was compared in a simulated marine environment. It is shown that when the Al _2 O _3 -containing particles are introduced, the number density of nonmetallic particles of the steel increases twice, and the average particle size decreases from approximately 2.4 μ m to 1.4 μ m. With the introduction of Al _2 O _3 -containing particles, the amount of pitting corrosion increases. Furthermore, pitting corrosion occurs more uniformly owing to the fineness of the Al _2 O _3 particles, thereby leading to smaller, shallower pits after the Al _2 O _3 particles are shed. Hence, the corrosion performance of the steel with Al _2 O _3 particles is significantly improved than that of the steel without Al _2 O _3 particles. By adding RE oxide particles into steel, the nonmetallic particles in steel are refined but not as effectively as that achieved by adding the Al _2 O _3 -containing particles. Different from Al _2 O _3 particles, Cu is obviously enriched in the location of RE oxide particles at the initial corrosion stage, which makes the steel exhibit the best corrosion resistance. Cu enrichment is attributed to the mobile Cu present in the rust layer and to the micro acid region formed around the RE oxide particles.

This study examined the imitative micro pit formation of pitting corrosion on 304 stainless steel under electrochemical control in a 3.0% NaCl solution. Results demonstrated that the micro pits changed from a conical to a cap shape during growth, indicating that their evolution in shape and growth did not follow the same morphology over time. Additionally, the piecewise polynomial method was employed to compare real-time micro pit growth morphology evolution with current density, which was consistent with cross-sectional images of actual micro pits, enabling the separation of the pitting corrosion stages. Furthermore, 3D images obtained from SRXTM were similar to cross-sectional images of real micro pits, further validating the technique’s usefulness in studying micro pits.

In the current work, magnesium (AZ91D) matrix composites reinforced with different weight fractions (5, 10, and 15%) of titanium diboride (TiB _2 ) and 1.5 wt% carbon nanotubes (CNTs) are fabricated using stir casting. The improvements in mechanical, wear and corrosion resistance properties are evaluated as per ASTM guidelines. The synergistic strengthening effect of TiB _2 and CNT is also studied. It was discovered that the AZ91D/(1.5CNT-10TiB _2 ) composite outperformed other magnesium matrix composites in terms of strength and ductility. Experimental characterization and quantity analysis revealed that the load transfer process of CNT, thermal mismatch, and grain refinement are the primary factors leading to the composite’s increased tensile strength. Porosity tends to increase due to variance in the thermal expansion coefficient of particles and matrix material; Orowan strengthening mechanism plays a prominent role in enhancing tensile strength. Because of the influence of synergistic strengthening, microparticles TiB _2 increased the proportion of load transmission mechanisms, and thermal mismatch facilitated the homogenous distribution of CNTs. Wear resistance and corrosion resistance increase with the inclusion of CNTs and TiB _2 content. An abrasive-type wear mechanism is seen in the SEM image, and the wear craters are also seen in all the SEM images. Adding TiB _2 significantly improves the cast composites’ resistance to corrosion because of grain refinement. Higher addition of TiB _2 influences higher pitting corrosion due to poor grain refinement.

β -titanium alloys are essential in many applications, particularly biomedical applications. Ti-14Mn β -type alloy was produced using an electric arc furnace from raw alloying elements in an inert atmosphere. The alloy was homogenized at 1000 °C for 8 h to ensure the complete composition distribution, followed by solution treatment at 900 °C, then quenched in ice water. The alloy was subjected to cold deformation via cold rolling with different ratios: 10, 30, and 90%. The phases change, microstructure, mechanical properties, and corrosion resistance of Ti-14Mn alloys were evaluated before and after cold rolling. The results showed that the β -phase is the only existed phase even after a high degree of deformation. The microstructure shows a combination of twinning and slipping deformation mechanisms in the deformed alloy. Microhardness values indicated a linear increase equal to 30% by increasing the ratio of cold deformation due to the strain hardening effect. The corrosion resistance of Ti-14Mn alloy was doubled after 90% cold rolling.

Corrosion of steel rebars and susceptibility of reinforcement steel to chloride ion attacks are the two major problems for the construction industries and thereby a huge amount of money is spent to repair it. Epoxy coating on the steel rebars can be one cost-effective solution to alleviate the detrimental effects of corrosion in concrete structures. In the present research, plain and epoxy coated rebar (ECR) samples were chosen to study the correlation between microstructure, hardness and corrosion performance. The microstructures of the investigated thermomechanically treated (TMT) rebars primarily reveal tempered martensitic rings at the outer surface followed by a narrow bainitic transition zone in between along with a ferrite-pearlite microstructure at the inner core. The corrosion resistance of plain and epoxy-coated rebars in naturally aerated 3.5% NaCl and 1% HCl solutions were studied using gravimetric test, open circuit potential (OCP) test, and linear polarization monitoring techniques. It has been witnessed that the corrosion current (i _corr ) has been shifted towards lower values and polarization resistance (R _p ) values are higher for ECR samples which is a clear indication of higher corrosion resistance of the ECRs than the plain rebars. Energy dispersive spectroscopy (EDS) analysis reveals the presence of iron hydroxides and iron oxides. However, x-Ray diffraction (XRD) analysis indicates the existence of various types of oxides, hydroxides, and oxy-hydroxides like iron chloride hydroxide [Fe _2 (OH) _3 Cl], goethite ( α -FeO(OH)), lepidocrocite ( γ -FeO(OH)), magnetite (Fe _3 O _4 ) and bernalite [Fe(OH) _3 (H _2 O) _0.25 ] in the epoxy coated rebar samples whereas, plain rebars indicate the presence of goethite ( α -FeO(OH)), maghemite ( γ -Fe _2 O _3 ), magnetite (Fe _3 O _4 ), hydrogoethite (Fe _2 O _3 .H _2 O), lepidocrocite ( γ -FeO(OH)) and iron oxide (Fe _21.34 O _32 ). All the experimental results confirm that ECR samples are more corrosion resistant under both acidic and saline environments.

