Stainless Steel In Chloride Solutions Research Articles

Electrochemical Behavior of Plasma-Nitrided Austenitic Stainless Steel in Chloride Solutions.

The application possibilities of austenitic stainless steels in high friction, abrasion, and sliding wear conditions are limited by their inadequate hardness and tribological characteristics. In order to improve these properties, the thermochemical treatment of their surface by plasma nitriding is suitable. This article is focused on the corrosion resistance of conventionally plasma-nitrided AISI 304 stainless steel (530 °C, 24 h) in 0.05 M and 0.5 M sodium chloride solutions at room temperature (20 ± 3 °C), tested by potentiodynamic polarization and electrochemical impedance spectroscopy. Optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy are used for nitrided layer characterization. The experiment results confirmed the plasma-nitrided layer formation of increased micro-hardness related to the presence of Cr2N chromium nitrides and higher surface roughness compared to the as-received state. Both of the performed independent electrochemical corrosion tests point to a significant reduction in corrosion resistance after the performed plasma nitriding, even in a solution with a very low chloride concentration (0.05 mol/L).

Influence of nitrogen content on the corrosion fatigue behavior of additively manufactured AISI 316L stainless steel in chloride solution

The characterization of the corrosion fatigue behavior is detrimental for steels manufactured by laser beam powder bed fusion (PBF-LB). In this study, the corrosion and corrosion fatigue behavior of the austenitic stainless steel AISI 316L processed via PBF-LB with and without increased nitrogen content is investigated. The nitrogen alloyed steel shows improved pitting corrosion and fatigue behavior. A fracture mechanical approach was used for the fatigue data as surface defects lead to a high scatter in the results which not only allowed to separate the influence of defects but also to identify the improved defect tolerance due to nitrogen alloying.

Crevice corrosion behaviors of Alloy 690 and 405 stainless steel in chloride solutions with different concentrations of thiosulfate

The crevice corrosion behaviors of Alloy 690 and 405 stainless steel (SS) in chloride (Cl−) solutions with different concentrations of thiosulfate (S2O32−) were investigated using a self-designed electrochemical testing device for crevice corrosion. The increase of concentration ratio of Cl−/S2O32− promotes crevice corrosion of Alloy 690. When crevice corrosion occurs between Alloy 690 and 405 SS, Alloy 690 outside the crevice is used as the cathode for reduction reaction of O2, and Alloy 690 inside the crevice is also used as the cathode for hydrogen evolution reaction, both of which jointly promote the anodic dissolution of 405 SS inside the crevice. The crevice corrosion mechanisms of Alloy 690 and 405 SS are also discussed.

Numerical analysis of topographic and Volta potential profiles during corrosion of duplex stainless steel in chloride solution

ABSTRACT Corrosion of duplex stainless steels (DSS) usually initiates at a specific phase, causing preferential phase-dissolution in aqueous environments. Although the scanning Kelvin probe force microscopy (SKPFM) can characterise the phase-corrosion at a micro- or even nanoscale, conventional data-processing methods are insufficient to analyse massive data to derive mechanistic information, and sometimes, even cause a misunderstanding of corrosion evolution. Here we utilised root mean square, power spectral density and fractal evaluations to analyse the time-dependent topographic and Volta potential results obtained by SKPFM during corrosion progression of 2205 DSS in a chloride solution. Corrosion of the DSS preferentially occurs in the ferrite phase and at the ferrite/austenite boundaries in the initial stage. The corrosion changes from the initial galvanic mechanism to mass transfer control with increased time. By using proper numerical tools, the Volta potential results are more insightful of analysing corrosion than the topographic profiles.

