Corrosion Behavior Of Stainless Steel Research Articles

High temperature corrosion behaviour of stainless steels and Inconel 625 in hydroxide salt

Biomass gasification had proven to be an alternative source of energy to coal gasification. However, it requires high temperatures of about 1000°C for biomass drying and reduction. On the other hand, to reduce the oxidation and corrosion of gasifier structural materials it is important to keep the gasifier working temperature as low as possible. One effective way of keeping the reduction temperature low is to use molten salts as catalyst during biomass gasification. However, by virtue, molten salts cause several corrosion issues in ferrous alloys. In this context, the present study investigates the effect of hydroxide molten salt on the corrosion behaviour of stainless steels such as 316 and 310 and Inconel 625. The samples exposed to the salt at 700°C for about 48 h was analysed for corrosion using weight loss method. A scanning electron microscopy analysis of the exposed samples revealed the depth of corrosion and change in microstructure due to molten salt attack. Although all the selected materials suffered severe corrosion, among all, Inconel 625 show higher corrosion resistance.

The Effect of CuCl2 on Pitting Corrosion of the Extra High Purity Type 316 Stainless Steel

The effects of Cu addition on corrosion behavior of stainless steels are known to be controversy1,2, which depends on the corrosion environment or the amount of alloying Cu. In chloride environment, alloying Cu is known to prohibit the growth of pitting corrosion. The dissolved Cu2+ acted as an inhibiter inside the pits3. On the other hand, there are few studies about the effect of Cu2+ ions in the solution on the pitting corrosion of the stainless steels. Since the commercially made stainless steels commonly contains more than 0.1 mass% Cu, the Cu2+ ions which was dissolved from stainless steels made it difficult to evaluate the effect of Cu2+ ions on the pitting behavior of the stainless steels. Although the amount of dissolved Cu2+ was quite few, the Cu2+ concentration inside the pits was expected to be much higher than the solution bulk because the pitting corrosion was very localized phenomenon. Therefore, Cu2+ in the solution and dissolved Cu2+ should be analyzed separately. To clarify the effect of Cu2+ in the solution on the pitting corrosion of the stainless steels, the amount of alloying Cu is needed to be low enough not to affect the corrosion morphology. In this study, extra high purity Type 316 stainless steel (316EHP) was used as specimen. The Cu content of the specimen was 6.8 × 10-4 mass %. The specimens were heat-treated at 1373 K for 3.6 ks and then quenched in water. The surfaces of the specimens were polished down to 1 µm with a diamond paste. After that, specimens were ultrasonically cleaned in ethanol. Electrochemical measurements were conducted in deaerated 0.1 M NaCl or 0.098 M NaCl-1 mM CuCl2. Except the electrode area (ca. 10 × 10 mm), the surfaces of the specimens were insulated by an epoxy resin. The potential scan rate was 3.33 × 10-4 V s-1 (20 mV min-1). The reference electrode was an Ag/AgCl (Sat. KCl) electrode. All the potentials cited in this work refer to the Ag/AgCl (Sat. KCl) electrode. After the electrochemical measurements, the surfaces were analyzed by SEM/EDS and XPS. The inclusions of the specimen were characterized by SEM/EDS. The inclusions were identified as a Cr-oxide. The anodic polarization curves were measured in deaerated 0.1 M NaCl or 0.098 M NaCl-1 mM CuCl2. Although no pitting was observed in 0.1 M NaCl, pitting was occurred in 0.098 M NaCl-1 mM CuCl2. In both solutions, the dissolution of inclusions was not confirmed. Therefore, the inclusions were not thought to be the initiation site of pitting. This indicates that the pitting potential of 316EHP was decreased by Cu2+ in the solution. Cu2+ ions were thought to act as an accelerator of pitting corrosion. To analyze the effect of Cu2+ ions on the forming passivation film, potentiostatic polarization measurements at 0.4 V were carried out in 0.098 M NaCl-1 mM CuCl2. As a result, existence of a Cu signal on the surface was confirmed by XPS although it was not detected by SEM/EDS. This result indicatets that the few amounts of Cu compound was deposited on the surface in passive region of the 316 EHP.

