Corrosion Rate Of Magnesium Alloy Research Articles

The effects of ECAP, Mn and Ca elements on the microstructure and corrosion properties of magnesium alloys were investigated

In this study, through reasonable composition design, three elements of Zn, Mn and Ca, which are harmless to human body, were selected for alloying magnesium. The effects of ECAP treatment on the microstructure and corrosion properties of Mg-4Zn-1Mn-0Ca, Mg-4Zn-1Mn-0.2Ca and Mg-4Zn-0Mn-0.2Ca alloys were studied. The corrosion mechanism of Mg-Zn-Mn-Ca alloys with different components in Simulated. Body fluid (SBF) was analyzed by weight loss method and electrochemical test. The grains and the second phase were refined by Equal Angular Channel Pressing (ECAP). It was found that after 8 ECAP deformations, the microstructure of the alloy was refined and more uniform than that of the extruded alloy. The corrosion resistance of the Mg-Zn-Mn-Ca alloy after ECAP deformation in simulated body fluids was studied by electrochemical testing techniques, immersion experiments and observation of the microstructure and morphology of corrosion products. The relationship between microstructure characteristics, the behavior of the magnesium metal matrix and the properties of corrosion products was revealed. The results show that the microstructure of the alloy is refined and the corrosion resistance is improved with the increase in extrusion passes in the SBF solution. The corrosion resistance of magnesium alloy after 8 ECAP deformation is the best, showing small Icorr and large Rt. With the extension of the soaking time, the surface of the alloy will form a passivation film, which will protect the matrix and avoid further corrosion of the alloy. It is found that in SBF, the corrosion of the alloy surface is mainly pitting, which indicates that Ca2+, HCO3- and HPO42- in SBF can reduce the corrosion rate of magnesium alloy.

Modulating the corrosion performance of magnesium alloys through hydroxyapatite coating

Magnesium and its alloys have attracted attention as medical bone implant materials due to their excellent biocompatibility, bone-like mechanical properties, and degradability. However, the clinical application of magnesium is limited by the fact that it corrodes too quickly in body fluids, leading to premature mechanical failure. Surface hydroxyapatite coatings can significantly reduce the initial corrosion of magnesium alloys, but suffer from the problems of non-dense coatings, many defects and poor adhesion strength to the substrate. In this study, we propose femtosecond laser construction of microemulsion cone structures on the surface of magnesium alloys to significantly enhance the densities and thicknesses of the coatings, as well as to improve the bonding strength of the coatings to the substrate, which ultimately reduces the corrosion rate. The corrosion rate of modified hydroxyapatite coating in simulated body fluid is only 0.146 mm/y, and it has the ability to rapidly induce hydroxyapatite mineralization and promote osteoblast proliferation. Furthermore, the surface morphology, chemical composition, and wettability of the laser-modified Mg alloy were analyzed. It was demonstrated that the microstructure and thin oxide layer formed on the surface of the magnesium alloy could provide more sites for HA nucleation, which promotes the deposition and growth of HA and the existence of a mechanical interlocking effect with the substrate. The application of femtosecond laser surface modification represents a rapid and efficacious approach to enhance the quality of hydroxyapatite coatings. This method has successfully controlled the corrosion rate of magnesium alloys with excellent biocompatibility, thereby overcoming potential obstacles to the use of magnesium alloys in clinical applications.

Prediction of electrochemical corrosion behavior of magnesium alloy using machine learning methods

