Stainless Steel In NaCl Solution Research Articles

Crevice Corrosion Behavior of 201 Stainless Steel in NaCl Solutions with Different pH Values by In Situ Monitoring.

Crevice corrosion (CC) behavior of 201 stainless steel (SS) in 1 M NaCl + x M HCl/y M NaOH solutions with various pH was investigated using SECM and optical microscopic observations. Results show that the CC was initiated by the decrease in pH value within the crevice. The pH value near the crevice mouth falls rapidly to 1.38 in the first 2 h in the strongly acidic solution, while the pH value was observed to rise firstly and then decrease in the neutral and alkaline solutions. It indicates there is no incubation phase in the CC evolution of 201-SS in a pH = 2.00 solution, while an incubation phase was observed in pH = 7.00 and 11.00 solutions. Additionally, there appeared to be a radial pH variation within the gap over time. The pH value is the lowest at the gap mouth, which is in line with the in situ optical observation result that the severely corroded region is at the mouth of the gap. The decrease in pH value inside results in the negative shift of open circuit potential (OCP) and the initiation of CC of 201-SS. The increased anodic dissolution rate in the acidic solution accelerates the breakdown of passive film inside, reducing the initiation time and stimulating the spread of CC.

Corrosive-Wear Performance of Grade 316 Stainless Steel Sliding Against Grade 316 Stainless Steel in NaCl Solution

Corrosive-Wear Performance of Grade 316 Stainless Steel Sliding Against Grade 316 Stainless Steel in NaCl Solution

Localized corrosion of 15–5 PH and 17–4 PH stainless steel in NaCl solution

Localized corrosion of 15–5 PH and 17–4 PH stainless steel in NaCl solution

Modeling and Predicting Reduction Reaction Kinetics for a Stainless-Steel in NaCl Solutions

A method for analyzing cathodic polarization curves on stainless steels is described and a framework for predicting the cathodic polarization response for UNS S13800 is developed, including a model for the diffusivity of dissolved oxygen as a function of chloride concentration and temperature. The cathodic polarization behavior of UNS S13800 in NaCl solutions, ranging from dilute to saturated, and across a range of temperature values was studied using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and X-ray photoelectron spectroscopy (XPS). Analysis of the data indicated that the concentration of the solutions affected the ability of the oxide to catalyze reduction reactions. Dilute-to-low concentration solutions exhibited different Tafel slopes in the ORR-activation region while middle-to-high concentration solutions exhibited a single Tafel slope. The XPS and EIS results show a slightly thicker oxide formed in the low chloride concentration solutions over the course of the 18 hour open circuit duration along with a higher concentration of Fe3+ species.. The EIS data also showed the oxide formed in the low chloride solution had a higher charge-transfer resistance while the oxide formed in the high chloride solution had a higher oxide resistance.

Effect of crevice gap on crevice corrosion initiation and development of 2205 duplex stainless steel in NaCl solution

The crevice geometry has an important influence on the initiation and development of crevice corrosion. The crevice gap size determines the volume of the crevice solution and the cross-sectional area of the material exchange channel between the crevice solution and bulk solution, and it is the dominant factor of the initiation and development mechanism of crevice corrosion. In this paper, the effect of crevice gap size on the crevice corrosion behavior of 2205 duplex stainless steel (DSS) in NaCl solution was investigated by electrochemical method combined with modeling. The quantitative contribution of the volume effect of crevice solution and the diffusion effect of H+ on the crevice corrosion initiation period, as well as the corrosion characteristics and mechanism at initiation and development periods of crevice corrosion, were discussed. Results show that the initiation process of crevice corrosion of 2205 DSS in 3.5 wt% NaCl solution follows the critical crevice solution mechanism. The crevice gap size affects the acidification rate of the crevice solution and the initiation period time of crevice corrosion through the volume effect and the diffusion effect. The influence of diffusion effect on the initiation period time was more significant than volume effect. The corrosion development process is mainly determined by the potential and current density distribution within the crevice, and thus follows the IR drop mechanism (I refers to the current and R refers to the resistance). The crevice gap size is the dominant factor for the development mechanism of crevice corrosion.

Accelerated deterioration mechanism of 316L stainless steel in NaCl solution under the intermittent tribocorrosion process

In this research, the tribocorrosion behavior of 316L stainless steel in simulated seawater was investigated under continuous and intermittent sliding at open circuit potential. The tribocorrosion mechanism was discussed in terms of wear morphologies, mechanical property as well as chemical composition. Meanwhile, microstructure evolution inside the wear track and open circuit potential recorded after sliding were analyzed to quantify the repassivation kinetics and evaluate the impact of the regenerated passive film on wear. The results showed that the wear rate increased under intermittent sliding when the pause time is long enough to repassivate after sliding. Repeated sliding promoted the refinement of the grain inside the sliding area, which was beneficial to the generation of the thicker and more compact passive film inside the wear track. The ruptured passive film often acted as abrasives during subsequent sliding. Therefore, the accelerated material loss under intermittent sliding was attributed to the periodic mechanical removal of the thickened passive film and the enhanced abrasive wear inside the wear track.

