Showing papers in "Journal of Bio- and Tribo-Corrosion in 2015"

A Review on TiO2 Nanotubes: Influence of Anodization Parameters, Formation Mechanism, Properties, Corrosion Behavior, and Biomedical Applications

Abstract: In this article, influence of anodization parameters on the formation of tubes, tube dimensions, formation mechanism, properties of TiO2 nanotubes (TNT), and their applications in biomedical field are reviewed. The fabrication of TNT of a different shape such as pore size, length, and wall thickness by varying anodization parameters including electrolytes, pH, voltage, electrolyte bath temperature, and current density is examined and discussed. The crystallographic nature of the nanotube obtained by various methods has also been discussed. Finally, the article concludes by examining the key properties including the corrosion aspect and various applications in biomedical field in depth.

Wear and corrosion interactions on titanium in oral environment : literature review

Abstract: The oral cavity is a complex environment where corrosive substances from dietary, human saliva, and oral biofilms may accumulate in retentive areas of dental implant systems and prostheses promoting corrosion at their surfaces. Additionally, during mastication, micromovements may occur between prosthetic joints causing a relative motion between contacting surfaces, leading to wear. Both processes (wear and corrosion) result in a bio-tribocorrosion system once that occurs in contact with biological tissues and fluids. This review paper is focused on the aspects related to the corrosion and wear behavior of titanium-based structures in the oral environment. Furthermore, the clinical relevance of the oral environment is focused on the harmful effect that acidic substances and biofilms, formed in human saliva, may have on titanium surfaces. In fact, a progressive degradation of titanium by wear and corrosion (tribocorrosion) mechanisms can take place affecting the performance of titanium-based implant and prostheses. Also, the formation of wear debris and metallic ions due to the tribocorrosion phenomena can become toxic for human tissues. This review gathers knowledge from areas like materials sciences, microbiology, and dentistry contributing to a better understanding of bio-tribocorrosion processes in the oral environment.

Tribocorrosion Behavior of Calcium- and Phosphorous-Enriched Titanium Oxide Films and Study of Osteoblast Interactions for Dental Implants

Abstract: Titanium (Ti) dental implants are frequently exposed simultaneously to a corrosive environment and cyclic micromovements at implant/abutment and implant/bone interfaces, becoming part of a tribocorrosion system Thus, wear debris and corrosion products/ions can be released to peri-implant tissues and induce inflammatory reactions leading to implant failure Moreover, the poor osseointegration is also one of the main problems affecting dental implants lifetime Surface modification strategies have been proposed to design novel Ti oxide-based multifunctional surfaces that are able to simultaneously improve cellular functions and provide enhanced tribocorrosion resistance Hence, the main objective of this work was the synthesis of Calcium (Ca)- and Phosphorous (P)-enriched Ti oxide films aimed to display superior wear/corrosion performance and simultaneously, to enhance osteoblast–material interactions Ca- and P-enriched films were synthesized by plasma electrolytic oxidation (PEO) and their characteristics were assessed by Field emission scanning electron microscopy, profilometry, energy-dispersive X-ray spectroscopy, X-ray diffraction, and water contact angle measurements PEO-treated samples were subjected to pin-on-disk reciprocating sliding tests in artificial saliva at 37 °C The viability of MG63 cells cultured on PEO-treated samples was investigated by MTT assay, and their adhesion ability by SEM and confocal laser scanning microscopy The wear/corrosion behavior of Ti was improved after PEO treatments and the electrolyte composition appeared to play a crucial role both on its corrosion tendency and mechanical wear resistance It is believed that this improvement is related to the higher rutile/anatase ratio exhibited by Ca- and P-enriched surfaces Osteoblasts were well spread on these surfaces displaying improved viability/proliferation compared to Ti

Wear and Corrosion Behavior of Al–Si Matrix Composite Reinforced with Alumina

Abstract: Al–Si alloy matrix composites reinforced with different weight fractions of Al2O3 particles up to 25 wt% were fabricated by stir casting method. The effect of weight fraction of Al2O3 and heat treatment on the wear behavior of Al–Si alloy and its composites was investigated. The results showed that wear resistance of the investigated composites was improved by heat treatment and Al2O3 particles addition. The effect of heat treatment on the corrosion behavior of composites compared with its matrix in 3.5 % NaCl at 600 rpm using electrochemical potentiodynamic polarization test was also investigated. The corrosion resistance of the composites with 10, 15, and 20 % Al2O3 particles was higher than that of the matrix alloy. Heat treatment of Al–Si alloy and its composites resulted in marked improvements in the corrosion resistance as compared with these materials in the as-cast condition.

