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The heat-treatment process exerts a substantial influence on both the quantity and morphology of reversed austenite in 17-4PH stainless steel. In this study, the effects of different ageing treatment methods on the microstructure and corrosion resistance of the steel were investigated. Through the observation of microscopic morphology, it was found that adjustment and ageing treatment and double ageing treatment were more conducive to the migration of elements in the steel than single ageing treatment, and they also improved the microstructure. In addition to improving the uniformity of alloy element distribution, uniformity also controls the reversed austenite content. By controlling the content and distribution of reversed austenite, the stability of the corrosion film formed at the interface can be improved, thereby improving the corrosion resistance of stainless steel. The stainless steel, after adjustment treatment and ageing treatment, has better corrosion resistance. The electrochemical corrosion resistance in a high-temperature and high-pressure underground environment was evaluated based on parameters including passivation current density and passivation potential. The results revealed a significant improvement of 50.5% in electrochemical corrosion resistance and a remarkable increase of 45.96% in pitting corrosion resistance. Furthermore, the FeCl3 pitting test demonstrated a substantial decrease of 63.16% in pitting density and a reduction of 27.96% in the uniform corrosion rate. [ABSTRACT FROM AUTHOR]

• The wooden structures unearthed at the Kasba Oudaya site exhibited cell wall collapse, while the nails displayed signs of surface weakening caused by chloride ion activity. • The presence of archaeological wood in the impregnation bath lowers the pH of the 10 % PEG-200 solution and accelerates its corrosive effect on steel. • Crevice corrosion develops at the nail-wood interface during impregnation with 10 % PEG-200 with significant diffusion of iron into wood. • The relative concentrations of chloride and sulfate in the 10 % PEG-200 impregnation bath change over time. • The 10 % PEG-200 soaking solutions provide favorable conditions for the development of various microorganisms. Electrochemical and biological analyzes were carried out on iron-wood composite archaeological objects from the "KASBA-OUDAYA" site in Morocco in 10 % PEG-200 solutions. Electrochemical measurements of steel combined with wood were made possible thanks to a proposed steel-wood configuration, with characterization of the surfaces after natural aging tests focused on the steel-wood interface by scanning electron microscope. The Mohr and Nephelometric method allow the determination of chloride and sulfate ions. While the biological study is ensured by isolation and enumeration of strains. The results revealed that the presence of wood in the PEG-200 solution decreased the pH of the solution and accelerated corrosion of steel. At the interface, we observe the development of pitting corrosion zones. In addition, PEG-200 solutions constitute a favorable environment for the proliferation of microorganisms. [Display omitted] [ABSTRACT FROM AUTHOR]

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

In this study, the effect of intermetallic compounds (ICMs) on the tribocorrosion behavior of the 7075 aluminum alloy was investigated. ICMs play important roles in the tribocorrosion resistance and mechanism of the sample. In the as-received sample, micron-sized Mg2Si, Al23Fe4Cu, and nanosized MgZn2 induced pitting corrosion and acted as abrasive materials. Accompanying the re-dissolution of Mg2Si and the growth of MgZn2, the pitting resistance worsened and adhesive wear took place. Subsequently, MgZn2 precipitated along the grain boundaries, which resulted in intergranular corrosion and aggravation of adhesive wear. [ABSTRACT FROM AUTHOR]

Corrosion and biofouling are wetting‐related phenomena that limit the effective use of metals in aqueous media. Nonwettable surfaces can mitigate the adverse effects of wetting by minimizing contact with water. However, current achievements in this field fall short of meeting industrial requirements due to the short lifetime of plastrons. This study proposes a method to measure the protective sustainability of plastron. Superhydrophobic (SHS) and aerophilic (APhS) surfaces are constructed on lightweight aluminum and are initially analyzed by conventional goniometry, which show comparable values. However, the plastron that develops underwater is substantially different. While SHS exhibit unevenly broken plastron, APhS show uniform, continuous plastron. As an example of the sustained protective performance of plastron, the corrosion resistance of SHS and APhS is presented. Potentiodynamic polarization, impedance spectroscopy, and long‐term immersion in seawater show a drastic enhancement in corrosion resistance, exclusively for APhS. In fact, almost no electrochemical signals are measurable, and no pitting corrosion is observed after 415 days of immersion in seawater. Conversely, SHS show no noticeable improvement and corrode faster than bare Al due to plastron loss. Since goniometric measurements do not provide information on plastron, it is essential to analyze the plastron for any non‐wettable surface utilized underwater. [ABSTRACT FROM AUTHOR]

The production of biocompatible ceramic–metal brazed joints is a subject of great interest. The development of new methods for obtaining biocompatible brazed joints will allow the production of new and more complex metal-ceramic implants with increased reliability and service life. At the same time, the titanium-zirconium-cobalt system is the most promising for the production of active rapid-quenched filler metals due to its low cost and low toxic effect on the human body. In this work, a ZTA-Ti joints manufacturing with various configurations using novel Zr-30Ti-20Co filler metal has been carried out. The filler metal contact angle on ZTA ceramic and titanium has been 78–80° and 53.2–33.0° in the 900–1000 °C interval. The XRD and EDS study revealed that the brazed joint consists of α-(Ti, Zr) and (Zr, Ti)2Co phases. Subsequent corrosion test according to the ASTM F 2129 standard showed that the brazed joint meets the biocompatibility criteria. However, there has been detected the (Zr, Ti)2Co phase pitting corrosion. At the same time, the content of cobalt ions in the Ringer-Locke solution after corrosion tests does not exceed the maximum safe limit. Mechanical shear strength tests have revealed that the joint fracture is brittle and the strength varies from 21.5 ± 2.5 up to 46.9 ± 19.2 MPa, depending on the joint configuration. [ABSTRACT FROM AUTHOR]

Samples of the Ni-based superalloy, RR1000, were exposed to 98% Na2SO4/2% NaCl salts at 700 °C with a flux of 1.5 µg cm−2 h−1 in flowing air + 300 ppm SO2 for a total of 250 h. Three pre-exposure conditions were studied: a bare reference alloy; fast heating to the test temperature followed by a 100 h hold; heating at a rate of 5 °C min−1 to the test temperature following by a 100 h hold. The surface oxide formed under the latter two conditions were Cr2O3 or NiCr2O4, respectively. The results show corrosion pit formation on the surface of the base, reference sample, and no pits present on the sample with the preformed Cr2O3. Some protection was found for the sample heated at 5 °C min−1 with a delay in the progression to accelerated corrosion attack. Additional testing under moisture containing air was also conducted. This showed no obvious difference in surface oxide morphology under the two tested heating rates for the short-term exposures examined but a difference was noted to be dependent on the moisture content of the air. [ABSTRACT FROM AUTHOR]

