Effects of serum proteins on corrosion behavior of ISO 5832–9 alloy modified by titania coatings

Stainless steel ISO 5832–9 type is often used to perform implants which operate in protein-containing physiological environments. The interaction between proteins and surface of the implant may affect its corrosive properties. The aim of this work was to study the effect of selected serum proteins (albumin and γ-globulins) on the corrosion of ISO 5832–9 alloy (trade name M30NW) which surface was modified by titania coatings. These coatings were obtained by sol–gel method and heated at temperatures of 400 and 800 °C. To evaluate the effect of the proteins, the corrosion tests were performed with and without the addition of proteins with concentration of 1 g L^?1 to the physiological saline solution (0.9 % NaCl, pH 7.4) at 37 °C. The tests were carried out within 7 days. The following electrochemical methods were used: open circuit potential, linear polarization resistance, and electrochemical impedance spectroscopy. In addition, surface analysis by optical microscopy and X-ray photoelectron spectroscopy (XPS) method was done at the end of weekly corrosion tests. The results of corrosion tests showed that M30NW alloy both uncoated and modified with titania coatings exhibits a very good corrosion resistance during weekly exposition to corrosion medium. The best corrosion resistance in 0.9 % NaCl solution is shown by alloy samples modified by titania coating annealed at 400 °C. The serum proteins have no significant effect onto corrosion of investigated biomedical steel. The XPS results confirmed the presence of proteins on the alloy surface after 7 days of immersion in protein-containing solutions.     

铝合金表面改性对有机涂层附着力的影响及腐蚀防护性能研究

利用电化学阻抗（EIS）、扫描微参比技术（SRET）、接触角、粗糙度、附着力、盐雾等测试方法,研究了铝合金阳极氧化与贻贝黏附蛋白（MAP）/CeO₂/硅烷γ-APS（MCA）表面复合修饰的腐蚀防护性能以及对改性聚氨酯涂层附着力和耐蚀性的影响。结果表明,MCA复合膜可抑制铝合金的腐蚀,并具有一定的自修复功能;阳极氧化和MCA表面复合修饰可为铝合金提供有效的早期腐蚀防护作用,且能提高铝合金表面粗糙度和润湿性,显著提升改性聚氨酯涂层在铝合金表面的附着力和耐蚀性,因而结合改性聚氨酯涂层和表面复合修饰可实现对铝合金长期有效的腐蚀防护。     

Effect of Aluminum Alloy Surface Modification on Adhesion of the Modified Polyurethane Coating and Its Corrosion Protective Performance北大核心CSCD

The ordinary organic coatings on aluminum alloy usually encounter a problem of low adhesion to the substrate, which results in destruction and failure of the long-term protective performance of the anticorrosion systems. The surface modification of aluminum alloy is able to enhance the adhesion of organic coating on aluminum alloys, and to improve their protective performance. In this work, a combined surface modification of anodic oxidation and mussel adhesion protein/CeO2/3-aminopropyltriethoxysilane composite film (MCA) was developed on the aluminum alloy. The adhesion of modified polyurethane coated on the treated aluminum alloy and its corrosion protective performance were evaluated comprehensively by using contact angle, adhesion strength, electrochemical impedance spectroscopy (EIS), and scanning reference electrode technique (SRET). The measurements of EIS and SRET demonstrated that the MCA composite film on anodic oxidized Al possessed self-healing function and provided effective protection against early corrosion of aluminum alloy. The pull-off test showed that both anodic oxidation treatment and MCA composite film modification were able to increase the adhesion of modified polyurethane coating on aluminum alloy, and their combined action were supposed to remarkably enhance the adhesion strength up to 17.1 MPa. The reason for the improvement of adhesion was that the anodic oxidation treatment and MCA composite film modification could improve the surface roughness of aluminum alloy, and enhance the surface wettability and surface polarity, which is beneficent to enhance the bonding of the modified polyurethane coating to aluminum alloy surface. The EIS results showed that no any corrosion occurred for the modified polyurethane coating on the treated aluminum alloy during 65 d immersion in 3.5wt.% NaCl solution. The impedance value in low frequency range of the modified polyurethane coating always maintained at a high order of magnitude on the aluminum alloy treated by anodic oxidation and MCA composite film modification, showing an excellent protective performance of the coating system. The evaluation of Neutral Salt Spray (NSS) indicated that the modified polyurethane coating on the treated aluminum alloy owned superior corrosion protection performance, and the adhesion strength remained 13.1 MPa and no any corrosion was found at the scratch locations even after 1200 h of salt spray testing. It was concluded that combination of anodic oxidation and MCA composite film were capable of significantly improving the adhesion of modified polyurethane coating on aluminum alloy and providing long-term effective corrosion protection for aluminum alloy. © 2021 Authors. All rights reserved.     