The Synergistic Effects of Cavitation Erosion-Corrosion in Ship Propeller Materials

Abstract: Synergy tests were performed for two most common propeller materials, duplex stainless steel (DSS) and nickel aluminium bronze (NAB), by means of an indirect ultrasonic vibratory system. Tests were conducted for pure cavitation erosion in distilled water, pure corrosion using in situ electrochemistry under 3.5 % NaCl solution and a combination of cavitation erosion–corrosion to understand the overall synergism existing between the two. The results were analysed using gravimetric as well as volumetric analysis. Alicona and Talysurf were employed for the surface topography, and scanning electron microscope was used to see the microstructural morphologies of the samples under different conditions. As a result, the electrochemical tests held at open circuit potential showed that, although DSS exhibited higher resistance to corrosion under seawater alone, NAB exhibited much higher resistance to corrosion when subjected to cavitation. From the experiments conducted, it was concluded that synergy had measurable impact on the cavitation erosion–corrosion of both NAB and DSS. NAB was found to be more susceptible to erosion under both the conditions as compared to DSS with prominent selective cavitation erosion of alpha phase in the microstructure. The overall synergism of NAB was found to be higher than that of DSS.

Wear and Corrosion Behavior of High-Cr White Cast Iron Alloys in Different Corrosive Media

Abstract: This study aims to investigate the effect of Cr/C ratio on wear and corrosion behavior of a group of high-Cr white cast iron (HCCI) alloys. Three different alloys of HCCI with different chemical compositions were tested against 3.5 % NaCl, 0.5 M H2SO4, and 0.5 M NaOH solutions as corrosive media. Electrochemical polarization technique has been used to determine the corrosion current density. The microstructure characteristics of HCCI alloys were analyzed by using optical microscope, SEM, EDS, and XRD. XRD analysis reveals that the microstructure of the HCCI alloys is composed of a network of chromium-rich carbides (M7C3) in an austenitic matrix. The abrasive wear resistance of HCCI alloys was found to be rely on their chemical composition and microstructure. The corrosion resistance of the HCCI alloys strongly depends on the Cr/C ratio and the ratio of chromium content in the M7C3 carbide to that in the matrix (CrM7C3/Matrix). The experimental results of this study showed that the alloy HCCI-2 with the lower Cr/C ratio exhibited the lowest abrasive wear loss while the alloy HCCI-1 with higher Cr/C ratio exhibited the highest abrasive wear loss. On the other hand, the HCCI-1 alloy was the most corrosion resistant and revealed the lowest current density. In addition, the corrosion current density of all specimens is elevated in 0.5 M H2SO4 solution in comparison with 3.5 wt% NaCl and 0.5 M NaOH solutions.

Corrosion Inhibition of Carbon Steel in 1 M Sulphuric Acid Solution by Extract of Eucalyptus globulus Leaves Cultivated in Tunisia Arid Zones

Abstract: The corrosion inhibition effect of the methanolic extract of Eucalyptus globulus leaves as an eco-friendly green inhibitor for corrosion control of carbon steel in 1 M H2SO4 solution was studied using weight loss measurements and different electrochemical methods. It was found that E. globulus extract acts as a strong inhibitor. Results showed that this compound acts as a mixed-type inhibitor. As the inhibitor concentration increased, the charge transfer resistance of carbon steel increased and double layer capacitance decreased. The results of weight loss measurements were in good agreement with other electrochemical methods results. It was found that this green inhibitor acts through adsorption on the metal surface. In addition, adsorption obeys the Langmuir isotherm.

Mechanical Strength and Wear of Dental Glass-Ionomer and Resin Composites Affected by Porosity and Chemical Composition