Investigation of Electrochemical Corrosion of SS316L in Different Electrolyte

Corrosion is defined as the destruction of metals and alloys by chemical or electrochemical reaction with its environment. The corrosion occurs because of the normal trend of metals to come back to their thermodynamically stable native state. Corrosion cannot be avoided, but it can be controlled and prevented by using suitable methods like cathodic protection, anodic protection, metallic coating, alloying and using inhibitors, etc. Of these, the application of inhibitors reduces the aggressiveness of the corrosive and unsafe aqueous surroundings and preventing the metal and alloy from corrosion by forming a protective layer over the metal surface. The corrosion behavior of stainless steel and other metals in seawater has been studied by many researchers [1-2]. Stainless steels (316L) have been used successfully in many applications in the marine environment. 316L is considered to be one of the most resistant of stainless steel under marine environments, and it has excellent mechanical properties at elevated temperatures and easy fabricability. It is an important structural material for many industrial units, especially the desalination plants. 316L is the most likely candidate for saline environment applications due to their excellent corrosion resistance.The present work was undertaken to study the corrosion behavior of SS 316L metal in different mediums such as Seawater and calcium chloride (Fig. 1) solution by polarization study. The effect of oxygen or air in the electrolyte solution will also be investigated. Corrosion parameters such as corrosion potential, corrosion current, linear polarization resistance, and corrosion rate will be compared and presented in the meeting.

Corrosion of stainless steel 316 in a ternary nitrate salt and its composite with expanded graphite for solar thermal applications

The most concern of using nitrate salt mixtures in a concentrated solar power plant is their corrosion to the working pipes and containers. This paper studied the corrosion behavior of stainless steel 316 in a ternary nitrate salt mixture at three different conditions using static corrosion method. The mass losses of each sample were carefully measured. The instantaneous and average corrosion rates were predicted. The surface and cross-sectional morphologies with the corrosion products of the 316SS coupons after the test were investigated using SEM (Scanning Electron Microscope) combined with EDS (Energy-dispersive X-ray spectroscopy) and XRD (X-ray Diffraction) analyses. The results showed that temperature is the main factor to affect the average corrosion rate, for example, 0.0032 mm/a at 300 °C and 0.016 mm/a at 500 °C during the test period. At 300 °C, adding 10 wt% EG can reduce the average corrosion rate by 20%. The cross-sectional morphologies revealed that the corrosion layer of 316SS coupon in the composite with 10 wt% EG was 1/3 thinner than that in pure salt mixture at 300 °C. That was because the CaCO3 phase formed by the reaction of Ca(NO3)2 and EG could work as a protective layer to prevent further corrosion to some extent.

Corrosion behavior of stainless steels in simulated PWR primary water: The effect of composition and matrix phases

Corrosion behavior in simulated pressurized water reactor (PWR) primary water was investigated for stainless steels with 16 and 22 wt% Cr having austenitic, ferritic, and duplex microstructure. For alloys with 22 wt% Cr, the Cr-rich inner oxide layer consisted of Cr2O3 and FeCr2O4 is formed. For alloys with 16 wt% Cr, the Cr-rich spinel inner oxide layer is formed. In-situ and ex-situ electrochemical impedance analyses and Mott-Schottky analysis was used to rank the corrosion resistance of the alloys. In addition to chemical composition, the phases (ferrite, austenite, and B2-NiAl) also affect the corrosion behaviors of the alloys.

Effect of Polishing on Electrochemical Behavior and Passive Layer Composition of Different Stainless Steels.

In the present paper, the effect of different polishing methods (mechanical and electrochemical) on passive layer chemistry and the corrosion behavior of stainless steels is investigated. It was found that CrNiMo austenites have a substantially better corrosion behavior than CrMnN ones. The nickel is enriched underneath the passive layer, while manganese tends to be enriched in the passive layer. It was also noted that immersion of manganese into an electrolyte preferentially causes its dissolution. It was found that high amounts of chromium (27.4%), molybdenum (3.3%), nickel (29.4%), with the addition of manganese (2.8%) after mechanical grinding, generates a better corrosion resistance than after electrochemical polishing. This is most likely because of the introduction of phosphates and sulfates into its structure, which is known for steels with a high amount of manganese. For highly alloyed CrNiMo steels, which do not contain a high amount of manganese, the addition of phosphates and/or sulphates via the electropolishing process results in a decrease in pitting corrosion resistance, which is also observed for high manganese steels. Electropolished samples show detrimental corrosion properties when compared to mechanically polished samples. This is attributed to substantial amounts of sulfate and phosphate from the electropolishing electrolyte present in the surface of the passive layer.

