Stainless Steel In NaCl Solution Research Articles

Microstructures and mechanical properties of CoCrFeNiAl0.3 high-entropy alloy thin films by pulsed laser deposition

Recently much attention has been paid to high-entropy alloy thin films (HEATFs) due to their excellent physical and chemical properties. Simultaneously, pulsed laser deposition (PLD) is an increasingly focused method for thin film preparation due to its remarkable advantages. In this study, CoCrFeNiAl0.3 HEATFs were prepared on silicon substrates in a high vacuum chamber at room temperature for different deposition time by PLD. The microscopic morphologies, chemical composition, elastic modulus, nanohardness and corrosion behaviors of the CoCrFeNiAl0.3 HEATFs were systematically investigated. The microscopic morphology shows that there are some nanoscale granules on the surface of the HEATFs. The nanoindentation results indicated that the CoCrFeNiAl0.3 HEATFs have higher nanohardness but lower elastic modulus than the bulk counterparts. With increasing the deposition time, elastic modulus and nanohardness become higher initially and then decrease, which reaches at highest as the deposition time for 2 h. Corrosion behaviors experiments verified that CoCrFeNiAl0.3 HEATFs have higher corrosion resistance than 316 L stainless steel in NaCl solution. Our results could provide a new advanced method for preparing HEATFs, and in-depth understanding the mechanics and corrosion behaviors of HEATFs for future application.

Synergistic inhibition behavior of sodium tungstate and penicillin G as an eco-friendly inhibitor on pitting corrosion of 304 stainless steel in NaCl solution using Design of Experiment

In this study the synergistic behavior of sodium tungstate and penicillin G as an environmental-friendly co-inhibitor on pitting corrosion of 304 stainless steel in 3.5 wt% NaCl solution has been investigated. The simultaneous effect of temperature and inhibitor on inhibition efficiency has been evaluated by employing Design of Experiment technique according to Central Composite Design method. The temperature and concentration of inhibitors were selected as independent factors, while the extent of passive region and inhibition efficiency were considered as the responses of independent factors. Cyclic potentiodynamic polarization and electrochemical impedance spectroscopy were employed to determine the responses experimentally. The surface morphology and chemical composition of surface film were characterized by a Scanning Electron Microscope. The electrochemical measurements showed that increase in the concentration of penicillin G up to 50 ppm as co-inhibitor in the presence of 2.5 mM sodium tungstate resulted in the highest possible extent of passive region and inhibition efficiency. The increase in the extent of passive region and inhibition efficiency due to addition of penicillin G as co-inhibitor to sodium tungstate showed the synergistic behavior of the mixed inhibitors in controlling pitting corrosion of 304 stainless steel. It was revealed that the extent of passive region and inhibition efficiency decrease by increase in temperature of the solution due to increase in the kinetics of corrosion reactions and desorption of inhibitor from surface. The SEM observations indicated that the mixed inhibitors could provide a smooth and uniform surface due to formation of a protective film.

A Comparative Study of Inhibitive Effect of Waste Product on Stainless Steel Corrosion in Sodium Chloride/Sulfuric Acid Environments

Eggshell powder (ES) inhibitive effect on Type 316 austenitic stainless steel (SS) corrosion in sodium chloride and sulfuric acid solutions was studied using weight loss, linear polarization, scanning electron microscopy, and energy-dispersive X-ray spectroscopy (SEM/EDX) techniques. Experimental observation proves the inhibitor to be effective in both media with inhibition efficiencies of 99.99 and 94.74% owing to the inhibitive action of ES molecules in the chloride and acid solutions. Stainless steel samples in chloride solution have significantly lower corrosion rate values than stainless steel samples in sulfuric acid solution at all concentrations studied. The preferential adsorption of residue ES monomers in the inhibitor decreased the corrosion rate value. Polarization curve measurements show that ES is a mixed type inhibitor for SS corrosion in 0.5 M H2SO4 and 3.5% NaCl solutions. The ES inhibited the SS corrosion in both studied media and its inhibition depends on exposure time, concentration, and environment. Stainless steel ES adsorption follows Langmuir adsorption isotherm. SEM/EDX investigation shows less corroded surface, fewer pits for SS in NaCl/ES solution with slight deduction in the chromium composition percentage, and other alloying elements compared to SS sample in H2SO4/ES solution. The applied techniques explained that ES is an effective inhibitor for Type 316 SS in NaCl solution than in H2SO4 solution. Good agreement between linear polarization and weight loss results was observed.

