Biocorrosion Rate Research Articles

ZrCuFeAlAg thin film metallic glass for potential dental applications

In this study, the application of a Ni-free Zr60.14Cu22.31Fe4.85Al9.7Ag3 thin film metallic glass (TFMG) was examined as an approach to retard the poor tribological properties of Ti-alloys for dental applications. The TFMGs were coated on biomedical Ti6Al4V substrate by single-target magnetron sputtering. The fretting resistance was assessed using a reciprocating tribo-tester against Si3N4 counterpart in air and in artificial saliva. Bio-corrosion resistance of TFMG-coated Ti6Al4V samples was tested via electrochemical polarizations and electrochemical impedance spectroscopy in artificial saliva. Biocompatibility of the TFMG was tested in vitro, in comparison with that of the Ti6Al4V alloy. The results showed that this TFMG not only possessed 1.8–2.8 times higher fretting resistance than the Ti6Al4V alloy under various tribological conditions, but also lower bio-corrosion rate and superior passive film. In-vitro assessments of cytotoxicity and cell adhesion indicated that the TFMG has no any cytotoxicity and well-flattened cell adhesion morphology, as good as the Ti6Al4V alloy. The present Ni-free Zr-based TFMG is expected to improve the lifetime and quality of biomedical implants or devices for dental applications.

Effect of severe plastic deformation and post-annealing on the mechanical properties and bio-corrosion rate of AZ31 magnesium alloy

Abstract In this work, the effect of fine grain sizes on the mechanical and bio-corrosion properties of AZ31 magnesium alloy was studied. Bio-corrosion refers to the accelerated degradation of metal within the human body. Fine-grained (~1.5 µm) AZ31 was obtained through Severe Plastic Deformation (SPD) via three cycles of Constrained Groove-Pressing (CGP) under elevated temperature. The effects of CGP and post-annealing (at 473 K for 15 and 30 min) on bio-corrosion were preliminarily investigated by potentiodynamic polarization measurements and constant immersion tests. Results obtained show that the as-processed samples with annealing exhibited improvements in yield strength and ductility while the bio-corrosion rate in Hank’s solution remains fairly similar during the early stage.

The influence of the internal microbiome on the materials used for construction of the transmission natural gas pipelines in the Lodz Province

This paper presents investigation results of the influence of gas microbes on the biocorrosion rate of the materials used for gas pipelines construction in the Lodz Province. Samples of two types of carbon steel and cast iron were stored in the laboratory pipeline model reflecting the real conditions of working natural gas pipelines were. In the next step the influence of cathodic protection with parameters recommended for protection of underground structures was tested. Analyses of biological corrosion products generated on the test surface were carried out using a scanning electron microscope with an X-ray analyzer. The level of ATP was measured to confirm presence of the adsorbed microorganisms on the observed structures. Corrosion rates were determined by gravimetric methods. In the course of the study it was revealed that the rate of biocorrosion of steel is lower than that for cast iron. Our results also proved that the weight corrosion rate depends on the number of adhered microorganisms. In addition, it has been found that application of the carbon steel cathodic protection decreases its weight corrosion rate. The information obtained will help to increase the knowledge on the rate of biological corrosion causing losses/pits inside gas pipline.

Electrophoretic deposition of nano-zirconia coating on AZ91D magnesium alloy for bio-corrosion control purposes

Magnesium alloys are considered as potential biodegradable biomaterials in hard tissue implants. However, the fast degradation rate of these alloys in the biological environment causes failure of the implant just prior to the desirable time. In the present work, in order to decrease and curb the bio-corrosion rate of AZ91D Magnesium alloy, zirconia, which is classified as a biocompatible ceramic, was coated on the alloy surface through electrophoretic deposition (EPD) technique. The effects of alterations in the EPD parameters such as current density, duration time and ZrO2 particles concentration on coating properties including thickness, morphology and adhesion were then characterized. Moreover, the electrochemical behavior of the coated alloys is evaluated by means of potentiodynamic polarization, immersion test, and electrochemical impedance spectroscopy. The electrochemical results indicated that the corrosion resistance of the coated alloy is enhanced significantly and the obtained film can successfully control the bio-corrosion rate of AZ91D alloy.