Effect of sesquiterpenes on the general corrosion behaviour of stainless steel in sulfuric acid: electrochemical and quantum chemical calculations

Under the effect of acidic exposure, stainless steel structures of industrial equipment are constantly losing their corrosion resistance, and consequently leading to extensive damage. With the aim of protecting stainless steel equipment from the general corrosion in sulfuric acid, we investigate the inhibitory effect of Dittrichia viscosa extract and the main isolated sesquiterpenes. Potentiodynamic polarization and AC electrochemical impedance are used to demonstrate the efficiency of the tested inhibitors. For a better understanding of the molecular properties and the inhibitory potential of each sesquiterpene, quantum chemical calculations are performed using a hybrid method of B3LYP function with 6-31G (d, p) basis set. The present study provides comprehensive results proving the inhibitory effect of sesquiterpenes on the corrosion of stainless steel in sulfuric acid. The inhibition efficiency of tomentosin attains 95% at 7.5 × 10−5 mol/L. The adsorption data of tomentosin fit well the Langmuir isotherm, while the thermodynamic study substantiates its chemical adsorption. Quantum chemical calculations suggest the reactive sites of interaction and corroborate the experimental findings. The present work might help to understand the corrosion behaviour of stainless steel in sulfuric acid and the inhibitory potential of different sesquiterpenes.

Influence of Calcium Scaling on Corrosion Behavior of Steel and Aluminum Alloys.

Calcium scaling is a serious problem encountered in the oil and gas industry because it is common that brines produced alongside oil and gas exhibit high concentrations of calcium ions, among others, which is expensive to remedy. The precipitation of calcium salts on the internal wall of the pipelines may occur because of the physical and chemical changes as fluids are produced from downhole to surface facilities. Although different researchers have address scaling and corrosion in the oil and gas industry, there are few reports in the literature relating the corrosion and scaling phenomena simultaneously. Despite there being indications that scales may produce corrosion problems, affecting the mechanical integrity of the infrastructure, there is minimal research in the literature addressing such relations. Previous studies presented aluminum alloys as excellent and reliable materials for applications in the petroleum industry, such as drilling activities. In this work, we evaluate the corrosion behavior of steel and aluminum alloys under highly scaling environments using supersaturated brines. Our results show that the presence of calcium carbonate and calcium sulfate as a scaling environment increases the corrosion rates for aluminum alloys and carbon steel; however, the same environments do not affect the corrosion behavior of stainless steel.

Corrosion Behavior of Stainless Steel 316 for Carbon Anode Oxide Reduction Application

Here, the stability of stainless steel 316 (SS-316) was investigated to identify its applicability in the oxide reduction process, as a component in related equipment, to produce a complicated gas mixture composed of O2 and Cl2 under an argon (Ar) atmosphere. The effects of the mixed gas composition were investigated at flow rates of 30 mL/min O2, 20 mL/min O2 + 10 mL/min Cl2, 10 mL/min O2 + 20 mL/ min Cl2, and 30 mL/min Cl2, each at 600℃, during a constant argon flow rate of 170 mL/min. It was found that the corrosion of SS-316 by the chlorine gas was suppressed by the presence of oxygen, while the reaction proceeded linearly with the reaction time regardless of gas composition. Surface observation results revealed an uneven surface with circular pits in the samples that were fed mixed gases. Thermodynamic calculations proposed the combination of Fe and Ni chlorination reactions as an explanation for this pit formation phenomenon. An exponential increase in the corrosion rate was observed with an increase in the reaction temperature in a range of 300 ~ 600℃ under a flow of 30 mL/min Cl2 + 170 mL/min Ar.