The corrosion of magnesium (Mg) alloys is a major challenge in many industrial applications because of their extreme reactivity, this greatly limits their applicability. The traditional methods in the prediction of corrosion rate depend on experimental or empirical models that can be time-consuming and expensive. Besides how to integrate experiments with faster machine-learning approaches is still a challenge of research. In recent years machine learning (ML) algorithms have proved and promised better magnesium corrosion predictability. In this study, different training algorithms such as linear regression (LR), decision tree (DT), extra tree (ET), random forest (RF), K-nearest neighbor (KNN), extreme gradient boosting (XGBoost), and Artificial Neural Network (ANN) were used to develop and predict corrosion rate of magnesium alloys based on magnesium chemical alloy composition as independent input variables. The data used for model preparation and validation were obtained from literature and experimental studies respectively. The feature selection methods were used to identify the most important and influential input parameters for magnesium alloy thus Shapley Additive Explanations (SHAP) interpretation was employed in this manuscript to facilitate feature visualization of the model. The results of the study show that the random forest (RF) algorithm has the greatest prediction impact than other machine learning algorithms. The magnesium alloy corrosion prediction model provides a better ability for the prediction of magnesium corrosion alloys. The study demonstrates the potential of ML models in the prediction of the corrosion behavior of Mg alloys and these models can be used to optimize an alloy composition for designing improved corrosion resistance of new Mg alloys.

Preparation of Tannic Acid/Hyaluronic Acid Coating to Improve the Corrosion Resistance of Implant Material Based on AZ31B Magnesium Alloy

Magnesium (Mg) has good biocompatibility, making it suitable as an implant material. However, Mg has a high corrosion rate because of the reaction between magnesium implants and fluids in the human body. To lower the corrosion rate of magnesium alloys, it is necessary to perform a coating process using tannic acid (TA) and hyaluronic acid (HYA), as we have done in this study. TA, an active ingredient, is relatively inexpensive, easy to find, and can effectively reduce the degradation rate. SEM characterization showed that the TA–HYA layer was formed by chelation between the Mg and TA surfaces. Furthermore, adding HYA to the coating covered the cracks caused by the TA layer and increased the hydrophilic properties. In vitro corrosion tests using Tafel polarization showed that the TA–HYA coating reduced the corrosion rate of the magnesium alloy from 7.379 mm/year to 0.204 mm/year. The immersion test in the SBF solution showed that the TA–HYA layer could bind Mg2+, which is beneficial for new bone growth.

Electrochemical behavior of the double-layer diamond-like carbon/plasma electrolytic oxidation on AZ31 alloy: A comparison of different PEO interlayers

In the present study, a double-layer diamond-like carbon (DLC)/plasma electrolytic oxidation (PEO) coating was developed on the AZ31 substrate and its electrochemical behavior was studied. In this regard, after fabrication of PEO coatings using two different electrolytes (silicate (PEOSi) and phosphate (PEO-Ph) compounds), DLC thin films were synthesized on the substrates using the radio frequency plasma-enhanced chemical vapor deposition (RFPECVD) method. Results showed the successful formation of thin and crack-free DLC layer with the thickness of about 1 μm on the middle PEO layers. However, the structure and chemical stability of the final DLC layer was dependent on the PEO composition. Moreover, the electrochemical studies in buffer phosphate saline (PBS) at the normal body temperature (37 ± 0.5 °C) showed that while both PEO-Ph and PEO-Si layers significantly decreased the corrosion rate of substrate, PEO-Ph revealed better electrochemical performance. On the other hand, DLC/PEO-Si was more effective than DLC/PEO-Ph to decrease the corrosion rate of substrates owing to the greater bonding of DLC coating on PEO-Si layer. In summary, crack-free DLC/PEO coatings could be a promising candidate to prevent from the high corrosion rate of magnesium alloys, making it appropriate for biomedical applications.

Prediction of Mg Alloy Corrosion Based on Machine Learning Models

Magnesium alloy is a potential biodegradable metallic material characterized by bone-like elastic modulus, which has great application prospects in medical, automotive, and aerospace industries owing to its bone-like elastic modulus, biocompatibility, and lightweight properties. However, the rapid corrosion rates of magnesium alloys seriously limit their applications. This study collected magnesium alloys’ corrosion data and developed a model to predict the corrosion potential, based on the chemical composition of magnesium alloys. We compared four machine learning algorithms: random forest (RF), multiple linear regression (MLR), support vector machine regression (SVR), and extreme gradient boosting (XGBoost). The RF algorithm offered the most accurate predictions than the other three machine learning algorithms. The input effects on corrosion potential have been investigated. Moreover, we used feature creation (transforming chemical component characteristics into atomic and physical characteristics) so that the input characteristics were not limited to specific chemical compositions. From this result, the model’s application range was widened, and machine learning was used to verify the accuracy and feasibility of predicting corrosion of magnesium alloys.

