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In this study, the localized corrosion susceptibility of AA2050‐T84, AA2198‐T851, and AA2024‐T3 alloys was compared by immersion in three test solutions, specifically sodium chloride solution (3.5% NaCl), EXCO solution, according to ASTM G34‐18, and a solution for intergranular corrosion (IGC) test recommended by ASTM G110‐15 and via scanning vibrating electrode technique (SVET). The results showed higher susceptibility of AA2050‐T84 alloy to all types of corrosion tested compared to the other studied 2XXX series alloys. Corrosion penetration was deeper in the AA2050‐T84 due to its microstructural characteristics as a difference in the micrometric Cu‐Rich intermetallic particle distribution on the surface and related to the distribution of the T1 (Al2CuLi) phase. [ABSTRACT FROM AUTHOR]

This study evaluated two distinct cryo-fracturing techniques using liquid nitrogen (LN2). The evaluation included tests for peak compression strength, acoustic emission, and energy absorption. The experiments compared single-exposure freezing time (FT) and multiple-exposure freezing–thawing cycle (FTC) processes on dried specimens. The outcomes indicated that FTC experiments demonstrated lower uniaxial compression stress (UCS) values compared to FT experiments because, during the thawing phase, the ice inside the pores reverts to liquid as the temperature rises. The difference between average baseline experiments versus FT180 and FTC6 indicated a reduction in stress of 14.5% and 38.5%, respectively. The standard error of our experiments ranged from 0.58% for FT60 to 5.35% for FTC6. The damage factor follows a downward trend in both FT and FTC experiments as the time of LN2 treatment augments. The amount of energy that can be absorbed in elastic or plastic deformation before failure is less for FTC specimens with the same total LN2 exposure time. Samples undergoing the freezing time process demonstrate a greater and denser quantity of acoustic emissions in comparison to freezing–thawing cycle processes, suggesting a positive correlation with uniaxial compressive strength outcomes. The large network of fractures formed by the FTC and PFTC techniques indicated that they have the greatest potential as stimulation approaches. The engineering results were improved by adding the geological context, which is essential to apply these findings to coals that have comparable origins. [ABSTRACT FROM AUTHOR]

Updated understanding on the effect of biofouling on corrosion rate is needed to protect marine structures as climate change is altering seawater physiochemistry and biofouling organism distribution. Multi-disciplinary techniques can improve understanding of biofouling development and associated corrosion rates on metals immersed in natural seawater (NSW). In this study, the development of biofouling and corrosion on welded Nickel Aluminium Bronze (NAB) was investigated through long-term immersion tests in NSW, simulated seawater (SSW) and air. Biofouling was affected by geographic location within the marina and influenced corrosion extent. The corrosion rate of NAB was accelerated in the initial months of exposure in NSW (1.27 mm.yr−1) and then settled to 0.11 mm.yr−1 (annual average). This was significantly higher than the 0.06 mm.yr−1 corrosion rate measured in SSW, which matched published rates. The results suggest that corrosion rates for cast NAB should be revised to take account of biofouling and updated seawater physiochemistry. [ABSTRACT FROM AUTHOR]

This study evaluated two distinct cryo-fracturing techniques using liquid nitrogen (LN2). The evaluation included tests for peak compression strength, acoustic emission, and energy absorption. The experiments compared single-exposure freezing time (FT) and multiple-exposure freezing–thawing cycle (FTC) processes on dried specimens. The outcomes indicated that FTC experiments demonstrated lower uniaxial compression stress (UCS) values compared to FT experiments because, during the thawing phase, the ice inside the pores reverts to liquid as the temperature rises. The difference between average baseline experiments versus FT180 and FTC6 indicated a reduction in stress of 14.5% and 38.5%, respectively. The standard error of our experiments ranged from 0.58% for FT60 to 5.35% for FTC6. The damage factor follows a downward trend in both FT and FTC experiments as the time of LN2 treatment augments. The amount of energy that can be absorbed in elastic or plastic deformation before failure is less for FTC specimens with the same total LN2 exposure time. Samples undergoing the freezing time process demonstrate a greater and denser quantity of acoustic emissions in comparison to freezing–thawing cycle processes, suggesting a positive correlation with uniaxial compressive strength outcomes. The large network of fractures formed by the FTC and PFTC techniques indicated that they have the greatest potential as stimulation approaches. The engineering results were improved by adding the geological context, which is essential to apply these findings to coals that have comparable origins.