The CoCrFeMnNi high entropy alloy (Cantor), and its variant incorporating 0.2 wt% reduced graphene oxide (rGO), denoted as Cantor + rGO, were successfully synthesized using mechanical alloying followed by spark plasma sintering. Comprehensive characterization utilizing FESEM, XRD, and TEM provided detailed insights into the microstructural features of the materials. The addition of rGO reduced crystallite size from 209 nm to 169 nm, promoted a uniform distribution of carbide phases of smaller size, and enhanced microhardness from 421.8 HV to 510 HV for Cantor and Cantor + rGO, respectively. The incorporation of rGO into the Cantor structure led to an increase in compressive yield strength (CYS) from 1100 MPa for Cantor to 1250 MPa for Cantor + rGO sample. A significant decrease in corrosion current density of samples from 6.1 ± 1.5 μA/cm2 for Cantor to 1.4 ± 0.9 μA/cm2 for Cantor + rGO was observed due to the addition of rGO reinforcement. Moreover, the pitting corrosion resistance was increased in rGO-reinforced Cantor, as revealed by cyclic polarization test. This research underscores the potential for utilizing rGO as a reinforcing agent to optimize the mechanical and corrosion resistance characteristics of HEAs, offering promising avenues for advanced materials in diverse applications. [ABSTRACT FROM AUTHOR]

In this study, three reinforced concrete (RC) columns with and without corrosion and different reinforcement details are tested under lateral cyclic loading. One of these columns is well-confined to represent modern RC bridge piers that are designed according to the current seismic design codes, and the second column has the same detail with corrosion damage. The third column is a lightly confined corroded column to represent aging RC bridge piers that are not designed to the current seismic design codes. The experimental results showed that corrosion significantly impacts the ductility loss more than the strength loss of the tested corroded columns. In addition, although the uncorroded column was designed according to the current seismic design code, severe inelastic buckling in the vertical bars was observed during the cyclic tests. [ABSTRACT FROM AUTHOR]

Aluminum alloys are the potential materials in the automobile and aerospace sectors due to their lower density, easy forming and excellent corrosion resistance. The demand of high strength-to-weight ratio materials in structural applications needs the engineering industries to seek aluminum alloy with new versions of hard and brittle ceramic particles. The microstructure, hardness, wear and corrosion behaviors of AA7075 composites with 2.5wt.% and 5wt.% TiC particles were studied. Microscopic analysis is evident that the transformation of the strong dendritic morphology to non-dendritic morphology on the incorporation of TiC into AA7075. Furthermore, the precipitation of the second-phase compounds such as Al2CuMg, Al2Cu and Fe-rich Al6(Cu, Fe)/Al7Cu2Fe) is promoted by TiC particles at inter- and intra-dendritic regions. Accordingly, the hardness of composites is improved by grain boundary strengthening and particulate strengthening mechanisms. Both coefficient of friction and wear rate have an inverse relation with TiC concentration. The base alloy without TiC shows adhesive-type wear-induced deformation due to the formation of an oxide film, while composite samples exhibit a mechanically mixed layer and abrasive-type wear behavior. Composite samples shows a higher corrosion rate due to the presence of numerous precipitates which promote pitting corrosion. [ABSTRACT FROM AUTHOR]

The interaction between dental alloys and saliva affects both their properties and those of metallic materials. Aim: to analyze the in vitro interaction between a series of titanium-based dental alloys and artificial saliva. Materials and Methods: Samples made of Titanium and Nitinol were studied. Corrosion under tension was chosen, and a spectrophotometer was used to record the spectra of the solutions after the electrochemical treatment of the samples. In vitro testing of the cytotoxic impact of the studied eluates was conducted through flow cytometry analysis. Results: Titanium is by far the most resistant biomaterial, exhibiting the lowest corrosion rate. The cyclic potentiodynamic curve for Nitinol indicates typical pitting corrosion. Flow cytometry shows increased percentages of live cells, very low percentages of dead cells, an almost complete disappearance of pre-apoptotic cells, and an increase in the number of apoptotic cells for both materials. Conclusions: Both materials demonstrate increased stability in the oral environment and reduced cytotoxic potential. [ABSTRACT FROM AUTHOR]

This work is devoted to evaluating the corrosion behaviors of SS 304L and SS 316L in monoethanolamine solutions (MEA) containing SOX and NOX pollutants, examining both lean and CO2-loaded conditions at 25 °C and 40 °C. Electrochemical techniques (potentiodynamic and cyclic polarization) were used along with Scanning Electron Microscopy, Confocal Microscopy and weight loss measurements. The results reveal that the introduction of SOX and NOX pollutants increased the corrosion rate, whereas CO2 loading primarily reduced the corrosion resistance in the lean MEA solution, while its impact on solutions with SOX and NOX was less pronounced. This suggests that SOX and NOX play primary roles in the metal's dissolution. Also, SS 316L demonstrated superior corrosion resistance compared to 304L in nearly all of the cases examined. Elevated temperatures were also found to intensify the corrosion rate, indicating a correlation between the corrosion rate and temperature. A microscopic observation and EDX analysis revealed that corrosion products are characterized by high concentrations of iron (Fe) and oxygen (O) as well as carbon (C). There is also an indication of the possible formation of amine complexes, suggesting a potential for amine degradation. No pitting corrosion was observed in SS 304L and SS 316L across any tested solution. Finally, the immersion results expose a tendency for passivity in all amine solutions and at both temperatures after several days of exposure. Moreover, they confirm the very low corrosion rate calculated from potentiodynamic curves due to minimal weight loss after 24 days of immersion. [ABSTRACT FROM AUTHOR]

Automobile structural components are subject to high stress, friction and corrosive environmental conditions. Though aluminum alloys exhibit lightweight and high corrosion resistance, there is a need to improve the high strength-to-weight ratio and resistance to friction. This paper presents microstructural analysis, hardness, dry sliding wear behavior, and corrosion behavior of AA7075 reinforced with silicon carbide (SiC) particles. The composite specimens were prepared at the concentration of 2.5 and 5wt.% SiC. The microstructure of AA7075 showed dendritic morphology while composite specimens showed nondendritic morphology grains. Reinforcement of SiC resulted in increased nucleation site and refinement of grain during solidification. XRD analysis of base alloy showed α matrix with η (MgZn2), T(Al–Zn–Mg–Cu) and Al7Cu2Fe phases, while the composite sample showed the presence of additional S(Al2CuMg) and θ (Al2Cu) phases. Composite samples showed higher hardness values than base alloy due to grain boundary strengthening and Orowan strengthening. The enhancement of hardness of AA7075 by 20% and 37.5% were obtained with the addition of 2.5 and 5wt.% SiC particles respectively and also predicted with less coefficient of friction and less wear rate at all the tested load conditions. At the same time, the respective reduction in wear rates of AA7075 was found to be 50 and 65%. The worn-out surface of the base alloy was found to have undergone extensive plastic deformation and resulted in delamination with extensive patches and no clear groove marks. The composite sample of 2.5wt.% SiC showed mild patches with clear groove marks, while the Composite of 5wt.% SiC showed groove marks with fine width parallel to sliding directions. The wear mechanism was found to be transferred from adhesive mode to abrasive mode through a mixed mechanical layer with an added concentration of SiC particles from 0wt.% to 5wt.%. Weight loss during immersion corrosion increases with an increase in the amount of SiC due to an increased amount of metallic phase which increases microgalvanic corrosion and pitting. Hence, composite samples showed decreased corrosion resistance than base alloy. [ABSTRACT FROM AUTHOR]