Synthesis of waterborne nanopolyanilne latexes and application of nanopolyaniline particles in epoxy paint formulation for smart corrosion resistivity of carbon steel

Polyaniline (PANI) latexes were synthesized by emulsion polymerization using dodecyl benzene sulfonic acid (DBSA) and sodium dodecyl sulfate (SDS) as a surfactant. Synthesized PANI–DBSA and PANI–SDS latexes were characterized by IR and UV‐visible spectroscopies, and surface morphology was analyzed by transmission electron microscopy. The PANI–DBSA were found to be nanograin shaped whereas PANI–SDS were as nanofibers. In the second stage rheological properties of waterborne PANI latexes were characterized by viscosity measurement and their dispersion stability in water. The surface morphology of the coating was examined by scanning electron microscope (SEM). The anti‐corrosion performance of uncoated carbon steel, PANI–DBSA and PANI–SDS coated carbon steel was evaluated by tafel slope analysis and immersion test studies of 0.5, 1, and 1.5% PANI/Epoxy coatings were done in 5% NaCl aqueous solution. The results indicated that the nanoPANI in epoxy coating might work as an adhesion promoter and corrosion inhibitor. The waterborne latexes, thus, were found to be highly suitable and avoid the use of organic solvents or strong acids under environmentally benign conditions. Copyright © 2010 John Wiley & Sons, Ltd.     

A3钢在缓蚀颜料提取液中的EIS研究

应用EIS研究了A3钢在不同 pH值的磷酸锌或三聚磷酸铝 3.5 %NaCl提取液中的腐蚀行为 .结果显示 ,相同条件下 ,A3钢的电阻值随溶液 pH值增加而增加 ,电容值则相反 .在磷酸锌3.5 %NaCl提取液中 ,因磷酸锌的溶解度太小 ,没有足够的量对金属基底A3钢进行有效的保护 .在 pH值为 6的三聚磷酸铝 3.5 %NaCl提取液中 ,A3钢表现出较明显的缓蚀现象 ,可能是因为三聚磷酸根离子与腐蚀产物Fe2 + 、Fe3+ 络合并在钢表面形成了一层致密的保护膜 ,从而有效地阻止了腐蚀介质的进一步入侵 .防蚀颜料的溶解度大小是决定它的缓蚀性能优劣的重要因素之一     

Preparation and characterization of anticorrosion Ormosil sol–gel coatings for aluminum alloy

Organically modified silicate (Ormosil) coatings have been synthesized through the sol–gel method for corrosion protection of aluminum alloy. Silica-based unmodified coatings were also designed to investigate the effect of tetraethoxysilane (TEOS) content on the properties of the coatings. The surface morphology of the coatings was characterized by scanning electron microscopy. The corrosion resistance was evaluated by immersion test, electrochemical impedance spectroscopy and potentiodynamic polarization measurements. In addition, the surface potential differences of the coated samples were determined by scanning Kelvin probe. The results showed that a better corrosion resistance of unmodified coating was prepared by controlling the TEOS/EtOH/H₂O molar ratio of 0.109/1/1.52. Ormosil coatings provided excellent barrier properties and corrosion resistance in comparison with the unmodified sol–gel coatings. The Ormosil coating modified with triethoxyoctylsilane exhibited corrosion resistance properties superior to the other Ormosil coatings after exposure to 3.5 wt% NaCl solution for 10 days.     