Corrosion behavior of 2205 duplex stainless steel in NaCl solutions containing sulfide ions

The corrosion behavior of 2205 duplex stainless steel (DSS) in sulfide-containing NaCl solutions at different pH values are investigated. In 0.8 g/L NaCl solutions, the 2205 DSS pitting corrosion resistance increased with Na2S addition. The pH has significant effects on the corrosion mechanism of 2205 DSS in a 35 g/L NaCl solution with sulfide. In 35 g/L NaCl solutions, addition of Na2S can improve pitting resistance of 2205 DSS at pH 11.5, but the Na2S addition promotes pitting corrosion at pH 9, 7 and 4. At pH 7, the pitting corrosion resistance of 2205 DSS is the worst with sulfide.

Evolution of the Corrosion Products Around Mns Embedded in 304 Stainless Steel in Nacl Solution

Evolution of the Corrosion Products Around Mns Embedded in 304 Stainless Steel in Nacl Solution

Electrosynthesis of a Duplex Coating Consisting of a Cerium-Based Layer and a Polypyrrole Film for the Corrosion Protection of AISI 304 Stainless Steel

Duplex coating consisting of an inner cerium-based layer and polypyrrole (PPy) film topcoat was electrodeposited onto AISI 304 stainless steel. The cerium-based coating was electrodeposited in solutions containing cerium nitrate at 50 ºC. The polymeric outer layer was electropolymerized in the presence of sodium bis(2-ethylhexyl) sulfosuccinate (AOT). The electrosynthesis was done under potentiostat conditions. The coatings were characterized by scanning electron microscopy (SEM) and energy dispersive x-ray spectrometry (EDX). The morphology of the double-layered cerium polypyrrole film shows a granular structure with the presence of agglomerates of small grains. 
 The anticorrosive performance of the coatings was evaluated in sodium chloride solution by linear polarization, open circuit measurements, and electrochemical impedance spectroscopy (EIS). Single films, cerium layer and PPy coating, and the duplex film all reduce the corrosion rate of AISI 304 stainless steel in NaCl solution. The duplex coating presents an improved corrosion resistance concerning the single films. The combination of the characteristics of the single layers is responsible for the superior corrosion protection efficiency of the double-layered cerium polypyrrole coating.

Evaluation of Corrosion Inhibition of 316L Stainless Steel by Permanganate Ions in Chloride Solution

The efficiency of permanganates to inhibit the scale deposit captured the attention for more investigation on their role as corrosion inhibitor. In this article, the effect of permanganate as corrosion inhibitor on 316L stainless steel in NaCl solution is investigated. The potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) have been performed by varying the electrode stirring speed, the concentration of permanganate ions, pH and the temperature. The results show that the permanganate ions increase the cathodic and anodic currents under effect of stirring speed, due to oxygen reduction reaction and the reduction of permanganate ions. Electrochemical results indicate that the deposit of manganese oxide (MnO2) inhibits the pitting corrosion. The inhibition efficiency is up to 98 % for 10−4 mol.dm−3 of permanganate. The temperature reduces the effectiveness of permanganates against pitting corrosion, the pitting potential shifts cathodically from +0.395 V vs. Saturated Calomel Electrode (SCE) at 298 K to +0.275 V vs. SCE at 343 K. Surface morphology of the deposit oxide films and electrode are studied by emission scanning electron microscopy, X-ray diffraction, Fourier transform infrared and Differential Scanning Calorimetry. The analysis of the deposit layer by X-ray diffraction revealed the presence of δ-MnO2 form, with a crystallite size of 3.17 nm. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Evolution of the Corrosion Products Around Mns Embedded in 304 Stainless Steel in Nacl Solution

Evolution of the Corrosion Products Around Mns Embedded in 304 Stainless Steel in Nacl Solution

Effect of Cu Addition on the Microstructure and Passivation Behavior of Sn Alloyed Ferritic Stainless Steel in NaCl Solution

In this work, the effect of Cu addition on the microstructure and corrosion passivation behavior of Sn alloyed ferritic stainless steel in 3.5 wt.% NaCl solution at 30 °C was investigated by optical microscope (OM), scanning electron microscope (SEM), energy-dispersion spectrum (EDS), potentiodynamic polarization curve and x-ray photoelectron spectroscopy (XPS). The results indicate that Cu addition has certain effect on grain refinement of ferritic stainless steel. Meanwhile, Cu addition has little influence on the cathodic corrosion process of ferritic stainless steel in 3.5 wt.% NaCl solution but shows beneficial effect on enhancing both the corrosion resistance of steel substrate and its passivation behavior. It has been found that the deposition of Cu particles at the bottom of corrosion pits is responsible for the better corrosion resistance and passivation behavior of ferritic stainless steel. Moreover, there is synergistic effect between Sn and Cu on enhancing the corrosion resistance of ferric stainless steel matrix and improving its passivation behavior in NaCl solution.