In vivo comparison of the degradation and osteointegration properties of micro-arc oxidation-coated Mg-Sr and Mg-Ca alloy scaffolds.

Magnesium (Mg) alloy have biodegradation and mechanical properties that are similar to those of human bone, making it a promising candidate material for inclusion in implantable medical devices. The osteointegration effect of Mg alloy scaffolds with different corrosion rates were studied and evaluated in large bone defect models. Mg-Sr and Mg-Ca alloy scaffolds with a 20-μm Micro-arc oxidation (MAO) coating were used to repair critical bone defects for subsequent assessment of each alloy's degradation and osteointegration by X-ray, Micro-CT, fluorescence and histological examination. At 12 weeks post-implantation, each defect was found to be effectively reconstructed by either of the Mg alloys based on X-ray and Micro-CT images. The corrosion rate (CR) of each Mg alloy - as calculated based on micro-computed tomography information - demonstrated that the MAO coating could provide effective protection for only 4 weeks post-surgery. From weeks 8 to 12, the CR of the Mg-Ca alloy scaffold increased from 1.34±0.23mm/y to 1.57±0.16 mm/y. In contrast, the CR of the Mg-Sr alloy scaffold decreased from 0.58±0.14mm/y to 0.54±0.16mm/y. However, fluorescence and histological examination revealed more mature, closely and regularly arranged newborn osteocytes at the Mg-Ca scaffold-fracture interface e from weeks 8 to 12 after surgery. The Mg-Sr scaffold was more corrosion resistant and the Mg-Ca scaffold yielded a better overall repair, which indicates that the CR of magnesium alloys matches the rate of new bone formation and is the key to repair bone defects as a bone substitute.

Effect of aging treatment on corrosion behavior of Mg-4Nd-2Gd-0.5Zr alloy

The effects of aging time on corrosion behavior of Mg-4Nd-2Gd-0.5Zr alloy in 3.5% NaCl solution were investigated by microanalysis, weight loss test and electrochemical test. The results show that the corrosion rate of Mg-4Nd-2Gd-0.5Zr alloy decreases first and then increases with the extension of aging time. Aging treatment alters the grain size and the distribution of the second phases. The second phases and grain size are the key factors affecting the corrosion rate of magnesium alloy. Among the tested alloys, the T6-8 h alloy shows the lowest corrosion rate, which is mainly attributed to the continuous distribution of second phases restricting the expansion of corrosion, hence the T6-8 h alloy showed the highest corrosion resistance. The corrosion rate of T6-16 h alloy increases obviously because of the growth of the grain size and the segregation of second phases, which accelerates the corrosion progress.

Corrosion protection properties of poly(4‐vinyl pyridine) containing multilayer polymeric coatings on magnesium alloy AZ31

AbstractThe aim of this study is to develop polymeric thin films for corrosion protection of magnesium alloy AZ31. As polymer matrix, poly(4‐vinyl pyridine) (P4VP) is selected due to its semiconducting properties and protonic conductivity. Polyacrylic acid is tested as crosslinking layers to improve interfacial adhesion. The macroscopic corrosion properties of the multilayer coatings are investigated by means of electrochemical methods, such as linear sweep voltammetry and electrochemical impedance spectroscopy (EIS), in corrosive media simulating technical and biomedical applications. It is demonstrated that thin multilayer coatings can suppress the corrosion rates of magnesium alloys. To our best knowledge, this is the first demonstration of the use of P4VP as a conducting polymer film with protonic conductivity for corrosion protection of magnesium alloys.

Silane coatings modified with hydroxyapatite nanoparticles to enhance the biocompatibility and corrosion resistance of a magnesium alloy.