This study describes the biofilm formation by sulphate-reducing bacteria (SRB) on different materials, which has implications for the biomedical, pharmaceutical, food and chemical process industries. SRB was chosen as a model organism being an anaerobic bacterium. Biofilm formation on different materials and corrosion of titanium by SRB were monitored with time using confocal laser scanning microscopy and fluorescent FISH probes were used to authenticate the SRB strain. The thickness of the mono-culture SRB biofilm has ranged from 4 to 24 µm during thed 12–84 hr; however, the maximum biofilm thickness (24 µm) was recorded after 60 hr of growth. Planktonic growth of the SRB strain showed a log phase up to 48 hr and the sulphide production ranged from 2 to 14 mg l−1. For a comparative account, the SRB biofilm formation on copper was chosen as a positive control. Finally, the putative role of extracellular electron transfer by SRB in the biocorrosion process and the plausible mechanism of pitting corrosion of titanium is described in detail. [ABSTRACT FROM AUTHOR]

Friction surfacing (FS) is a solid-state coating technology for metallic materials, where the deposition of a consumable material on a substrate is enabled via friction and plastic deformation. The deposited layer material commonly presents a significantly refined microstructure, where corrosion could be an issue due to this grain refinement within the layer deposited, possibly creating micro galvanic pairs. The present work investigates the corrosion behavior of the FS deposited material as well as stud base material and substrate using cyclic polarization tests and open circuit potential (OCP) monitoring. Comparing the FS deposited material and the respective consumable stud base material (both AA5083), the grain size is correlated with the results from the corrosion tests, where the deposited material shows more equiaxed and refined grains in comparison to the stud base material. The cyclic potentiostatic polarization tests showed that the stud base material is more resistant to pitting nucleation presenting smaller pits and a lower amount of pits compared to deposited material and substrate. As a complement to OCP test, the stud base material is also more stable on a chloride solution compared to the substrate and the deposited material. [ABSTRACT FROM AUTHOR]

AISI 304L stainless steel is widely used in the processing equipment and food and beverage handling industries due to its corrosion resistance, hygienic properties, and cost-effectiveness. However, it is prone to pitting and crevice corrosion phenomena, the development of which can be influenced by factors such as chloride concentration, temperature, humidity, and bacterial presence. Surface treatments, including roughness levels and residual tensile stress, can significantly affect the corrosion behavior and resistance of the material. This study aims to evaluate the impact of three different surface treatments on the durability of AISI 304L steel. The correlation between surface roughness resulting from pre-treatment and pitting potential values will be examined. Additionally, the influence of different concentrations of biocide additives on surface durability will be assessed to determine the maximum effective concentration for preventing pitting phenomena. Passivation processes will also be evaluated as a potential solution for improving the pitting potential and overall durability of the components. By optimizing surface treatments and biocide concentrations, improved corrosion resistance and durability can be achieved, ensuring the long-term performance and reliability of AISI 304L steel components in critical applications such as food processing and beverage handling. [ABSTRACT FROM AUTHOR]

Ti-6Al-4V selective dissolution occurs in vivo on orthopedic implants as the leading edge of a pitting corrosion attack. A gap persists in our fundamental understanding of selective dissolution and pre-clinical tests fail to reproduce this damage. While CoCrMo clinical use decreases, Ti-6Al-4V and the crevice geometries where corrosion can occur remain ubiquitous in implant design. Additionally, most additively manufactured devices cleared by the FDA use Ti-6Al-4V. Accelerated preclinical testing, therefore, would aid in the evaluation of new titanium devices and biomaterials. In this study, using temperature, we (1) developed an accelerated pre-clinical methodology to rapidly induce dissolution and (2) investigated the structure-property relationship between the dissolving surface and the oxide layer. We hypothesized that solution temperature and H 2 O 2 concentration would accelerate oxide degradation, increase corrosion kinetics and decrease experimental times. To assess this effect, we selected temperatures above (45 °C), below (24 °C), and at (37 °C) physiological levels. Then, we acquired electrochemical impedance spectra during active β dissolution, showing significant decreases in oxide polarization resistance (R p) both over time (p = 0.000) and as temperature increased (p = 0.000). Next, using the impedance response as a guide, we quantified the extent of selective dissolution in scanning electron micrographs. As the temperature increased, the corrosion rate increased in an Arrhenius-dependent manner. Last, we identified three surface classes as the oxide properties changed: undissolved, transition and dissolved. These results indicate a concentration and temperature dependent structure-property relationship between the solution, the protective oxide film, and the substrate alloy. Additionally, we show how supraphysiological temperatures induce structurally similar dissolution to tests run at 37 °C in less experimental time. Within modular taper junctions of total hip replacement systems, retrieval studies document severe corrosion including Ti-6AL-4V selective dissolution. Current pre-clinical tests and ASTM standards fail to reproduce this damage, preventing accurate screening of titanium-based biomaterials and implant designs. In this study, we induce selective dissolution using accelerated temperatures. Building off previous work, we use electrochemical impedance spectroscopy to rapidly monitor the oxide film during dissolution. We elucidate components of the dissolution mechanism, where oxide degradation precedes pit nucleation within the β phase. Using an Arrhenius approach, we relate these accelerated testing conditions to more physiologically relevant solution concentrations. In total, this study shows the importance of including adverse electrochemical events like cathodic activation and inflammatory species in pre-clinical testing. [Display omitted] [ABSTRACT FROM AUTHOR]

The corrosion behavior of 1018 carbon steel in LiCl/H2O mixtures has been evaluated by using potentiodynamic polarization curves, electrochemical noise and electrochemical impedance spectroscopy techniques. Two different concentrations of LiCl were employed, namely 35 and 40 wt. %, and the testing temperatures included 25, 35 and 70 °C. It was found that the steel showed a passive zone; the corrosion current density value increased with an increase in the solution temperature and concentration. The pitting potential value decreased with an increase in the testing temperature and the solution concentration. The corrosion process was under charge transfer control. This mechanism was unaltered either by the solution temperature or concentration. The charge transfer resistance value decreased with an increase in both the solution temperature and concentration. A localized, pitting type of corrosion dominated the corrosion morphology at 25 and 35 °C, whereas at 70 °C, the main type of attack was a mixed type of corrosion. [ABSTRACT FROM AUTHOR]