Electrochemical noise assessment of effect of sol parameters on the performance of an eco-friendly silane sol-gel coating on 304L stainless steel

ProposeThis paper aims to access the protective function of hybrid sol-gel coatings deposited on 304L stainless steel substrate in silane solutions containing a mixture of tetraethoxysilane, methyltriethoxysilane and glycidyloxypropyltrimethoxysilane with different pH values during various immersion periods.Design/methodology/approachThe 304L stainless steels coated through 10 and 30 s of immersion in the silane solutions with pH values of 2.1 and 2.8 were exposed to NaCl solution. The corrosion resistance of the coated substrates was studied through taking advantage of electrochemical noise method as well as atomic force microscopy (AFM), water contact angle and field emission-type scanning electron microscopy (FESEM) surface analysis.FindingsThe electrochemical current noise, PSD (I) plot, noise resistance and characteristic charge as parameters extracted from electrochemical noise method indicated the superiority of eco-friendly silane coating deposited on the substrate surface during 10 s exposure to the solution, due to the film uniformity and homogeneity as confirmed by FESEM and AFM. Moreover, immersion of the stainless steel in the silane solution with pH 2.1, characterized by higher hydrolysis ratio, led to more effective corrosion control in the NaCl electrolyte according to the results of electrochemical noise and FTIR measurements.Research limitations/implicationsThe noise resistance and characteristic charge as electrochemical noise parameters were only used in this research to evaluate the protective behavior of the water-based silane sol-gel coatings. Future studies should examine the correlation between electrochemical noise data and the parameters extracted from other electrochemical methods, e.g. electrochemical impedance spectroscopy.Practical implicationsThe data obtained in this research may provide an effective approach based on electrochemical noise method to screen the silane sol-gel coatings for protection of metallic substrates against corrosion.Originality/valueAccording to the literature, no report can be found studying the effect of immersion time on a silane solution, including glycidyloxypropyltrimethoxysilane, tetraethoxysilane and methyltriethoxysilane, as well as the silane solution pH on the corrosion resistance of 304L stainless steel in NaCl solution through electrochemical noise method.

The Role of Pitting at Mns Inclusions in Intergranular Corrosion of Sensitized Type 304 Stainless Steel in NaCl Solution

The degree of sensitization and susceptibility of intergranular corrosion of austenitic stainless steels are properly evaluated from immersion testing in acidic solutions as rapid screening methods. However, most of stainless steels are used in near-neutral pH environments, and the typical corrosion morphology in these environments is pitting. Acidification is known to occur inside pits due to the hydrolysis reaction of dissolving metal ions. Under practical service conditions around neutral pH such as seawater and river water, pitting is assumed to be closely related to the initiation of intergranular corrosion. It is well-known that non-metallic inclusions, such as MnS, act as the initiation sites for pitting of stainless steels. Chiba et al. demonstrated that a small inclusion-free area on Type 304 indicated superior pitting corrosion resistance even in 3 M NaCl. 1) It would appear that MnS inclusions strongly affect pitting and intergranular corrosion of sensitized stainless steels. To clarify the role of pitting at MnS inclusions in intergranular corrosion of sensitized Type 304 stainless steel (sensitized at 923 K), in situ observations were carried out during micro-scale anodic polarization in 1 M NaCl (pH 5.4). Micro-scale potentiodynamic anodic polarization was performed for a small area with a MnS inclusion at a sensitized grain boundary. Intergranular corrosion was initiated from the pit that was generated at the MnS inclusion located at the sensitized grain boundary. Acidification inside the pit probably caused intergranular corrosion due to the transition from passive to active state. In 1 M NaCl, the depassivation pH values at the sensitized grain boundary with and without MnS inclusions were 1.0 and 0.4, respectively. It is likely that the dissolution of MnS accelerates the depassivation and promote the initiation pf intergranular corrosion. The dissolution products from MnS are supposed to accelerate depassivation of Cr-depleted regions. 1) A. Chiba, I. Muto, Y. Sugawara, N. Hara, J. Electrochem. Soc., 160, C511-C520 (2013).

