Corrosion Stability Research Articles

Evaluation of corrosion resistant, antimicrobial and cytocompatible behaviour of cobalt based metallosurfactants self-assembled monolayers on 316L stainless steel surface

The present research is aimed at developing a more economic and ecological way to improve the biocompatibility of medical-grade stainless steel. In order to accomplish the purpose, the 316L stainless steel has been functionalized by depositing self-assembled monolayers (SAMs) of cost-effective Cobalt-based metallosurfactants (CoMS). The fabrication of well-defined SAMs on the surfaces was characterised using FTIR-ATR, spectroscopic ellipsometry and water contact angle measurements. The corrosion stability of functionalized surfaces in simulated body fluid was accessed by various electrochemical and spectroscopic techniques like cyclic potentiodynamic polarisation (CPP), chronoamperometry, electrochemical impedance spectroscopy, FE-SEM, XPS and ICP-MS studies. The metallosurfactant SAMs provided superior corrosion and bacterial protection especially against Gram-negative E. coli bacteria. The cytotoxicity of the SAMs against mouse embryonic fibroblast cell line (NIH-3T3) was assessed by MTT and fluorescent assays. The experimental results reveals that the metallosurfactant SAMs are multifunctional i.e., they enhanced the anticorrosive and anti-bacterial properties of the SS 316L without compromising the cytocompatibility of the surface which make them promising candidates for biomedical applications.

Fabrication of novel neodymium oxide coupled mesoporous titania for effective visible light-induced photocatalyst for decomposition of Ciprofloxacin

A novel procedure for constructing mesoporous Nd2O3/TiO2 nanocomposites with different Nd2O3 (0.5–2%) was performed utilizing a soft template and impregnation method. Aqueous solutions of ciprofloxacin (CIP) as a pollutant antibiotics model were utilized to estimate the photocatalytic ability of the mesoporous Nd2O3/TiO2 nanocomposites under visible exposure. The Nd2O3/TiO2 nanocomposites displayed promoted photocatalytic ability for CIP degradation compared with TiO2 NPs, with a maximum degradation of 100% over 1.5%Nd2O3/TiO2 nanocomposite during 150 min illumination time, which is almost eight folds greater than TiO2 NPs. The apparent rate constant of 1.5% Nd2O3/TiO2 nanocomposite exhibited 11.8 times larger than TiO2 NPs. The promotion of photocatalytic ability over Nd2O3/TiO2 nanocomposites was ascribed to the combination between Nd2O3 and TiO2, leading to enhanced formation of the •OH and •O2− accountable for CIP decomposition. The introduction of Nd2O3 into TiO2 was promoted transportation and separation of charge carriers. The Nd2O3/TiO2 photocatalysts exhibited good corrosive resistance and mechanical stability after five consecutive runs of CIP degradation. The photocatalytic performances and mechanism over Nd2O3/TiO2 nanocomposites were verified utilizing photoluminescence and photocurrent density measurements. The prepared mesoporous Nd2O3/TiO2 nanocomposites are promising for environmental remediation.

Long-Term Static and Dynamic Corrosion Stability of Nonwetting Surfaces.

Superhydrophobic surfaces (SHSs) and lubricant-infused surfaces (LISs) are two classes of nonwetting surfaces that have drawn attention due to their advanced functional properties including corrosion inhibition. Yet there is a conspicuous lack of corrosion study of SHSs and LISs with respect to their fabrication and material parameters, especially at high temperatures and under dynamic flow conditions over long durations, which is sought to be addressed in this article. Considering copper SHSs and LISs, a full factorial combinatorial study of two facile texturing processes, electrodeposition and etching, two different functionalization agents, stearic acid and mercaptan, and two types of infused lubricants, Krytox 104 and DOWSIL 510, is presented, encompassing over 650 measurements on 90 tested surfaces. All fabricated surfaces demonstrated water repellency with a contact angle above 150° and a sliding angle below 7°. For the first time, the study examines high-temperature corrosion stability and long-term corrosion durability of the nonwetting surfaces in both static fluid and dynamic turbulent flow conditions over a period of 30 days. LISs and SHSs are shown to provide excellent corrosion inhibition over all tested corrosion conditions, with negligible presence of corrosion species on the surfaces and no deterioration of the texturing. The surfaces are also shown to rejuvenate easily to the initial wettability and corrosion resistance values. This study provides valuable insights into the selection of materials and processing parameters for the fabrication of nonwetting surfaces for the application of interest.

Study on Corrosion Resistance and Conductivity of TiMoN Coatings with Different Mo Contents under Simulated PEMFC Cathode Environment.