Nickel-nano titanium oxide (Ni-TiO _2 ) composite coatings were developed on stainless steel 304 substrate using pulsed electro-deposition technique. Experiments were carried out employing ${L}_{27}$ orthogonal array, taking current density, frequency, and duty cycle as prime parameters. Coating characterization was done using FESEM with EDAX and XRD. Applying the Response Surface Methodology optimization method, the optimized values of the parameters were identified as duty cycle, frequency and current density with values of 24%, 10 Hz and 0.6 A cm ^−2 respectively. Vickers micro-hardness, surface roughness, wear resistance and corrosion resistance were measured initially for the as-coated sample. The sample that yielded the optimum parameters was then heat treated for an hour at 400 °C in a closed furnace and quenched in SAE 40 grade oil. Test results of post heat-treated sample produced maximum micro-hardness of 446.45Hv, reduced surface roughness of 0.292 μ m, superior wear rate of 3.20E ^−07 mm ^3 N ^−1 -m ^−1 and corrosion protection efficiency of 94.52% of Ni-TiO _2 coating at low frequency, along with enhanced wear and corrosion resistance as compared with the as-coated sample.

The changes in intermetallic phases of Mg-6%Al-5%Pb (Mg-Al-Pb) alloy prepared by powder metallurgy and their effects on electrochemical properties were studied. Experimental results showed that coarse Mg _17 Al _12 phases (with size ranges from 20 μ m to 70 μ m) and fine Mg _2 Pb phases (with the size of 100 nm scale) formed in the mixed Al, Pb and Mg powder during the hot press sintering procedure. Fine Mg _2 Pb phases exhibit strong diffusional ability to diffuse into Mg _17 Al _12 phases. Extruding further promotes the diffusion of Mg _2 Pb phases into Mg _17 Al _12 phases. Solution treatment produced a mixed microstructure which is Mg _17 Al _12 phase containing Mg _2 Pb phases inside and made other Mg _2 Pb phases homogeneously distributed in Mg matrix. Mg _17 Al _12 phases and the gathered Mg _2 Pb phases will accumulate the Mg(OH) _2 corrosion products, which impedes the subsequent discharge behavior. Homogeneously distributed Mg _2 Pb phases will fall off during discharge, which makes the discharge curve more stable. The mixed microstructure has positive effect on corrosion resistance and discharge potential. Therefore, solution-treated alloy shows the highest negative potential and the smoothest curve during the galvanostatic discharge test. Compared with the commercial AZ61 sheet, solution-treated alloy exhibit much higher anode properties in Mg/PbCl _2 battery test. Thus, the solution-treated alloy could serve as an excellent anode in seawater-activated batteries.

The powder metallurgy process is commonly used to produce nanocomposite samples so that, their properties depend on the process parameters and the weight fraction of reinforcements. In the current study, producing metal matrix nanocomposite with steel 316L as a matrix and mixing of hBN/TiC nanoparticles as a reinforcement is conducted. The total weight percentages of reinforcements are 6% wt and 8% wt (i.e. with an equal proportion for each nanoparticle). The powders were mixed for 10 h and then compacted at different pressures (300 MPa and 400 MPa) by cold isostatic pressure (CIP) conditions. The compacted powders were sintered at different temperatures (1350 °C and 1450 °C), and times (2 h and 4 h) in the furnace. The microstructural analysis of nanocomposite was performed by SEM, XRD, EDX, DTA, and also FT-IR tests. The results showed that by increasing the weight fraction of nanoparticles the microhardness and wear rate improved and, on the contrary, the flexural strength and corrosion rate decreased. The optimum result for the microhardness and wear rate were achieved when the sample contains 8% wt nanoparticles, compacted at 400 MPa and sintered at 1350 °C for 4 h. As well, the highest flexural strength and corrosion rate belong to the sample compacted and sintered at 400 MPa, 1450 °C for 2 h.