Importance of oxide film in endovascular biodegradable zinc stents

A better understanding of the surface oxide film on biodegradable metals could lead to the design of smarter, surface-responsive biodegradable stents with good biocompatibility and controlled degradation rates at different stages of implantation. In this study, the surface finish of zinc was manipulated through different material processing conditions, including oxidation, electropolishing and anodization. Implant wires with oxide films of varying surface characteristics were degraded in a living organism by using a rodent model to understand their response to a biological endovascular environment. It was found that the degradation rate was mainly dependent on the quality and stability of oxide film. Defects/cracks in the oxide film structure appear to serve as local corrosion sites, and their increased density accelerates the biocorrosion rate.

Metallic zinc exhibits optimal biocompatibility for bioabsorbable endovascular stents.

Although corrosion resistant bare metal stents are considered generally effective, their permanent presence in a diseased artery is an increasingly recognized limitation due to the potential for long-term complications. We previously reported that metallic zinc exhibited an ideal biocorrosion rate within murine aortas, thus raising the possibility of zinc as a candidate base material for endovascular stenting applications. This study was undertaken to further assess the arterial biocompatibility of metallic zinc. Metallic zinc wires were punctured and advanced into the rat abdominal aorta lumen for up to 6.5months. This study demonstrated that metallic zinc did not provoke responses that often contribute to restenosis. Low cell densities and neointimal tissue thickness, along with tissue regeneration within the corroding implant, point to optimal biocompatibility of corroding zinc. Furthermore, the lack of progression in neointimal tissue thickness over 6.5months or the presence of smooth muscle cells near the zinc implant suggest that the products of zinc corrosion may suppress the activities of inflammatory and smooth muscle cells.

A study of microbial population dynamics associated with corrosion rates influenced by corrosion control materials

This research aims to analyze the variations of microbial community structure under anaerobic corrosive conditions, using molecular fingerprinting method. The effect of adding various materials to the environment on the corrosion mechanism has been discussed. In the initial experiment, sulfate-reducing bacteria (SRB) were inoculated in a series of batch culture flasks containing sterile growth media. Several testing coupons of mild steel were placed into the SRB-enriched columns, which contained excess sulfate and lactate. After incubating for 20 days, three materials (MgO2, H2O2 and NaOCl) were added into the flasks so as to observe the effects on biocorrosion rate. Microorganism composition change was observed from the diversity profile using the PCR–DGGE (polymerase chain reaction – denaturing gradient gel electrophoresis) method. The results showed that hydrogen peroxide (H2O2) prompted the microbial community to change quickly and easily and enhanced the corrosion rates of coupons (3–6 times faster than the control run). This fact suggested that adding H2O2 could inhibit biological activities initially; however, it ultimately caused more serious corrosion due to breaking down the protective layer, composed of mainly FeS. When MgO2 was added into the SRB-enriched culture, the corrosion rate on the mild steel test coupons was inhibited to one third of that in the control column. The DGGE profile analysis shows that SRBs were clearly inhibited for a long time (more than 100 days) after adding MgO2. The durability of the MgO2 reaction could be demonstrated by DGGE variations as well as water quality monitoring results.

Effects of secondary phase and grain size on the corrosion of biodegradable Mg–Zn–Ca alloys

The bio-corrosion behaviour of Mg-3Zn-0.3Ca (wt.%) alloy in simulated body fluid (SBF) at 37°C has been investigated using immersion testing and electrochemical measurements. Heat treatment has been used to alter the grain size and secondary phase volume fraction; the effects of these on the bio-corrosion behaviour of the alloy were then determined. The as-cast sample has the highest bio-corrosion rate due to micro-galvanic corrosion between the eutectic product (Mg+Ca2Mg6Zn3) and the surrounding magnesium matrix. The bio-corrosion resistance of the alloy can be improved by heat treatment. The volume fraction of secondary phases and grain size are both key factors controlling the bio-corrosion rate of the alloy. The bio-corrosion rate increases with volume fraction of secondary phase. When this is lower than 0.8%, the dependence of bio-corrosion rate becomes noticeable: large grains corrode more quickly.

Microstructure, mechanical property and in vitro biocorrosion behavior of single-phase biodegradable Mg–1.5Zn–0.6Zr alloy

Abstract The microstructure, mechanical property, and in vitro biocorrosion behavior of as-cast single-phase biodegradable Mg–1.5Zn–0.6Zr alloy were investigated and compared with a commercial as-cast AZ91D alloy. The results show that the Mg–1.5Zn–0.6Zr alloy had a single-phase solid solution structure, with an average grain size of 34.7 ± 13.1 μm. The alloy exhibited ultimate tensile strength of 168 ± 2.0 MPa, yield strength of 83 ± 0.6 MPa, and elongation of 9.1 ± 0.6%. Immersion tests and electrochemical measurements reveal that the alloy displayed lower biocorrosion rate and more uniform corrosion mode than AZ91D in Hank's solution. The elimination of intensive galvanic corrosion reactions and the formation of a much more compact and uniform corrosion film mainly account for the better biocorrosion properties of the Mg–1.5Zn–0.6Zr alloy than AZ91D.

