Aims: Anodic polarization behavior of a combined iron-titanium electrode (two metals in electrical contact with each other) in aqueous solutions containing halide ions (F- and Cl-) was studied. Methods: he joint anodic dissolution of titanium and iron with subsequent thermal treatment makes it possible to obtain precursors of a highly dispersed mixed oxide system Fe2O3-TiO2. The phase and elemental composition and structural characteristics of obtained products were examined using X-ray diffraction and scanning electron microscopy. It has been experimentally confirmed that via changing the anode current density, hydrofluoric acid concentration in electrolyte and ratio of the working surface area of contacting metals, it is possible to effectively control the rate of anodic reactions and phase composition and morphology of anodic oxidation products for iron and titanium components in a combined electrode. Results: The main results of this study are as follows: Electrochemical method for the synthesis of complex dispersed oxide system Fe2O3-TiO2 based on joint anodic oxidation of contacting metals in aqueous media was suggested. Relationships between parameters of the electrochemical process and characteristics of the synthesized oxide system were revealed. Conclusion: By varying the parameters of the electrolysis process, it is possible to prepare complex oxyhydroxides with different ratios of iron and titanium, which makes it possible to synthesize precursors of iron titanates of preset composition and structure.
Background: Body fluids are highly corrosive as they contain chlorides and hydroxides ions, as well as salts, bacteria, proteins and dissolved oxygen. The pH of the body is usually around 7.4, although this value can vary in a range of 4 to 9 after surgery or because of haematomas, inflammations and infections. ASTM F745 (type 316L) stainless steel has been used for load bearing partial and total joint replacements and post trauma reconstructive surgeries. However, long exposure to the aggressive effect of chloride ion present in the human body, may increase the susceptibility to suffer localized corrosion. Although UNS S32750 has greater corrosion resistance to chloride ion, its magnetic characteristics inhibit its use in implantable devices. Nevertheless, this stainless steel could be used in temporary implants and orthodontic appliances such as brackets, wire arches and bands, due to its high resistance to corrosion, the greater mechanical resistance and the high capacity of plastic forming. Objectives: The objective was to evaluate the susceptibility to localized corrosion in simulated body fluid, in the pH range of 4 to 9. Another objective was to evaluate the cytotoxicity of Cr and Ni present in the chemical composition of both stainless steels. Cytocompatibility was also analysed by seeding cells on the surfaces of both stainless steels. Methods: Cyclic polariation test was performed to evaluate the susceptibility to localized corrosion in 0.9 wt% NaCl aqueous solution, at pH between 4 and 9, maintained at 37°C. For cytotoxicity evaluation, neutral red, MTT and collagen assays were performed using UMR-106 cell line. Cytocompatibility was analysed by seeding UMR-106 cells on the surfaces of both stainless steels. Results: F745-SS was more susceptible to suffer localized corrosion than UNS S32750. Although it showed a tendency to develop transpassive reactions at low pH, galvanostatic tests did not reveal the onset of localized corrosion. The results from the cytotoxicity assays indicated that no adverse effects were observed. UMR-106 osteoblastic cells showed high viability, however, a slight reduction in the collagen production was observed. The cytocompatibility was also satisfactory, since the cells seeded on the surfaces had adequate proliferation. Conclusion: F745-SS is more susceptible to suffer localized corrosion than UNS S32750 in the pH range between 4 and 9. UNS S32750 showed an extensive passive region, however, transpassive reactions were observed at lower pH. On the other hand, no cytotoxic effects were promoted by both stainless steels, although a slight reduction in collagen production was observed. Cells seeded on F745-SS and UNS S32750 surfaces had an acceptable proliferation, without evidence of changes in their morphology.