Effects of nitric acid passivation on the corrosion behavior of ZG06Cr13Ni4Mo stainless steel in simulated marine atmosphere

AbstractZG06Cr13Ni4Mo martensitic stainless steel was nitric acid‐passivated to improve its corrosion performance. The effects of nitric acid passivation on the surface morphology, chemical composition, electrochemical properties, semiconductor behavior, and long‐term corrosion performance of the stainless steel were investigated using various analytical techniques. An in‐depth analysis of X‐ray photoelectron spectroscopy (XPS) showed that the passive film formed after the acid passivation process showed high thickness and a duplex character as it consisted of a hydroxide layer and an oxide layer. The oxide layer affected the corrosion resistance and thickness of the passive film. The thickness of the passive film was calculated theoretically as well as experimentally by fitting the electrochemical impedance spectroscopy and XPS results. The electrochemical tests revealed that the dramatic increase in the corrosion resistance of the stainless steel after the passivation was due to the formation of a thick, low‐disorder passive film rather than Cr enrichment. The removal of inclusions resulted in higher pitting resistance, whereas the increased roughness showed a negative effect on the corrosion behavior of the stainless steel. During the wet–dry cyclic tests, the modification of the passive film was examined. The passivated stainless steel exhibited good corrosion resistance for up to 50 days of exposure in the simulated environment.

Influence of Ethanol on Pitting Corrosion Behavior of Stainless Steel for Bioethanol Fermentation Tanks.

The role of ethanol (C2H5OH) in pitting corrosion behavior of AISI 316L austenitic stainless steel was investigated in aqueous ethanolic solution with chloride. The pitting susceptibility and surface morphology of 316L in a series of ethanol-containing solutions were examined using X-ray photoelectron spectroscopy (XPS), optical microscopy with 3D stitching, immersion tests, and potentiodynamic polarization measurements. Results demonstrated that the ethanol concentration impacted little on the passive film stability while it dramatically influenced the pitting corrosion susceptibility. Corrosion rate of 316L after immersion tests first increased and then decreased as the concentration of ethanol increased from 0 to 10 M in ferric chloride solution. This, however, did not correspond to the breakdown potential which directly decreased from 489 to 249 mV as the water concentration decreased in ethanolic NaCl solutions. The pits density after both immersion and electrochemical tests showed that the initiation of pitting in ethanolic solution tended to occur at multiple points at the same time. The synergy effect on pitting behavior of hydrolysis enhancement and solubility reduction of metal cations due to the introduction of ethanol has also been discussed.

Electrochemical Corrosion Behavior of Graphene Oxide/Chitosan/Silver Nanoparticle Composite Coating on Stainless Steel Utensils in Aqueous Media

Graphene oxide (GO) ornamented with silver nanoparticles (AgNPs) was manufactured by a simplistic solution‐created methodology in chitosan (CS) solution. The morphology and elemental composition of AgNPs/GO/CS nanocomposite were considered by scanning electron microscope and energy dispersive X‐ray spectroscopy, respectively. The effects of AgNPs/GO/CS nanocomposite on the corrosion behavior of stainless steel were considered by electrochemical measurements and immersion assessments. The effects of pH, temperature and surface modification on the corrosion protection of stainless steel were investigated in constant composition of universal buffer by impedance, polarization and cyclic voltammetry techniques. Temperature and pH values were found to strongly influence the corrosion protection of stainless steel; the protection efficiency progressively reduced with enlarging the temperature and lessening the pH value. This study gives a new tactic for modifying commercial utensils utilizing safe and cost-effective graphene oxide for improving its action.

Effect of hydrogen on semiconductor properties and pitting initiation of 2205 duplex stainless steel passivation film

PurposeThis paper aims to study the effect of current density of hydrogen charging on the semiconductor properties and pitting initiation of 2205 duplex stainless steel (DSS) passivation film.Design/methodology/approachIn this work, the 2205 DSS is pre-hydrogenated and passivated. Then, the passivation film is tested by electrochemical impedance method, Mott–Schottky curve method and dynamic potential scanning method. The influences of hydrogen on the properties of the passivation film and the corrosion behavior of the matrix were studied by analyzing the curves obtained in the electrochemical test. The surface of the passivation film after pre-hydrogenation and anodic polarization was observed by using the ultra-depth three-dimensional microscopy and the scanning electron microscope. The integrity, density and corrosion morphology of the passivation film were studied and discussed.FindingsWith the increase of the hydrogen current density, the growth of the passivation film is hindered, the concentrations of donor and acceptor in the film are increased, the conductivity of the passivation film increases. In the anodic polarization, the dimensional passive current density increases with the increase of the hydrogen current density, and the pitting potential is reversed, the more likely the sample is pitting. In general, hydrogen hinders the formation of the passive film on duplex stainless steel, which increases the concentration of point defects in the passive film. Finally, the passive film is easy to crack and pitting.Originality/valueThe performance of passive film is an important condition to influence the corrosion behavior of stainless steel. However, little research has been done on the effects of hydrogen on the electrochemistry and pitting sensitivity of 2205 DSS passivation films. The effect of hydrogen on semiconductor properties and pitting initiation of 2205 DSS passivation film is needed to be investigated.