Microstructure and properties of Fe5Cr5SiTiCoNbMoW coating by laser cladding

ABSTRACTTo improve anti-corrosion and wear resistance, a new kind of Fe5Cr5SiTiCoNbMoW high-entropy alloy (HEA) coating was fabricated successfully on Q235 by laser cladding technology. The microstructure, phase structure, microhardness, anti-corrosion and wear resistance were researched using metallographic microscope, scanning electron microscope, X-ray diffraction, microhardness tester, electrochemical workstation as well as friction and wear testing machine, respectively. The experimental results show that the microstructure of cladding coating is composed of dendrite and eutectic crystal. The main phase in the coating is single body-centered cubic solid solution. The anti-corrosion of HEA coating is better than that of 304 stainless steel in NaCl solution. Moreover, the average microhardness of HEA coating is nearly 600 HV0.2, which is almost five times higher than that of Q235 substrate. The HEA coating is of low friction coefficient and mass loss, exhibiting excellent wear resistance.

Enhanced visible light-driven activity of TiO2 nanotube array photoanode co-sensitized by “green” AgInS2 photosensitizer and In2S3 buffer layer

The AgInS2/In2S3 nanoparticles (NPs) co-sensitized TiO2 nanotube array (NTA) photoanodes with high photoelectrochemical (PEC) conversion efficiency are prepared and optimized. The In2S3 buffer layer around AgInS2 absorber layer significantly improves the charge generation/separation efficiency of the prepared photoanode. Compared with single AgInS2 NPs sensitized TiO2 NTAs, the design of the AgInS2/In2S3 heterojunction NPs sensitized TiO2 NTAs further promotes the charge transfer in the system, and avoids the unmatched energy band alignment between AgInS2 and TiO2. The AgInS2(3)/In2S3(5) NPs co-sensitized TiO2 NTAs possess the best PEC conversion performance. The AgInS2 and In2S3 NPs distribute uniformly on TiO2 NTAs to form close interfacial adhesion. Simultaneously, the one-dimensional TiO2 nanotubes serve as the direct electron pathways and ensure the rapid collection of charge carriers generated by the system. Moreover, due to the more negative Fermi levels and energy band potentials of AgInS2 and In2S3, the prepared TiO2 NTA/AgInS2(3)/In2S3(5) photoanode also exhibits an excellent PEC cathodic protection performance for 316L stainless steel in NaCl solution.

Combining lithography and capillary techniques for local electrochemical property measurements

The relationships between composition, microstructure and electrochemical properties are of fundamental importance in understanding the corrosion of multiphase materials and thus in aiding in the design of new materials. A local electrochemical test system which combines a capillary device with a photolithographic mask has been developed to investigate the local electrochemical properties of a predefined micron-sized area with greater reliability and versatility than existing approaches. Independent electrochemical measurements were conducted on the different phases of a 2205 duplex stainless steel in NaCl solution, demonstrating the feasibility of the developed test system.

Corrosion Behavior of High-Nitrogen Stainless Steel in NaCl Solution

Corrosion Behavior of High-Nitrogen Stainless Steel in NaCl Solution

Microstructure, Mechanical and Corrosion Behaviors of CoCrFeNiAl0.3 High Entropy Alloy (HEA) Films

The HEA-CoCrFeNiAl0.3 thin film in this study has been successfully developed by radio frequency (RF) magnetron sputtering to meet the increasing demand in engineering applications. Its microstructure and surface profile were investigated accordingly. The as-synthesized HEA film was found to have a homogeneous element distribution and ultra-smooth surface, exhibiting a typical face-centered cubic (FCC) solid solution. The film showed better mechanical properties than its bulk counterpart, with a Young’s modulus and hardness of ~201.4 GPa and ~11.5 GPa, respectively. Furthermore, corrosion tests demonstrated decreased sensitivity to localized corrosion in comparison to the commercial 304 stainless steel in NaCl solution.

