Investigation of the influence of high-pressure torsion and solution treatment on corrosion and tribocorrosion behavior of CoCrMo alloys for biomedical applications

In this study, the influence of the high-pressure torsion (HPT) processing parameters and solution treatment (ST) on the corrosion and tribocorrosion behavior of CoCrMo (CCM) alloys was investigated for possible usage in biomedical applications. The corrosion behavior of the CCM alloys was investigated by using potentiodynamic scanning (PDS) and electrochemical impedance spectroscopy (EIS) tests. Tribocorrosion tests were carried out in a reciprocating ball-on-plate tribometer at 1 Hz, 1 N load, and 3 mm stroke length for 2 h. All electrochemical measurements were performed using a potentiostat in standard phosphate-buffered saline (PBS) solution at body temperature (37 ± 2 ◦C). The samples were characterized by using a scanning electron microscope (SEM), transmission electron microscope (TEM), optical microscope (OM), and X-ray diffraction (XRD). The deepness and width of wear tracks were examined by using a profilometer. The results showed that HPT and ST processes did not affect significantly the corrosion resistance of samples. However, the ST-treated samples had a higher material loss during sliding in standard phosphate-buffered saline (PBS) at body temperature as compared to HPT-treated samples.This work was supported by Yildiz Technical University Scientific Research Projects Coordination Unit under project number of 2016-07-02-KAP01, and partially by Portuguese Foundation for Science and Technology (FCT), Portugal, under UIDB/04436/2020 project

Optimization of Surface Properties of Plasma Electrolytic Oxidation Coating by Organic Additives: A Review

Plasma electrolytic oxidation (PEO) is an effective surface modification method for producing ceramic oxide layers on metals and their alloys. Although inorganic electrolytes are widely used in PEO, the organic additives have received considerable interest in the last decade due to their roles in improving the final voltage and controlling spark discharging, which lead to significant improvements in the performance of the obtained coatings. Therefore, this review summarized recent progress in the impacts of organic additives on the electrical response and the plasma discharges behavior during the PEO process. The detailed influence of organic additives, namely alcohols, organic acids, organic amines, organic acid salts, carbohydrate compounds, and surfactants on the corrosion behavior of PEO coatings is outlined. Finally, the future aspects and challenges that limit the industrial applications of PEO coating made in organic electrolytes are also highlighted

Corrosion performance and microstructural response of A380 matrix alloy reinforced with sol-gel TiO2-coated SiC particles: a perspective on previous studies

In this study, the corrosion susceptibility of aluminium matrix composites reinforced with sol-gel TiO2-coated silicon carbide particles has been investigated. The corrosion of the composite, fabricated by means of a liquid metal infiltration technique, was established in chloride-containing alkaline environments using the potentiodynamic polarisation technique. Microstructural and interfacial characterisation of the composite was carried out by using an optical microscope, scanning electron microscope, energy dispersion spectroscopy and X-ray diffractometer. The corrosion performance and its effect on the composite microstructure are discussed in relation to previous observations

Improving the Chemical Stability of Al Alloy through the Densification of the Alumina Layer Assisted by SiF62− Anion Hydrolysis

In this work, a high-density alumina layer with high chemical stability was successfully developed by controlling the hydrolysis of hexafluorosilicate (SiF62−) anions through the addition of various concentrations of sodium citrate (SCi) into the electrolyte of plasma electrolysis (PE). To achieve this aim, the substrate samples were anodized in alkaline aluminate–SiF62−-based electrolytes with 0, 5, and 10 g/L of SCi. The presence of SCi anions in the electrolyte led to the formation of a thick adsorbed electrochemical double layer (EDL) on the substrate surface. The EDL not only affected the movement of SiF62− anions towards the anode but also influenced their hydrolysis reaction, which in turn led to a controllable sealing of structural defects with the hydrolysis products, namely SiO2 and AlF3. Among three different oxide layers, the oxide layer obtained from the electrolyte with 5 g/L SCi showed the highest chemical stability in a corrosive solution, which was linked to the fact that a considerable increase in the compactness of the oxide layers was obtained by the incorporation of SiO2 and AlF3. The mechanism underlying the effects of SCi on triggering the hydrolysis of SiF62− anions and factors affecting chemical stability are discussed based on the experimental data and computational analysis

The effect of SiCp reinforcement on the corrosion behaviour of Al based metal matrix composites

In this study, the effect of SiC particle volume fraction on the corrosion behavior of Al-Si-Mg based SiCp reinforced metal matrix composites in both aerated and deaerated 3.5 wt.% NaCl aqueous solutions has been investigated. Composites reinforced with 10 and 20 vol.% SiC particles were produced by compocasting technique and then extruded. The corrosion susceptibility was analyzed by measuring the cyclic potentiodynamic polarization. The corrosion rates of the samples were determined by using E-pit, E-corr and i(corr) values obtained from polarization curves. The surface morphology of the composites was determined by an optical microscopy and scanning electron microscopy (SEM). In addition, X-ray diffraction (XRD) technique has been used in order to determine the phases occurring at the matrix/SiC interface. The obtained results indicate that the corrosion resistance of the composites decreased with increased SiC particle content

