Electrochemical Behavior Of Stainless Steel Research Articles

Effect of KOH concentration on corrosion behavior and surface morphology of stainless steel 316L for HHO generator application

Hydrogen production could be enhanced by increasing the potassium hydroxide (KOH) concentration, but higher KOH concentrations result in higher corrosion rates. Therefore, a deep investigation of the electrochemical behavior of stainless steel (SS 316L) in the KOH solution is needed. This study investigates the influence of KOH concentrations on the electrochemical behavior, surface morphology, structure, and sample phases of SS 316L. The investigations were conducted by some electrochemical techniques, UV-vis, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and X-ray diffraction (XRD). The corrosion rate was found to increase, and solution resistance to decrease with increasing KOH concentration. Samples tested in 5, 30, and 50 g l-1 of KOH showed corrosion rates of 0.457, 2.362, and 5.613 µm year-1, respectively. A wide passive region and the noblest pitting potential were noticed for the sample with 5 g l-1 of KOH. Moreover, Mott-Schottky plots and characteristic wavelengths of UV-Vis suggest the formation of iron and chromium oxides by the passivation of samples. The SEM analysis showed a dynamic change of surface morphology from the lowest to the highest concentration with the intergranular corrosion found at the grain boundaries area. In conclusion, concentrations < 50 g l-1 KOH could be recommended since they would support the optimum remaining life of SS 316 L plates in HHO generators.

A Comparative Study of 316L Stainless Steel and a Titanium Alloy in an Aggressive Biological Medium

The electrochemical behavior of stainless steel and titanium alloys is affected after prolonged contact with basic or acidic solutions, indicating a change in their surface properties. The human body often rejects invasive devices that aim to alter the biological or chemical composition of blood or other body fluids. Stents, fixation plates and screws, spinal implant devices, aneurysm clips, intramedullary nails and stems, temporary fixation devices and surgical instruments, etc. have been made from stainless steel AISI 316L for several years. Although the mechanical performance of implants and devices may be governed by their bulk properties, their interaction with the environment is managed by the characteristics of their superficial layer. In the case of biomedical devices, resistance to corrosion and biocompatibility has paramount importance. This study compares the corrosion behavior of 316L stainless steel and a titanium alloy in a Hank solution. The obtained results show that the titanium alloy has a higher potential than 316L stainless steel and lower corrosion current.

Electrochemical Behavior of Stainless Steels in Highly Concentrated Electrolytes

Due to the superior mechanical properties and corrosion resistance of stainless steels, their application as exterior material and current collector has been examined. Recently, concentrated aqueous solutions of lithium salts are highly expected as a novel electrolyte because they allow the safe operation of lithium ion batteries, different from conventional organic solvent based electrolytes. Therefore, understanding on the electrochemical behavior of stainless steels in concentrated aqueous solutions is crucial to judge the applicability of stainless steels to lithium ion batteries. It is well-known that electrochemical behavior of metals in concentrated aqueous solution is different from that in dilute aqueous solution. The difference is considered to be attributed to chemical state of water molecules. In the present work, electrochemical behavior of stainless steels in highly concentrated aqueous solution of lithium trifluoromethanesulfonate was examined.

Influence of Shot Peening on Residual Stress Distribution and Corrosion Resistance of Additive Manufactured Stainless Steel AISI 316L

The present study aims to analyze the influence of shot peening on the residual stress distribution and electrochemical behavior of stainless steel (SS) AISI 316L fabricated through the use of direct metal laser sintering (DMLS) process. Shot peening was performed using conventional peening machine with the use of cast steel shots for 100% coverage. High-magnitude compressive residual stress was observed on the surface layer of SS 316L after shot peening. Further, better electrochemical behavior was observed for the peened sample exhibiting low corrosion current density and higher corrosion potential when compared to the as-built DMLS surface. The outcomes of the present investigation will lead to substantial platform for further research in surface enhancement of additive manufactured stainless steel parts.

Electrochemical Behavior of Stainless Steels for Sudomotor Dysfunction Applications

AbstractAISI 304L is used in SudoscanTM technology (Impeto Medical Inc.) for the early diagnosis of small fiber neuropathy caused by type‐2 diabetes or cystic fibrosis. In a recent paper, several substitute electrodes were analyzed, among which the biocompatible nickel‐free AISI 430 appeared as an interesting material. In the present work, we compare in details the electrochemical behavior of AISI 430 with respect to the reference AISI 304L, using Electrochemical Impedance Spectroscopy (EIS) in mimetic electrolytic solutions of sweat. Apart of being cheaper than AISI 304L, AISI 430 has roughly similar characteristics but is slightly more sensitive to chloride ions concentration and, according to EIS and SEM analyses, forms a thicker, more homogeneous and protective oxide layer, which makes it a convenient electrode material.