Background: Nowadays investigations in the field of dental implants engineering are focused on bioactivity and osseointegration properties. Objective: In this study, the oxide-covered titanium was functionalized by vitamin D3 molecules via a simple self-assembly method with the aim to design more corrosion-resistant and at the same time more bioactive surface. Methods: Surface properties of the D3-coated titanium were examined by scanning electron microscopy, attenuated total reflectance Fourier transform infrared spectroscopy, and contact angle measurements, while long-term corrosion stability during immersion in an artificial saliva solution was investigated in situ by electrochemical impedance spectroscopy. Results: Results of all techniques confirmed a successful formation of the vitamin D3 layer on the oxide-covered titanium. Besides very good corrosion resistivity (~5 MΩ cm2), the D3-modified titanium surface induced spontaneous formation of biocompatible bone-like calcium phosphates (CaP). Conclusion: Observed in vitro CaP-forming ability as a result of D3-modified titanium/artificial saliva interactions could serve as a promising predictor of in vivo bioactivity of implant materials.
Background: Water scarcity is amongst the biggest problems the world is facing in the 21st century. To reduce the consumption of Potable Water (PW) in construction industries and to make concrete construction more sustainable, its replacement with Seawater (SW) has been explored. Technical literature on this subject is not widely available. Such investigations are necessary for determining suitable remedial measures for the effective utilization of seawater for making sustainable concrete. Objective: In the present study, use of Seawater (SW) has been explored as both mixing and curing water in concrete. To counter the adverse effects of seawater on strength and corrosion resistance, use of Fly Ash (FA) and Red Mud (RM) as cement replacements in the seawater concrete had been investigated. Methods: The possibility of the use of seawater in making concrete has been explored by literature and experimental investigations. The obtained results are discussed in light of the information available in the literature. Various tests were performed such as compressive strength, Half-cell potential, electrochemical impedance spectroscopy and microstructural analysis using SEM and XRD. Result: Results showed higher compressive strength and improved corrosion resistance for Seawater Concrete (SWC) with FA & RM as compared to Potable Water Concrete (PWC) specimens. SWC specimens without supplementary cementitious materials show lower electrical resistivity and potential more negative than -450 mV indicating severe corrosion. 30% FA and 5% RM is identified as the optimum combination for the most favorable response in terms of mechanical strength and electrical resistivity of seawater concrete. After 90 days, the compressive strength of 35.77 MPa was achieved. Conclusion: Combination of both FA and RM in SWC reduces chloride migration and increases chloride binding by the formation of Friedel’s salt. Half-cell potential (HCP) and Electrochemical Impedance Spectroscopy (EIS) results confirmed a reduction in corrosion rate in SWC specimens with fly ash and red mud.
Stress Corrosion Cracking (SCC) plays a central role in the development of improved structural nuclear materials. Complex interactions between microstructure, alloy composition, manufacturing and environmental factors make the understanding of this phenomenon difficult. This work aimed at reviewing the scientific literature on the SCC behavior of structural nuclear materials in order to identify the main factors that govern this phenomenon. Additionally, the interaction between these factors and materials selection is discussed in order to provide a comprehensive basis for the successful design of metallic materials with improved resistance to SCC.
Background: The electrochemical corrosion properties of bulk nanocrystalline aluminum (BNC-Al) produced by severe rolling technique and its traditional polycrystalline aluminum (TPC-Al) counterpart in 0.022, 0.044, 0.066, 0.11, 0.22, 0.44 mol/L HCOOH solutions were studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) at ambient temperature. Method: The corrosion current densities and capacitances of double electrode layer of BNC-Al were less than those of TPC-Al respectively, and the polarization resistances of BNC-Al were larger than those of TPC-Al in 0.022, 0.044 mol/L HCOOH solutions. However, the corrosion current densities and capacitances of double electrode layer of BNC-Al were larger than those of TPC-Al respectively, and the polarization resistances of BNC-Al were less than those of TPC-Al in 0.066, 0.11, 0.22, 0.44 mol/L HCOOH solutions. The passivation of BNC-Al was enhanced in 0.066, 0.11, 0.22, 0.44 mol/L HCOOH solutions. Results and Conclusion: These results demonstrated that the corrosion resistances of BNC-Al were enhanced in 0.022 and 0.044 mol/L formic acid solutions at a low potential and in 0.066, 0.11, 0.22, 0.44 mol/L at a high potential, compared to those of TPC-Al. The possible reasons for these electrochemical results for BNC-Al and TPC-Al were proposed in this work. Keywords: Electrochemical corrosion, nanocrystalline aluminum, potentiodynamic polarization, electrochemical impedance spectroscopy, ambient temperature, rolling technique.