Wettability of carbon fibers modified by acrylic acid and interface properties of carbon fiber/epoxy

The oxidation-reduction and pre-irradiation induced methods were employed to study the effect of acrylic acid modification on the wetting and adsorption ability of carbon fiber (CF) in epoxy solution and the interfacial properties of CF/epoxy. Systematic experimental work was conducted to determine the surface topography, surface energy, surface chemical composition, absorbability and tensile strength of carbon fibers and interfacial adhesion of CF/epoxy before and after modification. The roughness, surface energy, amount of containing-oxygen functional groups and wetting ability were all found to increase significantly after modifications. The tensile strength of carbon fibers was improved marginally by γ-ray pre-irradiation while was decreased little by oxidation-reduction modification. Consequently, the surface modifications of carbon fibers via both oxidation-reduction and pre-irradiation led to an improvement (more than 15%) of the interlaminar shear strength of CF/epoxy composites. The mechanisms of interfacial improvement of modified CF/epoxy composites are proposed.     

Corrosion protection of AA6061-T4 alloy by sol–gel derived micro and nano-scale hydroxyapatite (HA) coating

Micron and nano-scale hydroxyapatite (HA) were coated successfully on AA6061-T4 substrates by sol–gel method. Besides, the effects of coating thickness on adhesion strength and corrosion behaviour of the coatings were studied. Corrosion resistance was measured by potentiodynamic polarization test using a potentiostat under in vitro conditions. The coatings before and after corrosion tests were characterized by adhesion tests, a scanning electron microscopy attached with EDS and X-ray diffraction analysis. The results revealed that all the coatings exhibit a passive behaviour in Ringer’s solution. Specimens coated with nano-scale HA had the higher corrosion resistance than micro-scale coatings. The highest corrosion resistance appeared to be for the ~30 μm nano-scale HA coated substrates. However, for micro-scale HA coatings, the highest adhesion resistance was obtained at ~30 μm film thickness.     

Excellent protection of mild steel in sodium chloride solution for a substantial period of time using a hybrid nanocoating of poly vinyl alcohol and Titania

The production of eco-friendly hybrid sol–gel coatings for long term protection of metallic substrates from aggressive environments was one of the emerging areas, competing with conventional chromate and phosphate coatings. Herein, a nanocomposite has been synthesized from TiO₂ and PVA through a novel sol-gel route and the structure and morphology of the same was characterized using X-ray diffraction, FTIR, UV–Vis spectroscopy, FESEM with EDAX, and AFM studies. The flower-like structured composite offers excellent corrosion protection properties in NaCl solution of sea water salinity. Impedance and polarization studies were carried out to monitor the anticorrosion performance of the materials coating. This coating on mild steel offers 98% inhibition efficiency in NaCl. The influence of loading PVA on TiO₂ and its effect on corrosion efficiency have also been investigated. It is found that an optimum weight of 20 wt% PVA is required in the composite for beneficial corrosion resistance. 92% inhibition efficiency is registered by the coated MS in NaCl solution after 40 days of exposure and is quite encouraging compared to many of the recent reports. The Ti–O–Ti, and Fe-Ti-O linkage along with compactness and adherence of the material together contribute to better blocking of steel corrosion.     

Corrosion resistance of amorphous AlPO4 coating in salty atmospheres

The objective of the present study was to introduce a cost-effective and environmentally friendly coating to improve the corrosion resistance of the structures located in salt water. The coating solution, based on amorphous aluminum phosphate composition, was synthesized by sol–gel process and applied to AISI 304 stainless steel by dip coating technique. X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy analyses were employed to investigate the phase composition and morphology of the coating. Corrosion behavior of the uncoated and coated samples was investigated using standard salt spray test, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) in 3.5 wt.% NaCl solution. Salt spray test results for the bare substrate revealed a corrosion rate of six-time greater than that of the coated surface after 168 hr exposure time. Electrochemical test results declared that the amorphous AlPO₄ coating decreased the corrosion current density of the AISI 304 stainless steel by 10 orders of magnitude. Furthermore, according to the corresponding EIS measurements, the coated surface exhibited a superior anti-corrosion performance than uncoated sample. Overall, the results declared that the amorphous AlPO₄ coating could be a good choice for surface protection of stainless steel against electrochemical corrosion in salty environments.     