Abstract: The main aim of this study was to evaluate the influence of porosity, microstructure, and chemical composition on the wear and compressive strength of dental glass-ionomer or resin composite. Cylindrical samples (6 × 4 mm) were prepared from a nano-hybrid resin composite (Grandio®SO/RC, VOCO), a resin-modified glass ionomer (Vitremer™/VI, 3 M-ESPE) and a conventional glass ionomer (Ionofil®Molar/CO, VOCO). Porosity and topography of the materials were evaluated by optical and scanning electron microscopy (SEM). Roughness was evaluated by R a and R t parameters at 0.1 mm/s under cut-off of 0.8 mm. Then, compressive tests were performed at 1 mm/min. Wear tests were carried out at 20 N, 2.5 mm of displacement, at 1 Hz for 90 min in artificial saliva solution. The results were statistically analyzed with a one-way ANOVA and Tukey’s test (p < 0.05). Resin composite revealed a significantly lower porosity (1.21 ± 0.20 %) than glass-ionomer restoratives (5.69–7.54 %) as well as lower values of R a and R t roughness (p < 0.05). Also, resin composite showed significantly higher values of mechanical strength (334 ± 15.9 MPa) compared to conventional (78.78 ± 13.30 MPa) or modified glass ionomer (169.50 ± 20.98 MPa) (p < 0.05). For maximal depth of wear, resin composite also showed significantly lower values than glass ionomer (p < 0.05). Homogeneous wear morphology was noticed by SEM analyses on glass ionomers in opposition to resin composite. Glass ionomers showed a poor mechanical behavior associated to a high porosity and wear rate when compared to resin composite.

Synthesis, Characterization and Anticorrosion Studies of New Homobimetallic Co(II), Ni(II), Cu(II), and Zn(II) Schiff Base Complexes

Abstract: New homobinuclear Co(II), Ni(II), Cu(II), and Zn(II) complexes with Schiff base (H 2 L,1) have been synthesized and investigated using physicochemical techniques viz. IR, 1H NMR, 13C NMR, ESR, UV–Visible spectrometric methods, thermal gravimetric analysis, and magnetic moment measurements. The corrosion inhibition studies of the compounds on mild steel in (0.5 M) HCl have been investigated by weight loss, potential dynamics polarization, and scanning optical microscope. The adsorption of compounds was founded to obey the Langmuir adsorption isotherm model showing mixed type inhibition behavior. The in vitro antibacterial studies of the complexes against sulfate-reducing bacteria proved them as growth inhibiting agents.

Wear and Electrochemical Corrosion Behavior of Biomedical Ti–25Nb–3Mo–3Zr–2Sn Alloy in Simulated Physiological Solutions

Abstract: The wear and electrochemical corrosion behavior of the biomedical Ti–25Nb–3Mo–3Zr–2Sn (TLM) titanium alloy was investigated in various simulated physiological solutions. Different simulated physiological solutions comprised phosphate-buffered solution (PBS), PBS with bovine serum albumin (PBS+BSA), and PBS with hyaluronic acid (PBS+HA) were employed. A potentiostat and a reciprocating friction and wear tester were used to study the wear and corrosion behavior of the TLM alloy. The influence of the chemical composition of the simulated solutions on the tribo-electrochemical behavior was considered by potentiodynamic studies under reciprocating friction and wear conditions. It was found that the corrosion tendency of the TLM alloy was the most obvious in PBS+HA under static corrosion condition, while it was just opposite with wear. Compared with static corrosion, the corrosion resistance of the TLM alloy was decreased with sliding conditions. The values of i corr were two orders of magnitude higher than those at static corrosion. This phenomenon shows that the wear accelerated corrosion. Under coexisting condition of both electrochemical corrosion and wear, the wear rate of the TLM alloy mutually influenced by both factors will be accelerated. Plastic grooves and deformation were observed on the worn surfaces of the TLM alloy by scanning electron microscopy (SEM). Through the observation of SEM, the tribological mechanism was a typical corrosive wear, and the main wear mechanisms were abrasive with adhesive wear under the interaction between corrosion and wear. The XPS results show that the passive films include the TiO2, ZrO2, Nb2O5, Mo2O5, and Sn2O3.

Effect of Impacting Particle Kinetic Energy on Slurry Erosion Wear

Abstract: In the present investigation, the effect of kinetic energy of different materials of the same-sized solid particles is examined on copper as target material using slurry pot tester. Quartz, Silicon carbide and Alumina are the impacting solid particles used for conducting trials. It is understood that the kinetic energy and stress concentration of impacting particles on target surface are responsible for material removal from the target surface, also the effect of erodent property like its shape and density is more dominant at shallow impact angles compared to higher impact angles. However, it is reported in literature that the exponent of velocity varies from 1.87 to 4.00 for ductile materials. Thus, different materials with the same-sized solid particles at constant kinetic energy were used to conduct the experiments. It is observed that for three different materials mass loss for the same mean particle size is nearly constant at 90° orientation angle but variation is found in 30° orientation angle. Further, the SEM micrographs of these solid particles show that alumina have sharp edges and angular nature. Silicon carbide is sub-angular in nature while quartz is blocky in nature. SEM micrographs of eroded surfaces show that at shallow impact angles the material is mainly removed by the platelet mechanism and material is displaced in the direction of flow. Also it is observed that increasing the velocity for quartz particle increases the crater length as compared to other two materials. Erosion wear was found more when alumina are used as the impacting particle due to their angular nature. At normal impact, indentation craters with rim are observed with significance increase in crater size when quartz is used as impacting particles.

