Effect of stress on the passivation of Si-DLC coating as stent materials in simulated body environment

DLC coating can be used for vascular stents to prevent the stainless steel substrate from eluting Ni and Cr by plastic deformation and corrosion environment. The stress corrosion cracking (SCC) of Si-diamond-like carbon (Si-DLC) coated on 316L stainless steel was studied in a simulated body environment of a deaerated 0.89 wt.% NaCl electrolyte at 37 °C. This paper investigated the effect of Si-DLC coating on the SCC of 316L SS by slow-strain-rate test (SSRT), constant load test (CLT), and electrochemical impedance spectroscopy (EIS). The EIS data were monitored for the elastic and plastic regions under CLT to determine the electrochemical behavior of the passive film during SCC phenomena. The Si-DLC coated steel exhibited more ductility than uncoated steel and less susceptibility to SCC in this environment. According to X-ray photoelectron spectroscopy (XPS) analysis, the film repassivation occurs due to the presence of the silicon oxide layer on the Si-DLC film surface.     

Electrochemical,SEM and XPS investigations on phosphoric acid treated surgical grade type 316L SS for biomedical applications

A simple surface pre-treatment method was attempted to establish a stable passive layer on the surface of surgical grade stainless steel (SS) of type 316L for biomedical applications. Surgical grade type 316L SS specimens were subjected to H₃PO₄ treatment for 1 h by completely immersing them in the acid solutions to develop a passive barrier film. The effect of various concentrations of phosphoric acid on the localized corrosion resistance behavior of type 316L SS was investigated through electrochemical techniques using cyclic polarization studies and electrochemical impedance spectroscopy (EIS). X-ray photoelectron spectroscopy (XPS) was used to evaluate the nature and composition of the passive films. The surface morphology and relative elemental composition of the untreated and acid treated surfaces subjected to anodic polarization was studied by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX) techniques, respectively. Compared with untreated (pristine) 316L SS, the 40% acid treated surface formed a stable passive layer that had superior corrosion resistance.     

Corrosion behaviour and biocompatibility of nanoporous niobium incorporated titanium oxide coating for orthopaedic applications

This study investigates the surface characteristics, in vitro biocompatibility and electrochemical behaviour of nanoporous niobium incorporated titanium dioxide (Nb-incorporated TiO₂) coated 316L stainless steel (SS) for orthopaedic applications. The coating material was synthesized by sol-gel methodology and was deposited on 316L SS by using spin coating technique and heat treatment. The experimental conditions were optimized to obtain a coating with nanoporous morphology. The coating was characterized using attenuated total reflectance-Infrared spectroscopy (ATR-IR), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX), atomic force microscopy (AFM) and transmission electron microscopy (TEM). The analysis confirmed the formation of a crystalline nanoporous Nb-incorporated TiO₂ coating with hydrophilic nature. Mechanical studies validated that the coating has excellent adhesion to the specimen and appreciable hardness value. In vitro bioactivity test confirmed that the nanoporous morphology of the coating facilitated enhanced hydroxyapatite (HAp) growth. Electrochemical studies established that the insulative nature of the coating provides excellent corrosion resistance to 316L SS.     

Impact of hybrid self-assembled nanophase particle-based sol–gel coatings on the localized corrosion behavior of modified 9Cr–1Mo steel in chloride medium

Corrosion protection coatings were developed based on a hybrid self-assembled nanophase particle process (HSNAP) for the localized corrosion resistance of modified 9Cr–1Mo steel in 0.05 M NaCl solution. The coating sol was prepared using silane-zirconia precursors and a polymeric crosslinking agent. Scanning electron microscopy and X-ray photoelectron spectroscopy were used to study the morphology and composition of the coated specimens, respectively. The thickness of the coatings was determined by a thickness gauge meter and Raman imaging analysis. The corrosion resistance of coated specimens was analyzed using electrochemical impedance spectroscopy, and it was observed that HSNAP-coated specimens showed superior resistance to localized corrosion than the as-received specimens in chloride medium.     