Utilization of plant extracts for the corrosion protection of metallic alloys has increased significantly in the last few years. Ginger (GII), tea tree (TT) and grapefruit (GP) essential oil extracts were evaluated for their corrosion protection effect on mild steel in 0.5 M H _2 SO _4 media by potentiodynamic polarization, weight loss analysis, open circuit potential measurement, optical microscopy and ATF-FTIR spectroscopy. Corrosion rate from weight loss and polarization at 0% extract concentration decreased from 63.33 mm y ^−1 and 18.01 mm y ^−1 to values between 0.31 mm y ^−1 and 1.96 mm/y for weight loss, and 0.604 mm y ^−1 and 0.161 mm/y for polarization at optimal extract concentration. Generally, the extracts performed effectively with inhibition efficiency above 95%. The extracts displayed mixed-type inhibition properties though with significant effect on the cathodic plot while the anodic plots indicate activation control mechanism. Corrosion inhibition of GII extract obeyed the Langmuir and Frumkin isotherm model while TT extract inhibition adhered to Langmuir, Frumkin, Frundlich and Temkin isotherms. GP extract inhibition obeyed the Langmuir isotherm only. Correlation coefficient of the isotherms were generally above 0.9. Adsorption of the extracts aligned with chemisorption adsorption from thermodynamic calculations. Open circuit potential plots in the presence of the extracts/acid solution generally depict significant electropositive shift compared to the plot in the absence of the extracts which was relatively electronegative. Potential variations were observed on the plots of the extracts due to miniature active passive transit characteristics at the extract-metal interphase. ATF-FTIR spectroscopic data shows the functional groups in TT extract molecules adsorbed onto the steel exterior compared to GII and GP extract molecules which depict surface coverage from analysis of the wavelength and transmittance data. Optical image of mild steel after corrosion depicts significantly degraded exterior with corrosion pits. However, in the presence of the extracts the steel morphology was well protected.

Cobalt-based coatings have been widely applied to provide guidance to cavitation erosion (CE) and corrosion resistance since the coatings possessing superior mechanical and anti-corrosion properties. In this study, we prepared cobalt-based alloy (Stellite 21) coating and WC-17Co coating on 1Cr18Ni9Ti by HVOF. The CE resistances were evaluated in deionized water and 3.5 wt% NaCl solution (NaCl solution), and the anti-corrosion properties were studied using polarization tests. Results show that the WC-17Co coating had superior CE resistance than cobalt-based alloy coating in deionized water because of superior microhardness and fracture toughness characteristics. The WC-17Co coating presented much loose corrosion products (W/Co-oxides) in NaCl solution, which prone to be removed by the mechanical effect of the CE and accelerated the coating damage. On the contrary, the compact Cr oxides formed on cobalt-based alloy coating surface in NaCl solution could seal the pores, preventing to formation of erosion pits, and mitigate the damage of CE. Therefore, the cobalt-based alloy coating exhibited the best CE resistance in NaCl solution and had the potential to prevent CE in seawater.

This work deals with the electrochemical evaluation of a hybrid coating based on mucilage and prickly pear cochineal ( Dactylopius coccus ) for corrosion protective applications. The Opuntia streptacantha mucilage was extracted by grinding prickly pear cochineal, and three coatings containing mucilague (CM), cochineal-mucilage (CMC), and cochineal-mucilage without Tween 80 (CMC-T) were formulated. The aluminum working electrodes (WE) were coated by immersion and then left to dry for 72 h at room temperature. The formed coats were assessed by electrochemical impedance spectroscopy, electrochemical noise, and potentiodynamic polarization curves after 24, 72, and 168 h of immersion in a 3.5 wt% NaCl solution. These electrochemical measurements were performed in triplicate to check reproducibility. The Tween 80 plasticizer-free cochineal-mucilage-based hybrid coating reveals more excellent protection against corrosion than uncoated aluminum. Optical micrographs were used to set apart the conditions of the hybrid coating after its valuation, which show the protection of the metallic surface on which it was not coated. Results showed that the hybrid coating has suitable properties as a barrier against corrosion due to its ability to block the aggressive species diffusion by trapping them in the coating structure, which prevents their contact with the metal surface. This property is attributable to better mucilage and cochineal film homogeneity. Also, it acts as a corrosion inhibitor due to its semi-permeable behavior where only water molecules flow through its pores. This hybrid coating showed an excellent corrosion-resistant behavior to be used to protect aluminum.

Bioactive hydroxyapatite (HA) coating is applied on a commercially pure Ti by electrophoretic deposition (EPD). Optimizing the coating structure is necessary to obtain a stable layer and the best corrosion protection. The EPD was conducted at a constant voltage of 20, 30, and 40 V for 30 min in a HA/DMF (dimethylformamide) suspension. Uniform HA layers with a Ca/P ratio of 1.82 were successfully deposited on the Ti surface. The layers, which consisted of HA grains with the size of 1–5 μ m, exhibited a gradual increase in thickness of 32, 50, and 60 μ m with formation voltage. For the biomedical application, the suitable coating thickness was at least 50 μ m. The high compaction of HA grains deposited at 30 V led to an order magnitude higher polarization resistance and ten times lower corrosion current density relative to the other specimens. The porous HA layer formed at 20 V, and the presence of cracks in the 40 V-coating led to a lower corrosion resistance relative to the 30-V coating. The 20 V- and 30 V-coatings remained intact and triggered the deposition of HA during immersion in simulated body fluid for 28 days, while the 40 V-coating dissolved into the solution. The optimum EPD voltage for depositing a stable HA coating with reasonable coating thickness and the best corrosion resistance was 30 V.

In the present investigation, Al-5Zn-2.5Mg - 1.6Cu -xSn (x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0 wt%) alloys were fabricated using melting and casting technique. The microstructures of the alloys were studied using optical, scanning electronic microscope/EDS and X-ray diffraction. The corrosion behaviour was performed using electrochemical measurements and immersion tests while the wear behaviour was carried out by pin-on-disc technique. The findings revealed that incorporating Sn to the Al-5Zn-2.5Mg alloy improved its corrosion and wear resistance due to refining the grains. The corrosion potentials shifted from −884 to −943,−955, −996,−1008 and −1012 mV (Ag / AgCl), while the coefficient of friction declined from 0.69 to 0.62 , 0.51 , 0.34, 0.29 and 0.22 with increment of Sn content from 0.0 to 0.2, 0.4. 0.6, 0.8 and 1.0 wt%, respectively. On the other hand, the results illustrated that the wear rate diminished from 4.42 *10 ^−3 to 1.47 * 10 ^−3 (mm ^3 /Nm) with increasing Sn from 0.0 to 1.0 wt%. Furthermore, the findings showed that increment of Sn content stimulated the uniform corrosion on the surface of alloys.