The corrosion behavior of certain steels under extremely oxidative conditions, simulating the impact of water radiolysis on stainless steels, has been investigated. Radiolysis generates aggressive species, including radicals, solvated electrons, and hydrogen peroxide, potentially leading to corrosion over time in materials typically considered resistant. To expedite the kinetics of this phenomenon, drastic conditions were employed, involving high concentrations of peroxide in a strongly acidic environment. Under these conditions, corrosion can manifest rapidly. The varied responses of different steels are contingent upon their inherent nature and chemical composition, notably the chromium and nickel content. Steels with higher chromium and nickel concentrations exhibit increased resistance to corrosion, even in such severe environments. Microscopic corrosion mechanisms involve pitting and intergranular corrosion. Pitting results in the formation of craters on surfaces, while intergranular corrosion leads to the detachment of grains. [ABSTRACT FROM AUTHOR]

Prompted by the unexpected observation of the pitting of the weldments of a highly corrosion- and pitting-resistant duplex stainless steel, SAF2507, in chloride solutions with nitride addition, the pitting and corrosion resistance of SAF2507 and its weldments were investigated in chloride solutions with and without different levels of nitrite. The Incoloy 825 and 316L austenitic stainless steels were included for the purpose of developing a comparative appreciation. The microstructures of the weldments were characterised, and 316L showed a profound influence of nitrite addition in inhibiting pitting, while 'meta-stable' pitting transients that were clearly visible in the chloride solution without nitrite were absent when nitrite was added. Both the parent metal and the weldment of SAF2507 had similar pitting potential (Ep) in 0.1 M NaCl without nitrite, which was the highest Ep among the three alloys tested. Additions of nitrite at low concentrations had an inhibitive effect on pitting, whereas higher nitrite contents had a deleterious effect on pitting resistance. On the other hand, Incoloy 825 showed a trend of Ep ennoblement with an increasing nitrite content of 0.1 M NaCl, and the weldment underwent greater ennoblement. Moreover, 316L showed a trend similar to Incoloy 825; however, the Ep ennoblements were significantly more pronounced for both the weldment and the base metal of 316L. [ABSTRACT FROM AUTHOR]

Corrosion processes were studied in epigenic caves of the Moravian Karst (MK). Samples of naturally corroded speleothems and carbonate rocks collected in various MK caves were compared with limestone and calcite standards that were corroded under well-controlled conditions in the laboratory. Two stages of corrosion were distinguished: (1) an early stage of pitting and linear corrosion predisposed by point and line defects in the standards, and (2) an advanced stage characterized by deep corrosion of the entire standard surface. During the second stage, the internal structure of the corroded substrate remained partially preserved, however, if the water was extremely aggressive, the corrosion progressed to depth en-bloc regardless of the structure. In this paper, we (1) proposed a new corrosion mechanism based on the binding of aqueous calcium by clays and tested it experimentally in the cave, (2) characterized conditions that generally favor the formation of aggressive waters (water undersaturated with calcite) into seven categories incorporating them into a conceptual model of the karst vertical profile, and (3) discussed anthropogenic influences on these processes. [ABSTRACT FROM AUTHOR]

The effect of volume fraction and size of Ti4Ni2Ox particles on pitting, crevice, and fretting corrosion processes is studied by testing implanted elements of titanium nickelide based alloys as part of spinal pedicle screw devices in a 0.9% NaCl solution, tested elements being produced from ingots melted by various technologies (vacuum induction melting; combined skull melting with subsequent vacuum-arc remelting). It is shown that the vacuum induction melting method, which provides higher purity of the resulting material, in particular with respect to oxygen, and reduces the Ti4Ni2Ox volume fraction, is preferable for increasing titanium nickelide based alloy corrosion resistance in a biological environment. It is established that a reduction in volume fraction (and size, dmax) of Ti4Ni2Ox particles from 5.1 ± 1.2 vol.% (dmax = 10 μm) to 3.5 ± 0.7 vol.% (dmax = 7 μm) results in the pitting potential increasing from 552 ± 70 to 854 ± 123 mV and the fretting corrosion current decreasing from 11 ± 2.7 to 6.7 ± 2.8 μA. At the same time, the content of Ni ions in a test corrosion medium after crevice and fretting corrosion studies decreases from 84 ± 6 to 64 ± 5 and from 74 ± 6 to 57 ± 4 μg/liter, while the area of corrosion sites decreases by 1.3 and 1.8 times respectively. It is shown that a further reduction in Ti4Ni2Ox particle volume fraction down to 1.2 ± 0.2 vol.% (dmax = 5 μm) does not have a significant effect on corrosion resistance indices. [ABSTRACT FROM AUTHOR]

The results of the experimental study of the degradation of steel structures of sewer underground constructions are presented. The distribution of harmful gas elements (sulfur, hydrogen, oxygen) over the wall thickness of sewer pipes along corrosion defects in the form of pits, as well as the character of changes in the microhardness of the metal depending on the hydrogen content and service life, are shown. To confirm the metal softening with increasing hydrogen concentration, the stresses of the crystal lattice (distortion stresses) were measured. [ABSTRACT FROM AUTHOR]

Clean-integrity processing of nuclear-grade AISI 316L austenitic stainless steel components finished by the wire brush and sequent flap discs is performed for high-performance manufacturing of the nuclear power plant equipment. Two steel wire brushes of AISI 304 austenitic stainless steel and 65Mn carbon spring steel are used for the grinding under a spindle speed of 550–2000 rpm. Sequent polishing is carried out by the flap discs using silicon carbide cloth under 2000 rpm. An equivalent pitting corrosion resistance to that of the original stainless steel in 3.5% NaCl solution is obtained for finished samples by the combined processes. The contaminants composition of ground stainless steel samples is determined by the redness degree of chromaticity inspection. The contaminants microstructure and finishing-induced microstructure are dependent on the impedance phase angle change in eddy current impedance diagrams. The surface clean-integrity of nuclear-grade stainless steel is characterized by the series of nondestructive evaluation methods. [ABSTRACT FROM AUTHOR]