Coalbed methane (CBM) is a significant unconventional natural gas resource existing in matrix pores and fractures of coal seams and is a cleaner energy resource compared to coal and crude oil. To produce CBM, stimulation operations are required, given that the coal permeability is generally too low. Hydraulic fracturing is the most widely used technology for reservoir stimulation; however, there are a few challenging issues associated with it, e.g., huge water consumption. In the past decade, the use of liquid nitrogen (LN2) as a fracturing fluid has been intensively studied for stimulating CBM reservoirs, achieving considerable progress in understanding fracturing mechanisms and optimizing fracturing techniques. This paper presents a thorough review of experimental design and observations, modeling procedures and results, field applications, and published patents. Existing studies are divided into five different groups for discussion and comparison, including immersion tests, injection tests, jet drilling tests, numerical modeling, and field applications. Based on the comprehensive evaluation of the outcomes, it is obvious that cryogenic fracturing using LN2 is a promising eco-friendly fracturing technique that can effectively enhance coal rock permeability to increase the production of CBM. [ABSTRACT FROM AUTHOR]

Steelmaking processes require high‐performance lining materials with high refractoriness and thermal shock resistance, such as MgO–C bricks. Therefore, the interactions between three industrially fabricated MgO–C bricks differing in the used MgO grade and liquid steel are investigated by immersion tests in an Al‐deoxidized 42CrMo4 steel at 1600 °C, herein. The trials are carried out in a steel casting simulator. Macro‐ and microstructure of immersed specimens are characterized using light microscopy, scanning electron microscopy, and X‐ray diffraction, while the inclusion population in the solidified steel is analyzed using an automated feature analysis to determine the frequency, geometric characteristics, and elemental composition of the inclusions. Newly formed structures consisting mainly of MgO are observed on the immersed specimens differing in their superficial appearance and the frequency of phases assigned to the system Al2O3–CaO–MgO–SiO2 in dependence on the MgO grade. Based on the inclusion species occurring in the solidified steel, a specific rulefile is developed to classify the non‐metallic inclusions by their elemental composition. Significant differences in the frequency of detected inclusions and their distribution according to the developed rulefile depending on the MgO grade are identified by keeping the processing in the steel casting simulator constant. [ABSTRACT FROM AUTHOR]

The corrosion behaviors of Fe83‐XC1B11Si2P3CrX (X = 0, 1, 2, and 3 at%) amorphous alloys in 0.1 M NaCl solution have been investigated by immersion and electrochemical tests. With the addition of Cr content from 0 to 3 at%, the corrosion rate of amorphous alloys gradually decreases from 2.57 × 10−1 to 1.04 × 10−1 mm·year−1. The minor addition of Cr improves the corrosion resistance through the increase in the Ecorr value, which makes it easy to reach a passive state and suppress pitting corrosion. The corroded morphology and products of amorphous alloys have been tested by scanning electron microscopy (SEM) and energy‐dispersive spectroscopy (EDS). The SEM/EDS analysis shows that the high corrosion resistance is due to the formation of dense and stable chromium oxide during immersion in NaCl solutions. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to evaluate the long-term color stability of light-polymerized resin luting agents stored in different beverages. Methods: Eleven shades of two light-polymerized resin luting agents, Choice2 (A1, A2, B1, TRANSLUCENT, MILKY OPAQUE, and MILKY BRIGHT) and BeautiCem Veneer (H-Value, M-Value, L-Value, Ivory-D, Ivory-L) were selected in this study. Disk-shaped specimens were fabricated with 1.3 mm thickness and 15.0 mm diameter. A total of 198 specimens, 18 for each shade, were prepared and randomly divided into six storage conditions (purified water, coffee, cola, tea, red wine, and air). All shades of specimens were three times measured at three random locations (n = 9) at 24 h storage in air after specimen preparation and then measured after immersion at 1, 3, 6, 9, and 12 mos. using a colorimeter. Then, the color difference (ΔE) between the specimens at 24 h after preparation and after storage in each liquid for 12 mos. was calculated. Statistical analysis was performed using Steele--Dwass multiple comparison test of the ΔE values or one-way ANOVA and Tukey's honest significant difference test.Results: For all immersion conditions, ΔE was significantly higher than air (control). The ΔE of the shades in the various storage conditions showed no significant difference between Purified Water-Cola and Coffee-Tea. Comparisons of the color components L*, a*, and b* for each shade showed different behaviors among the shades.Conclusions: The results suggest that the color stability of light-polymerized resin luting agents may differ between different shades and beverages. [ABSTRACT FROM AUTHOR]