Preparation and colloidal dispersion behaviors of silica sol doped with organic pigment

Silica sol doped with organic pigment was prepared by hydrolyzing tetraethoxysilane with a basic catalyst via dispersing pigment in silica sol. The colloidal properties of SiO₂/pigment hybrid sol and its deposited film were investigated. The presence of pigment in SiO₂/pigment hybrid sol affects the Zeta potential, particle size and surface tension compared to the silica sol without pigment. The SiO₂/pigment hybrid sol exhibited good dispersion stability in the centrifuge process. The maximum absorption wavelength was consistent with that of the pigment disperse solution, indicating that the pigment in SiO₂/pigment hybrid sol remained unchanged. Thermogravimetric analysis of the contents of organic component in silica sol and SiO₂/pigment hybrid sol were conducted, and the differential value was ascribed to the weight of the pigment and the condensate of polyoxyethylene octylphenol ether (OP-10) and γ-Glycidoxypropyltrimethoxysilane (KH-560). The surface topography of SiO₂/pigment hybrid silica film was characterized by AFM. The analysis of silica sol doped with organic pigment provides useful information for an effective pathway to disperse pigment on fiber and other substrates.     

Influences of colloidal stability and electrokinetic property on electrodialysis performance in the presence of silica sol

Negatively charged silica sol is known to lead to fouling of anion exchange membranes during electrodialysis (ED) as a result of its deposition on the membrane surface. It is known that the fouling potential is related to the physical and electrochemical properties of the silica particles as well as those of the anion exchange membranes. In this study, the properties of the silica sol were characterized in terms of its particle size, turbidity, and zeta potential in order to predict their effects on the electrodialysis performance. In the stability of colloidal particles, the critical coagulation concentrations of silica sol were determined as functions of ionic strength, cation species, and solution pH. In the electrodialysis of NaCl solution containing silica sol with various concentrations of CaCl(2), the colloidal behavior related to deposition and transport was examined during and after electrodialysis. The electrodialysis experiments clearly showed that the deposition and transport of silica sol during electrodialysis were related to the colloidal stability of dispersion.     

Role of hydroxyl group in cerium hydroxycinnamate on corrosion inhibition of mild steel in 0.6 M NaCl solution

The corrosion inhibition mechanism of cerium hydroxycinnamate compounds has been studied and compared as an effective corrosion inhibitor for steel in an aqueous 0.6?M NaCl solution. Surface analysis results showed that the surface of steel coupons exposed to solutions containing cerium hydroxycinnamate compounds has less signs of corrosion attack due to a formation of the protective film, while the surface of mild steel coupons exposed to 0.6?M chloride solution without inhibitor additions was severely corroded due to pitting. Electrochemical results performed a good inhibition performance and information of the formed protective deposit that hinders the electrochemical corrosion reactions with a dominance of anodic inhibition mechanism. The results also indicated that the addition of cerium hydroxycinnamate compounds to 0.6?M NaCl solution could mitigate electrochemical corrosion reactions, reduce protective and double layer CPE magnitudes, and improve protective and charge transfer resistances. Furthermore, cerium 2-hydroxycinnamate showed better efficient corrosion inhibitor in comparison with cerium 4-hydroxycinnamate for steel in aqueous media containing 0.6?M chloride ion.     