Tribocorrosion Behavior of Ti6Al4V Coated with a Bio-absorbable Polymer for Biomedical Applications

Abstract: The modification of titanium-based surfaces has been recently studied to accelerate the osseointegration process of endosseous implants. Indeed, bioabsorbable polymer veneers carrying antimicrobials or bone growth factors to the implant–bone interface could enhance such osseointegration process. The main aim of this work was to study the tribocorrosion behavior of veneering biodegradable poly(d,l-lactide) on titanium surfaces in an artificial saliva solution. Cylinders of Ti6Al4V were prepared by grit-blasting with 250-µm alumina particles followed by HF/HNO3 etching technique to increase the roughness of the top surface. After surface modification and cleaning, the rough surface was covered with poly (d,l-lactic acid) (PDLLA) by spin-coating technique. Reciprocating sliding tests were performed against an alumina ball at a normal load of 0.5 N, a sliding frequency of 1 Hz, and linear displacement amplitude of 3 mm using a tribometer. The sliding tests associated to open-circuit potential (OCP) measurements were performed in artificial saliva solution to mimic the oral conditions for 60 min. After tribocorrosion tests, the worn surfaces were inspected by scanning electron microscopy. The results revealed a lower coefficient of friction (COF) on PDLLA than that recorded on Ti6Al4V. A protective effect of PDLLA against wear and corrosion of Ti6Al4V was noticed on the reciprocating sliding under OCP measurements for 60 min. Furthermore, a gradual degradation of PDLLA was detected, which could be useful in situ to release of therapeutic substances to be incorporated into the bioabsorbable polymer.

Synergistic Erosion and Corrosion Behavior of AA5052 Aluminum Alloy in 3.5 wt% NaCl Solution Under Various Impingement Angles

Abstract: Erosion–corrosion behavior of AA5052 aluminum alloy was studied in 3.5 wt% NaCl solution containing silica sand as erodent particle. The tests were carried out according to ASTM G119-09 standard using a slurry jet apparatus at a jet velocity of 3 m/s, sand concentration of 90 g/l, and various impingement angles of 25°–90°. The pure erosion rates were also obtained using cathodic protection of the samples during erosion–corrosion tests. Results showed that maximum pure erosion and erosion–corrosion rates occurred at impingement angle of 30°. On the other hand, a negative synergism rate was obtained under all conditions tested. Energy dispersive spectrometry analysis suggested that the negative synergism could be attributed to the existence of a protective oxide layer formed on the eroded surface of the samples during erosion–corrosion tests. Results also showed that corrosion rates during flow corrosion (i.e., no sand) and erosion–corrosion were much higher than the pure corrosion rate in a stagnant condition. Furthermore, there almost was no change in the corrosion rates at various impingement angles of 25°–90°. Scanning electron micrographs showed erosion features like raised lips and wear tracks at the impingement angle of 30°, and plastic deformation due to particle impact at the impingement angle of 90°.

Mechanical and Electrochemical Synergism of API X42 Pipeline Steel During Erosion–Corrosion

Abstract: Hydro-transportation is an economic and flexible way to transport natural resources such as oil and gas from excavation to the extraction plants, refineries, and consumer-ready products to markets. However, interaction between solid particles, corrosive fluid, and target material often results in significant mutual reinforcement due to the combined action of erosion and corrosion. In this study, erosion–corrosion behavior of API pipeline steel has been assessed in 2 g l−1 NaCl solution purged with CO2 as the corrosive media and aluminum oxide as the erodent. Four different particle velocities (36, 47, 63, and 81 m s−1) were employed, while the angle of incidence was kept constant at 90°. The synergism between erosion and corrosion has been studied by means of a newly designed test approach to mitigate the limitations of the in situ method and to identify the effect of erosion on corrosion and vice versa. The corrosion process was monitored using potentiodynamic polarization and weight loss measurements. Total material loss rate and the components of erosion, corrosion, and their synergistic interactions have been determined. Scanning electron microscopy examination and experimental results show that there is an immense correlation between erosion and corrosion. Significant synergism was observed due to the interaction of different erosion and corrosion mechanisms.