Coalbed methane (CBM) is a significant unconventional natural gas resource existing in matrix pores and fractures of coal seams and is a cleaner energy resource compared to coal and crude oil. To produce CBM, stimulation operations are required, given that the coal permeability is generally too low. Hydraulic fracturing is the most widely used technology for reservoir stimulation; however, there are a few challenging issues associated with it, e.g., huge water consumption. In the past decade, the use of liquid nitrogen (LN2) as a fracturing fluid has been intensively studied for stimulating CBM reservoirs, achieving considerable progress in understanding fracturing mechanisms and optimizing fracturing techniques. This paper presents a thorough review of experimental design and observations, modeling procedures and results, field applications, and published patents. Existing studies are divided into five different groups for discussion and comparison, including immersion tests, injection tests, jet drilling tests, numerical modeling, and field applications. Based on the comprehensive evaluation of the outcomes, it is obvious that cryogenic fracturing using LN2 is a promising eco-friendly fracturing technique that can effectively enhance coal rock permeability to increase the production of CBM.

Abstract This paper presents qualitative techniques for evaluating shale–fluid interaction. Undesirable shale–fluid interactions lead to wellbore instability, formation damage and other problems that cost the petroleum industry millions of dollars annually. A simple desktop test method, such as immersion testing, can help production engineers choose the appropriate shale inhibitors such as salt, tetramethylammonium chloride (TMAC) and polymers that can effectively reduce the impact of oilfield fluids invading shale and causing it to swell or disperse. The swelling tendency of shale is highly dependent on clay mineralogy and other properties, such as porosity and permeability. A series of immersions tests was performed to study the combined and isolated effects of salt, TMAC, and polyacrylamide on preventing shale from becoming unstable. The merit of each fluid system in shale inhibition is probed for Woodford, Chattanooga and Pride Mountain shale. Rheology of bentonite slurries is studied with different salts and TMAC to probe their efficiency in preventing the swelling of bentonite clay. Additionally, rheology of bentonite with anionic and cationic polyacrylamide and salt is investigated.

The corrosion performances of Mg–4Y–xAl (x = 1, 2, 3, and 4 wt%) alloys in the 3.5% NaCl electrolyte solution are investigated by electrochemical tests, weight loss measurement and corrosion morphology observation. The results indicate that corrosion modes for the alloys are localized corrosion and the filiform type of attack. With Al concentration increasing from 1 to 4 wt%, the corrosion rate of Mg–4Y–xAl alloys decreases firstly and then increases, and WA42 alloy shows the best corrosion resistance. The addition of Al element to Mg–4Y alloys leads to the formation of Al2Y and Al11Y3 intermetallic compounds and reduces the proportion of Mg24Y5 phase. Corrosion resistance of the Mg–4Y–xAl alloys mainly depends on the size and distribution of the second phases. Besides, the addition of excessive Al can greatly consumes the Y element in the matrix, thus leading to a less protective film on the alloys. The effect of the relative Volta potential changes between the second phases and α‐Mg on corrosion resistance of Mg–4Y–xAl alloys is insignificant. The main corrosion products of the Mg–4Y–xAl alloys are Mg(OH)2, Mg3(OH)5Cl·4H2O, Mg0.72Al0.28(CO3)0.15(OH)1.98(H2O)0.48, and Mg4Al2(OH)12CO3·3H2O. [ABSTRACT FROM AUTHOR]

This study investigates the corrosion of steel samples immersed in water with a dynamic corrosion setup at different pH values for three different velocities and three different exposure time. The characteristics of material surface were observed by utilizing Atomic Force Micrographs (AFM). Under the dynamic and static conditions, the rate of corrosion of the steel samples in deionized water (DIW) was calculated through the weight loss measurements. It has been found that the corrosion rate of steel samples under static conditions was higher with the lower pH values. It was observed that the corrosion rate was maximum at pH = 4 and the minimum at pH = 6. The static corrosion tests suggest that the corrosion rate was high in the first two days then decreased with the increasing of time of tests. The effect of wall shear stress and time of immersion was evaluated under the dynamic corrosion tests. The results suggest that increased wall shear stress lead to an increase the corrosion rate specially at pH = 4. [ABSTRACT FROM AUTHOR]