不锈钢金属双极板TiW和TiTa膜的制备及性能

针对质子交换膜燃料电池金属双极板耐蚀性和导电性有待提高的问题,本文用磁控溅射双靶共溅的方法,在316L不锈钢基体表面沉积TiW和TiTa两种非贵金属膜层。通过X射线衍射、扫描电子显微镜-能谱仪、X射线光电子能谱仪、电化学和接触电阻测试等方法,表征了涂覆膜层后不锈钢的微观结构、表面形貌、化学组成、耐腐蚀性和导电性。实验结果表明,磁控溅射制备得到的TiTa膜表面较为均匀,且TiTa膜沉积的不锈钢具有较好的耐腐蚀性,其恒电位极化电流密度能够维持在0.3μA/cm²;从导电性来看,TiW膜与碳纸之间的接触电阻小于TiTa膜。综合考虑材料的各项性能,认为沉积TiTa膜的316L不锈钢有用作金属双极板材料的潜力。     

The electrochemical studies of the corrosion resistance behaviour of hydroxyapatite coatings on stainless steel fabricated by electrophoretic deposition

HA was coated on stainless steel (SS) 316L by using electrophoretic deposition to impart corrosion resistance upon SS 316L. Consequently, corrosion behaviour of HA coated SS 316L deposited from applied voltages 10 V to 60 V (denoted as HA/SS316L-10V until -60V) was evaluated in comparison with pristine SS 316L by various electrochemical studies. As results, linear potentiodynamic polarisation result suggested that HA/SS316L-40V exhibits highest open circuit potential indicating that successful protection of HA coating. Additionally, cyclic polarisation studies revealed that HA coated SS 316L improves pitting corrosion resistance. Finally, EIS results demonstrated that higher polarisation resistance and lower capacitance values for HA/SS316L-40V.     

Stainless steel as new substrate for coil coating

Increasing needs of very high resistance to cosmetic corrosion, of more extended service life and reduced maintenance costs for infrastructures, civil and industrial buildings open new fields of application for coil coated stainless steel. This paper describes the adhesion and corrosion properties of new coil coated stainless steel materials produced in industrial coil coating lines. The use of an electrochemical test (electrochemical impedance spectroscopy) can give detailed information on the reactivity of the system and allow the performance of different substrates (AISI 409, 430, 316 and 304) coated with different polymers (polyvinylidene and polyester) to be compared. The results obtained show the interesting properties of this new class of coil coated products. The materials were tested for a long time (about 200 days) in an aggressive environment (3.5% sodium chloride solution) also in the presence of macrodefects. In particular, VIVINOX 430, 304 and 316 revealed no reactivity, corrosion or disbonding, thus supporting the expectancy of very long trouble free exposure also in very aggressive natural environments. (VIVINOX is the brand name of the AST (Acciali Speciali Terni) line of coil coated stainless steel.)     

Corrosion protection by zirconia-based thin films deposited by a sol–gel spin coating method

This paper focuses on the structure and corrosion behavior of 316L stainless steel coated by inorganic ZrO₂, hybrid ZrO₂–PMMA, and combined inorganic–hybrid films. The coatings were deposited by a particulate sol–gel spin-coating route, using carboxymethyl cellulose as a nanoparticle dispersant. The electrochemical evaluations were conducted in a simulated body fluid, via potentiodynamic polarization and impedance spectroscopic experiments. According to the results, the hybrid coating presented a better corrosion protection compared to the inorganic coating, due to a lesser density of structural defects. However, the best corrosion resistance was found for a combined coating which consists of an inorganic bottom layer and a hybrid top layer, due to a desirable compromise of good adhesion and low defect density.     

Effect of sub-layer temperature during HFCVD process on morphology and corrosion behavior of tungsten carbide coating

WC coating was deposited on the polished and cleaned 316L stainless steel by Hot Filament Chemical Vapor Deposition (HFCVD) technique at 400°C and 500°C. Field Emission Gun Scanning Electron Microscope (FEG-SEM) was used to study the corrosion morphology of the WC coatings. Energy dispersive spectroscopy (EDS) was used to analyze the chemical composition of the coatings. Coating porosity was measured by immersion in water. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques were used to study the corrosion behavior of the coating in the solution of 1 mol/L H₂SO₄. Results showed that the WC coatings have a honeycomb microstructure where its porosity was increased at higher temperature of the sub-layer. Also, the WC coating significantly increases the corrosion resistance of 316L stainless steel. And increasing the sub-layer temperature in the HFCVD method reduces the corrosion resistance of the WC coating. Corrosion morphology was indicative of pitting corrosion of the WC coating.     