The corrosion of magnesium alloys is often considered to differ in behaviour and development with time from most other metals and alloys because they show evolution of hydrogen right from first exposure. However, data extracted from the open literature indicate that magnesium alloys develop corrosion mass-loss trends with time that are consistent with the so-called bimodal pattern, which is topologically similar to those of other alloys. Examples are given of such trending for magnesium alloys under immersion, half-tide and various atmospheric exposure conditions. The critical roles of corrosion pitting and its development into localised corrosion are discussed. For high-purity magnesium alloys, the transition to longer-term corrosion, which is rate-controlled by the hydrogen evolution cathodic reaction, occurs quickly, within days. Comments are made about the application of measurements of hydrogen evolution and of electrochemical methods to make rapid estimates of shorter-term corrosion rates. [ABSTRACT FROM AUTHOR]

In the present study, an immersion experiment was carried out to examine how N80 steel corrodes when exposed to formation water containing dissolved CO2 and supercritical CO2 (Sc-CO2) along with water vapor. We employed electrochemical and surface analysis methods to examine the influence of various factors, including the temperature and duration of immersion, on the extent of corrosion. The results show that the corrosion patterns of N80 steel in a supercritical CO2 environment and CO2-saturated formation water differed significantly. The presence of similar corrosion features was suggested by the constant structure of the corrosion products identified in the formation water. However, the morphology of the corrosion product was complex in the supercritical CO2 environment, exhibiting features of pitting and localized corrosion. Furthermore, a non-linear trend in the corrosion rate was observed between 40 °C and 120 °C. Specifically, the rate of corrosion declined from 40 °C to 80 °C, but it then resumed its growth from 80 °C to 120 °C. These findings suggest that very high temperatures could lead to the destruction of corrosion products and subsequently enhance the corrosion process. [ABSTRACT FROM AUTHOR]

An improvement of residual strength after corrosion is the key to augment the tolerance to the damage of aviation components made from light-weight Al-Li alloy. In this study, the electrochemical behavior, corrosion resistance, and residual strength of 2060-T8 Al-Li alloy in 3.5 wt.% NaCl solution for various corrosion period durations were systematically analyzed. Corrosion pits of 174 ± 18 µm in depth were distributed on the surface of the alloy exposed to corrosive solution for 720 h. Additionally, although linearly decreasing with average corrosion pit depth, a suitable level of damage tolerance was shown by the measurement of significant residual strength. The underlying mechanism of the corrosion was understood from the description of the corrosion behavior of the 2060-T8 alloy. [ABSTRACT FROM AUTHOR]

The electrochemical co-deposition of Cr-Co oxide coatings at room temperature on 304 stainless steel (SS) was studied using an electrolyte composed of a mixture of ethylene glycol (EG), hydrated metal chloride salts (MCln∙YH2O), and water as a secondary hydrogen donor (HBD). Metallic Cu and Ni undercoats were applied to improve the adhesion of a posterior Cr-Co metallic and oxide layer. The electroactive events that took place during both electrodeposition processes were studied using cyclic voltammetry (CV) and chronoamperometry. The microstructure and composition of the surface layers were studied using scanning electron microscopy (SEM/EDS), X-ray diffraction (XRD) and cross-sectional elemental mapping via transmission electron microscopy (TEM). The surface of steel with the Cr-Co:EG-H2O coating showed greater resistance to pitting corrosion (123.93 mV) compared to untreated stainless steel (62.3 mV). This sample showed a large hystere-sis area, which is associated with high resistance to pitting corrosion by the occurrence of a re-passivation of the sample at a Erep value of 24.31 mV. After the cyclic potentiodynamic polariza-tion (CPP) test, the lowest specific mass loss (0.001 mg/cm2) was achieved for the AISI 304 SS sample coated using EG-water solvents (Cr-Co:EG-H2O), while the untreated AISI 304 SS reached a higher specific mass loss (0.01 mg/cm2). The Electrochemical Impedance Spectroscopy (EIS) tests showed that the uniform corrosion resistance varied significantly from the untreated AISI 304 SS (35 kΩ) to the coated sample (57 kΩ), which is attributed to the protection provided by the chromium and cobalt oxides coating. The best corrosion resistance achieved was correlated with a superhydrophobic character (with a contact angle of 158.41°) of the Cr-Co coatings. This was in turn a consequence of a needle-like morphology characteristic of these oxides. [ABSTRACT FROM AUTHOR]

The corrosion resistance and pitting corrosion behavior of free-cutting austenitic stainless steels with different contents of sulfur were systematically studied by electrochemical workstation and scanning electron microscope. As the content of sulfur in the steel decreased from 0.270 to 0.089%, the corrosion rate decreased from 10.55 to 2.83 μm/a. The morphologies of manganese sulfide inclusions in the 0.089% S-containing steel were short rod-shaped and globular. The morphologies of manganese sulfide inclusions in the 0.270% S-containing steel were cluster-shaped, long strip-shaped and globular. Various-morphology manganese sulfide inclusions could lead to different degrees of damage to the metal matrix during the process of the pitting corrosion. The order of damage degree from the most to the less was cluster-shaped > long strip-shaped > short rod-shaped. [ABSTRACT FROM AUTHOR]

The reinforcement corrosion is a major and most frequent reason of degradation for reinforcedconcrete (RC) structures throughout the world, leading to their premature deterioration before design life was attained. Corrosion weakens the mechanical properties of rebar by ingress of aggressive ions due to various environments. In this study, a total of 99 specimens with six different diameters were tested, for three exposure periods, and six different environments, to assess the influence of corrosion on mechanical properties of reinforcing bars. Degradation relationships of strength and ductility with exposure period and rebar diameter, were analyzed, and three equations were proposed to formulate the relations. It was found that, the ultimate strength of 8.6% of the corroded bars falls below the original yield strength; after 5 years of exposure in natural atmosphere, reduction in mechanical properties was insignificant; a detergent solution environment could cause the strength loss of 24.8%.

This research aimed to investigate the heat-affected zone of lean duplex stainless steel grade X2CrNiN22-2. Different heat-affected zone microstructures and grain morphologies were developed by Gleeble simulations. The governing microstructures were evaluated by metallographic techniques and electrochemical corrosion measurements. It was found that the 1200-800 °C cooling time significantly affects the microstructure, austenite content, and corrosion properties. The average austenite content in the case of 1 s cooling time is 30.7 ± 1%, which increased with the longer cooling times up to 38.6 ± 0.9%. The rapid cooling times resulted in a more ferritic microstructure, which promoted nitride precipitation in the ferrite grains. The nitride precipitations acted as nucleation sites for pitting initiation in 3.5 wt.% NaCl solution. The lowest pitting potential was measured in the case of the most rapidly cooled sample: 573 ± 31 mV, while the balanced, annealed microstructure had much better pitting corrosion resistance, showing a pitting potential of 1308 ± 62 mV vs. the Ag/AgCl (KCl sat.) reference electrode. The results of this research can be used in designing welding parameters for the welding of the X2CrNiN22-2 lean duplex stainless steel. [ABSTRACT FROM AUTHOR]