A fabrication of iridium oxide film pH micro-sensor on Pt ultramicroelectrode and its application on in-situ pH distribution of 316L stainless steel corrosion at open circuit potential

An all solid-state pH micro-sensor has been developed using anodic electrodeposition of an iridium oxide (IrOx) film onto a 10μm platinum ultramicroelectrode. The electrochemical growth of the IrOx film was accomplished by 100 potential sweeps at 50mV/s, at different potential ranges of electrochemical deposition, followed by heat treatment at 100°C for 2h. The pH micro-sensor shows quick response to the pH variation, excellent sensitivity, stability and long lifetime in a wide pH range between 1.0 and 13.0. The slope of potential-pH response curve is found to dependent on the Ir(III)/Ir(IV) ratio of in the film, determined by XPS analysis, which is a consequence of scanning potential range during the anodic electrodeposition. The sensor has been employed to explore the localized pH distribution during the corrosion of 316L stainless steel in NaCl solution at open circuit potential and results show that localized anodic and cathodic sites on the 316L stainless steel can be accurately monitored and the pH difference between the cathodic and anodic zones increases from 0.22 to 1.27 with the prolonging of the immersion time.

Microstructures and corrosion resistance of Fe-based amorphous/nanocrystalline coating fabricated by laser cladding

Fe-based amorphous/nanocrystalline coatings were fabricated with industrial FeCoCrMoCBY alloy plate on the mild steel surface by laser cladding. The formation, microstructure were investigated with optical microscope (OM), transmission electron microscope (TEM) and X-ray diffraction (XRD). The results indicate that few pore and just only some cracks are formed in all of the coatings. With increase of heat input, some crystal phases of a-Fe, Fe3C and Fe23C6 are precipitated gradually in the coating layers, and the microhardness of the coating layers decreases gradually, while the maximum microhardness is up to 1300 Hv near to 5 times high than that of substrate. Though the passive currents of coating layers increase with increase of heat input, all of coating layers exhibit low corrosion current density, passive current density and wide passive region, which means all of coating layers present excellent corrosion resistance, even more superiors than that of 316L stainless steel in NaCl solution.

Thickness-properties synergy in organic–inorganic consolidated melting-gel coatings for protection of 304 stainless steel in NaCl solutions

Homogeneous and crack-free methyl-substituted organic–inorganic hybrid glass coatings (thickness up to 10μm) were deposited on AISI 304 stainless steel. Different hybrid glasses obtained from consolidation of the diluted melting gels with various methyltriethoxysilane (MTES)/dimethyldiethoxysilane (DMDES) ratios were evaluated considering chemical structure, coating adhesion and corrosion protection. The 70MTES/30DMDES (molar%) melting-gel coating provided improved corrosion protection for this steel due to the synergy of different properties: a highly cross-linked inorganic structure, a coating plasticity based on the hybrid network, and a good adhesion to the substrate through hydroxyl groups. Electrochemical results show a good barrier film with a passive range of 500mV, a low anodic current density (0.03nAcm−2) and impedance values of 109.5Ωcm2 after two months of immersion in 3.5wt.% NaCl solution.

Local Electrochemistry and In Situ Microscopy of Pitting at Sensitized Grain Boundary of Type 304 Stainless Steel in NaCl Solution

To elucidate the pit initiation behavior of sensitized stainless steels, the anodic polarization of a single grain boundary was examined in 0.1 M NaCl (pH 5.4) at 298 K using a micro-electrochemical system. For Type 304 heat-treated at 923 K for 2 h, no pitting was initiated on a small area (ca. 100 μm × 100 μm) with a sensitized grain boundary without MnS inclusions. However, stable pitting was observed on the electrode area that was larger than ca. 200 μm × 200 μm. In situ microscopy revealed that the first step in corrosion was a spherical pit generated at a MnS inclusion at a sensitized grain boundary, and that intergranular corrosion started at the pit. The local depassivation of the Cr-depleted zone along the sensitized grain boundary was thought to be introduced by the dissolution of the inclusion. The co-existence of the MnS inclusion and the Cr-depleted zone was considered to be the critical factor in the pit initiation of sensitized stainless steels in NaCl solutions.