Corrosion behavior of amorphous carbon deposit in 0.89% NaCl by electrochemical impedance spectroscopy

Amorphous carbon films were deposited on SS316L substrates using a DC magnetron sputtering system, aiming at the application of the coated SS316L for biomedical implants. The biocompatibility and chemical stability of the carbon layers have been previously demonstrated. The films were deposited on top of sputtered titanium coatings introduced as a buffer layer to enhance film-substrate adhesion. The corrosion resistance of the a-C/Ti/SS316L systems was investigated by electrochemical techniques. The electrolyte used in this work was 0.89 wt.% NaCl at pH 7.4, which simulates body fluid ionic concentrations. The coated samples displayed corrosion resistance values in the saline solution much higher than the stainless steel substrates and the role of the Ti coating thickness was analysed in order to determine the optimal system for biological applications.     

Study of CNx films on 316L stainless steel for orthodontic application

In order to improve the friction property and corrosion resistance of 316L stainless steel (316LSS) in orthodontic application, carbon nitride (CNx) films were synthesized by using IBAD technique at a set of assisted N ion beam currents. X-ray photoelectron spectroscopy and Raman spectroscopy were used to characterize the bonding state and the microstructure of the CNx films. Results of tribological tests indicated that the 316LSS coated by CNx films exhibited lower friction coefficients than the uncoated one both in air and in artificial saliva. The electrochemical tests in artificial saliva confirmed that the corrosion resistance of 316LSS was evidently improved after coated with CNx films.     

Improvement of the electrochemical behavior of steel surfaces using a TiN[BCN/BN]n/c-BN multilayer system

The aim of this work is to improve the electrochemical behavior of AISI 4140 steel substrates by using a TiN[BCN/BN]_n/c-BN multilayer system as a protective coating. We grew TiN[BCN/BN]_n/c-BN multilayers via reactive r.f. magnetron sputtering technique, systematically varying the length period (Λ) and the bilayer number (n), maintaining constant the total thickness of the coating and all other growth parameters. The coatings were characterized by FTIR spectroscopy that showed bands associated to h-BN bonds, and c-BN stretching vibrations centered at 1385 cm^− 1 and 1005 cm^− 1, respectively. Film composition was studied via X-ray photoelectron spectroscopy where typical signals for C1s, N1s and B1s are shown. The electrochemical properties were studied by electrochemical impedance spectroscopy and Tafel curves. In this work, the maximum corrosion resistance for the coating with (Λ) equal to 80 nm was obtained, corresponding to n = 25 bilayers. The polarization resistance and corrosion rate were around 10.1 kOhm cm² and 0.22 mm/year; these values were 83 and 15 times higher, respectively, than uncoated AISI 4140 steel substrate (0.66 kOhm cm² and 18.51 mm/year). Optical microscopy was used for surface analysis after corrosive attack. The improvement of the electrochemical behavior of the AISI 4140 coated with this TiN[BCN/BN]_n/c-BN multilayer system can be attributed to the presence of several interfaces that offer resistance to diffusion of Cl⁻ of the electrolyte toward the steel surface.     

Corrosion protection of stainless steel by a new and low-cost organic coating obtained from cashew nutshell liquid

In this work, the corrosion protection of 316L steel was promoted by an electro-synthesized polymer obtained from the technical cashew nutshell liquid (t-CNSL). Spectroscopic techniques confirmed the polymer formation. The polymer was dispersed in the ethyl acetate solvent and used to form coatings on 316L steel substrates. The coated samples were subjected to electrochemical tests in a saline environment. The coated electrode with poly(t-CNSL) polymer was exposed to the corrosive medium for 24 days, and superior corrosion protection was observed compared with the uncoated sample. The open circuit potential measurements showed that the coated sample possessed a more positive corrosion potential when compared with the uncoated substrate. The electrochemical impedance spectroscopy results indicated that the coated electrode's polarization resistance (R_p) recorded ~1.0 MΩ cm² after 24 days of exposure. A decrease in polarization resistance was observed with the exposure time due to the presence of micropores in the t-CNSL coating. The polarization curves exhibited that the coated electrode with poly(t-CNSL) has lower corrosion current density and less negative corrosion potential than the uncoated steel electrode. Therefore, t-CNSL favors the manufacture of thin poly(t-CNSL) coatings for corrosion protection purposes besides being a low-cost material.     