Electrochemical-Kinetics, Computational and Machine Learning Model for Prediction of Azo Dye as Eco-Friendly Corrosion Inhibitor for Stainless Steel in Chloride Solution

Electrochemical-Kinetics, Computational and Machine Learning Model for Prediction of Azo Dye as Eco-Friendly Corrosion Inhibitor for Stainless Steel in Chloride Solution

Damage mechanisms in cavitation erosion of nitrogen-containing austenitic steels in 3.5% NaCl solution

Interruptions of the passive layer of stainless steels by cavitation erosion expose the bare metal surface to the environment and can lead to cavitation-erosion-corrosion damage and synergistic effects. However, the probability for pitting corrosion is decreased during cavitation exposure of stainless steels in chloride solutions because mechanical passive film removal shifts corrosion potentials to lower cathodic values. In this study, the impact of 3.5 wt% NaCl in water on mass loss and damage features of two austenitic stainless N-containing steels is investigated to amend the understanding of cavitation erosion of passivating steels. Ultrasonic cavitation tests were carried out on steels 316LVM and CNMo0.95 in distilled water and 3.5% NaCl solution. Exposed surfaces were characterized qualitatively by light- and electron-microscopy and quantitatively by confocal microscopy. Damage mechanisms vary between the two steels but not with NaCl content in the solution. 316LVM also displayed the same mass loss in both solutions. CNMo0.95 possesses twice the strength as 316LVM, resulting in lower intensities of ductile damage mechanisms and slower damage progression. Mass loss of CNMo0.95 was lower in 3.5% NaCl solution compared to distilled water, which was primarily assigned to the effect of the salt content in the water on cavitation bubble formation.

Modeling unidirectional corrosion damage evolution in a SS 316 pencil-electrode experiment

A three-stage, unidirectional pit growth model is developed to simulate corrosion damage evolution in a pencil electrode experimental setup. Stage I models initial pit growth, in the absence of a salt film, under activation control and a constant current density. Stage I is terminated when the ionic metal concentration reaches its saturation limit. Stage II models stable pit growth under diffusion control where the metal ion flux is the same as the dissolution rate of the metal at the bottom of the pit. During Stage II, the applied bulk potential is decreased at a specified scan rate. When the bulk potential reaches the transition potential, Stage III begins. In this stage the pit growth is under activation control that is defined by a prescribed polarization curve. Stage III continues until the metal repassivates as the potential is decreased. The governing system of equations for each stage is solved analytically, where possible, or numerically to determine the potential drop and the concentrations of sodium, chloride, and metal ions within the pit. The pit depth as a function of time is determined from Faraday's Law in Stages I and III, and from a mass balance at the electrolyte/metal interface in Stage II. The cumulative pit depth is compared with experimental pit depths in the literature for stainless steel in chloride solution.

Phosphate-doped polyaniline/Al2O3 nanocomposite coating for protection of stainless steel

Purpose This work aims to prepare and characterize of protective anticorrosion phosphate-doped polyaniline (PANI) nanocomposite coatings for stainless steel (SS) in chloride solution. Design/methodology/approach PANI composite coatings were electrodeposited from aqueous sulfuric acid solution containing monomer and Al2O3 nanoparticles using cyclic voltammetry technique. Doping by phosphate was done by aging the coated steels for different periods (1–168 h) in phosphate solution. The polymer film composite was investigated by Fourier-transform infrared spectroscopy and scanning electron microscopy techniques. Potential-time, anodic polarization and electrochemical impedance spectroscopy were used to study the protection efficiency of the coatings. Findings The Al2O3 nanoparticles were incorporated into the deposited PANI layer but they decreased the deposition of polymer. The nanoparticles and the phosphate anions enhanced the protective PANI layer for passivation and protection of SS in the chloride solution. Originality/value The replacement of counter anions by phosphate ions improved significantly the PANI and its nanocomposite as protective coating of SS in chloride solution.

Copper alloying content effect on pitting resistance of modified 00Cr20Ni18Mo6CuN super austenitic stainless steels

The effect of Copper (Cu) on pitting resistance of modified 20Cr-18Ni-6Mo-0.2 N Super austenitic stainless steels was studied by chemical immersion, electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy. It has been found that Cu affects on the average weight loss rate, the number of pitting pits, pitting pit surface area, passive film surface quality, charge transfer resistance and nanostructure of passive film. The passive film of the super austenitic stainless steels in chloride solution has three layers. This study provides a theoretical basis for the study of stainless steel used in harsh marine media.