Corrosion inhibitors generated from plants and organic compounds are critical for achieving a greener environment. In this work we investigated the corrosion inhibition of pomegranate arils extract (PAE) for mild steel in 1M HCl by potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), and profilometry measurements. The effects of PAE concentration (100, 200, 400 mg l ^–1 ) and temperature (298, 313, and 333 K) on the PAE inhibition efficiency were evaluated. Polarization measurements revealed that PAE was a mixed anodic-cathodic inhibitor. Corrosion inhibition efficiency was around 74% at a PAE concentration of 400 mg l ^–1 at 298K. However, at 333 K, the corrosion current density in the solution containing 400 mg l ^–1 of PAE was measured to be 1.28 mA cm ^−2 , which was higher than that in the blank solution (0.92 mA cm ^−2 ). This increase in corrosion rate at 333 K demonstrates the negative influence of high temperatures on PAE inhibition efficiency. The PAE green inhibitor was discovered to have a physical adsorption characteristic and to obey the Langmuir adsorption isotherm.

Experimental studies have been conducted on the microstructure, mechanical, and corrosion characteristics of magnesium alloy RZ5 that has been butt welded. Pulsed tungsten inert gas (PTIG) and friction stir welding (FSW) are two distinct welding techniques that have been considered. The weld metal of the PTIG joint exhibited finer grain cast structures of 10 μ m with coarser intergranular eutectic τ -Phase particles as compared to the coarse-grained cast base metal microstructure of 104 μ m. The FSW joints microstructural investigation revealed that the precipitates with globular morphology had spread out throughout the wrought ultrafine α -Mg grains of 2 μ m. X-ray elemental distribution and phase analysis indicated that in base metal and weld joints, the grain boundaries and interior zones were enriched with Zn and Zr elements with corresponding secondary phases. Microhardness measurements showed the softening is reduced in the heat-affected zone of FSW compared to PTIG joints. The stir zone exhibits the highest hardness of 120.4 HV _0.2 which is 40% higher than the fusion zone hardness of PTIG welds. Electrochemical polarization scans and immersion testing indicated that the weld zone of the FSW joint exhibits higher corrosion resistance than the RZ5 base alloy and PTIG welds. The corrosion data (i.e., higher corrosion potential, lower current density, and higher breakdown potential) obtained from the polarisation scans are correlated with the microstructural features after immersion testing.

Hydrogen-free diamond-like carbon (DLC) films with thickness of 36 μ m and 50 μ m have been prepared on Si and AISI 304L stainless steel substrates, respectively, by filtered cathodic vacuum arc (FCVA) together with a high-voltage pulse power. The structure, chemical bonding state, mechanical properties and wear, corrosion resistance and anti-erosion performance were evaluated. The thick DLC films with compressive stress of 0.71 GPa and hardness of 3160 HV were obtained. The preparation of the low stress but high hardness coating mainly due to the appropriate high negative bias and short pulse duration, which could result in an alternate ion bombardment and deposition. The 50 μ m-thick coating showed corrosion resistance with high polarization resistance of 4.69 × 10 ^8 Ω·cm ^2 and low corrosion current density of 5.47 × 10 ^−8 A·cm ^−2 . Thick coating exhibited outstanding sand particle erosion resistance with low average mass loss rate of 0.035 mg g ^−1 . Under high-speed sand erosion conditions, the coating remains unbroken, without peeling or cracking were observed on the erosion center. In addition, DLC coatings showed good tribological performance under dry, water- and oil-lubricated condition.

Friction Stir Welding (FSW) was carried out to examine the influence of filler materials and varying process parameters on the microhardness and the joints corrosion resistance properties. Aluminium alloys 6082 and 5052, having 8 mm thickness was joined by varying parameters. The primary process parameters are rotational speed, tool travel speed, plunge depth, filler holes centre distance and filler ratio. The hardness at the weld nugget zone and corrosion rate evaluations were analyzed. The best results were obtained for the parameter combinations of 1150 rpm tool rotation, 130 mm min ^−1 tool travel, 0.2 mm tool plunge, the filler holes centre distance 2 mm and a powder filler made of 95% magnesium and 5% chromium.

The present study investigates the microstructural, mechanical and corrosion properties of Ti-7Mo-8Nb alloy manufactured through powder metallurgy. The performance of the developed alloy is benchmarked against cast Ti-6Al-4V. Microstructure examination of Ti-7Mo-8Nb revealed a Widmanstätten structure containing equiaxed β grains along with acicular α phase. In regards to the mechanical properties, Ti-7Mo-8Nb possessed higher compressive yield strength, higher hardness but lower elastic modulus than Ti-6Al-4V. The elastic modulus of Ti-7Mo-8Nb was almost 44.9 GPa, approaching the usually desired value of 30 GPa for cortical bone. Wear test revealed also a lower wear rate for Ti-7Mo-8Nb. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) experiments were carried out for both Ti-7Mo-8Nb and Ti-6Al-4V immersed in Hank’s solution as a simulated body fluid at a temperature of 37 °C. Both experiments revealed higher corrosion resistance for Ti-7Mo-8Nb manifested by lower corrosion and passivation current densities, higher negative phase angle, higher impedance modulus and larger Nyquist semicircle diameter as compared to Ti-6Al-4V alloy. The superior corrosion properties of Ti-7Mo-8Nb are indicative of the development of a more stable passive layer on the surface. The fitting of EIS data into an equivalent circuit suggested the formation of a double oxide layer consisting of an inner compact base passive film along with an external porous layer. The presented combination of high strength, high corrosion resistance along with low elastic modulus puts forward the Ti-7Mo-8Nb alloy as a good candidate for orthopedic biomedical applications.