Potential of zinc based-graphene oxide composite coatings on mild steel in acidic solution

This study introduces varying concentrations of graphene oxide (GO) as a filler into zinc chromate in forming composite coatings to improve the corrosion protection of mild steel. The purity of synthesized GO was inferred through the application of complementary characterization techniques, including FT-IR, XRD, Raman, SEM-EDX, and TEM analyses. GO doped zinc chromate coatings were deposited on the surface of mild steel through the brushing method. Electrochemical studies, i.e., electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PD) were conducted to elucidate the anticorrosion properties of the coated mild steel exposed to 0.5 ​M HCl solution. It was revealed that the highest anticorrosion protection was attained at low doping amount of 0.5% of GO with a corrosion rate of 0.036 mpy. Surface analyses revealed that incorporating GO into zinc chromate coating can effectively improve the anticorrosion properties and adhesion strength.     

Conducting polyaniline/nano-zinc phosphate composite as a pigment for corrosion protection of low-carbon steel

Zinc phosphate (Zn₃(PO₄)₂) nanocrystals were synthesized and used for making conducting polyaniline/nano-zinc phosphate composite by chemical oxidative method. The product was characterized by UV–visible absorption spectroscopy. The crystal structure, morphology and thermal stability of the product were studied by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and thermo gravimetric analysis, respectively. The epoxy-based paint containing conducting polyaniline/nano-zinc phosphate composite pigment was applied on low-carbon steel samples. Corrosion protection performance of the painted low-carbon steel samples in 3.5 mass % sodium chloride solution was evaluated using electrochemical technique. Transmission electron microscopic image revealed the formation of core shell structure of the composite. Composite was found to be more thermally stable than the conducting polyaniline. The corrosion rate of conducting polyaniline/nano-zinc phosphate-painted low-carbon steel was found to be 5.1 × 10^?4 mm per year, about 34 times lower than that of unpainted low-carbon steel and 10 times lower than that of epoxy nano-zinc phosphate paint-coated steel. The study reveals the possibility of using conducting polyaniline/nano-zinc phosphate as a pigment for corrosion protection.     

表面改性对VGCF分散性质的影响

针对气相生长碳纤维极易团聚及与树脂基体界面结合能力较差的难题,采用双氧水-浓硝酸二步法对VGCF进行表面改性处理。利用X射线衍射仪、热重分析仪、傅立叶红外光谱仪、紫外可见分光光度计等测试分析了改性前后VGCF的表面结构和在溶剂中的分散性,并以形状记忆聚氨酯为基体,采用溶液混合法制备了气相生长碳纤维/形状记忆聚氨酯的复合材料,测试了复合材料的力学性能。经过改性后,VGCF的石墨晶型结构几乎没有改变,VGCF表面的含氧官能团浓度得到较大提高,且其在有机溶剂中的分散性及分散稳定性也得到很大提高;在气相生长碳纤维/形状记忆聚氨酯的复合材料截面中,扫描电镜观察表明表面改性使得VGCF在基体中的分散性及与基体的界面结合能力都得到一定程度的提高;经二步法改性处理后的气相生长碳纤维比未处理气相生长碳纤维对复合材料的力学性能的增强效果更为明显。     

Effect of hydrophobicity on the stability of sol–gel silica coatings in vacuum and their laser damage threshold

Silica antireflective coatings modified by hexamethyldisilazane (HMDS) were deposited on clean substrates (silicon wafer or K9 glass blanks) by sol–gel processing. The effects of HMDS on the contamination resistant capability and laser-induced damage threshold (LIDT) of coatings were investigated. Transmission electron microscopy revealed that a stable sol with uniformly distributed silica particles with an average particle size of about 15 nm was acquired by adding appropriate amount of HMDS into the standard SiO₂ sol. With the modified sol the resultant coatings were hydrophobic and the contact angle for water increased with increasing amount of HMDS in the reaction mixture. Such increase in hydrophobicity was not the result of surface roughness. The antireflective properties were retained after HMDS-treatment and the maximum transmission values were above 99 %. The introduction of HMDS into silica sols had also increased the LIDT of coatings from 24.3 to 37.0 J cm^?2 when the molar ratio of HMDS to tetraethoxysilane was 0.05:1. The increase in LIDT was attributed to the decrease of nodular defect and uniform microstructures of coatings as an effect of the HMDS modification. After some of the hydroxyl groups on the surface of the SiO₂ particle were replaced by methyl groups, from which the SiO₂ particle gained a water-repellent surface, the stability of coatings in vacuum was increased. The maximum transmission values of modified coatings decreased by only 0.25 % after storage under vacuum for 168 h. In contrast, the standard sol–gel silica coatings decreased about 2 % under similar conditions. The LIDT of modified coatings remained as high as 30.8 J cm^?2, more than that of standard coatings stored for the same duration in air.     