TiMoN coatings with different Mo contents on a SS316L substrate are deposited by using closed field unbalanced magnetron sputtering ion plating (CFUMSIP) technology to enhance the corrosion resistance and durability of stainless steel (SS) bipolar plates (BPs) in proton exchange membrane fuel cell (PEMFC) during the start-up/shut-down process. The electrochemical test results illustrate that TiMoN-4A coating has extremely good corrosion resistance compared to other coatings. The potentiostat polarization (+0.6 VSCE) tests indicate that the corrosion current density (Icorr) of TiMoN-4A coating is 5.22 × 10−7A cm−2, which meets the department of energy 2020 targets (DOE, ≤1 × 10−6 A cm−2). Otherwise, TiMoN-4A coating also exhibits the best corrosion resistance and stability in potentiostatic polarization, electrochemical impedance spectroscopy (EIS), and high potential (+1.2VSCE) polarization tests. The interfacial contact resistance (ICR) measurement results show that TiMoN-4A coating has the minimum ICR of 9.19 mΩ·cm2, which meets the DOE 2020 targets (≤10 mΩ·cm2).

Construction of multilayer superhydrophobic film on Al alloy and corrosion resistance mechanism

The higher corrosion rates of aluminum alloys limit applications. In order to provide the service life, this paper uses anodic oxidation as a transition layer, adopts the layer-by-layer self-assembly technology was used to prepare anodized/perfluorooctyltriethoxysilane (POTS)/polypropylene (PP) (APP) composite films on aluminum alloys, and the film-forming mechanism was studied by molecular dynamics simulation and quantum chemical calculation. The APP composite film has excellent superhydrophobicity (contact angle of 157°), thermal shock stability and abrasion resistance. Electrochemical tests show that the resistance value of the super-hydrophobic composite film is increased from 103 to 109 Ω cm2, and the corrosion current density is reduced from 10−5 to 10−9 A/cm2. Acid-base test and salt spray test show excellent corrosion resistance and stability, can be widely used in complex environments, and have broad application prospects.

Investigation of Wafer-Level Fabricated Permanent Micromagnets for MEMS.

Monolithic integration of permanent micromagnets into MEMS structures offers many advantages in magnetic MEMS applications. A novel technique called PowderMEMS, based on the agglomeration of micron-sized powders by atomic layer deposition (ALD), has been used to fabricate permanent micromagnets on 8-inch wafers. In this paper, we report the fabrication and magnetic characterization of PowderMEMS micromagnets prepared from two different NdFeB powder particle sizes. A remanence of 423 mT and intrinsic coercivity of 924 mT is achieved at the low ALD process temperature of 75 °C, making this process compatible with MEMS technology. The magnetic reversible mechanism in the micromagnets is discussed with the help of the Wohlfarth equation. To ensure the operability of such integrated micromagnets in different application environments, we conducted a set of experiments to systematically investigate the thermal and corrosive stability. NdFeB micromagnets with larger powder particle size (d50 = 25 µm) exhibit high thermal stability in air. Furthermore, the corrosion stability of the micromagnets is significantly improved by an additional silicon oxide passivation layer deposited by plasma-enhanced chemical vapor deposition (PECVD). The presented results demonstrate the durability of PowderMEMS micromagnets, enabling their application in various fields, e.g., microfluidics, sensors, actuators, and microelectronics.

Controlling the mechanical properties and corrosion behavior of biomedical TiZrNb alloys by combining recrystallization and spinodal decomposition

Excellent comprehensive mechanical properties and corrosion resistance of TiZrNb equiatomic ratio medium-entropy alloy were obtained through recrystallization and spinodal decomposition. In addition to solid solution strengthening and recrystallization, the excellent mechanical properties can also be attributed to the hindering effect of nanoprecipitation formed via spinodal decomposition on the movement of dislocations. The high atomic arrangement density due to spinodal decomposition reduces the surface energy of the alloy passivation film, thereby increasing the activation energy of dissolution and the bonding energy between atoms, which improve the corrosion resistance and stability of the alloy passivation film. This work provides a new strategy to control the mechanical properties and corrosion resistance by combining recrystallization and spinodal decomposition.