Neem extract as an inhibitor for biocorrosion influenced by sulfate reducing bacteria: A preliminary investigation

This work investigates the inhibition effect of Neem (Azadirachta indica) extract on microbiologically influenced corrosion (MIC) of API 5L X80 linepipe steel by a sulfate-reducing bacterial (SRB) consortium. The SRB consortium used in this study included three phylotypes; Desulfovibrio africanus, Desulfovibrio alaskensis and Desulfomicrobium sp. Steel coupons were incubated in the presence of the SRB consortium without and with 4wt.% Neem extracts for different periods of time. The morphology, compositions of the interfaces and subsequent corrosive pitting were characterized with field emission scanning electron microscopy (FE-SEM) coupled with energy dispersive spectroscopy (EDS). In addition, electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR) and open circuit potential (OCP) were used to investigate the in situ corrosion behavior under the two different conditions. The results revealed that Neem extract has the capability to reduce the biocorrosion rate by approximately 50%. Neem has significantly reduced the propensity of linepipe steel to SRB caused MIC by minimizing the cell growth and has subsequently suppressed the sulfide productions, sessile cell density and biofilm development.

Investigation of the Microstructure and Bio-Corrosion Behaviour of Mg-Zn and Mg-Zn-Ca Alloys

Biomedical applications of magnesium alloys have attracted increasing attention due to their unique combination of advantages. However, the poor corrosion resistance is an obstacle to magnesium alloys being used as biodegradable materials. As zinc (Zn) and calcium (Ca) are non-toxic and recognized as nutritionally essential elements in the human body, in this study Zn and Ca were selected as alloying elements to produce suitable bio-corrosion properties. The grain size was reduced significantly from 141.4 μm to 97.3 μm by adding Ca. The bio-corrosion performance of the two alloys (Mg-3Zn and Mg-3Zn-0.3Ca) was characterized using immersion tests in simulated body fluid at 37 °C. The alloys were dominated by pitting corrosion. Heat treatment was used to alter the microstructure and influence further the corrosion rate. The correlation between microstructure and bio-corrosion rate was evaluated, in the light of the alloying elements and the heat treatment employed.

Corrosion resistance and cytotoxicity of a MgF2 coating on biomedical Mg–1Ca alloy via vacuum evaporation deposition method

To reduce the biocorrosion rate and enhance the biocompatibility by surface modification, MgF2 coatings were prepared on Mg–1Ca alloy using vacuum evaporation deposition method. The average thickness of the coating was about 0.95 µm. The results of immersion test and electrochemical test indicated that the corrosion rate of Mg–1Ca alloy was effectively decreased after coating with MgF2. The MgF2 coating induced calcium phosphate deposition on Mg–1Ca alloy. After 72 h culture, MG63 cells and MC3T3‐E1 cells were well spread on the surface of the MgF2‐coated Mg–1Ca alloy, while few cells were observed on uncoated Mg–1Ca alloy samples. In summary, MgF2 coating showed beneficial effects on the corrosion resistance and thus improved cell response of the Mg–1Ca alloy effectively and should be a good surface modification method for other biomedical magnesium alloys. Copyright © 2013 John Wiley & Sons, Ltd.

In Vivo and In Vitro Degradation Behavior of Magnesium Alloys as Biomaterials

The corrosion behavior of pure Mg, AZ31, and AZ91D were evaluated in various in vitro and in vivo environments to investigate the potential application of these metals as biodegradable implant materials. DC polarization tests and immersion tests were performed in different simulated body solutions, such as distilled (DI) water, simulated body fluid (SBF) and phosphate buffered solution (PBS). Mg/Mg alloys were also implanted in different places in a mouse for in vivo weight loss and biocompatibility investigations. The in vivo subcutis bio-corrosion rate was lower than the corrosion rate for all of the in vitro simulated corrosive environments. The Mg/Mg alloys were biocompatible based on histology results for the liver, heart, kidney, skin and lung of the mouse during the two months implantation. Optical microscopy and scanning electron microscopy were carried out to investigate the morphology and topography of Mg/Mg alloys after immersion testing and implantation to understand the corrosion mechanisms.