This research study explores to analyze the testing performance of chemical corrosion and erosion by chemical action in high carbon high chromium steel die. Due to fuel scarcity, many European and other developing countries have identified and given importance to various industrial wastes to be used for the biofuel production. They are mostly for briquetting biomass, made out of low and high density organic materials and green waste. The machine is utilized to form the briquette, by compression in the metallic die, which needs to be changed after every 40 tons of work done, depending on the briquette contents. There are several chemical testing methods, which are developed to find the rate of corrosion developed due to the raw materials in the die. There are specific analytical equipments available and utilized to analyze the rate of chemical corrosion in alloys and metals. Such analysis is carried out by obtaining samples of new die of the briquette machine and upon the life cycle of completion of the die, the completely utilized die. The assessment of corrosion formation and rate in both these dies can help to determine by immersing in salt water, clear drinking and sewage water. Also, the corrosion indication can be determined by immersing the die in several acids like acetic acid, sulfuric acid-H2SO4, and also NaOH, to determine the corrosion materials in the die using spectrophotometric analysis. The final results depend on the corrosion difference observed between the new and used die. The completely used specifically molded die gets affected due to high heat, wearing process due to the composition condition of the flow and contents in the biomass like hemicellulose in many heteropolymers, plant cell walls, starch, a complex polymer available in plant walls called lignin, and small cells like Hemi Cellules. [ABSTRACT FROM AUTHOR]

Mechanical property and corrosion behavior of 7A46 aluminum alloy under peak-ageing (T6), double-ageing (DA) and pre-ageing (PA) followed by double-ageing (PA-DA) are systematically investigated. The hardness and strength of aged 7A46 alloy follows an order of T6>PA-DA > DA and the rank of corrosion resistance is PA-DA > DA > T6. The small size and dispersed distribution of matrix precipitates (MPs) lead to the high hardness and strength of T6 alloy, and low hetero-phase potential differences and less formation probability of corrosion galvanic couples enhance the corrosion resistance of PA-DA alloy. Intergranular corrosion (IGC) test results reveal that considerable potential differences promote the formation rate and the quantity of corrosive-batteries between the matrix and grain boundary precipitations (GBPs) or precipitate-free zones (PFZs). The exfoliation corrosion (EXCO) rate and the weight gain trend of corrosion products are related to the oxide film formation rate and corrosion products accumulation. Localized anodic dissolution and hydrogen embrittlement can induce the stress cracking corrosion (SCC). • The strengthen mechanism of 7A46 alloy is studied. • The mechanical strength is related to the small dispersed particles. • The alloy exhibits the best corrosion resistance under PA-DA condition. • The corrosion rate of the alloy under PA-DA condition is lower than that under T6, DA condition. [ABSTRACT FROM AUTHOR]

Abstract Purpose Immersion tests in purified water were conducted to evaluate the leaching behaviors of filler elements contained in computer-aided design/computer-aided manufacturing (CAD/CAM) composite resin. Methods Four commercial CAD/CAM resin composite blanks were tested: Shofu block HC 2 layer, Cerasmart, Katana Avencia block, and KZR-CAD HR Block 2. The specimens in the size of 10.0 × 12.0 × 2.0 mm were immersed in a 50-mL conical tube containing 40 mL of purified water, and then placed in a constant-temperature oven set at a temperature of 37, 60, 70, or 80° C and stored statically for 30 days. After storage, the concentrations of leached elements in the immersion solution were measured with an inductively coupled plasma atomic emission spectrometer. To characterize the surface of the specimen after the immersion test, secondary electron images were obtained. Results The immersion test resulted in the leaching of Si, the main component, from all materials tested. Some materials were found to have leached high amount of Ba or Sr in addition to Si, and remarkable surface degradation was observed. The amount of leached elements increased with increased immersion temperatures. Conclusions Filler elements in CAD/CAM composite resins used in this study leached into purified water. The leached elements and its quantities greatly differed among materials and depend on the types of the oxides composing the filler. The amounts of leached elements varied in a temperature-dependent manner. [ABSTRACT FROM AUTHOR]

Rare earth (RE) elements are beneficial to improving corrosion properties in low-carbon and low-alloy steels. In this paper, corrosion performance of Q235B steel and Q355B steel samples after RE alloying under wet-dry cycle immersion conditions were analyzed. Experimental results show that corrosion rate was significantly decreased. It was probably due to the grain refinement by RE alloying, which increased the density of protective rust layers and improved corrosion resistance. The formation of small-sized spherical RE inclusions also inhibited the precipitation of MnS and weakened micro galvanic corrosion. Additionally, RE atoms tended to segregate towards grain boundaries and a RE concentration region is formed between rust layers and matrix to impede the access from contacting corrosive ions. A corrosion resistance schematic of RE atom segregation was proposed based on microstructure morphology and element distribution results.