Staged Local Dissolution of Stainless Steel in Chloride Solutions

The paper defines galvanostatic polarization parameters (current density and test duration), to simulate self-dissolution conditions; the results are confirmed by potentiostatic tests. It is shown that under the conditions of self-dissolution simulation, increasing the solution concentration reduces the nucleation rate, while prolonging the pitting development time. Spectral analysis of chronopotentiograms reveals low-frequency potential fluctuations that characterize the nucleation and passivation of pits at the onset of pitting corrosion. The paper describes the basic regularities, observed in the alteration of surface electrochemistry by impedance spectroscopy; such alteration corresponds to the transition from the passive area to the pitting area. The researchers propose optimal electric equivalent circuits to reflect the surface conditions in early nucleation of pits. The paper also proposes an additional pitting resistance criterion, that is, cumulative electric-charge density.

Staged Local Dissolution of Stainless Steel in Chloride Solutions

The paper defines galvanostatic polarization parameters (current density and test duration) to simulate self-dissolution conditions; the results are confirmed by potentiostatic tests. It is shown that under the conditions of self-dissolution simulation, increasing the solution concentration reduces the nucleation rate, while prolonging the pitting development time. Spectral analysis of chronopotentiograpms reveals low-frequency potential fluctuations that characterize the nucleation and passivation of pits at the onset of pitting corrosion. The paper describes the basic regularities observed in the alteration of surface electrochemistry by impedance spectroscopy; such alteration corresponds to the transition from the passive area to the pitting area. The researchers propose optimal electric equivalent circuits to reflect the surface conditions in early nucleation of pits. The paper also proposes an additional pitting resistance criterion, that is, cumulative electric-charge density.

The effect of CeCl3 inhibitor on the localized corrosion of stainless steel in chloride solutions

AbstractStainless steels have been used extensively in many sectors such as medical and household appliances as well as construction. This has been primarily due to their high resistance to corrosion attacks, reasonable cost, and excellent mechanical properties. However, when placed in corrosive media stainless steel is susceptible to localized corrosion attacks, especially when placed in chloride solutions. The paper explores the issue of corrosion liability of austenitic (AISI 316) and duplex (UNS S32205) stainless steels in et aconditions of seawater environment as well as under the influence of an inhibitor in the same environmental conditions. The behavior of stainless steels was examined via electrochemical testing relying on DC and AC techniques, optical metallographic analysis, scanning electron microscopy, and X‐ray diffraction analysis. Duplex stainless steel showed better resistance to localized corrosion but a higher tendency toward general corrosion in all examined solutions. Cerium chloride in a chloride solution showed inhibiting properties for both the AISI 316 and the UNS S32205.

The temperature-dependent pitting and repassivation behaviors of UNS S31803 duplex stainless steel in chloride solutions

An improved electrochemical method named thermal pulse technique was designed to measure the current flowing from a potentiostatically maintained UNS S31803 electrode in 1 M NaCl solution, while various thermal pulses were applied on the solutions. Both the critical pitting temperature (CPT) and the repassivation temperature (Tr) were measured in one thermal pulse. The Tr data presented an inverted V-shape trend as the cooling rate decreased. Both the CPT and Tr values declined after multiple thermal pulses. The cyclic potentiodynamic polarization curves present a sharp transition of pitting and repassivation potential at the temperature ranged between the CPT and Tr.

Effects of Heat Treatments on the Corrosion Behavior of 13Cr Stainless Steels in Chloride Solutions Containing Carbon Dioxide

Various electrochemical measurements were adopted to explore the effects of heat treatments on the corrosion resistance of 13Cr martensitic stainless steels in Cl– solutions containing carbon dioxide. Phase contents and lattice strains were measured by Matlab image processing and X-ray diffraction, respectively. The compositions of passive film were tested by X-ray photoelectron spectroscopy. The results showed that the enhancement of austenitized temperature can improve the pitting resistance, whereas uniform corrosion resistance can be injured by the formation of retained austenite. The quenched specimen exhibited enhanced passivation stability in long-term immersion tests. Tempering at 280°C as the optimum process can guarantee 13Cr stainless steel a refined microstructure with reasonable internal stress and easy to obtain an intact protective passive film, which can serviced in complicated CO2 and Cl– corrosion environment.