Modeling the rate of biocorrosion and the effects of redox-reactions of metals in water environment

Laboratory studies were conducted to assess the effectiveness of biocorrosion through oxygen diffusion in zinc metal in water environment. The present investigation was undertaken to determine the corrosion rate of zinc metal in water environment with respect to Plank-Nernst Equation modified to monitor and predict the biocorrosion rate through oxygen diffusion which resulted to biofilm formation. The modified developed mathematical model of Plank-Nernst equations to evaluate the corrosion rate of zinc metal upon the influence of oxygen diffusion in a flowing system was given as CR = 534w / DAtoeλ21 where l = 0.5 when compared with the normal corrosion rate equation, CR = 534w / DAtoeλ21 then the results obtained showed a good match. The biocorrosion rate of zinc metal was tested in salt and fresh water environment and the results obtained showed that corrosion was faster on zinc metal immersed in salt water environment than the fresh water environment; this was attributed to the physicochemical parameters of the salt/fresh water environment. Key words: Modeling, corrosion, redox-reaction, biocorrosion, metal, water environment.

Novel Magnesium-Nanofluorapatite Metal Matrix Nanocomposite with Improved Biodegradation Behavior

Designing and preparation of magnesium alloys with adjustable biocorrosion rates in the human body and precipitation ability of bone-like apatite layer have been of interest recently. Application of metal matrix composites (MMC) based on magnesium alloys might be an approach to this challenge. The aim of this work was fabrication and evaluation of biocorrosion and bioactivity of a novel MMC made of magnesium alloy AZ91 as matrix and fluorapatite (FA) nano particles as reinforcement. Biodegradable Magnesium-nano fluorapatite metal matrix nanocomposite (AZ91-20FA) was made via a blending-pressing-sintering method. In vitro corrosion tests were performed for evaluation of biocorrosion behavior of produced AZ91-20FA nanocomposite. The results showed that the addition of FA nano particles to magnesium alloy can reduce not only the corrosion rate in a simulated body environment but also accelerate the formation of an apatite layer.

Research activities of biomedical magnesium alloys in China

The potential application of Mg alloys as bioabsorable/biodegradable implants have attracted much recent attention in China. Advances in the design and biocompatibility evaluation of bio-Mg alloys in China are reviewed in this paper. Bio-Mg alloys have been developed by alloying with the trace elements existing in human body, such as Mg-Ca, Mg-Zn and Mg-Si based systems. Additionally, novel structured Mg alloys such as porous, composited, nanocrystalline and bulk metallic glass alloys were tried. To control the biocorrosion rate of bio-Mg implant to match the self-healing/regeneration rate of the surrounding tissue in vivo, surface modification layers were coated with physical and chemical methods.

A study on alkaline heat treated Mg–Ca alloy for the control of the biocorrosion rate

To reduce the biocorrosion rate by surface modification, Mg–Ca alloy (1.4 wt.% Ca content) was soaked in three alkaline solutions (Na 2HPO 4, Na 2CO 3 and NaHCO 3) for 24 h, respectively, and subsequently heat treated at 773 K for 12 h. Scanning electron microscopy and energy-dispersive spectroscopy results revealed that magnesium oxide layers with the thickness of about 13, 9 and 26 μm were formed on the surfaces of Mg–Ca alloy after the above different alkaline heat treatments. Atomic force microscopy showed that the surfaces of Mg–Ca alloy samples became rough after three alkaline heat treatments. The in vitro corrosion tests in simulated body fluid indicated that the corrosion rates of Mg–Ca alloy were effectively decreased after alkaline heat treatments, with the following sequence: NaHCO 3 heated < Na 2HPO 4 heated < Na 2CO 3 heated. The cytotoxicity evaluation revealed that none of the alkaline heat treated Mg–Ca alloy samples induced toxicity to L-929 cells during 7 days culture.

The Effect of Pre‐Processing and Grain Structure on the Bio‐Corrosion and Fatigue Resistance of Magnesium Alloy AZ31

Magnesium alloys are considered as candidate materials for temporary implants. Fatigue resistance and controllable rate of corrosion in bodily fluids are essential for such applications. The effect of the grain structure produced by hot rolling and equal channel angular pressing on the fatigue behaviour and the bio-corrosion rate were studied for alloy AZ31. The results suggest that mechanical processing can be used to control both properties.