Tribocorrosion Mechanisms of Ti6Al4V in Artificial Saliva by Zero-Resistance Ammetry (ZRA) Technique

Abstract: Degradation mechanisms of biomedical alloys involve two different phenomena, corrosion and wear, which simultaneously act and may cause the failure of implants and prosthesis. In this work, tribocorrosion of Ti6Al4V biomedical alloy in artificial saliva is studied at open circuit potential (OCP) by a new electrochemical technique that allows measuring the galvanic potential and current between the wear track (anode) and the passive material (cathode) through zero-resistance ammetry. The experimental set-up was conceived for physically separating the depassivated area from the passive material, thus allowing to quantify the mechanically activated corrosion at OCP. Two different counterparts, SiC and Al2O3, were used against the Ti6Al4V alloy in order to analyse the influence of the initial contact pressure on the tribocorrosion mechanisms. A galvanic model based on the cathodic reaction kinetics can describe the current and the potential evolution with time during sliding. It has been observed that at the highest initial contact pressures, wear follows the Archard law, while at lower contact pressures, third body appeared and wear can not be described by the Archard law. Quantification of the evolution of the depassivated wear track with time was obtained and the deviation from the Archard predictions was analysed.

Tribocorrosion Behavior of Duplex S/Cr(N) and S/Cr(C) Coatings on CoCrMo Alloy in 0.89 % NaCl Solution

Abstract: In the present study, magnetron sputtering was used to deposit two types of duplex coatings, S/Cr(N) and S/Cr(C), onto ASTM F75 CoCrMo cast alloy, aiming at improving the tribocorrosion behavior of the medical alloy The duplex coatings were fabricated and structured such that the inner layer comprised carbon S phase with a CoCrMo matrix by sputtering a CoCrMo alloy target in the presence of carbon containing atmosphere The duplex coatings were found to be elastically compatible with the CoCrMo alloy, and possess higher hardness and a larger hardness-to-modulus ratio than the uncoated alloy Tribocorrosion tests were conducted in 089 % NaCl solution at 37 °C under elastic contact and unidirectional sliding conditions The results showed that the duplex S/Cr(N) coating was very effective in improving the tribocorrosion behavior of the alloy at all applied potentials, in terms of reduced friction and much improved resistance to total material loss (TML) by up to more than one order of magnitude On the other hand, the duplex S/Cr(C) coating was effective only at open circuit and anodic potentials (APs), but not at cathodic potentials The uncoated alloy exhibited low friction and low TML at a large cathodic potential and experienced peculiar frictional behavior at the tested AP The results are discussed in terms of material transfer, hydrogen charging, third body effects, and synergism between wear and corrosion

Micro-abrasion-corrosion Maps of 316L Stainless Steel in Artificial Saliva

Abstract: The role of salivary media is essential during mastication and ingestion processes; yet it can hinder the performance of foreign materials in the oral cavity. The aim of this study was to examine the effects of applied load and applied electrical potential on the tribo-corrosion mechanisms of 316L stainless steel in an environment similar to oral cavity conditions. 316L stainless steel is a material commonly used in dentistry for orthodontic braces, wires and in some cases as dental crowns. This is due to its favourable corrosion resistance. Relatively few studies have examined the materials performance in an oral environment. The results of this work were used to generate polarisation curves and wastage and mechanism maps to describe the material’s tribo-corrosion behaviour. A significant difference in corrosion current densities was observed in the presence of abrasive particles suggesting the removal of the protective chromium oxide passive film. It was found that the corrosion resistant nature of 316L stainless steel resulted in a wear mechanism which was micro-abrasion dominated for all test conditions.