类金刚石薄膜在模拟体液中的电化学阻抗

利用双放电腔微波等离子体源全方位离子注入设备,分别采用等离子体增强化学气相沉积技术、等离子体源离子注入和等离子体增强化学气相沉积复合技术两种工艺对医用3161,不锈钢进行类会刚石薄膜表面改性。利用电化学阻抗谱法考察了两种工艺制备的类金刚石薄膜在模拟体液中的抗腐蚀性能。结果表明：与采用等离子体增强化学气相沉积技术制备的类金刚石薄膜相比,在72h的浸泡时间内,采用等离子体源离子注入和等离子体增强化学气相沉积复合技术制备的类金刚石薄膜防腐蚀性能明显增高,腐蚀阻抗较高,碳注入层可有效抑制溶液渗入薄膜和基体之间的界面,起到了腐蚀防护层的作用。动电位极化测试表明：采用复合技术制备的类金刚石薄膜在模拟体液中的腐蚀倾向性更低,钝态稳定性更好。     

The corrosion resistance of 316L stainless steel coated with a silane hybrid nanocomposite coating

The present work aims at evaluating the corrosion resistance of 316L stainless steel pre-treated with an organic–inorganic silane hybrid coating. The latter was prepared via a sol–gel process using 3-glycidoxypropyl-trimethoxysilane as a precursor and bisphenol A as a cross-linking agent. The corrosion resistance of the pre-treated substrates was evaluated by neutral salt spray tests, linear sweep voltammetry and electrochemical impedance spectroscopy techniques during immersion in a 3.5% NaCl solution. In addition, the effect of the drying method as an effective parameter on the microscopic features of the hybrid coatings was studied using Fourier transform infrared spectroscopy and scanning electron microscopy. Results show that the silane hybrid coatings provide a good coverage and an additional corrosion protection of the 316L substrate.     

New sol–gel formulations to increase the barrier effect of a protective coating against the corrosion of steels

Films were deposited onto AISI 430 stainless steel substrates by dip–coating technique. The aim is to reach the AISI 304L stainless steel anti-corrosion properties by a coated AISI 430 stainless steel system. Sol formulation is done from the starting precursors tetraethylorthosilicate (TEOS) and 3(trimethoxysilyl)propyl methacrylate (MAP). After the hydrolysis of these precursors, sol–gel reactions occur before the addition (or not) of a controlled quantity of cerium nitrate. The addition of the PEG (polyethylene glycol), used as plasticizer has been studied in this paper and both physical and chemical properties of the synthesized hybrid films were studied by varying PEG ratios. Based on SEM observations and mass gain measurements, the thickness of the films has been adjustable. Another parameter plays a key role: the drying step of the whole system. It has been investigated and optimized in this paper to lead to coatings with a high barrier effect. The efficiency of the anti-corrosion protection of hybrid-coated stainless steel was investigated by potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) after immersion of the material in a 3.5% NaCl solution.     

Efficient one-step fabrication of superhydrophobic nano-TiO2/TMPSi ceramic composite coating with enhanced corrosion resistance on 316L

TiO₂ Nanoparticle/Trimethoxy(propyl)silane (TMPSi) ceramic composite coating was deposited on 316L steel using a one-step electrophoretic deposition (EPD) method. Silane coupling agent (TMPSi) was added to the EPD bath in different concentrations (from 0.5 to 15 vol %) to decrease the surface energy of the deposited coating. TiO₂ coating is hydrophilic whereas by adding varying concentrations of TMPSi, the obtained nanocomposite coating showed much better hydrophobicity. Surface wettability was measured by water contact angle (WCA) and sliding angle (SA) tests. Moreover, the effect of TMPSi concentration was determined by comparing the WCA and SA values. Surface morphology was studied through Field Emission Scanning Electron Microscopy (FESEM), and the presence of micro/nano meter roughness on the surface was confirmed. The distribution of elements were investigated by EDS analysis in which their uniform dispersion was observed. Corrosion behavior of 316L samples before and after the coating process was studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests in 3.5 wt % NaCl solution. The polarization curve proved that the superhydrophobic ceramic nanocomposite coatings (WCA = 168° and SA = 3.1°) were able to decrease the corrosion rate of bare 316L (from 12.180 to 5.621 (μm per year)).     