Electrochemical Behavior of Type 304 Stainless Steel in Ionic Liquid Containing Small Amount of Water

The influences of the water content on the electrochemical properties of Type 304 stainless steel were studied through cyclic voltammetry and chronoamperometry in the ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMI-TFSI). The electrochemical behavior of stainless steel was explained by the reactivity of water in the ionic liquid with the main constituent elements of the stainless steel, such as Fe, Cr, and Ni. A protective passive film formed on the surface of stainless steel in EMI-TFSI with the water content controlled in the range of 5.5 ppm to 5000 ppm. For a water content less than 5.5 ppm, however, the stainless steel was not passivated and, therefore, was corroded by the dissolution. The amount of eluted metal ions from Type 304 stainless steel were much less than Fe and Ni. Furthermore, the dissolution process did not change in a wide temperature range from room temperature to 120°C.

Electrochemical behaviour of stainless steel in acidic fluoride media

Abstract The growth mechanism and electrochemical properties of an oxide film on AISI 304 grade stainless steel were studied in 0.01 and 0.1 mol L−1 fluoride solutions with different pH values (4.5, 5.5, 6.5) by means of electrochemical techniques. The anodic growth and stability of the oxide film on the stainless steel were characterized using cyclic voltammetry. Potentiodynamic analysis suggests that the oxide film growth occurs according to the high-field mechanism. Electric field strength, high-field growth exponential law constants, ionic conductivity through the film and half jump distance were determined. The electrochemical properties of the oxide film, formed spontaneously at the open circuit potential, were studied using electrochemical impedance spectroscopy. The results showed that the fluoride concentration has more considerable influence on the dissolution rate and the resistance of the oxide film than the pH.

Effect of hydrochloric acid on electrochemical behaviour of 430 stainless steel

The hydrochloric acid pickling process ensures high speeds with little pollution, for which a systematic study of the electrochemical behaviour of stainless steel in the oxidised hydrochloric electrolytes is of great significance. In this research, proper oxidiser was introduced into pickling solution with different concentrations of hydrochloric. Research indicated that as the concentration of hydrochloric acid rose, the charge transfer resistance Rt decreased, and that the decrease was more significant with high HCl content. When the HCl concentration was below 15%, the reaction was controlled by the anodic reaction, while the reaction was controlled by the cathodic reaction when the HCl concentration was above 15%. As the concentration of hydrochloric acid rose, the residue of oxide scales reduced and the surface of the stainless steel became soomther.

Electrochemical Behavior of 430 Ferritic Stainless Steel in HCl Solution at Different Temperatures

The environmental concerns brought during pickling process of stainless steel in HNO3-containing acids need urgent attention. Choosing the hydrochloric acid pickling process as study object, this paper conducted a systematic study of the effect of temperature on the electrochemical behavior of stainless steel in hydrochloric acid solution. Research indicated that as temperature rose, the corrosion potential of 430SS in hydrochloric acid solution moved to positive direction with band to a narrow 0.1V. Meanwhile, the current intensity increased which indicated the acceleration of corrosion rate. In addition, the anode Tafel slope increased firstly and decreased later while the cathode Tafel slope increased slightly.

Effect of Temperature on Electrochemical Behavior of Stainless Steel in Phosphoric Acid

Electrochemical behavior of 304L and S32304 stainless steel in different temperature and concentration phosphoric acid solution by means of polarization curve and electrochemical impedance spectroscopy. The results showed that with the increase of the phosphoric acid solution temperature, the corrosion voltage and the corrosion current of the stainless steel increase and the polarization resistance and solution resistance decrease. The corrosion-resistant properties of S32304 stainless steel are superior to that of 304L stainless steel.

Effect of molybdenum and tungsten polyoxometalates on the composition of surface layers and electrochemical behavior of stainless steel in sulfuric acid

The composition and thickness of the surface layers formed on ferrite steel at various applied potentials in pure 1 N H2SO4 and in the presence of polyoxometalate (POM) anions ( in cationic composition are observed near the passivation potential. At anodic potentials the surface oxide layer is enriched by chromium oxide. The thickness of this layer does not exceed 2-3 nm. If polymolybdate or polytungstate anions are added to sulfuric acid, they are located mostly in the uppermost oxide layer. The anodic currents decrease notably with an increase in POM concentration. At the passivation potential the oxide layer thickness exceeds 3-4 nm and it is substantially enriched by molybdenum. On the samples kept for 1 h in 1 N H2SO4, a protective layer is formed in the presence of POM and an after-affect is achieved. This layer remains stable upon transfer into pure 1 N H2SO4, especially in the case of