Combined Influence of Fluoride and Biofilms on the Biotribocorrosion Behavior of Titanium Used for Dental Applications

Abstract: Dental implant failures occur mainly due to biofilm infections and mastication micro-movements or load stresses that may induce wear degradation. Dental implants' microgaps are highly susceptible areas for bio- film formation and fluoride retention. Although fluoride is an antimicrobial agent widely used in caries prevention, its influence on biofilms under sliding wear remains unknown. The main aim of this work was to assess the effect of mixed biofilms and fluoride on the tribocorrosion behavior of titanium. Streptococcus mutans and Candida albicans mixed biofilms were cultured for 8 days on ground and polished commercially pure titanium. Biofilms' formation was influenced by topography: higher roughness surfaces presented higher levels of biomass. Reciprocating sliding tests were performed on both surfaces, with and without biofilms, immersed in artificial saliva in the absence or presence of fluoride (30 and 227 ppm F - ). The low friction coefficient registered indicated the lubricating effect of biofilms on titanium surfaces. Fluoride was also found to have lubricating properties on titanium during sliding, probably due to the precipitation of calcium fluoride (or like) salts. The presence of fluoride influenced the biotri- bological behavior of titanium surfaces covered with biofilms, facilitating their structural disruption and detachment. Nevertheless, open circuit potential tests reduced the corrosion of titanium in the presence of fluo- ride (227 ppm F - ) and biofilms. In conclusion, it is

Design, Development, and Testing of a Compact Tribocorrosion Apparatus for Biomedical Applications

Abstract: Orthopedic and dental implants experience the synergistic effect of wear and corrosion, i.e., tribocorrosion, which has been a major contributor to the premature failure of implants. This work focuses on the development of a compact and cost-effective tribocorrosion apparatus for the investigation of fretting and wear. The custom-built apparatus is validated with an analysis of the tribocorrosion behavior of Ti–6Al–4V disks in artificial saliva (pH = 6.5, T = 37 °C). Electrochemical impedance spectroscopy, potentiodynamic, free potential, and potentiostatic analyses were used for electrochemical characterization of Ti–6Al–4V disks. White light interferometry and scanning electron microscopy were used to analyze wear scars on the Ti–6Al–4V disks. Total wear loss was calculated to be 12.4 ± 1.5 µg, and the synergistic weight loss ratio (0.78 ± 0.1) showed that Ti–6Al–4V disks experience synergy of wear and corrosion, with wear being the dominant component.

Tribocorrosion Behavior of Overlay Welded Super Duplex Stainless Steel in Chloride Medium

Abstract: The tribocorrosion behavior of super duplex stainless steel overlay weldment, sliding against alumina counterpart in a pin-on-disk tribometer in 1 M NaCl solution, was investigated under open circuit potential and potentiostatic conditions. The results demonstrated the significant effect of applied potential on the tribocorrosion behavior; by shifting the potentiostatic potential from cathodic to anodic range, the material degradation increased due to the introduction of synergistic wear-accelerated corrosion. Moreover, by shifting from cathodic to anodic potentiostatic polarization, the wear track became smoother and the coefficient of friction decreased. Although some evidences of corrosion-accelerated wear, such as occasional corrosion pits as well as reduction of work hardening inside the wear track, were observed, based on the synergistic approach followed, it was inferred that the dominant degradation components of the overlay welded specimen were sequentially wear and wear-accelerated corrosion.

Influence of Electrochemical Potentials on the Tribological Behavior of Silicon Carbide and Diamond-Coated Silicon Carbide

Abstract: Due to their high corrosion stability in combination with advantageous tribological performance, sintered silicon carbide ceramics are widely used in industrial applications. Both the corrosion stability and the tribological behavior can be affected by electrochemical processes. Tribological investigations were carried out using an electrochemical three electrode setup. The influence of electrochemical potentials on the friction and wear behavior of different sintered SiC materials in 1 M NaCl-solution was investigated to analyze the complex interplay between mechanical, chemical, and electrochemical interactions during tribo-corrosion. The results revealed that friction and wear of SiC were decreased under cathodic electrochemical polarization depending on the material composition. In addition, tribological tests at different electrochemical potentials showed that the coefficient of friction can be switched immediately. The results indicated that the tribological behavior is strongly affected by the increased double-layer repulsion due to the electrochemical potentials, which supports the hydrodynamic lubrication.

Three-Body Abrasion Corrosion Studies of High-Cr Cast Irons: Benefits and Limitations of Tribo-electrochemical Methods

Abstract: High-Cr white cast irons (WCIs) are multiphase alloys commonly used in aqueous industrial environments in applications that require both high abrasion and high corrosion resistance. Various electrochemical techniques can be useful in elucidating tribocorrosion characteristics of metallic materials undergoing wear in a corrosive environment. This study is focused on the interpretation of electrochemical measurements applied to three-body abrasion corrosion contacts of high-Cr WCIs. Particular attention has been paid to determine whether tribo-electrochemical data can pick up any effects that the multiphase microstructure of WCIs may have on the tribocorrosion characteristics, especially in environments containing chloride ions. Since both wear and corrosion of multiphase alloys are usually not uniform, their tribocorrosion behaviour is difficult to study and is still poorly understood. The experimental results are discussed in terms of benefits and limitations of tribo-electrochemical techniques such as polarization (potentiostatic, potentiodynamic) and electrochemical noise (galvanic coupling, potentiostatic) in studying abrasion corrosion behaviour of high-Cr WCIs. The application of high-resolution surface analysis techniques (microprobe, NanoSIMS, C-AFM and SKPFM), used in support of the electrochemical data interpretation, is also demonstrated.