In this study the corrosion behaviour of 17-4 PH (precipitation hardening) stainless steel alloys, produced by adding Ta different amounts with the method of powder metallurgy, and aged at different times was investigated. Four different amounts tantalum (0.15, 0.30, 0.45 and 0.60% weight) was added to the alloy. The prepared powders were produced green compacts at ∅10 × 6 mm dimensions (800 MPa) after mixing with turbule for 2 hours. Green compacts produced were sintered for 1 h at 1300°C under a vacuum of 10–6 mbar. The sintered samples were aged 1, 4 and 8 hours at 480°C after being in solution at 1050°C. Polarization measurements were performed in a corrosion cell, using three different electrode technique. In the corrosion tests, 0.1 M H2SO4 was used as the electrolyte medium. As a result of the studies, the alloy the hardness and densities were increased with increasing Ta amount. Similarly, the hardness and densities of produced samples were with increasing aging time. The corrosion tests revealed that increasing the amount of Ta added to the alloy increased the alloy's resistance to corrosion. The alloy's corrosion resistance decreased as aging time increased. The active corrosion mechanism was seen to be pitting corrosion in all alloys. [ABSTRACT FROM AUTHOR]

Gallium oxide crystal materials has enormous potential in the fields of power devices and optoelectronics due to its excellent performance and the advantage of being able to grow by melt method. In recent years, numerous experts at home and abroad have also started researching gallium oxide single crystal materials. High quality and low defect gallium oxide single crystal materials are extremely important for subsequent epitaxy and device preparation. At present, the mainstream growth method internationally is edge-defined film-fed growth method (EFG), which has advantages such as short growth cycle, large size, and stable growth. However, there is still great room for progress in crystal defect control. This article focuses on the morphology of corrosion pits in gallium oxide single crystals, and processes samples of gallium oxide single crystals grown by EFG. Corrosion experiments were conducted under different acid and alkali conditions. A detailed introduction was given to the different observed corrosion pit morphologies, and the impact of crystal defects on the corrosion pit morphologies was analyzed. This is of great significance for the future research on the growth mechanism of gallium oxide single crystals and crystal defects. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to discuss the influences of surface severe plastic deformation (S2PD) on the electrochemical corrosion, pitting corrosion, intergranular corrosion, stress corrosion cracking of aluminum (Al) alloys and attempt to correlate the microstructural/compositional changes with the performances. Design/methodology/approach: This study provides a novel gradient design of structure/composition caused by S2PD for the purpose of enhancing Al alloys' corrosion resistance. Findings: S2PD has a significant effect on corrosion behavior of Al alloys through tuning the grain size, residual stress, composition, grain boundary phase and second phase particle distribution. Originality/value: Although Al alloys are known to form a protective Al2O3 film, corrosion is a major challenge for the longevity of Al structures across numerous industries, especially for the infrastructures made of high-strength Al alloys. Traditional strategies of improving corrosion resistance of Al alloys heavily relied on alloying and coatings. In this review, gradient design of structure/composition caused by S2PD provides a novel strategy for corrosion protection of Al alloys, especially in the enhancement of localized corrosion resistance. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to investigate NiTi alloys' characterization and corrosion behaviour produced by two different powder metallurgy (PM) methods. Design/methodology/approach: It was pre-formed under a protective atmosphere at 900 °C under a force of 45 MPa and sintered for 1 h under 10–6 Mbar in an atmosphere-controlled heat treatment furnace at 1,100 °C. The relationship between microstructural properties, SEM, XRD, density, microhardness and corrosion behaviour of pre-alloyed NiTi alloys produced by two different methods with the production method was investigated. Findings: As a result of the studies, TiO, NiTi, NiTi2 and Ni3Ti intermetallics were determined in XRD examinations. The best surface roughness was observed in the mechanically milled (MM'ed) pre-alloyed NiTi alloy compared to the pre-alloyed NiTi alloy mixed with turbula. The corrosion tests performed in 3.5% NaCl solution determined that the MM'ed pre-alloyed NiTi alloy had better corrosion resistance than the pre-alloyed NiTi alloy mixed with turbula. Pitting corrosion was visualized in the SEM images taken from the corrosion surfaces. Originality/value: Two different PM methods produced pre-alloyed NiTi powders, and the effects of these methods on the mechanical and corrosion resistance of NiTi alloys were systematically investigated for the first time. [ABSTRACT FROM AUTHOR]

Using a hexafluorozirconic acid bath, a zirconium-based conversion coating was applied to aluminum counter electrodes of flexible dye-sensitized solar cells. In the presence of and iodine base electrolyte, this substrate was studied for its microstructure, structural phase, and corrosion performance using scanning electron microscopy (SEM), energy dispersive x-ray spectrum (EDS), and x-ray diffraction (XRD) analyses, corrosion soaking, ultraviolet–visible spectroscopy (UV/Vis), polarization, and electrochemical impedance spectroscopy. EDS and XRD results confirmed the formation of the coating on aluminum. In addition, SEM analysis revealed that the counter electrode coating covers the active cathode sites on the aluminum surface. According to the corrosion soaking and UV/Vis test results, the zirconium-treated counter electrode has more corrosion resistance. From electrochemical tests, it was found that the corrosion rate, pitting corrosion resistance, and polarization resistance for the replacement counter electrode were 0.037 mm/year, 0.222 Ω, and 12,505 Ω, respectively. A flexible dye-sensitized solar cell with an aluminum counter electrode and zirconium-based conversion coating therefore makes sense. [ABSTRACT FROM AUTHOR]

In this study, the effects of SiC and TiB2 reinforcement particles on the corrosion behaviors of the surface composites of an Al5052 substrate produced with a gas tungsten arc welding (GTAW) technique were investigated. The electrochemical behaviors of the base metal (BM) and surface composites were evaluated by open-circuit potential monitoring, potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) in two solutions: 0.5 M H2SO4 and 3.5% NaCl. The results of PDP and EIS showed that by adding reinforcement particles on the surface, the corrosion resistance decreased in both environments relative to BM. Among Al5052-based surface composites, the AA5052/SiC + TiB2 composite in 3.5% NaCl solution and AA5052/TiB2 in H2SO4 solution showed the lowest corrosion resistance due to the formation of microgalvanic couples in the Al matrix. The corrosion resistance of Al5052-based surface composites in 3.5% NaCl solution was much better than that in 0.5 M H2SO4. Furthermore, scanning electron microscopy (SEM) analysis confirmed the PDP and EIS results. The SEM image of the corroded surface of AA5052/TiB2 exhibited severe pitting corrosion in both solutions relative to the other composites. In contrast, the AA5052/SiC composite showed a relatively lower corrosion rate in both 3.5% NaCl and 0.5 M H2SO4. Hardness tests provided evidence for improved mechanical properties of the composites in comparison with the BM. In particular, composites containing TiB2 showed the highest hardness, followed by AA5052/SiC + TiB2 composites. [ABSTRACT FROM AUTHOR]