Corrosion resistance of 3004 and 4044 aluminium alloys (3004Al and 4044Al) in neutral chloride (0.5%–4.5% concentration), sulphate (0.00625M-0.1 M concentration), and chloride-sulphate (0.00625 M H _2 SO _4 /0.5%–4.5% chloride concentration) solutions was studied with potentiodynamic polarization, open circuit potential, cyclic polarization, and optical microscopy. Results show 4044Al exhibited higher resistance to general corrosion while 3004Al was more resistant to localized corrosion. Corrosion of 4044Al decreases with increase in chloride concentration while 3004 Al increases. Corrosion rate values for 3004Al and 4044Al in sulphate solution were generally similar between 0.061–0.395 mm y ^−1 and 0.168–0.213 mm y ^−1 , respectively. In chloride-sulphate solution, corrosion rate of 3004Al increased from 0.130 mm y ^−1 to 1.563 mm y ^−1 at peak chloride concentration whereas the corrosion rate of 4044Al is near constant. The passive film on 4044Al is found to weaken significantly with increase in chloride concentration. Passivation values varied from 0.39 V at 0.5% chloride concentration to 0.01 V at 4.5% concentration while the potential at which stable pitting occurred increased. The passivation range values for 3004Al are relatively stable with respect to chloride concentration. Results from cyclic polarization experiments show the deterioration rate of both alloys in NaCl solution is subject to chloride concentration. The results show the alloys corrode at all NaCl concentrations (0.5%–4.5%) with the lowest pitting corrosion risk in 0.5% and 1.5%NaCl solutions. The highest pitting corrosion risk of the alloys occurred in 3.5% NaCl solution. Significant localized morphological deterioration is visible throughout the entirety of 4044Al relative to the adjacent Al alloy matrix compared to total surface deterioration on 3004Al.

The microstructure, element distribution and pitting corrosion resistance of Gas Tungsten arc welding (GTAW) duplex stainless steel welded joints under 100% argon (Ar) and 98% Ar + 2% nitrogen (N _2 ) shielding gas were studied by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and electrochemical corrosion methods. These results show that the addition of N _2 to the shielding gas promotes the formation of austenite ( γ ) phase in the weld joint. Also, the austenite phase distribution is dendritic and the ferrite ( δ ) and austenite phases in the heat-affected zone are no longer banded structures. Moreover, the austenite phase in the welded joint is enriched in nickel (Ni) and nitrogen (N) elements, while the ferrite phase is enriched in chromium (Cr) and molybdenum (Mo) elements. The pitting corrosion index (PREN) of the austenite/ferrite ( δ / α ) phase boundary is lower than that of δ and γ phases, which leads to their preferential corrosion. The appearance of chromium nitride (Cr _2 N) decreases the corrosion resistance of the weld seam and the heat affected zone. N _2 in the 98% Ar + 2% N _2 shielding gas can restrain Cr _2 N precipitation, increase the pitting corrosion index of secondary austenite structure ( γ _2 ), and improve the pitting corrosion resistance of welded joints.

The electrodeposition of aluminum on mild steel in a molten salt electrolyte consisting of a mixture of AlCl _3 /NaCl/KCl (weight percent ratio of 80:10:10) was studied. Parametric studies were carried out to evaluate the effect of different parameters such as current density, electrolysis time, and intermediate coating layer on the coating morphology and coating-to-substrate adhesion. The quality and morphology of the coating were investigated using scanning electron microscope (SEM) and x-ray map analyses. The effect of heat treatment of the coated samples on the interface stability and formation of intermetallic compounds at the Al-Fe interface was also investigated. Cross-sectional examination by SEM as well as energy dispersive spectroscopy (EDS) line scan showed that upon annealing at temperatures in the range of 350 °C–550 °C, brittle Fe-Al intermetallic layers were formed at the interface. This shows that high-temperature service conditions can adversely affect the coating properties. The apparent activation energy of the formation of such intermetallic layers was calculated based on thickness measurements on these layers. The optimum conditions for electroplating were determined as current density of 0.022 A.cm ^−2 and electroplating time of 60 min. Potentiodynamic polarization tests were used to evaluate the corrosion resistance of the samples in 3.5 wt% NaCl solution. Considering the corrosion rate of coated samples which is much lower than the bare substrate, it was concluded that the electrodeposited coatings could efficiently protect the steel substrate against corrosion in corrosive media.