The corrosion resistance of 316L stainless steel coated with a silane hybrid nanocomposite coating

The present work aims at evaluating the corrosion resistance of 316L stainless steel pre-treated with an organic–inorganic silane hybrid coating. The latter was prepared via a sol–gel process using 3-glycidoxypropyl-trimethoxysilane as a precursor and bisphenol A as a cross-linking agent. The corrosion resistance of the pre-treated substrates was evaluated by neutral salt spray tests, linear sweep voltammetry and electrochemical impedance spectroscopy techniques during immersion in a 3.5% NaCl solution. In addition, the effect of the drying method as an effective parameter on the microscopic features of the hybrid coatings was studied using Fourier transform infrared spectroscopy and scanning electron microscopy. Results show that the silane hybrid coatings provide a good coverage and an additional corrosion protection of the 316L substrate.     

Modified Sol–Gel Based Nanostructured Zirconia Thin Film: Preparation,Characterization, Photocatalyst and Corrosion Behavior

In this work, AISI 316L stainless steel was coated by nanostructured zirconia using the sucrose assisted sol–gel dip-coating route. Then, the effect of different calcination temperatures and the thickness of the coating on the corrosion protection of 316L stainless steel was investigated. Here, Zr(acac)₄ and sucrose were used as starting materials and gelation agents, respectively. Thermogravimetry and differential thermal analysis, X-ray powder diffraction (XRD), Fourier transform infrared, scanning electron microscopy and energy dispersive X-ray spectroscopy were used to characterize the coatings. XRD revealed that the pure tetragonal phase of zirconia was obtained at the calcination temperature of 300–500 °C. However, the mixture of monoclinic (m) and tetragonal (t) phase found in the zirconia coating calcined at 650 °C. Also, by increasing the calcination temperature from 300 to 650 °C, the mean of the crystallite size of structures was increased from 7 to 27 nm. AFM result show that the average roughness value of the sample calcined at 300 °C is 10.5 nm and the dimensions of the particles on the surface of this sample smaller than 50 nm. The potentiodynamic polarization and electrochemical impedance spectroscopy results revealed that the as-synthesized nanostructured sol–gel zirconia coatings exhibited a barrier property for the protection of the substrate. However, the highest corrosion resistance was obtained by the zirconia coating calcined at 300 °C. This was as a result of the desirable compromise of good adhesion, low defect density, and high barrier behaviour. Furthermore, zirconia nanoparticles were synthesized by calcination of the gel at the different temperature. The photocatalytic activity of samples was tested for degradation of methyl orange solutions. It is found that ZrO₂ nanoparticles calcined at 500 °C have higher photocatalytic activity than the other samples under UV light.     

Enhanced corrosion resistance properties of radiofrequency cold plasma nitrided carbon steel: Gravimetric and electrochemical results

Cold plasma nitriding treatment was performed to improve the corrosion resistance of C38 carbon steel. Nitriding process was conducted using a radiofrequency nitrogen plasma discharge for different times of treatment on non-heated substrates. The modification of the corrosion resistance characteristic of the C38 steel due to the treatment in acid medium (1 M HCl) were investigated by gravimetric and electrochemical tests such as potentiodynamic polarisation curves and electrochemical impedance spectroscopy (EIS). It was shown that the plasma nitriding treatment improves the corrosion resistance. Indeed, in the gravimetric tests, nitrided samples showed lower weight loss and lower corrosion rate in comparison to untreated one. In the Tafel polarisation tests, the nitrided samples showed greatly reduced corrosion current densities, anodic dissolution and also retarded the hydrogen evolution reaction. Using EIS method, an adequate structural model of the interface was used and the values of the corresponding parameters were calculated and discussed. The results obtained from weight loss and electrochemical studies were in reasonable agreement. X-ray photoelectron spectroscopy (XPS) was carried out to establish the mechanism of corrosion inhibition of nitrided C38 steel in 1 M HCl medium. The enhancement of the corrosion resistance is believed to be related to the iron nitride compound layer formed on the C38 steel surface during plasma nitriding, which protected the underlying metal from corrosive attack in the aggressive solutions.