The fast corrosion rate of magnesium alloys has restricted their use as biodegradable implants. Hence developing a practical approach to retard the corrosion rate of the AZ31 magnesium alloy, as well as promoting cell adhesion and proliferation is of great importance. Silane coatings were applied through dip coating, on samples pretreated in hydrofluoric acid. Samples were immersed in simulated body fluid at 37 °C, and the coating performance was assessed by electrochemical impedance spectroscopy. The coating morphologies of samples were investigated through field emission scanning electron microscopy and a cell viability/proliferation (MTT) test was performed to evaluate cellular response. A 2.2 μm-thick coating was accomplished, which increased the corrosion resistance to three orders of magnitude higher than that of the bare sample. Hydroxyapatite nanoparticles were added to the silane coating to improve biocompatibility and facilitate bone formation. Changing the concentration of hydroxyapatite nanoparticles not only helped to optimize the barrier properties of the silane coating but also ameliorated MG-63 osteoblastic cell growth. The findings showed great promise to enhance and maintain the corrosion barrier property and induce high osteoblastic differentiation by employing 1000 mg L−1 of hydroxyapatite nanoparticles.

Influence of pickling time on electroless Ni–P coating on magnesium alloy

AbstractIn this study, a simple pickling process in H3PO4 and NH4HF2 solution was used for electroless Ni–P plating on AZ61 magnesium alloy. It is found that the corrosion rate of magnesium alloy during pickling significantly decreased because NH4HF2 was added into H3PO4 pickling solution. Ni–P coating plated only with pickling process shows poor adhesion because of the low F/O ratio of the substrate surface. However, F/O ratio, adhesion, and corrosion resistance of Ni–P coating are obviously enhanced after pickling followed by activation. The optimal pretreatment process is pickling for 120 s and activation for 4 min, under which the Ni–P coating has an optimum F/O ratio of 1.8 and the coating gets a dense structure, better adhesion, and higher corrosion resistance.

Formation and In Vitro Evaluation of a Deep Eutectic Solvent Conversion Film on Biodegradable Magnesium Alloy.

The chemical conversion films from deep eutectic solvents (DESs) have recently been shown to reduce the corrosion rate of magnesium alloys, which are recognized as a kind of promising materials applied in the human body. However, the biocompatibility of the conversion films has not been investigated. This study proposes an uncommon DES system composed of lithium chloride and urea to fabricate the chemical conversion films on Mg and its alloy. The fabrication process of the conversion film is facile, which is performed by the heat treatment of the substrate in the DES at about 200 °C for 30 min. It is found that the thermal decomposition of the DES can release hydrogen, which diffuses into the Mg substrate to form MgH2-based conversion films. The DES conversion film possesses a porous structure on pure Mg, whereas it becomes dense on the alloy with some cracks. X-ray photoelectron spectroscopy shows that MgCO3 and oxides also exist in the DES conversion films, which depends on the substrate. Electrochemical corrosion test and in vitro biocompatibility tests, including hemolysis, cytotoxicity, antibacterial, and cytoskeleton staining experiments, are performed in a simulated body environment, which shows that the corrosion resistance and biocompatibility of the substrates have been improved significantly. We expect that the DES heat treatment method will be applied to the fabrication of corrosion-resistant and biocompatible surfaces for biodegradable Mg alloys.

Electrochemical Impedance Spectroscopy for the Measurement of the Corrosion Rate of Magnesium Alloys: Brief Review and Challenges

From a technological point of view, measurement of the corrosion rate of magnesium (Mg) and its alloys is critical for lifetime predictions of Mg-based structures and for comparative assessments of their corrosion protection ability. Whilst weight loss, hydrogen evolution, and polarization curves methods are frequently used for measuring the corrosion rate, the determination of values by electrochemical impedance spectroscopy (EIS) is relatively scarce and has only been realized recently. This technique seems to be the most suitable for monitoring corrosion rate values due to its “non-destructive” character, its reproducibility, and its reliable determination of small corrosion rates, much lower than those measured by other techniques. This review aims to picture the state-of-the-art technique of using EIS for measuring the corrosion rate of Mg. This paper starts by introducing some fundamental aspects of the most widely used methods for monitoring the corrosion rate of Mg/Mg alloy and continues by briefly explaining some of the fundamental concepts surrounding EIS, which are essential for the user to be able to understand how to interpret the EIS spectra. Lastly, these concepts are applied, and different approaches that have been proposed to obtain quantitative values of corrosion rate since the 1990s are discussed.