This paper presents the findings of an experimental study on the corrosion performance of both conventional and corrosionresistant steel reinforcements in normal-strength concrete (NC), high-performance concrete (HPC), and ultra-high-performance concrete (UHPC) columns in an accelerated corrosion-inducing environment for up to 24 months. Half-cell potential (HCP), linear polarization resistance (LPR), and electrochemical impedance spectroscopy (EIS) methods were used to assess the corrosion activities and corrosion rates. The reinforcement mass losses were directly measured from the specimens and compared to the results from electrochemical corrosion rate measurements. It was concluded that UHPC completely prevents corrosion of reinforcement embedded inside, while HPC offers higher protection than NC in the experimental period. Based on electrochemical measurements, the average corrosion rate of mild steel and high-chromium steel reinforcement in NC in 24 months were, respectively, 6.6 and 2.8 times that of the same reinforcements in HPC. In addition, corrosion-resistant steel reinforcements including epoxycoated reinforcing bar, high-chromium steel reinforcing bar, and stainless-steel reinforcing bar showed excellent resistance to corrosion compared to conventional mild steel reinforcement. There was no active corrosion observed for epoxy-coated and stainless steel reinforcements during the 24 months of the accelerated aging; the average corrosion rateS of high-chromium steel was 50% of that of mild steel in NC based on the electrochemical corrosion measurements; and the average mass loss of high-chromium steel was 47% and 75% of that of mild steel in NC and HPC, respectively. The results also showed that the LPR method might slightly overestimate the corrosion rate. Finally, pitting corrosion was found to be the dominant type of corrosion in both mild and high-chromium steel reinforcements in NC and HPC columns. [ABSTRACT FROM AUTHOR]

This study provides two case studies involving carbon steel and 3%-Cr steel exposed to a CO2–H2S environment with a moderate scaling index. The carbon steel tubing show shows pitting and severe corrosion, whereas the 3% chromium steel tubes are undamaged. XRD results showed that the chromium-rich layer did not alter scaling on both tubes. Investigations using SEM and EDS reveal the formation of a dense and compact layer in the 3%-Cr steel, which serves to resist corrosion. In contrast, carbon steel has a porous structure and is easily detachable due to wall shear stress caused by slug movement. In 3%-Cr steel, the EDS analysis reveals a compact layer with a significant number of chromium, which is an indication of a Cr-rich iron oxide layer. Potentiodynamic polarization shows that the anodic curve is shifting, which means that the rate of corrosion is slowing down. This study shows that 3% Cr steel is a good choice for a mixed CO2–H2S environment with a high total dissolved solid (TDS). [ABSTRACT FROM AUTHOR]

The AISI 304 (X5CrNi19‐10) stainless steel is widely used for the production of various metal parts in power plants. A procedure for testing the influence of the dust from a power plant on resistance to general and pitting corrosion of the AISI 304 stainless steel is developed and performed. The quantitative (XRD method) and qualitative (Fourier–transform infrared spectroscopy [FTIR] method) composition of the dust present in the power plant is determined. Applying the Mott–Schottky method, the properties of the passive layer are analyzed, while a degree of chromium depletion of the grain boundary is determined by the electrochemical potentiokinetic reactivation method with double loop method. Values of polarization resistance (linear polarization resistance and electrochemical impedance spectroscopy methods) and the corrosion current density (polarization measurements) indicate that the stainless steel has a higher resistance to general corrosion in the dust solutions than in the etalon solution. Also, based on the measured value of the pitting potential (Epit) and the difference between the values of the pitting potential and the corrosion potential (Epit – Ecorr), it can be seen that stainless steel has a higher resistance to localized types of corrosion, such as pitting corrosion, in dust solutions than in the etalon solution. [ABSTRACT FROM AUTHOR]

This study investigates the monitoring of corrosion in the distribution network pipeline in Patna (Bihar), India, using a weight loss method and an image processing technique. The seven coupons were injected into the pipeline of the distribution network and ejected after 45, 90, 135, 180, 225, 270, and 315 days. The corrosion rate was calculated by weighing the initial and final weight of coupons. It was found to be 0.035, 0.078, 0.048. 0.035, 0.028, 0.052, and 0.039 mm/year during 45, 90, 135, 180, 225, 270, and 315 days, respectively. Scaling rate found at 45, 90, 135, 180, 225, 270, and 315 days was 0.006, 0.037, 0.042, 0.049, 0.011, 0.018, and 0.033 mm/year, respectively. Surface analysis was performed using the scanner method and MATLAB software. Coupons were first scanned using a scanner adjusted to 4800 ppi. A scanned image was imported into MATLAB. An algorithm was used based on color analysis. The output of a text file was generated that gave the corrosion pit in terms of pixels. The MATLAB analysis shows that the surface corrosion area sum of both sides of the coupon was 6.24, 6.39, 6.49, and 6.48 cm2 in 45, 90, 135, and 180 days, respectively. This study concludes that scale formation on the pipe surface decreased the corrosion rate. Corrosion and scaling were found in the opposite trend. SEM analysis shows that pitting corrosion was increasing with increasing duration of time. Physicochemical analysis shows that the water was alkaline. The presence of a greater concentration of hardness, alkalinity, and less concentration of chloride, sulfate, and DO water was found to have a scaling tendency. XRD analysis of iron dust represents the presence of salts in water, which is responsible for the scaling behavior of water. [ABSTRACT FROM AUTHOR]

Highly formable interstitial‐free steel has been subjected to corrode in wet‐dry salt spray (WDSS) and immersion corrosion (IMCC) conditions in 5, 10, 20, 30, and 45 days to investigate its corrosion behavior in simulated‐marine environment at the same temperature using 5 wt.% NaCl. The corrosion mechanisms and their effects have been studied and compared on the basis of weight loss and mechanical properties. Results revealed that corrosion rate in WDSS is about 9.5 times higher than IMCC. The corrosion coefficient (n) values for WDSS and IMCC have been observed as 0.99 and 0.35, respectively, which are evident for the protective nature of rust. The corrosion mechanisms and rust constituents may attribute different corrosion kinetics in both conditions. Moreover, the rate of degradation in yield strength and fracture strain in WDSS is 2 and 2.5 times higher than IMCC respectively; however, in the case of ultimate tensile strength the degradation rate is nearly same. It has also been observed that the higher pitting corrosion in WDSS may lead to change the failure mode from ductile to mix‐mode after 30 and 45 days of corrosion as authenticated from scanning electron microscopic images. [ABSTRACT FROM AUTHOR]