This paper presents qualitative techniques for evaluating shale-fluid interaction. Undesirable shale-fluid interactions lead to wellbore instability, formation damage and other problems that cost the petroleum industry millions of dollars annually. A simple desktop test method, such as immersion testing, can help production engineers choose the appropriate shale inhibitors such as salt, tetramethylammonium chloride (TMAC) and polymers that can effectively reduce the impact of oilfield fluids invading shale and causing it to swell or disperse. The swelling tendency of shale is highly dependent on clay mineralogy and other properties, such as porosity and permeability. A series of immersions tests was performed to study the combined and isolated effects of salt, TMAC, and polyacrylamide on preventing shale from becoming unstable. The merit of each fluid system in shale inhibition is probed for Woodford, Chattanooga and Pride Mountain shale. Rheology of bentonite slurries is studied with different salts and TMAC to probe their efficiency in preventing the swelling of bentonite clay. Additionally, rheology of bentonite with anionic and cationic polyacrylamide and salt is investigated. [ABSTRACT FROM AUTHOR]

The formation of the intermetallic compounds at the interface between cold-sprayed coatings and steel as well as interaction between coatings and aluminum melt was investigated. Coatings of AA7075 (AlZn5.5MgCu) and AA4145 (AlSi10Cu4) were deposited on the sheets of the deep drawing steel DC04. The coated samples were then immersed in the aluminum melt AlSi9Mn at the temperature of T = 610 °C for different durations in the range 30 s < t < 10 min. The reaction layer growth was examined metallographically and by means of scanning electron microscope with energy-dispersive spectroscopy. Furthermore, the intermetallic phases were identified by X-ray diffraction analysis and characterized by microhardness measurements. For both coatings, β-AlFeSi phases were shown to be the major constituent in the reaction zone. The growth kinetics of the intermetallic phases appeared to be similar for AA4145 and AA7075 coatings, while their morphology was completely different. [ABSTRACT FROM AUTHOR]

The relationship among microstructures, mechanical properties and corrosion behaviors of spray formed 7055 aluminium alloy has been investigated upon peak-aging (T6), double-aging (DA) and retrogression and re-aging (RRA). The research is estimated by hardness test, tensile test, immersion test, detailed microstructure observation and potentiodynamic polarization under different aging treatments. Results demonstrate that the corrosion resistance rank of aging treatments is as follow: DA > RRA > T6. The continuous grains boundary precipitations (GBPs) and coarse Al 7 Cu 2 Fe particles increase the corrosion susceptibility. The appearance of the pit cavity attributes to coarse grains and the considerable potential difference between the matrix and GBPs or precipitate-free zones (PFZs) during intergranular corrosion (IGC) process. The wedging stress from hydrogen cracks and the accumulation of the corrosion products help induce the exfoliation corrosion (EXCO). Anodic dissolution and hydrogen embrittlement cause stress corrosion cracking (SCC) of the alloy under different aging treatments. The strengthening mechanism attributes to the distribution of matrix phases (MPs), η′ phase and Al 3 Zr particles. [ABSTRACT FROM AUTHOR]

This paper reports the comparative evaluation of the corrosion behaviour of AZ31B magnesium alloy under immersion and potentiodynamic polarization test in NaCl solution at different chloride ion concentrations, pH value and exposure time. The specimens were exposed to immersion and polarization environments in order to evaluate their corrosion rates. Empirical relationship was established to predict the corrosion rate of AZ31B magnesium alloy. Three factors, five level, central composite rotatable design matrix was used to minimize the number of experimental conditions. Response surface methodology was used to develop the relationship. The developed relationship can be effectively used to predict the corrosion rate of AZ31B magnesium alloy at 95% confidence level for both the testing. This research work proves a better corrosion resistance of AZ31B magnesium alloy at the alkaline solution than the acidic and the neutral solutions, moreover, low corrosion rate was found at low concentrated solution and higher exposure time respectively.

In dual purpose water/power co-generation plants, the presence of high concentration of Cu and Ni in the re-circulating brine/condensate as a result of condenser tubes corrosion has been attributed as one of the several causes of corrosion damage of flash chamber materials and water touched parts of the boilers. The present investigation deals with the effect of dissolved nickel in the concentration range of 10 ppb to 100 ppm on the corrosion behavior of mild steel and SS 304L in two aqueous medium namely, distilled water and artificial seawater. The effect of pH, dissolved oxygen and flow condition of aqueous medium on the corrosion behavior was also monitored. The experimental techniques include immersion test and electrochemical tests which include free corrosion potential measurements and potentiodynamic polarization measurements. The corrosion rate of mild steel and SS 304L under different experimental conditions was determined by weight loss method and spectrophotometric determination of iron ion entered into the test solution during the period of immersion. The pH of the test solution was also monitored during the entire period of immersion. The left over nickel ions present in the test solution after completion of immersion was also estimated using Atomic Absorption Spectrophotometer. The surface morphology of the corroded steel surface was also examined using scanning electron microscopy (SEM). The results of the studies show that SS 304L largely remains unaffected in both distilled water and artificial seawater under different experimental conditions. However, the effect of nickel on the corrosion behavior of mild steel is quite pronounced and follows interesting trends.