Gravimetric and Statistical Data Analysis of the Protection Performance of <i>Aloe vulgaris</i> and <i>Nicotiana tabacum</i> Leaf Extracts on 1070 Aluminum and Mild Steel

The protection performance Aloe vulgaris (AV) and Nicotiana tabacum (NT) leaf extracts on 1070 aluminum (Al) were separately studied while the combined admixture of the extracts (AVNT) on mild steel (MS) was also studied in 3.5% NaCl solution by gravimetric analysis. Data output showed AV and NT effectively stifled the redox reaction process responsible for Al corrosion in NaCl with protection performance data above 98% throughout the exposure hours signifying strong resilience of the extract molecules withstanding the corrosive anions and thermodynamic stability with respect to exposure time. AVNT performed effective on mild steel at relatively lower efficiency, but with final values above 80% efficiency. Statistical data for standard deviation shows the degree of variation of protection performance data for AV, NT and AVNT extracts from mean value is minimal signifying consistent data value with respect to exposure time. Data also showed 100% of AV and NT protection performance data are above 98% efficiency value at +0% margin of error while 14.29% of AVNT protection performance data are above 95% efficiency at margin of error of +14.97%. Data from analysis of variance shows AV extract concentration and observation time strongly influences the performance out of AV at rated value of 42.06% and 29.41%. NT extract concentration solely dominated the performance output of NT at 95.37% while the performance of AVNT was independent of its concentration with values below threshold significance. However, AVNT performance varied significantly with observation time signifying progressive improvement in performance in over time.

Experimental investigation and neural network modeling of binary eutectic/ expanded graphite composites for medium temperature thermal energy storage

ABSTRACT The main objective of this present research work is to investigate the feasibility of LiNO3 + NaCl/expanded graphite (EG) composite phase change material for medium-temperature thermal energy storage systems. EG was used as supporting material to enhance the eutectic PCM samples thermal conductivity. The XRD, FTIR and SEM results reveal that EG particles are uniformly dispersed to the PCM material and show better chemical stability. The phase transition temperature and latent heat values of pure eutectic PCM and composite eutectic PCMs are experimentally measured with the help of differential scanning calorimetry (DSC). The calculated thermal conductivity intensification of composite PCM with 9% EG composition is 5.75, significantly more than pure PCM salt. The composite PCM showed good thermal reliability performance even after 500 thermal cycles. The charging time of the PCM significantly decreases with EG loading. The corrosion rate of five metal specimens is determined when embedded in pure PCM and composite PCM samples at more than phase transition temperature for 1440 h. The metal specimens embedded in composite PCM show good corrosion stability. Among all the selected metal specimens, stainless steel 316 L showed better corrosion resistivity in both PCM samples. Furthermore, an artificial neural network model is developed to predict the DSC output parameters such as temperature and heat flow at various EG loading (%), heating rate, and conversion points.

Fabrication of enhanced corrosion protection of PEO/PFOTES nanocomposite film coatings on aluminum alloy deposited by plasma electrolytic oxidation

In this study, PEO/PFOTES nanocomposite film was synthesized by Plasma electrolytic oxidation (PEO) followed by 1H, 1H, 2H, 2H-Perfluorodecyltriethoxysilane (PFOTES) sealing on Al 6061 alloys by dip-coating method. The relationship between surface morphology, coating thickness, and surface wettability of PEO samples and siloxane sealed samples were examined by FE-SEM and contact angle techniques. Furthermore, corrosion resistance of PEO coating and siloxane sealed samples were confirmed by Potential dynamic polarization and corrosion stability analysis in 3.5% NaCl solution. In conclusion, PFOTES sealing has the effect of changing the surface to super-hydrophobic, increasing corrosion resistance, and lowering corrosion rate. The 10P siloxane-coated sample shows the lowest corrosion rate, 4.916 × 10-5 mm/year, with a lower current density. In addition, the corrosion study also confirmed the excellent corrosion stability of PEO/PFOTES nanocomposite film over 864 h.

High Temperature Corrosion Stability of Ceramic Materials for Magnetohydrodynamic Generators

Abstract Corrosion by alkali metals and their compounds poses a significant challenge to the long-term material stability and service life for both metal alloys and ceramics at high operating temperatures. Chemical reactivity between alkali metals and materials underlie numerous industry challenges ranging from fireside corrosion in biomass-fired boilers to reaction with silica-based refractory ceramics in glass furnaces. The problem is particularly significant in magnetohydrodynamic (MHD) generators, where potassium or cesium compounds are introduced to improve the electrical conductivity of the working fluid. Thus, resistance to attack by alkali metal vapor is an important consideration in the selection and fabrication of ceramic electrodes and insulators for MHD generators. We evaluated several refractory ceramics to assess phase stability and known reactions with potassium and its compounds at high temperatures (T > 1,200 °C). Refractory ceramics were tested for potassium vapor corrosion using a modified ASTM standard test method with in situ monitoring of gas composition. Unlike other materials, the magnesia (MgO) and ceria (CeO2) samples did not exhibit corrosion, and no phase or mass changes were observed. This indicates that CeO2 and MgO could exhibit long lifetimes as plasma facing components in MHD generators. Ultimately, this development provides valuable data in evaluating critical materials performance issues that can attest to the viability of high temperature direct fired MHD generator applications.