Condensing furnace residential heaters are starting to replace outdated and less efficient non-condensing units in homes across the US. However, the burning of natural gas in these new units produces acidic gases, which can form acid droplets (H2SO4, HNO3, H2CO3, etc.) that are corrosive to low-grade heat exchanger metallic materials. Type-1 aluminized steel has been used in industrial applications, such as marine, heating, and automobile parts, due to its resistance to oxidation at elevated temperature. Many components of the condensing furnaces, including heat exchangers, are made from type-1 aluminized steel. We investigated the interaction of type-1 aluminized steel substrates with two acidic condensate liquids by 500 h corrosion exposures as well as short-term electrochemical impedance measurements. SEM plan and cross-sectional view images revealed damage to the Al-Si rich layer and exposure of the steel substrate. The non-uniform damage in the Al-Si rich layer was likely attributed to a pitting corrosion mechanism and induced by high acidity of the condensate liquid. Electrochemical impedance measurements in an acidic condensate revealed lower corrosion resistance of the aluminized steel surface with a weld line, identifying welded sections as preferential corrosion initiation sites. [ABSTRACT FROM AUTHOR]

In this work, the microstructural features, mechanical properties, and localized corrosion performance of a single-layered wall of nickel-based superalloy Inconel 617 produced via wire arc additive manufacturing (WAAM) were examined. Microstructural analysis revealed the existence of cellular and equiaxed dendrites in the bottom layers, while elongated columnar dendrites having a size up to 2 mm were observed in the middle and top layers due to different cooling rates and temperature gradients. Electron micrographs and energy-dispersive x-ray spectroscopy analysis confirmed the segregation of precipitates in the interdendritic regions of the austenitic matrix. Carbides such as Ti (C, N) and Cr23C6 existed in the interdendritic regions and are caused by the diffusion of Cr, Mo, and C elements during the WAAM process. Assessment of the mechanical properties revealed the excellent hardness (244-286 HV) and tensile properties of WAAM-printed IN617. The average yield strength, tensile strength, and elongation of IN617 specimens were 400 MPa, 724 MPa, and 43%, which is comparable with the ASTM B168-19 standard grade. The fracture surface analysis highlighted the ductile mode of fracture with dimples and micro-voids. Potentiodynamic polarization results illustrated the absence of significant anisotropic nature of the pitting resistance in 3.5% NaCl solution. The corrosion rate of the WAAM-printed IN617 specimens ranged between 1.02 and 1.07 mpy in 3.5% NaCl solution and the size of the pit was having a size of 30 to 100 µm. Electrochemical measurements indicate that the excellent pitting behavior is attributed to the formation of stable passive films along with higher corrosion potential and lower current density values. This study shows that the WAAM process can be potentially applied to other alloys for fabricating structures to obtain critical information on the corrosion damage. [ABSTRACT FROM AUTHOR]

The effect of quenching modes on the structure, phase composition and hardness of austenitic-ferritic stainless steel 20Kh25N8AD3M2 is studied by optical microscopy, x-ray diffraction phase analysis and hardness measurement. Corrosion tests are conducted in a 3% aqueous solution of NaCl with the use of potentiometry and potentiodynamic analysis. Heat treatment modes improving the resistance of steel 20Kh25N8AD3M2 to general and pitting corrosion are suggested. It is shown that aluminum and titanium used to deoxidize the steel can cause pitting corrosion even after quenching. [ABSTRACT FROM AUTHOR]

The powder metallurgy method was used to manufacture three Ti-based alloys: Ti-15%Zr-2%Ta-4%Sn (Ti-Zr-Ta-4Sn), Ti-15%Zr-2%Ta-6%Sn (Ti-Zr-Ta-6Sn), and Ti-15%Zr-2%Ta-8%Sn (Ti-Zr-Ta-8Sn). Electrochemical measurements and surface analyses were used to determine the effect of Sn concentration on the corrosion of these alloys after exposure to a simulated body fluid (SBF) solution for 1 h and 72 h. It was found that the passivation of the alloy surface significantly increased when the Sn content increased from 4% to 6% and then to 8%, which led to a significant reduction in corrosion. The impedance spectra derived from the Nyquist graphs also explained how the addition of Sn significantly improved the alloys' polarization resistances. According to the change in the chronoamperometric current at an applied anodic potential over time, the increase in Sn content within the alloy significantly reduced the currents over time, indicating that the uniform and pitting corrosion were greatly decreased. The formation of an oxide layer (TiO2), which was demonstrated by the surface morphology of the alloys after exposure to SBF solution for 72 h and corrosion at 400 mV (Ag/AgCl) for 60 min, was supported by the profile analysis obtained by an X-ray spectroscopy analyzer. It was clear from all of the findings that the tested alloys have a remarkable improvement in resistance to corrosivity when the Sn content was increased to 8%. [ABSTRACT FROM AUTHOR]

In this paper, micro-crack initiation and propagation behavior ol aluminum alloy 7050-T7651 with dilferent pre-corrosion time are investigated via in-situ SEM tensile tests. Based on the in-situ and online SEM observation, the ellect of corrosion damage on the micro-crack behavior is discussed. Experimental results show that: with the corrosion time increases, the density ol corrosion pits increases, while the bearing capacity ol the specimen decreases; rough surlaces ol the specimen notch and corrosion pits are the preferred location lor micro-crack initiation, the number ol micro-crack increases with the extension ol corrosion time. The main crack dominates the failure process is generated by the coalescence ol micro-cracks from notch and adjacent corrosion pits. When corrosion damage is relatively light, crack branching occurs due to the existence ol corrosion pits near the tip ol the main-crack; when corrosion damage is relatively heavy, multiple micro-cracks induced by corrosion pits will joint with the main-crack and allect the main-crack propagation direction and path. Shear stress plays an important role in the crack propagation process, and the cracking mode belongs to T / TT mixed fracture mode. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is to investigate the initial corrosion behavior of pure Mg, AZ31 and AZ91 alloys in phosphate buffer solution (PBS) and to characterize the features in corrosion type and resistance of the corrosion product layer. Design/methodology/approach: The scanning electron microscopy, equipped with energy-dispersive spectroscopy, X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy have been used to characterize the as-corroded samples. Besides, the Mg2+ concentration in PBSs has been determined by inductively coupled plasma atomic emission spectrum. Findings: It has been found that pure Mg suffers pit corrosion, and AZ31 initially undergoes pit corrosion and then uniform corrosion dominates with an extended immersion duration. However, AZ91 exhibits the uniform corrosion with the highest corrosion rate among the three materials. Besides, the corrosion product layer on AZ31 has the best compactness and corrosion resistance. Originality/value: The findings add depth in understanding the corrosion of pure Mg and its alloys in PBS and also have guiding significance in exploring the effects by alloyed elements to develop new biomaterials with better performance. [ABSTRACT FROM AUTHOR]