Enhancements of Passive Film and Pitting Resistance in Chloride Solution for 316LX Austenitic Stainless Steel After Sn Alloying

In the present work, the electrochemical behavior and properties of the passive film of a new Sn-alloyed 316LX austenitic stainless steel were investigated. With the increase in Sn content in 316LX austenitic stainless steel from 0 to 0.21%, the critical pitting temperature value increased from 32.6 to 38.8 °C, and the pitting potential increased from 0.252 VSCE to 0.317 VSCE. Electrochemical impedance spectroscopy results showed that the corrosion resistance of passive film rose with the increase in Sn content, indicating a more stable passive film. The Mott–Schottky measurement revealed an n-type passive film with a decreased carrier concentration on the 316LX austenitic stainless steel surface. The Cr, Sn2+ and Sn4+ (SnO, SnOHCl or SnO2) enrichments were observed in the passive layer by X-ray photoelectron spectroscopy. The enrichment of Sn and Cr in the passive film can account for the enhanced pitting resistance of 316LX austenitic stainless steel in chloride solution.

Galvanic corrosion susceptibility between X53CrMnNiN219 and X45CrSi93 stainless steels in chloride solution using electrochemical measurements

PurposeIn this study, corrosion behavior of X53CrMnNiN219 austenitic stainless steel (SS) and X45CrSi93 martensitic SS, as well as the galvanic corrosion produced by coupling of these dissimilar alloys, are evaluated in a 3.5 Wt.% NaCl solution at temperature 25°C ± 1°C.Design/methodology/approachThe corrosion parameters were estimated through a series of electrochemical tests, including Tafel polarization, electrochemical impedance spectroscopy (EIS), and zero-resistance ammeter (ZRA) technique.FindingsThe results of polarization measurements indicate that the value of corrosion current in the galvanic pair is slightly higher than that of both the austenitic and martensitic SS during the initial time of immersion in the chloride solution, which is an indication of compatibility of members in the couple. The galvanic current density measured by ZRA technique shows negative values throughout the test; accordingly, the martensitic SS acts as anode of the pair and corrodes preferentially. Localization index values are limited to the mixed corrosion process, showing relative susceptibility of the martensitic alloy to the uniform and localized corrosion (pitting) due to chloride ions.Originality/valueThe originality is the evaluation of galvanic corrosion susceptibility of X53CrMnNiN219 and X45CrSi93 SSs in chloride solution by the various electrochemical methods consisting of Tafel polarization, EIS, and (ZRA) technique. To our knowledge, no work has been reported on this issue for these chemical compositions under this condition up to now.

Effect of Applied Stress on Pit Initiation of Sensitized Type 304 Stainless Steel in Chloride Solution

Stainless steels are widely used due to their superior corrosion resistance. In the actual applications of stainless steels, sensitization is sometimes caused by welding. When Cr-depleted zones are formed, intergranular stress corrosion cracking (IGSCC) readily occurs at heat affected zone in chloride environments under applied stress. Pitting corrosion is well known to be the initiation site for SCC 1. Elucidation of the effect of applied stress on pitting corrosion is necessary to ascertain the initiation mechanism of IGSCC. In this research, electrochemical measurements were conducted under applied stress, and the effect of applied stress on pitting corrosion of sensitized stainless steels was analyzed. Two types of commercial AISI 304 (18Cr-8Ni) austenitic stainless steel sheets were used in this study (low S and re-sulfurized steels). The chemical compositions are shown in Table 1 (mass %). After solution treatment (1373 K, 30 min, W.Q.), the specimens were subjected to sensitization treatment (923 K, 2 h, W.Q.). After these heat-treatments, the surfaces of the specimens were successively polished with a diamond paste down to 1 μm. The surfaces of the specimen, except for the electrode area, were covered with resin. Tensile tests were performed using a Beben microtest 5 kN module that was a horizontal type tensile test machine. In air, the tensile stress was increased to 180 MPa (=80% of the 0.2% proof stress of the steels) with a crosshead speed of 0.02 mm min−1, and then kept constant. After that, in order to preserve the electrolyte, a small acrylic cell was attached to the gauge section of the specimen surface with a micro-scale electrode area. Electrochemical measurements were performed at 180 MPa. To elucidate the effect of applied stress on pit initiation of sensitized Type 304 (low S), immersion tests in 4 M MgCl2 (pH was adjusted at 5.0) were conducted under applied stress for 24 h. Electrode areas were changed from 100 to 500 square µm. In the absence of applied stress, the critical electrode area in which pitting corrosion was observed was ca. 230 square µm. Under applied stress, pitting corrosion was observed even when the electrode area was ca. 100 square µm. The critical electrode area required for pit initiation decreased by applied stress, indicating applied stress promotes pit initiation. Previous research suggested that the pit initiation mechanism can be divided into three steps: acidification around sulfide inclusion; depassivation of stainless steel; and local active dissolution of stainless steel2. In situ observations were conducted during potentiodynamic polarization in 0.1 M Na2SO4 to elucidate the dissolution behavior of the sulfide inclusion of Type 304 (re-sulfurized). Around the corrosion potential, the dissolution of the sulfide inclusion was promoted under applied stress. The depassivation pH values in naturally aerated in 1 M MgCl2 were measured with and without stress. The pH of the solution was lowered stepwise with HCl. Depassivation pH without and with stress were 0.6 and 0.8, respectively. It is thought that the stainless steel was readily depassivated under applied stress. To investigate the rate of active dissolution, potentiodynamic polarization was carried out in 4 M MgCl2 at pH 0.0. However, no difference in current densities was observed without and with applied stress. It is supposed that applied stress affects depassivation pH of the steel matrix and accelerates the MnS dissolution, and hence pit initiation is seemed to be promoted by applied stress. References H. Masuda, Corros. Sci., 49, 120–129 (2007).A. Chiba, I. Muto, Y. Sugawara, and N. Hara, J. Electrochem. Soc., 160, 511–520 (2013). Figure 1