Background: In this paper, a comparative study of the correctness of the results of registration of corrosion kinetics with the methods of current-voltage curves (V / a) and Coulometric Registration of Corrosion Products (CDCP method) was carried out. Methods: It is shown that the action of the electric field under polarization changes the character of the corrosion process and, in particular, stimulates the formation of the oxide layer, leading to a distortion of the results of the loss of the mass of the metal. Results and Conclusion: The convergence of the results of coulometric and "tafel" measurements of mass loss is established only on "pure" metal. After the formation of the oxide layer, the "tafel" results show a protective effect, which does not exist in a real corrosion process. Keywords: Registration, kinetics, corrosion, methods, coulometry, voltammetry, comparison of results.
Background: Two techniques of laser optical interferometry have been reviewed for detection of crevice corrosion of low carbon steel samples in aqueous solutions. The first technique used an optical corrosion-meter to detect localized corrosion such as crevice corrosion, of the low carbon steel samples in seawater. The concept of the optical corrosion-meter was based on incorporating holographic interferometry and the cyclic polarization test. The second technique used a modified electrochemical noise technique based on holographic interferometry to detect crevice corrosion of the low carbon steel samples in 1 M of sodium hydroxide (NaOH) solution. Objective: Emphasis on the significant role of the optical techniques of detecting crevice corrosion of carbon steel in aqueous solutions alongside to the DC methods. Method: The optical corrosion-meter and the modified electrochemical noise technique were used in the present investigation. Results: Observations of crevice corrosion of the carbon steel samples in seawater by the optical corrosion-meter were found to be in agreement with the cyclic polarization test. In addition, the modified electrochemical noise technique was found to be very useful for quantitatively distinguishing of localized corrosion, passivation, and uniform corrosion of the carbon steel samples in 1 M NaOH solution. Conclusions: The optical techniques of detecting crevice corrosion of carbon steel in aqueous solutions were found efficient opto-electrochemical instruments for substantiating results of those DC methods. Keywords: Electronic instruments, electrochemical properties, electromagnetic field, optical corrosion-meter, holographic interferometry, electrochemical noise technique, and opto-electrochemistry.
Background and Objective: The effects of representative solder flux residue weak organic acids on electrochemical migration (ECM) of tin in thin electrolyte layer were studied using a technique based on the coupling of in situ electrochemical measurements and optical observations, as well as ex situ characterizations. Methods and Results: The results showed that the increasing amount of weak organic acid decreased the probability of ECM and dendrites formed were mainly composed of metallic tin. Tin ions reacted with organic compound ions from hydrolysis of weak organic acids to form complexes with electronegativity, which retarded the transfer of tin ions. Some complexes can be oxidized to the insoluble tin oxides on the anode surface and blocked the dissolution of anode during tin ECM. Conclusion: The growth rate of tin dendrite was found to be limited by the dissociation of complexes. Mechanisms involved were proposed to explain the role of weak organic acid in the tin ECM.