A large scale self-supported WP–W2C nanoporous network for efficient hydrogen evolution reaction in alkaline media

A large-scale WP–W2C heterojunction with a nanoporous structure is constructed to enhance the HER performance and corrosion stability under high pH conditions, high temperatures and large current densities that satisfy industrial requirements.

Modification of gas-thermal coatings by laser radiation

The results of the researches which determine the dependence of gas-thermal coating porosity on the laser radiation parameters are given in the article. It determines such operational characteristics as thermocyclic and corrosion stability. In order to solve the problem, at the first stage the based on analytic dependences effect of a laser radiation to surface layers of gas-coating is described. The discontinuity of coating was taken into account, what was explained by presence of open and closes pores. It was shown that it’s necessary to produce the temperature range of “point of fusion — boiling point” on the surface of coating for the decrease of coating porosity as the action of laser radiation. The increase of the temperature above this range which is generated by the rise of the radiation rate results to evaporating of coating surface layers leading to its complete elimination in the thermal affect zone. At the second stage the experimental researches were realized. They consisted in the laser treatment of two types gas-thermal coating with a preliminary evaporation. The coatings which are based on the metal lic (PN-85-U-15) and non-metallic (Al2O3) components were analyzed. The quantitative assessment of porosity modification were realized by means of the based on Visual Studio 2008 program. This image processing program allows to compare the microstructure of the occupied by pores and coating material areas pixel-by-pixel. It has been established that the action of laser radiation leads to reduction of average porosity of gas-thermal coating. This reduction is: — the porosity in the initial position for coating of a PN 85-U-15-based alloy is 17 %; after the laser treatment it’s 5...8 %; — the porosity in the initial position for ceramic coating of Al2O3 is 24,5 %; after the laser treatment it’s 15...18 %.

Anomalous codeposition of NiCo alloy coatings and their corrosion behaviour

Here, we report the electrodeposition NiCo alloy coatings from a new bath using the glycine, as additive. A bright and uniform coatings NiCo alloy have been developed at different current densities and their corrosion performances have been evaluated. The surface morphology, composition and phase structure of alloy coatings have been analyzed using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and X-ray diffraction (XRD) techniques, respectively. The compositional information of NiCo alloy coatings revealed that the proposed bath follows anomalous type of codeposition over range of current density studied (1.0–4.0 A dm−2), by demonstrating more Wt. % of Co in the deposits, than in the bath. A constant increase in the Wt. % of Ni with current density was found, supported by XRD analyses; and it may be attributed to the depletion of more readily depositable Co+2 ions at cathode film by following the principle of codeposition of NiCo alloy. The corrosion study revealed that NiCo alloy deposited at 4.0 A dm−2, represented as (NiCo) 4.0 A dm-2 coating is the most corrosion resistant compared to all other coatings. The highest corrosion stability of (NiCo) 4.0 A dm-2 alloy attributed to its highest Ni content (38.6 wt%) and increased surface smoothness, supported by EDS and SEM study.

Tuning surface wettability of aluminum surface and its correlation with short and long term corrosion resistance in saline solutions

In this work, we fabricated superhydrophilic aluminum alloy (AA 6063) with a hierarchical labyrinth-like structure using a facile and environmentally benign chemical etching method. The patterned samples were functionalized by stearic acid molecules to obtain superhydrophobic samples with water contact angle (CA) >160°, at optimum conditions. Although the superhydrophobic samples initially exhibited up to two orders of magnitude better corrosion resistance compared to as-received samples, their corrosion performance and CA gradually reduced upon prolonged exposure to 3.5 wt% NaCl solution. Hence, we experimetally show that the initial high CA in superhydrophobic surface layers cannot be used as a measure of their long-term corrosion stability.