The influence of the addition of nano-scaled bioactive glass (nBG) powder into polycaprolactone (PCL) coatings on the biodegradation and bioactivity of pure Mg was investigated in the present work. Scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS), Fourier transform infrared spectroscopy (FTIR) and electrochemical methods were employed to characterize the morphology, chemical composition and anticorrosion properties of the coatings. The results indicate that nBG addition in PCL increases the degradation of PCL in physiological solution; depending on the amount of nBG in the composite coating, the barrier properties of PCL therefore can be modified. At the same time, the addition of nBG facilitates the formation of hydroxyapatite during 7 days immersion in simulated body fluid (SBF). [ABSTRACT FROM AUTHOR]

The present research investigated the effect of H2S/CO2 partial pressure, sulphur deposition and corrosion inhibitor on the corrosion behaviour of L360QCS pipeline steel in H2S/CO2 environments by immersion tests, scanning electron microscope analysis and electrochemical measurements. The results show that the corrosion rate (CR) of L360QCS steel decreased first and then increased with increasing pH2S and pCO2.The CR is closely associated with the protectiveness of corrosion film. Sulphur deposition can cause an acceleration of the corrosion of steel in H2S/CO2 environments. Furthermore, the CR increased obviously with increasing pH2S and pCO2 in sulphur deposition environments. After addition of continuous corrosion inhibitor, the CR decreased significantly in H2S/CO2 environments. Prefilming corrosion inhibitor could enhance the inhibition effect in the presence of continuous corrosion inhibitor. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports the comparative evaluation of the corrosion behaviour of AZ31B magnesium alloy under immersion and potentiodynamic polarization test in NaCl solution at different chloride ion concentrations, pH value and exposure time. The specimens were exposed to immersion and polarization environments in order to evaluate their corrosion rates. Empirical relationship was established to predict the corrosion rate of AZ31B magnesium alloy. Three factors, five level, central composite rotatable design matrix was used to minimize the number of experimental conditions. Response surface methodology was used to develop the relationship. The developed relationship can be effectively used to predict the corrosion rate of AZ31B magnesium alloy at 95% confidence level for both the testing. This research work proves a better corrosion resistance of AZ31B magnesium alloy at the alkaline solution than the acidic and the neutral solutions, moreover, low corrosion rate was found at low concentrated solution and higher exposure time respectively. [Copyright &y& Elsevier]

Abstract: Biodegradable metals offer great potential in circumventing the long-term risks and side effects of medical implants. Austenitic Feph name="sbnd" />C feature a well-balanced combination of high strength and considerable ductility which make them attractive for use as degradable implant material. The focus of this study is the evaluation of the degradation performance of these alloys by means of immersion testing and electrochemical impedance spectroscopy in simulated body fluid. The Feph name="sbnd" />C are characterized by an increased degradation rate compared to pure Fe, as revealed by both techniques. Electrochemical measurements turned out to be a sensitive tool for investigating the degradation behavior. They not only show that the polarization resistance is a measure of corrosion tendency, but also provide information on the evolution of the degradation product layers. The mass loss data from immersion tests indicate a decreasing degradation rate for longer times due to the formation of degradation products on the sample surfaces. The results are discussed in detail in terms of the degradation mechanism of Fe-based alloys in physiological media. [Copyright &y& Elsevier]

Abstract: Silica coatings have been obtained through the organic sol–gel route on magnesium–zinc alloys (ZE41) using low sintering temperatures for their corrosion protection. Tetraethoxysilane (TEOS) was used as alkoxide precursor, and the coatings, monolayer and 3-layers, were deposited by dip-coating technique at a controlled extraction speed of 35cm/min. Temperatures of 135°C were applied for several hours for coating densification avoiding mechanical deterioration of the magnesium alloy. To optimize the corrosion behaviour of the coatings different concentrations of sol solution were investigated. The corrosion resistance of the different coatings were tested by immersion in 3.5wt.% NaCl aqueous solution and by electrochemical corrosion techniques. Low temperature silica coatings provided corrosion protection for up to 7days without degrading the mechanical properties of the magnesium alloy used. [Copyright &y& Elsevier]

Abstract: The corrosion behavior of three Fe–Mn–Si–Cr–Ni–(Co) shape memory stainless steels (SMSS) in 0.5M H2SO4 solution was studied through electrochemical and immersion tests. The test results were compared with that of a type 304 (SS 304) austenitic stainless steel. The three SMSSs exhibited a passive behavior in 0.5M H2SO4 solution; however, their anodic behavior in the active dissolution region was markedly different. The passive current densities of the SMSSs were similar to that of SS 304, although the critical anodic current required for passivation was higher. The corrosion rate of the SMSSs was much higher than that of SS 304. It was observed that the amount of Cr and Mn plays an important role in the corrosion behavior of SMSSs. The best corrosion behavior in acid media was shown by the SMSS that contained the highest amount of Cr and the lowest amount of Mn. [Copyright &y& Elsevier]