Analysis of Tribo-corrosion Properties of MAO/DLC Coatings Using a Duplex Process on Ti6Al4V Alloys

Abstract: In recent years, various technologies have been increasingly investigated for the surface modification of Ti and Ti alloys. Microarc oxidation (MAO) is one of the effective techniques to improve surface properties. However, it has some disadvantages for sliding wear applications and/or aggressive environments. In this study, the combined MAO and closed field unbalanced magnetron sputtering process was used to deposit duplex MAO/diamond-like carbon (DLC) coatings on Ti6Al4V alloy. Analysis of the microstructures, morphology, and crystallographic structure were performed by using a SEM, Raman, and XRD. The wear, corrosion, and tribo-corrosion properties of the coatings were investigated using the pin-on-disk wear test, potentiodynamic polarization test, and combining tribo-corrosion test unit, respectively. The results of this study have shown that duplex MAO/DLC coatings exhibit better wear, corrosion, and tribo-corrosion properties than the DLC or MAO monolayer on Ti6Al4V alloy substrate. MAO/DLC coatings exhibited dense structure, lower coefficient of friction and corrosion current density, and higher tribo-corrosion resistance. The results have also shown that MAO/DLC duplex coatings on Ti6Al4V substrates increased the tribo-corrosion resistance by acting as a barrier layer.

Temporomandibular Joint Replacement Device Research Wear and Corrosion Technology Transfer from Orthopedics

Abstract: The general requirements for joint replacement devices emphasizes the importance of device material biocompatibility, with no inflammatory or toxic response to wear beyond a tolerable level, the appropriate mechanical properties for the desired application, and lastly economically viable manufacturing and processing methods. Implicit in these requirements is the importance of understanding wear and failure mechanisms of implanted devices. However, compared to orthopedic total joint replacement (TJR) devices, functional wear failure mechanisms for temporomandibular joint (TMJ) TJR implants have not been clearly defined. Our research group has started initial translational investigations involving the analysis of failed retrieved TMJ TJR devices alloy microstructure compared to control, never implanted, TMJ TJR devices utilizing established orthopedic TJR device retrieval tribocorrosion evaluation protocols. This and future studies will guide future material choices and functional design improvements for TMJ TJR devices. Orthopedic TJR implant schemes may also be improved by understanding the degradation mechanism of TMJ TJR implants, as the materials employed in both TJR devices are similar.

Atmospheric Pressure Plasma Jet Treatment of Human Hair Fibers

Abstract: Human hair fibers in virgin and dyed forms were treated with atmospheric pressure helium, helium/oxygen, argon, and argon/oxygen plasma jets at 20 W of power. The effects of 10-min plasma treatment on surface morphology and chemistry were studied by scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. The plasma treatment was quite effective for removing the organic residues from the surface and creating oxidized functional groups. Helium plasma had a mild cleaning effect on the surfaces while argon/oxygen plasma had the strongest corrosive effect. Mild hydrogen peroxide treatment for the same duration had neither the cleaning nor the oxidizing power of the plasma jets. These types of plasma jets have the potential to replace peroxide treatment. The corrosive jets can be used to restore dyed hair fibers. In addition, the jets can be used to clean the surfaces of hair fibers to prepare samples for analytical investigations where the organic residues may induce problems.

Does Surface Topography Improve Electrochemical Behavior of Ti-6Al-4V Alloy in Different Saliva pH Levels?