High Temperature Corrosion Behavior of High Velocity Oxy Fuel Sprayed NiCrMoFeCoAl-30%SiO2 and NiCrMoFeCoAl-30%Cr2O3 Composite Coatings on ASTM SA213-T22 Steel in a Coal-fired Boiler Environment

High-velocity oxy fuel (HVOF) sprayed coatings can improve the corrosion resistance of bare ASTM SA213-T22 boiler steel. In this report, we have investigated the NiCrMoFeCoAl-30%SiO2 and NiCrMoFeCoAl-30%Cr2O3 composite coatings were deposited on bare ASTM SA213-T22 boiler steel for corrosion protection. High-temperature corrosion studies were conducted in a molten salt (Na2SO4-60%V2O5) environment at 700ºC under thermo-cyclic conditions. The as-sprayed composite coatings are characterized for microstructure and mechanical properties. The thermo-gravimetric method was utilized to understand the kinetics of corrosion. Characterization of the corrosion products was examined by using scanning electron microscope (SEM)/ Energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) techniques. The obtained results suggest both the composite coatings are favorable to corrosion resistance over the bare ASTM SA213-T22 boiler steel. The NiCrMoFeCoAl-30%Cr2O3 composite coating was concluded to present a superior corrosion resistance in the high-temperature corrosion environment because of the uniform distribution of the composite coating matrix and the development of protective protection Cr2O3 in the scale. The molten salt heat-treated chromium oxide containing coating shows good corrosion stability than the silica composite. This could be attributed to the high temperature assisted formation metal chromates, chromites and oxide layers.

Electronic structure manipulation via composition tuning for the development of highly conductive and acid-stable oxides

Our combined computations and experiments suggest the Mg-Ti-O chemical spaces for novel ternary oxide compounds that can offer high conductivity and corrosion stability to be used in fuel cell applications.

Влияние стадийного азотирования на строение и свойства мартенситной стали 13Х11Н2В2МФ

A new method of gas nitriding is presented, which produces obtaining high-quality diffusion layers that meet the requirements of the use for various purposes, including aviation ones. Peculiar properties of highly alloyed martensitic steel nitriding after stadial thermo-gas-cyclic nitrogenization under partially dissociated ammonia with air additives have been examined. The results of metallographic studies, diagnostic leach, tests for wear resistance, impact hardness and corrosion stability, depending on the test mode are presented.

Effect of cryogenic treated tool electrode during electric discharge drilling (EDD) of Inconel 800

Inconel 800 is widely used material for construction of equipment and which requires corrosion resistance, heat resistance, strength, and stability. These properties make them potential material for components in aerospace industries, gas turbine etc. The conventional drilling in Inconel 800 sometimes become uneconomical because of low productivity, poor quality and inaccurate geometry. Electric Discharge Drilling (EDD), a variant of EDM, is one such process which can produce high accuracy holes, thus improving overall productivity and reducing the cycle time. This paper describes an experimental study on EDD of Inconel 800 using self-developed EDD set up. The holes were drilled using copper tool electrode. The effect of tool electrode treatment (cryogenic and untreated), discharge current (Id), pulse-on time (TON), gap voltage (Vg) and tool electrode speed (N) on material removal rate (MRR), electrode wear rate (EWR) and radial overcut (ROC) have been studied. The experimental runs were carried out using L18 (21 × 34) orthogonal array and result were analyzed using Taguchi’s methodology. It was observed that the optimal parameter setting for MRR are TET (cryogenically treated), Id (15A), TON (120 µs) and N (200 rpm), for EWR- TET (cryogenically treated), Id (9A), TON (120 µs) and N (200 rpm) and for ROC- TET (cryogenically treated) and Id (12 A). It was also observed that with the use of cryogenically treated tool electrode an appreciable improvement in the MRR by 9.89%, EWR by 21.73% and ROC by 36.15% is achieved, which confirm the viability of using the cryogenically treated tool electrode and relevance to industry.

Discrete curvature-based shape configuration of composite pipes for local buckling detection based on fiber Bragg grating sensors

For the high strength, good corrosion resistance and stability, carbon fiber reinforced polymer (CFRP) composites can be made into pipes to transfer gasses and oils in submarine environment. Structural performance and shape of CFRP composite pipes are particularly important to sustain the regular operation of the delivery system. To obtain the in-field shape and identify the local buckling of CFRP composite pipes, quasi-distributed optical fiber sensing techniques have been developed based on the multiplex of fiber Bragg grating (FBG) sensors. Theoretical investigation on shape profile configuration of the pipes based on the measured strains has been performed. Relationship between the accuracy of configuration algorithm and the sensor layout has also been explored. Experiments have been conducted to check the effectiveness and accuracy of the proposed sensing technique and curve configuration algorithm. Results validate good measurement performance of the proposed sensors and high accuracy of the shape-configuration algorithm. Suggestions on the sensor layout of long-distance pipe structures are provided with the comprehensive consideration of overall structural shape control and economical factor. The study can be adopted to instruct the establishment of the structural health monitoring system, identify the buckling and assess the safety operation of pipe structures.