Hydrophobic surface contained Ca and/or Ce myristate fabricated on AZ31 by one-step electrodeposition for corrosion protection in NaCl

Controlling the corrosion rate of magnesium alloys is the critical way to demonstrate their excellent performance in the practical application, it is imperative to design and construct a surface to allow better expeditions adaptation to the application environment. A hydrophobic coating with a good adhesion to the substrate is required. In this study, calcium myristate coating, cerium myristate coating and calcium/cerium myristate mixed coating were fabricated respectively on the surface of AZ31 magnesium alloy by a one-step electrodeposition. The coating characteristics were studied. The corrosion behavior of the coated samples was investigated and the corrosion mechanism was also discussed. The results showed that all three coatings exhibited hydrophobicity with little difference. The presence of Ce ions in the electrolyte promoted the formation of the corresponding coating, and the Ce coating with cracks had the maximum thickest and a poor adhesion to the substrate The Ca coating and Ca/Ce mixed coating presented a good adhesion to the substrate. Compared with the single myristate coatings, the mixed coating exhibited improved corrosion performance. The EIS evolution reveals that the protection effect of the coatings gradually decreases during the immersion process, which is caused by the formation of porous hydrated coating on the surface.

Femtosecond green laser processing of magnesium alloy

In this paper, a femtosecond green laser with wavelength of 515 nm was used to process the AZ31 magnesium alloy. The laser ablation threshold and ablation rate of Mg alloy were calculated. The mechanism of femtosecond green laser process was determined. The effects of surface microstructures on corrosion rate of AZ31 magnesium alloy was compared and analyzed. The results show that the laser ablation threshold of AZ31 magnesium alloy is 1.46 J/cm2, the ablation rate is 0.68 μm/pulse in the laser fluence of 8.36 J/cm2, the ablation rate increases with the laser fluence increasing. The high-quality holes can be fabricated with the laser fluence of 8.36 J/cm2 and the pulse number of 1000. In terms of the corrosion rate of magnesium alloy, the groove structure is less than that of the columnar structure and less than that of the smooth surface, among which the corrosion rate on the microstructural surface is about 1/3~1/2 of that on the smooth surface in 24 hours.

Investigations on the surface topography, corrosion behavior, and biocompatibility of friction stir processed magnesium alloy AZ91D

Magnesium and its alloys have been identified as potential biodegradable implant materials for orthopaedic applications considering their bone equivalent density, biocompatibility, and biodegradability. However, the rapid corrosion rate of magnesium alloys in the physiological environment is a severe problem. This study attempts to simultaneously improve the microhardness and reduce the corrosion rate of AZ91D alloy by friction stir processing. Magnesium alloy AZ91D is friction stir processed by varying the process parameters namely tool rotation speed and tool traverse speed. The effects of friction stir processing parameters on the microstructural evolution, surface topography, microhardness, and corrosion rate of AZ91D alloy are investigated using the hybrid models, which are developed by integrating the quadratic function and radial basis function. The results indicate that the optimum process parameters for friction stir processing of AZ91D alloy is 750 rpm and 45 mm min−1. Cytotoxicity test revealed that the biocompatibility of friction stir processed AZ91D alloy is in good agreement with the biocompatibility of the AZ91D alloy.

Controlling corrosion rate of Magnesium alloy using powder mixed electrical discharge machining