This study investigates the effect of zirconia addition with different percentages on Ni-Cr alloy using a powder metallurgy technique. The scanning electron microscope with energy dispersive spectroscopy is used to analyze the microstructure of Ni-Cr and Ni-Cr-x ZrO _2 (where x is 3, 6, 9 wt.%) alloys. The x-ray diffraction method is used to determine the phases for Ni-Cr and Ni-Cr/ZrO _2 alloys. The corrosion and ion release tests were also achieved using potentiodynamic polarization and atomic absorption spectroscopy. According to the microstructural investigation, the results found that the Ni-Cr alloy’s grain size tends to reduce with the addition of ZrO _2 with obtaining the smallest grain size with 6 wt.% addition. The potentiodynamic polarization exhibited that the modified alloys are more resistant to corrosion in the saliva medium than the Ni-Cr alloy. Furthermore, the role of ZrO _2 in dissolution test shows the development in the passive layer’s resistance compared to unmodified alloys with reducing the Ni release from 2.5 ppm to 0.2 ppm. It can conclude that the addition of ZrO _2 has significantly improved Ni-Cr’s biocompatibility and extend the area of implementations.

Fireproof mud is a widely-used sealing and plugging material in power and construction industry, yet it may cause aging/corrosion problems to its directly contacted materials, leading to high safety risk. However, studies about the aging/corrosion behavious caused by fireproof mud are surprisingly rare. To fill in such a research gap, aging and corrosion of galvanized steel and polyvinyl chloride (PVC)-shielded cable caused by fireproof mud under simulated hygrothermal environment have been systematiclly investigated, based on which the mechanisms of these processes have been proposed. The results show that the corrosion of galvanized steel is mainly influenced by chloride anions from the fireproof mud, which can be aggravated/ alleviated if the fireproof mud is acidic/alkaline. For the aging of PVC shielded cable, one main reason is acidic/alkaline chemical corrosion caused by acidic/alkaline fireproof mud, the other is radical chain reaction of the PVC polymer in hygrothermal environment. These discoveries can offer important guidance for correct and safe use of fireproof mud in industries, thus ensure safe industrial production.

Fabrication of NiP-SiC nanocomposite coatings through the electroless deposition in a commercial electrolyte containing the low concentrations of SiC nanoparticles on carbon steel substrate was studied in this work. The confirmation of co-deposition of Ni matrix and SiC nanoparticles was investigated by evaluating the effect on morphology, crystal structure, and corrosion behavior of the heat-treated coatings which were investigated by scanning electron microscope, x-ray diffraction (XRD), and electrochemical measurements, respectively. The XRD results revealed that the heat-treated NiP and NiP-SiC coatings consisted of Ni and Ni _3 P phases, which the calculated faction of Ni _3 P phase for NiP and NiP-SiC samples is 58.2 and 62.2%, respectively. The corrosion resistance of nanocomposite samples is higher than that of pure NiP sample (9 to 76% corrosion inhibition efficiency. The tribological behavior of the coatings was characterized by microhardness measurement and ‘pin on disk’ wear test. By co-deposition of SiC nanoparticles, the hardness of heat-treated NiP is significantly increased (near 25%) and the wear loss is reduced (near 48%), especially at high sliding distance during wear test. The sample prepared through the surfactant-free electroless bath containing the 1 g l ^−1 SiC nanoparticle showed the best corrosion as well as wear resistance.

In this work, anodic oxide layers on the surface of an AZ31 magnesium alloy were obtained by plasma electrolytic oxidation (PEO) process under low frequency pulsed current. For this, electrolytical solutions containing hexamethylenetetramine and sodium fluoride were used. The morphology and chemical composition of formed coatings were examined by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Also, salt spray test, hydrogen evolution and electrochemical tests (potentiodynamic polarization and electrochemical impedance spectroscopy) were conducted in order to study the corrosion behavior of the coated samples. It was found that the use of low frequency pulsed current for the PEO process reduces the film porosity and increases its thickness, compared with PEO films obtained by continuous anodization. The effect of the pulsed current signal was also analyzed for a two steps PEO process, observing changes in the morphological characteristics of the coatings which allow a better corrosion according electrochemical tests (short term corrosion measurements). However, long term tests results as hydrogen evolution and salt spray tests, indicated the opposite. Both the film porosity and thickness were affected by either the pulsing of the current or the use of a two-step process.

Corrosion behavior of Inconel 617 in supercritical carbon dioxide at 650 °C and 15 MPa for 1000 h was investigated. X-ray diffraction, high-resolution transmission microscopy, and Raman spectrum were used to observe and analyze the corrosion products formed on Inconel 617. The results showed that the corrosion products formed on Inconel 617 were composed of a thick Cr _2 O _3 layer, a thin Al _2 O _3 layer and a carbon-penetrated zone from the interface between carbon dioxide and the oxide scale to the substrate. Carbon was deposited on the surface of the oxide scales, which was verified by Raman results. The oxidation of Inconel 617 suffered in supercritical carbon dioxide was more serious than the carburization of Inconel 617.

Systematic works on the effect of grain size on the corrosion resistance of low carbon steel are scant. In the present work, a spectrum of grain sizes was obtained by simple heat treatment routes in a typical low-carbon steel. It was revealed that two distinct stages for the dependency of corrosion current density ( i _corr ) on the grain size exist. Above a limiting average grain size of ∼22 μ m, i _corr decreased slowly with increasing grain size. However, below this limiting value, i _corr increased rapidly, which was related to the increased density of grain boundaries as interpreted by theoretical calculation of number of grains per unit area. Conclusively, a grain size of ∼22 μ m (ASTM grain-size number of 8) was considered to be an optimum value according to the mechanical and corrosion standpoints.