Tribo-corrosion behavior of Zn-Ni-Cu and Zn-Ni-Cu-TiB2 coated mild steel

In this investigation , Zn-Ni-Cu and Zn-Ni-Cu-TiB₂ were coated on a mild steel specimen using a high velocity oxy fuel thermal spray (HVOF) process. The surface morphology and coated powder distribution of coated specimens were characterized using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and X-ray-Elemental mapping. The pin-on-disc (ASTM G99-17) method was used to examine the wear resistance of the coated and uncoated mild steel specimens. Both coated Zn-Ni-Cu and Zn-Ni-Cu-TiB2 on mild steel saw reduced wear volume loss than uncoated mild steel. The coated samples of Zn-Ni-Cu and Zn-Ni-Cu-TiB2 on Mild Steel were put through a scratch test to determine the adhesion strength of the coating with the substrate. The adhesion strength of coated Zn-Ni-Cu and Zn-Ni-Cu TiB2 mild steel was higher than that of untreated mild steel, indicating a solid link between the coating and substrate and minimal delamination. Using the Vickers hardness test to measure the hardness caused by the coating, it was shown that coated samples of Zn-Ni-Cu and Zn-Ni-Cu-TiB2 coated mild steel had significantly higher hardness than uncoated mild steel. Using ASTM G1-03 and ASTM G-31 standards, a 0.2 M HCl immersion cycle test was conducted for 28 days to test the corrosion resistance of coatings in an acidic media (672Hrs). When compared to Zn-Ni-Cu and Zn-Ni-Cu-TiB2 coated mild steel, the weight loss for the uncoated mild steel was significantly larger. Additionally, XRD examination showed that coated samples had less rust on their surface than uncoated samples. Both Zn-Ni-Cu and Zn-Ni-Cu-TiB2 on Mild Steel were anti-corrosive, as evidenced by increased corrosion potential and reduced corrosion current density when compared to uncoated mild steel, according to electrochemical impedance spectroscopy (EIS)/Tafel study in 0.2 MHCl. The outcomes of each test were very encouraging and demonstrated the durability of these coatings against wear and corrosion.     

Encapsulation of aluminum flakes with hybrid silica/poly(acrylic acid) nanolayers by combination of sol–gel and in situ polymerization methods: a corrosion behavior study

A combination of sol–gel method and in situ polymerization was used to form a hybrid silica/poly(acrylic acid) nanolayer for the corrosion protection of aluminum pigments. To this end, the pigment particles were first coated with a silica layer by sol–gel method. Tetraethylorthosilicate was used as a precursor and during a condensation reaction, an inorganic silica layer was formed. Then, 3-methacryloxypropyltrimethoxysilane was attached on the surface and in situ polymerization of acrylic acid (AA), as a hydrophile monomer, was performed. The obtained Al/Si/PAA flakes were characterized by different methods such as Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, scanning electron microscopy, and transmission electron microscopy (TEM). The attached PAA chains on the surface were deattached by HF aqueous solution and analyzed by gel permeation chromatography. Also, the surface energy of samples was measured using Owens and Wendt equation by means of contact angle data. As results, the characterizing tests approved the successful encapsulation of Al pigments and TEM image showed a 10–15 nm silica layer and a 20–25 nm PAA layer. Although the Al/Si pigments showed a quantity of evolved hydrogen, the hybrid coated pigments had excellent anticorrosive properties in acidic and alkaline solutions. Also, the surface free energy of Al/Si/PAA showed an increase compared to that of Al.