Review – Interactions between diatoms and stainless steel: focus on biofouling and biocorrosion

There is a considerable body of information regarding bacterially enhanced corrosion, however, this review focuses on diatoms (unicellular algae) whose contribution to biocorrosion is less well studied. The reasons why diatoms have been neglected in studies of biocorrosion in natural waters are discussed and the question whether diatoms should be considered as inert with respect of electrochemical processes is considered. A particular focus is given to the case of stainless steels (SS), which are widely used in variety of applications in natural waters. Basic information on the cell biology of diatoms is included in the review, particularly with respect to their ability to ‘sense’ and adhere to surfaces. Investigations at the nanoscale are reviewed as these studies provide information about the behavior of cells at interfaces. Recent advances include the use of atomic force microscopy (AFM), although only a few studies have been applied to diatoms. Regarding the electrochemical behavior of SS, the mechanisms by which diatoms influence the potential ennoblement process is discussed. Such studies reveal the association of diatoms, in addition to bacteria, with biocorrosion processes.

Electrochemical behaviour of stainless steel in PWR primary coolant conditions: Effects of radiolysis

Few data are available in the literature on the role of the water radiolysis on the corrosion of stainless steel core components in PWR operating conditions (300 °C, 155 bar). The present approach uses a high energy proton beam to control the production of radiolytic species at the interface between a stainless steel sample and water in a high temperature and high pressure (HP–HT) electrochemical cell working in the range 25 °C/1 bar–300 °C/90 bar. The cell is designed to record the free corrosion potential of the AISI 316L/water interface mounted in line with a cyclotron delivering the proton beam. The evolution of the potential is compared before, during and after the proton irradiation. The first results are obtained with an aqueous solution containing boron, lithium and dissolved hydrogen, as in PWR primary coolant circuit. The stainless steel/water interfaces are irradiated between 25 °C and 300 °C with protons emerging at 22 MeV at the interface. The flux is varied by five orders of magnitude, from 6.6 × 10 11 to 6.6 × 10 15 H + m −2 s −1. The evolution of the free corrosion potential is highly dependent on the temperature and/or pressure. For a given temperature and pressure, it evolves with the flux and the ageing of the AISI 316L/water interfaces. An important role of the temperature of irradiation on the electrochemical response was observed. These results give a better understanding of the role of radiolysis on stainless steel corrosion in high temperature conditions.

In vitro evaluation of the electrochemical behaviour of stainless steel and Ni-Ti orthodontic archwires at different temperatures

The aim of this study was to compare the electrochemical corrosion behaviour of stainless steel (SS) and nickel-titanium (Ni-Ti) orthodontic archwires in Ringer's solution at temperatures ranging from 15 to 55°C by using linear sweep voltametry and electrochemical impedance spectroscopy. Polarization curves show that the corrosion current density of SS is greater than that of Ni-Ti alloy. Since the corrosion current density is directly proportional to the corrosion rate, a great corrosion current density shows a lower resistance against corrosion. Therefore, in comparison with SS, Ni-Ti alloys have a lower corrosion rate. Results show that the temperature of the solution affects the corrosion rates of the alloys. As the temperature increases, the corrosion resistance of both of the alloys decreases, although these variations were not so large. Impedance measurements show that the electrochemical behaviour of Ni-Ti exhibits higher polarization resistance and lower capacitance, which means that passive film formed on this alloy is more homogeneous and thicker in comparison with SS. Results also show that polarization resistance of both alloys decreases slowly with increases in the temperature of the solution.

Redox behavior of biofilm on glassy carbon electrode

Marine and freshwater biofilm usually shift the open circuit potential (OCP) of stainless steel towards the electropositive direction by + 450 mV vs SCE. The nature of oxide film and bacterial metabolism were also correlated with ennoblement process by various investigators. Glassy carbon electrode (GCE) was used in the present study and a shifting of potential in the positive side (+ 450 mV) was noticed. It indicates that biofilm contributes to the ennoblement process without any n/ p-type semiconducting oxide film. The nature of the cathodic curve for the biofilm covered GCE is compared with the previous literature on the electrochemical behavior of stainless steel. The present study explains the oxidation and reduction peaks of biofilm covered GCE by cyclic voltammetry. Electrochemical impedance result reveals the diffusion process within the manganese biofilm. The present study confirms the previous investigations that the manganese biofilm rules the electrochemical behavior of materials and suggests that oxide film is not necessary to assist the ennoblement process.