Pitting at the δ/γ Boundary of Type 304 Stainless Steel in NaCl Solution: The Role of Oxide Inclusions and Segregation

The role of inclusion compositions and the pit initiation mechanism at the δ/γ boundary of cast Type 304 stainless steel was investigated in 1 M NaCl. Three types of inclusions were detected: large CaO-SiO2-MgO-Al2O3 slag inclusions (Type I) and small SiO2-Al2O3-MnO-Cr2O3-TiO2 complex oxide inclusions that were located at the δ/γ boundaries (Type II) or found in the γ phases (Type III). In Types II and III, a small amount of Ca was occasionally detected. In micro-scale polarization, the size of the electrode area was changed from 0.01 to 10 mm2, and the number densities for the stable and meta-stable pit initiation sites were estimated to be 0.1 and 1 site mm−2, respectively. Type II inclusions acted as the pit initiation sites at the δ/γ boundary. At the δ/γ boundary without an inclusion, a meta-stable pit was initiated. The segregation of P and S was detected at the boundary where the pit was initiated, but no accumulation of Si was observed. At a randomly selected boundary of δ/γ on the steel, no clear segregation of P and S was observed, but the Si concentration was two to three times higher than the average Si concentration in the steel.

Corrosion and tribocorrosion behaviour of super‐thick diamond‐like carbon films deposited on stainless steel in NaCl solution

Super‐thick diamond‐like carbon (DLC) film is a potential protective coating in corrosive environments. In the present work, three kinds of DLC films whose thickness and modulation periods are 4 µm and 3, 21 µm and 17 and 21 µm and 7, respectively, were fabricated on stainless steel. The effect of different thickness and modulation periods on corrosion and tribocorrosion behaviour of the DLC‐coating stainless steel was investigated in 3.5 wt% NaCl aqueous solution by a ball‐on‐flat tribometer equipped with a three‐electrode electrochemical cell. The DLC‐coating stainless steel served as a working electrode, and its OCP and potentiodynamic polarization were monitored before and during rubbing. The wear–corrosion mechanism of the DLC films was investigated by SEM. The results showed that the increasing thickness can prolong significantly lifetime of DLC films in NaCl aqueous solution. In particular, the modulation period has a significant impact on the tribocorrosion resistance of the DLC super‐thick films. The study suggested that the increasing thickness of compressive stress layer could suppress film damage by reducing crack propagation rate. Thus, the super‐thick DLC film with thickness of 21 µm and 7 periods presented the best tribocorrosion resistance among all studied films. Copyright © 2016 John Wiley & Sons, Ltd.

Optimization of the Electrochemical Acceleration for Actual Corrosion Behavior of Hot-Dip Aluminized Ferritic Stainless Steel in NaCl Solution

Optimization of the Electrochemical Acceleration for Actual Corrosion Behavior of Hot-Dip Aluminized Ferritic Stainless Steel in NaCl Solution

Electrochemical Corrosion and Critical Pitting Temperature of S32750 Super Duplex Stainless Steel in NaCl Solution

The electrochemical corrosion behavior and critical pitting temperature (CPT) of S32750 super duplex stainless steel in 3.5%NaCl solution were investigated by electrochemical techniques. The morphologies of the steel before after pitting corrosion were observed by scanning electron mi- croscope. The CPT of the S32750 steel was identified as 71 ℃. A passive film could form on the steel surface when the solution temperature was below the CPT. While, when the solution tempera- ture was above the CPT, pitting corrosion occurred on the steel surface as the result of the break- down of the passive film due to the increase of the Cl - activity. Pitting corrosion became more seri- ous with the increasing temperature. Moreover, the corrosion models of the steel below and above the CPT were sketched respectively.

Critical conditions for pit initiation and growth of austenitic stainless steels

The pitting behaviour of 316 stainless steel in NaCl solution was investigated using potentiodynamic (PD) and potentiostatic (PS) polarization. Tests with the mode change from PD to PS at potentials close to the pitting potential showed that the potential could play a role in the stable pitting by maintaining the pit stability product. The metastable pit growth was studied by changing the mode at potentials far below the pitting potential and by characterizing the first current density spikes. The results suggested that the cumulative electric charge density governs the metastable pit initiation as a critical condition.

Inhibition Pitting Corrosion of A-890-1B Stainless steel in NaCl Solution by 5-amino-1,3,4 - thiadiazole -2- thiol

Inhibition Pitting Corrosion of A-890-1B Stainless steel in NaCl Solution by 5-amino-1,3,4 - thiadiazole -2- thiol