The effect of SiCp reinforcement on the corrosion behaviour of Al based metal matrix composites

In this study, the effect of SiC particle volume fraction on the corrosion behavior of Al-Si-Mg based SiCp reinforced metal matrix composites in both aerated and deaerated 3.5 wt.% NaCl aqueous solutions has been investigated. Composites reinforced with 10 and 20 vol.% SiC particles were produced by compocasting technique and then extruded. The corrosion susceptibility was analyzed by measuring the cyclic potentiodynamic polarization. The corrosion rates of the samples were determined by using E pit, Ecorr and icorr values obtained from polarization curves. The surface morphology of the composites was determined by an optical microscopy and scanning electron microscopy (SEM). In addition, X-ray diffraction (XRD) technique has been used in order to determine the phases occurring at the matrix/SiC interface. The obtained results indicate that the corrosion resistance of the composites decreased with increased SiC particle content

Corrosion performance and microstructural response of A380 matrix alloy reinforced with sol–gel TiO 2

In this study, the corrosion susceptibility of aluminium matrix composites reinforced with sol-gel TiO2-coated silicon carbide particles has been investigated. The corrosion of the composite, fabricated by means of a liquid metal infiltration technique, was established in chloride-containing alkaline environments using the potentiodynamic polarisation technique. Microstructural and interfacial characterisation of the composite was carried out by using an optical microscope, scanning electron microscope, energy dispersion spectroscopy and X-ray diffractometer. The corrosion performance and its effect on the composite microstructure are discussed in relation to previous observations

Corrosion behavior of an artificially aged (T6) Al-Si-Mg-based metal matrix composite

The influence of age hardening on the corrosion behavior of Al-Si-Mg-based metal matrix composites (MMCs) has been investigated in aerated and deaerated 3.5 wt% aqueous NaCl solutions. Silicon carbide particle (SiCp) reinforced composites consisting of 10 and 20 vol% SiC(p)s are produced by the compocasting technique. After the extrusion process, the composites are artificially aged (T6). The corrosion resistances of the aged composites are analyzed by measuring the cyclic potentiodynamic polarization. The surface morphology of the composites before and after the corrosion tests are determined by using metallographic methods and scanning electron microscopy (SEM). In addition, the X-ray diffraction technique (XRD) has been used to determine the phases that occur at the matrix-reinforcement interface. The results demonstrate that the E-pit values of unreinforced matrix alloy and composites increase negatively with increasing aging time. It is also observed that corrosion preferentially starts at the interface of Al-Mg2Si and Al-SiCp

Incorporation of Zinc Hydroxide Sulphate (ZHS) Nanoplates into Epoxy Resin to Improve Its Corrosion Protection

Zinc hydroxide sulphate (ZHS) nanoplates were synthesized and then characterized by various methods, including field-emission electron microscopy (FESEM), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron microscopy (XPS), thermal gravimetric analysis (TGA), and the Brunauer–Emmett–Teller (BET) theory. Then, the synthesized ZHS nanoplates were incorporated into the epoxy coating on a ST 37 steel alloy. No change in the morphology of the epoxy coating was observed after incorporating 1 wt. % ZHS nanoplates. Uniform distribution of the incorporated ZHS nanoplates inside the epoxy coating was confirmed by transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS). Atomic force microscopy (AFM) images showed that the surface roughness (Sa) of the neat epoxy coating was about 1.1 µm, which was increased to about 2.1 µm by the incorporation of the ZHS nanoplates. The water contact angle on the coating was changed from 82.1 to 90.8° after incorporating the ZHS nanoplates, which may be attributed to the surface roughness. Electrochemical impedance spectroscopy (EIS) experiments showed that the polarization resistance of the epoxy coating in a 3.5 wt. % NaCl solution after 28 days of immersion was about 2.03 MΩ cm2, and increased to about 9.47 MΩ cm2 after adding the ZHS nanoplates. In addition, the capacitance of the ZHS-containing epoxy coating after 28 days of immersion in the corrosive solution was about 0.07 nsnΩ−1cm−2. The obtained value was more than four times lower than the value obtained for the neat epoxy coating (0.32 nsnΩ−1cm−2). The results of the EIS measurements indicated a significant increase in the corrosion resistance of the epoxy coating after the addition of the ZHS nanoplates. The improvement in the corrosion was explained by the filling of the possible defects and trapping of the aggressive agents by the incorporated ZHS nanoplates. FESEM and EDS analyses at the end of the immersion period confirmed the results of the corrosion tests