ChemInform Abstract: The Electrochemical Behavior of Stainless Steels in Hot Nitric Solutions as Related to the SCC Phenomenon

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Electrochemical behaviour of stainless steel 304 alloy in erosion–corrosion conditions and synergism effect

A study has been made of the erosion–corrosion behaviour of stainless steel (SS) 304 in tap water in the presence and the absence of solid particles. Water at ambient temperature impinged in various angles (15–90°) on specimen surfaces at different velocities (7·85–14 m s–1) and sand concentrations (0·43–2%). In this research, potentiodynamic, electrochemical impedance spectroscopy and weight loss measurements were used to study the damage mechanism and to estimate corrosion rate. The SEM micrographs and optical microscopy images were used to study the corrosion morphology. Under test conditions, protective passive film and non-protective film formations formed on SS 304 surface. It was found that maximum corrosion–erosion rate happened at the impact angles between 60 and 75°. The synergism effect was positive in all conditions and it was greater for the lower angles, the higher velocities and the higher solid contents.

Enzymatic Approach in Microbial-Influenced Corrosion: A Review Based on Stainless Steels in Natural Waters

The electrochemical behavior of stainless steels (SS) in natural waters is characterized by the ennoblement of their free corrosion potential (E(corr)). This phenomenon depends strongly on the settlement of biofilms on SS surfaces. Many hypotheses have been proposed to explain the biofilm action, in particular the enzymatic catalysis plays an important role by shifting the cathodic and/or anodic processes. However, there are still only few studies relating the use of purified enzymes. In contrast with bacteria-associated corrosion, the direct influence of enzymes is still poorly documented. The aim of this review is to show the benefits of the enzymatic approach in the study of biocorrosion. Indeed, enzymatic systems may constitute convenient models to mimic microbial influenced corrosion and to evaluate the behavior of metallic materials in natural waters.

Understanding barium sulfate precipitation onto stainless steel

This paper investigates the influence of barium sulfate scaling and scaling inhibitors on the electrochemical behaviour of stainless steel. The results of a synchrotron radiation grazing incidence X-ray diffraction (SR-GIXRD) and electrochemical impedance spectroscopy (EIS) study on stainless steel shows that different scaling inhibitors interact uniquely with the substrate when barium sulfate is precipitated on the electrode surface. The main effect of the substrate in the presence of inhibitor is a tendency to form smaller barium sulfate particles. The SR-GIXRD patterns obtained in the presence of the two inhibitors were different to each other and to the control, with the carboxylate showing greater amounts of barite solids precipitated together with iron(III) and (II) sulfate, while the phosphonate showed low amounts of barite solid were precipitated. The presence of iron sulfates on the electrode surface as detected by SR-GIXRD, in the case of NTA, suggests that scaling inhibitors are not always benign, and can promote the dissolution of iron species from the substrate.

Electrochemical behaviour of stainless steels in media containing iron-oxidizing bacteria (IOB) by corrosion process modeling

Localized corrosion mechanism of stainless steel (SS) types UNS S30403 and UNS 31603 in the presence of iron-oxidizing bacteria Sphaerotilus spp. isolated from rust deposits was studied electrochemically. OCP transient, cyclic anodic and cathodic potentiodynamic polarization curves were measured on steel electrodes through their exposure to 3% NaCl solution supplemented with Sphaerotilus culture. The exposure period was composed of three parts: (a) 5 days incubation of steel electrodes in sterile 3% NaCl solution; (b) addition of 3 days-old Sphaerotilus culture to 3% NaCl at 3:2 v/v ratio with subsequent electrodes exposure for 11 days up to complete sedimentation of ferric oxides and (c) subsequent exposure of electrodes for 14 days in upper and bottom (sediments layer) fractions of the experimental medium. The results revealed an instantaneous gradual shift of the transient potential of both steels towards negative potentials from steady-state value of −0.15 V to −0.35 to −0.42 V (SCE) during the whole exposure interval since IOB culture addition into sterile 3% NaCl solution. No evidence of pitting corrosion was found on SS samples subsequent to their exposure to sterile 3% NaCl solution, though in the presence of IOB culture, numerous pits were revealed on 304 L steels specimens exposed to iron hydroxides sediments layer. Electrochemical characteristics (OCP or corrosion potential – E CORR, breakdown potential – E BD, repassivation potential – E RP, passivation current – i PASS) periodically measured by cyclic polarization method, allowed monitoring the electrochemical behavior changes of experimental SS and to establish the initiation of pitting corrosion in the presence of IOB, resulting in crevice effect caused by biogenic ferric oxides deposits precipitated on steel surface. Overall, steel 316L demonstrated higher resistance to pitting corrosion compared to 304L.