Biomedical implant can be divided into permanent and temporary employment. The duration of a temporary implant applied to children and adult is different due to different bone healing rate among the children and adult. Magnesium and its alloys are compatible for the biodegradable implanting application. Nevertheless, it is difficult to control the degradation rate of magnesium alloy to suit the application on both the children and adult. Powder mixed electrical discharge machining (PM-EDM) method, a modified EDM process, has high capability to improve the EDM process efficiency and machined surface quality. The objective of this paper is to establish a formula to control the degradation rate of magnesium alloy using the PM-EDM method. The different corrosion rate of machined surface is hypothesized to be obtained by having different combinations of PM-EDM operation inputs. PM-EDM experiments are conducted using an opened-loop PM-EDM system and the in-vitro corrosion tests are carried out on the machined surface of each specimen. There are four operation inputs investigated in this study which are zinc powder concentration, peak current, pulse on-time and pulse off-time. The results indicate that zinc powder concentration is significantly affecting the response with 2 g/l of zinc powder concentration obtaining the lowest corrosion rate. The high localized temperature at the cutting zone in spark erosion process causes some of the zinc particles get deposited on the machined surface, hence improving the surface characteristics. The suspended zinc particles in the dielectric fluid have also improve the sparking efficiency and the uniformity of sparks distribution. From the statistical analysis, a formula was developed to control the corrosion rate of magnesium alloy within the range from 0.000183 mm/year to 0.001528 mm/year.

Influence of hydrogen bubbles adhering to the exposed surface on the corrosion rate of magnesium alloys AZ31 and AZ61 in sodium chloride solution

The influence of the presence of hydrogen bubbles adhered to the corroding specimen surface on the EIS estimations of corrosion rate of magnesium alloys is considered. The EIS corrosion rates for AZ31 specimens exposing a small area were four times higher than the real values determined by gravimetric or hydrogen evolution measurements. In contrast, no significant differences in the corrosion rate have been observed in the case of the AZ61 specimens. A progressive deterioration in the protective properties of the corrosion products layer formed during the test was observed only on AZ31 specimens exposing a small area.

Enhanced Anti-corrosion Ability and Biocompatibility of PLGA Coatings on MgZnYNd Alloy by BTSE-APTES Pre-treatment for Cardiovascular Stent

Bioabsorbable magnesium alloys are widely studied for various implant applications, as they reduce the risks such as severe inflammatory response existing in permanent metallic implants. However, the over-fast corrosion rate of magnesium alloy is usually an obstacle in biomedical applications. Here we report a simple two-step reaction to introduce anticorrosive silane pre-treatment on MgZnYNd alloys before coating with poly (glycolide-co-lactide) (PLGA). The first step is to immerse the NaOH-activated MgZnYNd with bistriethoxysilylethane (BTSE) to form a cross-linked silane coating layer with enhanced corrosion resistance; the second step involves immobilizing amine functional groups for forming hydrogen bond with outer PLGA coating by treating the BTSE-modified MgZnYNd with 3-amino-propyltrimethoxysilane (APTES). We characterized the BTSE-APTES pre-treated PLGA coating on MgZnYNd by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), static contact angle and Acid Orange 7 measurement. Nano-scratch test was to verify that the scratch resistance of the PLGA coating with BTSE-APTES pre-treatment was superior to direct PLGA coating. Standard electrochemical measurements along with the long-term immersion results indicated that the BTSE-APTES pre-treatment rendered better in vitro degradation behavior. Cell adhesion and cell viability tests with both vascular smooth muscle cells (VSMC) and human umbilical vein endothelial cells (EA. hy926) demonstrated that BTSE-APTES pre-treated MgZnYNd substrate had significantly more beneficial effects. The favorable anti-corrosion behavior and biocompatibility of BTSE-APTES pre-treated PLGA coatings on MgZnYNd alloy suggest that the novel two-step silanization procedure may have the great potential to enhance the performance of the magnesium-based biomaterials and provide a valid solution for the conversion modification of cardiovascular implants, taking the magnesium-based bioabsorbable materials closer to clinical application.

Silane/TiO2 coating to control the corrosion rate of magnesium alloys in simulated body fluid

A silane-based coating modified with titanium IV iso-propoxide was developed to slow down the corrosion rate of AZ31 and ZE41 magnesium alloys intended as biodegradable implants materials. Electrochemical impedance spectroscopy (EIS) was used to monitor the corrosion evolution over 7 weeks in simulated body fluid at 37°C. A homogeneous crack-free 3μm-thick coating provided corrosion protection for 2 and 3 weeks to the ZE41 and the AZ31, respectively.The corrosion mechanisms and the nature of the corrosion products of the coated systems are discussed and correlated to the coating morphology before and after the immersion tests.