The corrosion mechanism of three aluminum ingot mold materials used by Chinese aluminum electrolytic enterprises in molten aluminum was studied: The three materials are pearlite cast iron(PCI) contains vermicular graphite, lamellar graphite, and spherical graphite respectively. After 800 °C molten aluminum corrosion for 4 h, the intermetallic compound (IMC) layers of Fe _2 Al _5 and FeAl _3 is formed at the interface. It was found that the volume of spherical graphite in IMC was reduced to 20%, and lamellar graphite aggregated in the IMC layer. The average thickness of the Fe _2 Al _5 layer in PCI1, PCI2 and PCI3 is about 180 μ m, 100 μ m and 101 μ m, respectively. The weight loss rate of PCI1 is 2.57 (mg cm ^−2 )min ^−1 , PCI2 is 2.20 (mg cm ^−2 )min ^−1 , and PCI3 is 2.24(mg cm ^−2 )min ^−1 . There are dispersed Cr and Mo carbides in the IMC layer. Si-rich ribbon-shaped region was found at the interface between cast iron and IMC. The needle-like precipitates (Al _4 C _3 ) were observed only at the only at the boundary between cast iron and IMC in PCI1.

Titanium and the alloy Ti-6Al-4V are standard in implantology, despite the fact that the alloys may suffer from biomechanical incompatibility. The appropriate solution is the use of titanium β -alloys with a low modulus of elasticity and high strength. An additional advantage of these alloys is improved corrosion behaviour in environments that may contain fluoride ions, i.e. the oral cavity. Ti-25Nb-4Ta-(X)Sn alloys, where X is 4, 6, 8 and 10 weight per cent, were prepared. The phase composition, ultimate tensile strength, yield strength, Young modulus, elongation and hardness were measured. The corrosion behaviour in physiological saline, acidified physiological saline with and without the fluoride ions, was determined using, potentiodynamic polarization and electrochemical impedance spectroscopy. Bioactivity was predicted on the base of exposure in the simulated body fluid extended by impedance detection of the Ca/P layer formation. From the point of view of mechanical properties, alloys with a higher tin content are ideal for load-bearing applications. The corrosion resistance of these alloys in physiological saline is similar to titanium and significantly higher in the fluoride ions containing environment. The bioactivity test - exposure in SBF has shown quite identical results of the studied alloys and titanium, both in terms of kinetics and total composition of precipitated calcium-phosphate layer. Possible cytotoxicity effects were excluded by the exposure with murine fibroblasts. This study describes the mechanical properties and corrosion resistance in non-fluoride and fluoride containing media, predicts bioactivity and verifies non-cytotoxicity of new titanium alloys and demonstrates that they are a suitable substitute for currently the most widely used alloys (Ti-6Al-4V, Ti-6Al-7Nb) in terms of both mechanical properties and corrosion resistance for dental implants.

Initial solution treatment (ST) of aluminium alloys prior cryorolling (CR) enhances the ultrafine grain structure formation hence, improving their mechanical and corrosion properties. However, determining the appropriate ST temperature is crucial to obtain the optimum properties. In this work, ST followed by cryorolling of AA 5052 alloy was performed at varying temperatures; 480 °C, 510 °C and 540 °C. Mechanical and microstructural characterization of the cryorolled samples with and without ST and the base metal were performed using Vickers hardness tester, universal tensile testing machine, FESEM, EBSD and HRTEM. All the ST cryorolled samples showed the finer structure and better mechanical and corrosion performances than those without ST and the base metal. The smallest crystallite size and lattice strain achieved were 24.88 nm and 3.86 × 10 ^−3 respectively at 540 °C. The hardness, yield and tensile strength increased with increasing the ST temperature with the highest values of 85.2 Hv, 254.82 MPa and 303.35 MPa, respectively, at 540 °C. Cryorolled sample solution treated at 540 °C also showed the highest corrosion resistance based on low corrosion current and high corrosion potential. The work gives the appropriate ST temperature at which improved microstructure, mechanical and corrosion properties of the cryorolled AA5052 can be obtained.

This research paper portrays the enrichment of mechanical, wear and corrosion properties of the Aluminium 6061 matrix composite by incorporating hybrid reinforcements. Aluminium 6061 alloy is stir casted with different proportions of boron nitride (BN), Aluminium oxide (Al _2 O _3 ) and graphite particles. Tensile test reveals that the tensile strength and ductility for the Al 6061-30 BN -10Al _2 O _3 - 5C is improved due to the presence of higher BN content along with 10% Al _2 O _3 . Significant improvement in microhardness (63HV), compressive strength (187 Pa) and impact strength (12 J) for the Al 6061-30 BN -10Al _2 O _3 - 5C when compared with the bare Al 6061 alloy. The dispersion of BN with Al _2 O _3 improved the wear resistance for the Al 6061-30 BN -10 Al _2 O _3 - 5 C composite, where as the unreinforced bare Al alloy has caused the major surface degradation resulting in poor wear property and the worn out surfaces are examined through the scanning electron microscope. The main wear mechanism is identified as adhesive wear. The corrosion test results clearly reveals that the corrosion resistance is higher for the Al 6061-30 BN -10Al _2 O _3 - 5C (−0.526 ± 0.004 V) with a lower current density of −0.983 ± 0.004 μ A cm ^−2 than the other composites and bare Al 6061.