Abstract: Silica coatings have been applied on the surface of ZE41 magnesium alloy following the organic sol–gel route and the dip-coating technique. Three different concentrations of sol solution and two densification temperatures of the coating (400°C and 500°C) were used to optimize the compaction of the coatings and as a result reach the corrosion protection of the metallic substrate tests in 3.5wt.% NaCl aqueous solution. Crack-free coatings with thickness in the 2–3μm were obtained on the ZE41 magnesium alloy. The combination of high alkoxide concentration in the sol–gel formulation, and the high sintering temperature (500°C) leads to coating (D500) with the optimal physical barrier against the corrosion process. This coating was capable of resisting more than 7days in contact with the aggressive electrolyte suffering minor corrosion degradation. A corrosion mechanism for each of the tested specimens has been proposed. [ABSTRACT FROM AUTHOR]

The short service life of bearings in galvanising industry is a result of a complex set of deterioration mechanisms. This work addressed the effect of temperature and molten bath reactivity on the material of the bearings respectively. Three commercial alloys, the Co-Cr-W Stellite 6 and Co-Cr-Mo-Si Tribaloy (T400 and T800) alloy systems, were deposited by plasma transferred arc on AISI 316L plates. Coatings were evaluated for the effect of temperature exposure on hardness, microstructure and sliding abrasive wear. The reactivity with the molten 55Al-Zn alloy was assessed by immersion tests in an industrial bath. Results showed that exposure at 600°C for 168 h resulted in an increase in hardness, microstructure changes and loss of wear resistance for the Stellite 6 coatings. A superior performance to temperature was shown by Tribaloy T800 with a stable abrasive wear resistance. The three alloys exhibited a strong reactivity with the 55Al-Zn molten bath. An intermetallic layer formed on the coatings as the Al from the bath reacted with elements from the Co based alloys. This reactivity consumed the coatings, causing a reduction on thickness particularly on those processed with the T800 alloy. [ABSTRACT FROM AUTHOR]

Abstract: The deposition of titanium diboride (TiB2) films over tool steel substrates (AISI H13 premium/EN X40 CrMoV 5-1-1) is being investigated due to its excellent corrosion resistance and chemical stability against liquid aluminium. The use of nitrided steels as substrates for TiB2 deposition may contribute to increase its adhesion and the overall steel resistance in applications such as forging, extrusion and die casting of aluminium. Duplex coatings were obtained by the PVD deposition of TiB2 films over heat treated and nitrided steel using non-reactive DC magnetron sputtering from a TiB2 target, varying the substrate bias voltage. Well structured and crystalline TiB2 films were obtained for the selected deposition conditions, the best crystalline coatings being obtained for the positively biased substrates. Selected films produced over die-casting pins at a bias voltage of +50V were tested for resistance to liquid aluminium soldering by immersion tests, and compared with the nitrided steel. The duplex TiB2 coating has a much larger chemical resistance to attack by molten aluminium alloy than the just nitrided steel. Where there is soldering, steel is rapidly attacked and a complex Al–Fe–Si intermetallic forms. [Copyright &y& Elsevier]

Purpose The purpose of this study was to evaluate the long-term color stability of light-polymerized resin luting agents stored in different beverages.Methods Eleven shades of two light-polymerized resin luting agents, Choice2 (A1, A2, B1, TRANSLUCENT, MILKY OPAQUE, and MILKY BRIGHT) and BeautiCem Veneer (H-Value, M-Value, L-Value, Ivory-D, Ivory-L) were selected in this study. Disk-shaped specimens were fabricated with 1.3 mm thickness and 15.0 mm diameter. A total of 198 specimens, 18 for each shade, were prepared and randomly divided into six storage conditions (purified water, coffee, cola, tea, red wine, and air). All shades of specimens were three times measured at three random locations (n = 9) at 24 h storage in air after specimen preparation and then measured after immersion at 1, 3, 6, 9, and 12 mos. using a colorimeter. Then, the color difference (ΔE) between the specimens at 24 h after preparation and after storage in each liquid for 12 mos. was calculated. Statistical analysis was performed using Steele-Dwass multiple comparison test of the ΔE values or one-way ANOVA and Tukey's honest significant difference test.Results For all immersion conditions, ΔE was significantly higher than air (control). The ΔE of the shades in the various storage conditions showed no significant difference between Purified Water-Cola and Coffee-Tea. Comparisons of the color components L*, a*, and b* for each shade showed different behaviors among the shades.Conclusions The results suggest that the color stability of light-polymerized resin luting agents may differ between different shades and beverages.