FAC, Flow Accelerated Corrosion, arises in the inside wall surface of carbon steel pipes which carry boiler supply water. Metal loss rates due to this sort of corrosion is relatively high; 1mm/y usually, over 4mm/y some cases. Damage areas are comparatively wide: the axis-directional extent of the hole created in pipe wall is several times of the pipe diameter. The EPRI, Electric Power Research Institute USA, presented the corrosion rate-predicting equation to estimate the corrosion rate from a lot of parameters: properties of boiler supply water such as temperature and pH, dissolved oxygen concentration, etc., as well as flow conditions such as flow velocity, etc. The accuracy of estimation, however, was very low. This author interprets this failure as follows: FAC is not uniform corrosion but localized corrosion, whereas the metal loss rate of uniform corrosion is dependent on the physical properties and the flow conditions of water as well. The metal loss rate of localized corrosion is dependent only on the difference in “anodic dissolution rates”. Anodic dissolution rates are dependent on the temperature because it concerns chemical reactions. The degree of the temperature dependency of the rate in ordinary temperature range is, however, small. So that, usual temperature gradient cannot cause any difference in anodic dissolution rates to initiate any localized corrosion. Nevertheless, in case of carbon steels, there is singular temperature range where the temperature dependency of anodic dissolution rate is reversed and decreased. It is the range called passivation. In this temperature range anodic dissolution rate decreases rapidly with temperature because the composition of oxide which deposits in the corroding surface approaches that of passive state film. As a result, even a small temperature gradient brings about great difference in anodic dissolution rate, and localized corrosion occurs. The concentration of dissolved oxygen in the surface of carbon steel submerged in water is dependent on oxygen supply rate from bulk. Anodic dissolution rate is lower at the surface where the oxygen supply is higher because iron oxides of higher grade are generated there which suppress metal dissolution. Anodic dissolution rate is higher at the surface where the oxygen supply is lower because lowgrade oxides arise. Thus, differences in the rate of dissolved oxygen supply bring about differences in anodic dissolution rates, and this causes localized corrosion. In stagnant water areas in pipe flow, oxygen supply to the pipe wall surface is apt to be retarded. Accordingly, differences arise in anodic dissolution rate between the stagnant water area and the surrounding. Thus, the localized corrosion is easy to be generated at those locations. In short, temperature gradient, passivation and stagnant water are three main factors which bring about the localized corrosion which was named “flow accelerated corrosion” by the EPRI. Based on the generation mechanism described above, technique to detect and mitigate the localized corrosion was presented. Technique to protect pipes from rupture, even if the detection of the corrosion failed, was also given. Keywords: Carbon steel pipes, flow accelerated corrosion (FAC), metal loss rates, boiler supply water, thermal power plants, nuclear power plants.
Background:Despite the process of rusting being well known, it was uncertain whether rust was contagious or not through temporary contact that is, involving no permanent bonding.Objective:The study investigated whether rust could be transmitted through temporary contact using controls.Methods:Eight rusted steel wool rolls, each less than 3.50 g were staggeringly arranged in groups of four onto two non-rusted steel plates, each measuring 400 x 200 mm, with control cells in between. After 10 days, rust stains formed on the plates and the rolls were removed. The conspicuous stains were monitored every month by means of manual tracing. After six monthly observations, the first month tracings were superimposed onto each respective plate.Results:Although intrinsic rust had formed on the control and experimental cells, the original stains remained constant in shape and size.Conclusion:Rust is probably not transmitted to other metals by simple contact
Background: Lithium tantalate (LiTaO3) thin film was synthesized and in situ coated on tantalum substrate via anodic oxidation. Methods: The effects of temperature, voltage and time on composition, morphology and hardness of film were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Vickers hardness, respectively. Results: Our results showed that surface hardness of all coated samples has been increased compared with that of pure tantalum. The value of hardness was found to gradually increase with temperature, voltage and reaction time of the coating process. Selected specimens, after coating, were immersed into 10 wt% NaOH solution at 50oC for 96h to explore their anti-corrosion performance. Immersing results indicated that LiTaO3 coated samples have a smaller mass loss and corrosion rate compared to those of pure Ta substrate. Pure tantalum sample and those coated by LiTaO3 thin film were further examined by electrochemical methods including open-circuit potential (OCP), potentiodynamic polarization curves and electrochemical impedance spectra (EIS). Conclusion: We have found that samples coated with LiTaO3 thin film exhibit higher potentials and lower corrosion current densities than those of pure tantalum substrate, according to the results and analysis of OCP curves and potentiodynamic polarization curves. Upon anodic oxidation, samples display higher polarization resistance with higher resistance to corrosion.