(Invited) Micro-Electrochemistry of Pit Initiation at Non-Metallic Inclusions of Stainless Steels and Roles of Alloying Elements in Improving Corrosion Resistance

A micro-electrochemical system for in situ high-resolution optical microscopy was developed and applied to the real-time observation of pit initiation at MnS inclusions in Type 304 stainless steel in NaCl solutions. Metastable and stable pits were found to be initiated at the MnS/steel boundaries during potentiodynamic polarization. After polarization, it was confirmed that deep trenches were generated at the boundaries. Therefore, metastable and stable pits were determined to be initiated in the trenches. From the real-time observation, it was found that the initial rounded form of metastable and stable pits became polygonal in shape within 1 s. After that, the dissolution proceeded in the depth direction with no change in the appearance of the pit as observed externally. In the case of the metastable pitting, the duration of this stage was approximately 1.5 s, and then the pit repassivated, and the polygonal metastable pit remained. The in-depth growth stage for stable pitting was relatively longer (approx. 3.5 s), and the pit grew deeply into the steel matrix and wrapped beneath the inclusion, leading to the formation of a large occluded cavity, in which the corrosivity considerably exceeded the critical conditions for autocatalytic pit growth. The anodic dissolution behavior of CrS, TiS, and Ti4C2S2 inclusions was compared with that of MnS. The dissolution potential of CrS inclusions was in the transpassive region of stainless steels. Stable pits were initiated in this potential region. In contrast, TiS and Ti4C2S2 inclusions did not dissolve in the passive or the trans-passive regions of stainless steels, and no pits were initiated at these inclusions in NaCl solutions. The calculations made from the potential-pH diagrams for CrS, TiS, and Ti4C2S2 systems indicated that Cr-oxide or Ti-oxide enriched surface films would form, and this was confirmed by surface analysis. The Cr-oxide or Ti-oxide enriched layers on the inclusions inhibited the anodic dissolution of the inclusions in the passive or trans-passive regions of stainless steels. In contrast, MnS inclusions dissolved in NaCl solutions, and pits were initiated at the inclusions. While MnS inclusion surfaces were covered by Mn-oxides, the corrosion resistance of Mn-oxides was not sufficient to prevent inclusion dissolution and subsequent pit initiation. The oxide enriched surface layers on the sulfide and carbo-sulfide inclusions were shown to significant enhance pit initiation resistance at the inclusions. In addition to the above findings, the roles of the addition of Ce and Mo were studied. From the results of micro-scale polarization, thermodynamic calculations, and scanning electron microscopy, it was suggested that the Ce3+ ions inhibit trench formation at the inclusion/steel matrix boundary, resulting in improved pitting corrosion resistance at sulfide inclusions. And also, the active dissolution rate of the steel was suppressed by Mo alloying. This suggests that, even after trenching at high potentials, Mo alloying inhibits the initiation of pitting inside the trenches.

Transforming g-C3N4 from amphoteric to n-type semiconductor: The important role of p/n type on photoelectrochemical cathodic protection

Photoelectrochemical cathodic protection is emerging as a green and environmental method to protect metals against corrosion. Graphitic carbon nitride (g-C3N4) shows great application potential in this area because of its high efficiency, high stability and low cost. However, the pristine g-C3N4 shows amphoteric properties, resulting in its failure in providing photoelectrochemical cathodic protection for the coupled metal in NaCl solution. In this work, a K&I co-doping technique was performed to modulate the band structure of g-C3N4, and an n-type g-C3N4 (n-C3N4) was obtained. The changes in the molecular structure were studied by SEM, HRTEM, XRD, EDS, XPS and FT-IR technologies. The n-type semiconductor characteristics were verified by the photoinduced i-V curves, SKP potential distributions and pH drift techniques. The n-C3N4 can generate positive photocurrent in the whole investigated potential range, making it able to provide photoelectrochemical cathodic protection for the coupled 316L stainless steel in NaCl solution. This work is very helpful for promoting the application of g-C3N4 in the fields of the photoelectric conversion and the photoelectrochemical cathodic protection.