Magnesium alloys have been investigated as temporary biomaterials for orthopedic applications. Despite their high osseointegration and mechanical (bone-like) properties, Mg alloys quickly degrade in simulated physiological media. Surface coatings can be deposited onto Mg alloys to slow the corrosion rate of these biomaterials in chloride-rich environments. TiO2 films show high potential for improving the corrosion resistance of magnesium alloys. This article presents the structural observations and corrosion behavior of TiO2 thin films deposited onto a MgCa2Zn1Gd3 alloy using atomic layer deposition (ALD). Surface morphologies were observed using scanning electron microscopy (SEM) and atomic force microscopy (AFM), and Raman analysis of the deposited TiO2 films was also carried out. The corrosion behavior of the uncoated alloy and the alloy coated with TiO2 was measured in Ringer's solution at 37 °C using electrochemical and immersion tests. The microscopic observations of the TiO2 thin films with a thickness of about 52.5 and 70 nm showed that the surface morphology was homogeneous without visible defects on the TiO2 surface. The electrochemical and immersion test results showed that the thin films decreased the corrosion rate of the studied Mg-based alloy, and the corrosion resistance was higher in the thicker TiO2 film. [ABSTRACT FROM AUTHOR]

Abstract: The electrochemical corrosion behaviors of Fe41Co7Cr15Mo14C15B6Y2 bulk metallic glasses (BMGs) were investigated by immersion tests and potentiodynamic polarization experiments. The results of immersion test in 1N HCl, 1N HNO3, 1N NaOH and 3.5% NaCl solutions show that the corrosion rate of Fe41Co7Cr15Mo14C15B6Y2 metallic glasses is very low in all kinds of solutions, particularly in 3.5% NaCl solution. It indicates that the corrosion resistance in NaCl solution is superior to the other three solutions. The corrosion rate in 3.5% NaCl solution is much lower than those of other Fe-based amorphous alloys. Moreover, Fe41Co7Cr15Mo14C15B6Y2 metallic glass has excellent corrosion resistance in different concentrations of NaCl solutions through the further polarization experiments. [Copyright &y& Elsevier]

Rare earth (RE) elements are beneficial to improving corrosion properties in low-carbon and low-alloy steels. In this paper, corrosion performance of Q235B steel and Q355B steel samples after RE alloying under wet-dry cycle immersion conditions were analyzed. Experimental results show that corrosion rate was significantly decreased. It was probably due to the grain refinement by RE alloying, which increased the density of protective rust layers and improved corrosion resistance. The formation of small-sized spherical RE inclusions also inhibited the precipitation of MnS and weakened micro galvanic corrosion. Additionally, RE atoms tended to segregate towards grain boundaries and a RE concentration region is formed between rust layers and matrix to impede the access from contacting corrosive ions. A corrosion resistance schematic of RE atom segregation was proposed based on microstructure morphology and element distribution results. [ABSTRACT FROM AUTHOR]

Magnesium alloys with rare earth metals are very attractive materials for medical application because of satisfactory mechanical properties. Nevertheless, low corrosion resistance is an obstacle in the use of Mg alloys as resorbable orthopedic implants. The paper presents results of mechanical and corrosion properties of MgCa5-xZn1Gdx (x = 1, 2, and 3 wt. %) alloys. Based on the microscopic observations it was stated that the studied alloys show a dendritic microstructure with interdendritic solute rich regions. The phase analysis reveals an occurrence of α-Mg and Mg2Ca, Ca2Mg6Zn3 phases that are thermodynamic predictions, and stated Mg26Zn59Gd7 phases in MgCa5-xZn1Gdx (x = 1, 2, and 3 wt. %) alloys. The Mg26Zn59Gd7 phases are visible as lamellar precipitations along interdendritic regions. It was confirmed that an increase of Gd content from 1 to 3 wt. % improves ultimate tensile (Rm; from 74 to 89 MPa) and compressive strength (Rc; from 184 to 221 MPa). Moreover, the studied alloys are active in Ringer's solution. They are characterized by an increase of corrosion potential (Ecorr) of about 150 mV in comparison with values of open circuit potential (EOCP). The best electrochemical parameters (e.g., corrosion current density, icorr, polarization resistance, Rp, and Ecorr) were obtained for the MgCa3Zn1Gd2 alloy. [ABSTRACT FROM AUTHOR]