Abstract: The objective of this study was to evaluate the corrosion kinetics and microstructural change of a Ti–6Al–4V alloy with machined and treated surfaces (sandblasted with aluminum oxide or double acid-etched) at three salivary pH levels. For an electrochemical test (n = 5), open-circuit potential and electrochemical impedance spectroscopy analyses were conducted in artificial saliva at pH 3, 6.5, and 9 in the three types of Ti–6Al–4V surfaces. The capacitance (CPE) and the polarization resistance (R p) of the titanium oxide layer were determined. Disk surfaces were characterized using scanning electron microscopy, atomic force microscopy, and profilometry, which provided the surface roughness (Ra) of the disks before (baseline) and after the electrochemical test. The corrosion parameters were compared by two-way ANOVA. One-way ANOVA was applied for analyzing Ra values of the specimens before and after the electrochemical process. For results that were statistically significant, the Tukey HSD test was used. The level of significance used for all tests was 0.05. The highest value of R p was observed on disks with machined surfaces and treated with double acid-etching (p = 0.264), which was independent of the salivary pH level. Sandblasting decreased the R p of Ti–6Al–4V at all pH levels (p < 0.05). The machined surface showed the lowest CPE, followed by the surfaces treated with double acid-etching, and the highest values were observed for the sandblasting (p < 0.05), which were all independent of the pH. It was concluded that a higher corrosion process was observed in the Ti–6Al–4V alloys surface sandblasted with aluminum oxide. Acidic pH tended to reduce total impedance values. Acid-etching may be a suitable treatment for dental implants as it provides good corrosion resistance and increased contact area for bone adhesion.

Influence of Molybdenum on Tribo-Corrosion Behavior of 316L Stainless Steel in Artificial Saliva

Abstract: The influence of molybdenum on the tribo-corrosion behavior of 316L stainless steel in artificial saliva was investigated using potentiodynamic polarization curve, electrochemical impedance spectroscopy and sliding wear testing. The results showed that the passive capability of 316L stainless steel in artificial saliva was enhanced with increasing Mo. The anti-corrosion property of the passive film on 316L stainless steel was improved with increasing Mo via increasing transfer resistance of the passive film. Sliding wear testing results showed that the friction coefficient of 316L stainless steel in artificial saliva decreased with the increased Mo.

Methodology development for investigation of slurry abrasion corrosion by integrating an electrochemical cell to a miller tester

Abstract: Material losses in slurry handling systems constitute a significant fraction of cost in oil sands, mining, and mineral processing operations. It is thus important to better understand wear attack mechanisms and major factors affecting wear in such applications. In this work, a methodology and a testing system have been developed to study the abrasion–corrosion synergism during slurry abrasion based on a Miller test machine by incorporating a three-electrode electrochemical cell. The proposed methodology has then been validated experimentally using QT 100 steel. It has been shown that cathodic protection using such system setup is effective in suppressing the corrosion effect on the total material loss. In general, corrosion-induced enhancement on slurry abrasion loss rate increases with slurry corrosivity but inversely with sliding speed.

Torsional Fretting Wear Behavior of Duplex DLC Coatings Deposited on Ion Nitriding Treated LZ50 Steel

Abstract: Duplex ion nitriding/DLC coatings were prepared on LZ50 steel. Characterizations were detected by scanning electron microscopy, atomic force microscope, Raman spectroscopy, dynamic ultra-micro hardness tester, and profilometer. The torsional fretting wear behaviors of DLC coatings and substrate LZ50 steel against GCr15 steel ball in dry conditions were studied under angular displacement amplitudes within a range of 0.1°–5°, constant normal load of 50 N, and rotational speed of 0.8° s−1. DLC coatings presented dense structure and high hardness. Compared with the substrate, DLC coatings removed the mix fretting regime and shifted the slip regime to low angular displacement amplitudes. The friction torques of DLC coatings were lower than that of the substrates. In the partial slip regime, the damage of DLC coatings was low. In the slip regime, the damage mechanism combined with delamination, abrasive wear, and graphitization. The DLC coatings exhibited good capability for anti-torsional fretting damage.

Pure Mechanical Wear Measurement of Carbon Steel in Oil–Water Fluids

Abstract: The pure mechanical wear (PMW) component of the corrosive wear of carbon steel (CS) in oil–water fluids was investigated by surface morphology and composition analysis after tests. Negative potential protection method and sacrificial anode (SA) of Zn–Al–Cd and Mg–Mn were used to eliminate the corrosion effect in oil–water fluids with different flow patterns and explore the optimal program for the PMW research. The influences of the area ratios of SA to CS samples on the PMW behaviour of CS samples were also studied. Experimental results demonstrated that the system of oil–NaHCO3 aqueous solution + SA of Mg–Mn was the best mean. The area ratio of SA to CS samples should be controlled within a proper range of 0.5–2.