A multiphysics model for studying transient crevice corrosion of stainless steel

The transient crevice corrosion behavior of 304 stainless steel in NaCl solution has been investigated by a multiphysics coupling model. The model considers local electrochemical reactions, transport of different species, and homogeneous reactions. The moving mesh method is used to obtain the geometrical change of the crevice wall with time due to corrosion. The level set method is employed to quantitatively describe the influence of the precipitation process on electrochemical reactions. The transient crevice corrosion morphology, potential and current distributions, and pH and chloride ion concentration distributions are obtained by simulation. The effect of crevice geometry factors on the corrosion process is also discussed. The simulation results are in good agreement with the experiments, showing that the model has high reliability.

Study on the photocathodic protection of 304 stainless steel by Ag and In2S3 co-sensitized TiO2 composite

The photo-catalytic activity of TiO2 was greatly enhanced by co-sensitization with Ag and In2S3, and its application to protect 304 stainless steel from corrosion was reported. TiO2 nanotube arrays (TiO2 NTAs,) with large specific surface area and hollow nanostructures favored the immobilization of In2S3 and Ag. In2S3 as a narrow band gap semiconductor could broaden the light absorption range of TiO2. Surface plasmon resonance of Ag could accelerate the separation of photo-induced carriers generated from TiO2 and In2S3. The photo-induced potential drop of 304 stainless steel in NaCl solution measured 530 mV, and the photo-current density reached 45 µA/cm2 with visible light irradiation coupled with Ag and In2S3 co-sensitized TiO2 composite.

Electrochemical Investigation of Oxygen Reduction Reaction on Type 316L Stainless Steel in NaCl Solutions in a Confined Space

Steel plate joints are commonly produced in the manufacturing process of steel structures such as automobiles and bridges. The steel plate joints suffer from aqueous corrosion in atmospheric environments. Especially, severe corrosion is often observed in the confined spaces between the steel plates because aqueous electrolytic solutions can be kept in the spaces. In this case, corrosion reaction rate of the steels in the confined space is basically controlled by the reduction reaction rate of dissolved oxygen. Therefore, it is important to estimate oxygen reduction reaction rate in the confined spaces to predict corrosion deterioration of steel plate joints. In this study, electrochemical investigation of oxygen reduction reaction rate in a confined space was performed. The material used in this study was austenitic stainless steel type 316L bar with various diameters from 5 to 20 mm. The type 316L bar was cut into a small cylindrical piece and the piece was embedded in epoxy resin after being contacted with a lead wire. The surface of the embedded stainless steel sample was ground with SiC papers down to JIS200 grit and then cleaned ultrasonically in EtOH. Test solutions were aqueous NaCl of different concentrations from 0.05wt% to 5wt%. The solutions were prepared with Milli-Q water and reagent grade sodium chloride. For the electrochemical measurements, the sample was set horizontally in a plastic vessel and then an acrylic rod of 20 mm in diameter, which was used as a crevice former, was placed above the sample surface to make a confined space between the sample and the rod. The gap between the sample surface and the rod was changed from 20 um to 200 um by using a laser displacement meter. Electrochemical measurements were conducted by a conventional three electrode method with a platinum wire (Pt) and a Ag/AgCl in a saturated KCl (SSE) as a counter electrode (CE) and a reference electrode (RE), respectively. Cathodic polarization curves for the sample were measured with various gaps at a potential sweep rate of 0.5mV/s. Cathodic polarization behavior for the sample measured in the confined spaces was similar as that measured in a bulk solution; a limiting current region due to oxygen reduction reaction was observed on the samples of various diameters in a confined space. It was confirmed that the limiting current density decreased with decreasing in the gap. This is attributed to be the difference in the oxygen diffusion rate on the sample in the confined space.

Pitting corrosion inhibition of 304 stainless steel in NaCl solution by three newly synthesized carboxylic Schiff bases

Three newly synthesized Schiff base derivatives, sodium (E)-4-(nitrobenzylideneamino)-benzoate (SNBB), sodium (E)-4-(benzylideneamino)-benzoate (SBB), and sodium (E)-4-(hydroxybenzylideneamino)-benzoate (SHBB) were investigated as pitting corrosion inhibitors for 304 stainless steel in neutral 0.1 M NaCl. Potentiodynamic polarization evidenced major shifts in pitting potential to more positive values with increasing inhibitor concentration. The scanning vibrating electrode technique (SVET) imaged metastable pitting in 0.1 M NaCl, but not in the presence of the inhibitor, indicating that it prevented pit nucleation. The inhibition performance was established under anodic polarization conditions, because only minute local anodic activity due to metastable pit formation could be observed when the steel was exposed to SNBB-containing solution, whereas the metal would undergo pit propagation at the same potential in the inhibitor-free solution. X-ray photoelectron spectroscopy (XPS) analysis evidenced chromium enrichment at weak points (pores) of the passive film at anodic polarization condition where sudden release of Fe cations is possible. In this way, the SNBB molecules will migrate to these sites to react with the Fe ions and form a chelate compound which will deposit finally at those sites and plug them, whereas no effect occurred at the open circuit potential (OCP).

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.