Pitting Corrosion of Supermartensitic Stainless Steel in Chloride Solutions Containing Thiosulfate or H2S

Deepwater oil and gas extraction environment have high salinity, low oxygen content, and the presence of carbon dioxide and hydrogen sulfide (H2S). Handling of H2S-containing gaseous mixtures should be carried out in laboratories with special installations, owing to the high toxicity of this gas. An alternative is the use of non-toxic substances that can generate H2S in the medium, such as sodium thiosulfate. The objective of this work is to study the viability of substituting H2S by thiosulfate for the evaluation of the susceptibility to pitting corrosion in sour environments of the supermartensitic stainless steel (SMSS). The electrochemical behavior of SMSS in NACE TM0177-2016 solution C solution containing different concentrations of H2S or thiosulfate ions at 10−3 mol/L was performed by using cyclic potentiodynamic polarization (CPP). The condition of shorter OCP time (300 s) prevents the formation of a passive layer and allows the generation of H2S due to the reaction of the solution with the metal surface. The CPP curves of SMSS in the media containing 3% H2S/Ar (2.96 kPa) and 10−3 M of thiosulfate ions (OCP 300 s) were similar, the pitting potential was about − 322.5 ± 8.7 and − 338.8 ± 11.4 mVAg/AgCl, respectively, and the pit morphology showed several small pits on the steel surface in both conditions, suggesting the viability of the use of thiosulfate-containing brines to simulate H2S solutions.

Pitting corrosion behaviour of 2101 duplex stainless steel in chloride solutions

ABSTRACTThe corrosion behaviour of 2101 duplex stainless steel (DSS) in NaCl solution was studied and compared with that of 2205 DSS. The effects of chloride concentration and solution temperature on pitting corrosion behaviour were focused. The relative sensitivity to pitting corrosion of the constituent phases in both 2101 and 2205 DSSs was also explored. Pitting corrosion susceptibility was evaluated by conducting cyclic polarisation curve measurement. The corrosion morphology was examined by a scanning electron microscope equipped with energy dispersive spectrometer. The experimental results showed that the pitting corrosion resistance of 2101 DSS was inferior to that of 2205 DSS by exhibiting a lower threshold chloride concentration and a lower critical pitting temperature. For both 2101 and 2205 DSSs, the ferrite phase was more susceptible than austenite phase to pitting corrosion.This paper is part of a supplementary issue from the 17th Asia-Pacific Corrosion Control Conference (APCCC-17).

Pitting Resistance of the Modified 13Cr Martensitic Stainless Steel in Chloride Solution

Pitting Resistance of the Modified 13Cr Martensitic Stainless Steel in Chloride Solution