In this research, the low temperature process for growing graphene from solid carbon source PMMA under atmospheric pressure was firstly investigated. Through adjusting the growth temperature (600 °C–800 °C) and other process parameters, using the chemical vapor deposition method, single or double layers of graphene grown on a copper substrate. Without control pressure, this way improved controllability of graphene preparation and reduced production costs. The morphology, quality of graphene was revealed by SEM, XPS, Raman, UV–vis. Additionally, the conductive test results illustrate that the graphene on the surface of the copper matrix slightly soars the conductivity of copper. This is due to the process of annealing and growth that alters the structure of the material. The results of the Tafel experiments, electrochemical impedance spectroscopy (EIS) measurements and cyclic voltammetry (CV) tests demonstrate that the graphene film can effectively improve the corrosion resistance of the copper matrix. Compared to the single layer graphene coating, double-layers graphene coating has a better anti-corrosion effect. This is in that the double-layers graphene coating can block the defects of the single-layer graphene in time, and better prevent the intrusion of Cl ^− into the copper matrix, so as to achieve a good anti-corrosion effect.

Recent advancements in bone implant materials have led to the development of various alloys. In this study, the degradation behavior of the as-cast Mg-3 wt% Zn-1 wt% Ca-0.5 wt% Sr alloy in vitro was investigated using x-ray diffraction (XRD), scanning Kelvin probe force microscopy (SKPFM), and scanning electron microscopy (SEM). Our results demonstrated that the alloy microstructure was composed of α-Mg, a Ca _2 Mg _6 Zn _3 phase, and a Mg _17 Sr _2 phase. The Ca _2 Mg _6 Zn _3 phase, which had the smallest absolute potential, was shown to have cathodic protection, while the α-Mg, which had the largest absolute potential, was shown to prefer corrosion. The in vitro corrosion products of the as-cast alloy were Mg(OH) _2 , a Ca-P compound, and HA. At the beginning of the corrosion, the hydrogen evolution rate of the alloy was fast due to the thin corrosion product layer. With the extension of the corrosion time, the corrosion layer thickened and the hydrogen evolution rate slowed down and stabilized to 1.25 × 10 ^−5 mol cm ^−2 · h . Due to the high concentration of Ca and Mg ions near the second phase, HA was quickly deposited and an ion exchange channel between the solution and the alloy was formed, making it easier for the Mg, Ca, and Sr ions to enter the solution and promote the formation of HA. The hysteresis effect of Sr element was found, that is, Sr ions were released into the solution after etching for a period of time, which promoted the formation of HA and HA-containing Sr (Sr/HA).

The corrosion behavior of aluminum 1060 in hydrated salt phase change materials (PCM) melts comprised of Na _2 HPO _4 ·12H _2 O - Na _2 SO _4 ·10H _2 O was investigated through electrochemical tests as a function of pH. The pH of PCM medium was adjusted by adding H _2 SO _4 or NaOH. Electrochemical impedance spectroscopy reveals the existence of concentration difference layer at aluminum/PCM interface ascribed to the adsorption of PCM species and the formation of aluminum oxides. The observed anodic branch of DC polarization exhibits potential independence which is ascribed to the formation of surface oxide film and the accumulation of hydrogen molecules inside surface pores. The oxide film formed at neutral condition is characterized as the most compact and corrosion resistant while as the environmental pH shifts away from 7 the oxides/aluminum dissolution is accelerated and more aluminum 1060 substrate is exposed.

The effect of retrogression re-aging treatment (RRA) on the corrosion behavior of 7055 Al-Zn-Mg alloy was studied in this paper. Results provided that corrosion resistance could be greatly improved by RRA. After the RRA treatment, the isolated precipitates occurred on grain boundaries (GBs) and the low angle grain boundaries (LAGBs) presented a larger fraction compared to that of single-stage peaking aging treatment. The samples after RRA treatment also show better corrosion resistance than that of single-stage peak aging treatment. In addition, of the electrochemical impedance spectroscopy (EIS) analysis showed that the impedance spectrum was consisted of semi-infinite layer diffusion impedance and stagnant Weber impedance. The semi-infinite layer diffusion impedance corresponded to a limited retention layer on the electrode surface while the Weber impedance represented a stagnant layer of corrosion products generated by the anode branches. The aluminum alloy after RRA treatment achieved higher R _f and low C _f , C _p values and its corrosion current density was ten times smaller compared to the single-stage peak aging samples with the 10% hardness losing.

Multi-thermal fluid is used to enhance heavy oil recovery, but it also causes severe corrosion failure of metallic tubing and its mechanism is still open to debate. In the present work, the c orrosion behavior of commercial steels with different Cr content (3 wt%, 9 wt%, and 25 wt%) in simulated CO _2 -O _2 -H _2 O multi-thermal fluid environments were studied by immersion corrosion test and microstructural characterization. The results exhibit that the Cr content of steel determines the type of corrosion products. The less protective corrosion scale is mainly composed of FeCO _3 , (Fe, Cr) _3 O _4 , and Fe _2 O _3 , which is formed on the surface of 3Cr and 9Cr steels. The protective corrosion scale is mainly Cr _2 O _3 , which is formed on the surface of 25Cr steel. Only when the Cr content in steel is sufficient (i.e. 25 wt%) to repair the serious depletion of Cr in the metal near the scale/metal interface in time, can protection of the corrosion scale be sustained, to improve its ability to resist the corrosion of multi-thermal fluids.