Asphalt binder research papers characterized by X-ray diffraction are reviewed. The Xray results reveal the aromaticity and crystallite size parameters of asphaltene in asphalt binders as reported in the research literature. The research data is discussed in terms of asphalt molecular structure on a length scale, methodology, and petroleum oil fields. Box plots and summary statistics created for each parameter are compared and discussed as they relate to eleven data sets from various asphaltene-crude-oil-geological-regions.
Fractal dimension is a versatile method to study and evaluate corrosion from the point of view of metallic conditions, namely: surface roughness, electrochemical measurements and microscopy images. Aluminum corrodes at different rates, under different pH electrolytes with or without the presence of chloride ions. In this work, corrosion and the surface roughness for aluminum corrosion at different pH electrolytes: acid, with and without chlorides, neutral and basic solutions, were obtained. It was measured and obtained using electrochemical and optic techniques. The results of Electrochemical Impedance Spectroscopy (EIS) and Noise Measurements (ENM), Digital Holographic Microscopy (DHM), Scanning Electron Microscope (SEM) micrographs and their respective Fractal Dimension analysis were obtained.. For the different experimental techniques and conditions, fractal dimension was obtained and presented, reflecting the surface condition of aluminum corrosion as a function of pH solution.
Background: Deceleration of the corrosion rate of Mg by surface chemical method via hydrofluoric acid treatment has a special interest because it is a simple, cost-effective, and efficient method for the coating of interior as well as the exterior part of any size and shape of implant material. However, conversion coating by hydrofluoric acid treatment fails to produce a long-term stable coating of Mg in ionic solutions caused by the formation of cracks on the surface during the process. Consequently, the corrosive ions of the SBF solution enter through the cracks that accelerate the dissolution by local galvanic corrosion. On the above view, we aim to develop a simple strategy for enhancement of corrosion resistance of the hydrofluoric acid treated Mg bioimplant material. Methods: This method is comprised of dip coating of hydrofluoric acid treated Mg sample in the polymethylhydrosiloxane followed by curing at 170°C for 30 min. The samples were characterized by electron probe microanalysis, X-ray photoelectron spectroscopy and electrochemical test. Results: The electrochemical test results reveal that the corrosion rate of the coated Mg sample in the simulated body fluid solution is decreased by more than 8500 times than the bare sample. The long term immersion data indicate that the chemical resistance of the coated Mg sample in the SBF solution even after 25 days is better than the bare Mg metal. Conclusion: Polymethylhydrosiloxane coating is efficient to enhance the corrosion resistance of hydrofluoric acid treated Mg metal in simulated body fluid solution.
Background: Many studies were done to assess the mechanical characteristics of the bandage casts with regards to different specifications of materials under different parameters. Many patents have been designed on the various types of casting materials such as POP, fiberglass and polyester. A recent trend in the patent is to explore a hybrid combination for bandage casts to withstand structural failure, crack formation or deformation. Objective: This study aims to study the effect of impact force on plaster of Paris, fiberglass and hybrid bandage casts. Methods: There different bandage casts were constructed using plaster of Paris, fiberglass and a hybrid combination of plaster of Paris and fiberglass. They were subjected to Charpy impact test, three-point flexural test, and Rockwell B hardness test. Results: The impact characteristics, energy absorption properties, ductility, rigidity, strength, stiffness and indentation hardness of the hybrid bandage cast were found to be greatly influenced from being a composite of two casts and interfaces. It was found that the impact energy capable of being absorbed prior to fracture for the plaster of Paris, fiberglass and hybrid were 1.225 Joules, 11.125 Joules and 6.750 Joules, respectively Conclusion: Hybrid bandage casts possessed improved impact characteristics compared to plaster of Paris bandage casts and more cost-effectiveness as compared to fiberglass bandage casts
Background:Magnesium and magnesium alloys are currently being explored for biodegradable metallic implants. Magnesium’s biocompatibility, low density, and mechanical properties could offer advantages in the development of low-bearing orthopedic prosthesis and cardiovascular stent materials.Objective:Magnesium’s susceptibility to corrosion and increased hydrogen evolution in vivo compromises the success of its potential applications. Various strategies have been pursued to control and subsequently evaluate degradation.Methods:This review provides a broad overview of magnesium-based implant materials. Potential coating materials, coating techniques, corrosion testing, and characterization methods for coated magnesium alloys are also discussed.Results:Various technologies and materials are available for coating magnesium to control and evaluate degradation. Polymeric, ceramic, metallic, and composite coatings have successfully been coated onto magnesium to control its corrosion behaviour. Several technologies are available to carry out the coatings and established methodologies exist for corrosion testing. A few magnesium-based products have emerged in international (European Union) markets and it is foreseen that similar products will be introduced in the United States in the near future.Conclusion:Overall, many coated magnesium materials for biomedical applications are predominantly in the research stage with cardiac stent materials and orthopaedic prosthesis making great strides.
Background and Method: The growth mechanism of sulphide films formed on copper in anaerobic 0.1 M NaCl + 5 x 10-4 M Na2S solution has been investigated under natural corrosion conditions for exposure periods up to 1691 hours using scanning electron microscopy, focused ion beam cross-sectioning, and a Au marker procedure. Results and Conclusions: The film formed by a chemical deposition process via an outward growth mechanism. This process was controlled by cuprous ion transport in the film combined with sulphide diffusion in solution. Keywords: Sulphide film, copper, corrosion, diffusion, crystal growth, microscopy.
Background: Surface wrinkle responding to external stimuli has potential applications in information storage, sensors, construction of special surfaces and so on. Ferrocene and azobenzenecontaining polymer Poly[2,2-Bis(4-glycidyloxyphenyl)propane-co-4-(4-ferrocenylimidephenylazo) benzenamine] (PAZO-Fc) and azobenzene-containing polymer Poly[2,2-Bis(4-glycidyloxyphenyl) propane-co-4- (4-nitrophenylazo)benzenamine] (PAZO) which have redox- and/or photo-responsive properties were synthesized by ring opening polymerization method. Methods: The structures were characterized by 1H NMR, FT-IR and GPC. TGA and DSC curves were recorded to study their thermal properties. Cyclic Voltammetry (CV) and Ultraviolet-visible (UV-vis) absorption studies showed redox- and photo-responsive properties of PAZO-Fc. Results and Conclusion: The polymers were dissolved in THF and then spin-coated on a plasma-treated PDMS substrate to induce surface wrinkling by heating. The effect of light irradiation and redox reagents on the regulation of surface wrinkles was investigated. This kind of regulation has potential application in information storage. Keywords: Ferrocene, azobenzene, bisphenol A diglycidyl ether, surface wrinkling, regulation, film preparation.
Background: The corrosion rate of biomedical magnesium alloys must be controlled to avoid excessive degradation in the physiological medium. Conversion coatings produced in fluoride-based electrolytes can be employed as a suitable corrosion protection route for these materials. The use of concentrated HF solutions is the most common procedure in the current literature. The aim of the present work was to employ a less concentrated HF solution to produce protective fluoride-based films on the AZ31B alloy and to investigate the effect of the treatment time on its corrosion resistance. Methods: The fluoride-based films were obtained in 10 wt.% HF solution at room temperature for 3 h, 6 h and 12 h. The top surfaces and cross-sections of the fluoride films were observed by scanning electron microscopy. The surface chemistry was assessed by X-ray photoelectron spectroscopy. The corrosion resistance was evaluated by potentiodynamic polarization. Results: Scanning electron microscopy and confocal laser scanning microscopy micrographs revealed that the fluoride-based layer became more cracked and rougher as the treatment time increased from 3 h to 12 h. X-ray photoelectron spectroscopy (XPS) analyses indicated that the surface layers were composed of Mg(OH)xF2-x or Mg(OH)2-xFx compounds, independently of the treatment time. The fluoridebased films enhanced the corrosion resistance of the AZ31B alloy. Conclusion: Surface morphology plays a core role in the corrosion behavior of the coated AZ31B alloy and can be controlled by the treatment time. The smooth surface of the 3 h-film presented the best corrosion resistance. Keywords: AZ31B, magnesium, fluoride coating, XPS, corrosion, physiological medium.