Corrosion Behavior of 304 Stainless Steel Exposed to a Simulated Salt Lake Atmosphere

The corrosion behavior of stainless steel exposed to a simulated salt lake atmosphere has been investigated by analyzing the evolution of surface morphologies and corrosion products, the initiation and development of pits, and the electrochemical characteristics. The results indicated that (Mg6Fe2(OH)16(CO3)(H2O)4.5)0.25, a layered double hydroxide, has been detected for the first time in the corrosion products formed on stainless steel exposed to a simulated salt lake atmosphere. The specimens exposed to MgCl2 deposit conditions were corroded more severely than those exposed to NaCl deposit conditions, which was attributed to the differences in the deliquescence relative humidity and efflorescence relative humidity values of MgCl2 and NaCl. In addition, a special corrosion morphology consisting of a concentric circle of yellowish material was observed on the specimens exposed to MgCl2 deposit conditions, which was attributed to the formation of Mg(OH)2, inhibiting the diffusion and migration of OH− ions to the anode region. The maximum pit depth followed a power function with respect to corrosion time. The corrosion mechanism of stainless steel exposed to a simulated salt lake atmosphere is also discussed.

The pH in Crevice Measured by a Semiconductor Chemical Sensor and Relationship with Crevice Corrosion Behavior of Stainless Steel

The pH in Crevice Measured by a Semiconductor Chemical Sensor and Relationship with Crevice Corrosion Behavior of Stainless Steel

Koroziono ponašanje nerđajućeg čelika EN 1.4301 u kiseloj sredini u prisustvu PBTCA inhibitora

In this study, corrosion behaviour of stainless steel in 0.5 M and 1 M hydrochloric acid was examined. Also, commercial corrosion inhibitor which contain 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA) is examined as potential inhibitor for stainless steel EN 1.4301 in 0.5 M hydrochloric acid. For experimental research it was used DC-technique (Tafel extrapolation, linear polarization method and potentiodynamic polarization). The obtained results show that the inhibitor is effective in mentioned acid environment and the protection efficiency depends primarily on the concentration of the inhibitor. Based on the obtained results this inhibitor has moderate inhibition efficiency, since the highest efficacy was achieved Ei = 55.7%. According to the corrosion mechanism the inhibitor is behaved as a mixed inhibitor.

Forming, fracture and corrosion behaviour of stainless steel 202 sheet formed by single point incremental forming process

This work aims to determine the forming limit of stainless steel 202 sheet having 0.8 mm thickness during Single Point Incremental sheet metal Forming (SPIF) process. A L18 orthogonal array was designed using taguchi method for performing SPIF. The process parameters used were spindle speed, feed rate and vertical step down having three levels each and ball diameter having two levels. A straight groove test was conducted for 18 samples and strain based Forming Limit Diagrams (FLD) and stress based FLDs were plotted. Stress triaxiality and strain triaxiality were determined. The fractographs were analyzed and dislocation density was measured from x-ray diffraction line profile analysis. The corrosion behaviour of both undeformed sample and deformed sample were also studied. It was found that the formability is increased with increasing the spindle speed, decreasing the vertical step down and feed rate. The sum of strain was found to be 0.91 which is twice greater than that of conventional forming process. It is also found that the dislocation density is 2.35 times greater for the sample possesses higher formability than the sample possesses least formability. The goodness of fit in strain based FLD and stress based FLD are found to be 0.989 and 0.968 respectively.

Effects of molten-salt LiNO3 on high-temperature corrosion behaviour of absorption tubes of a concentrating solar power system

ABSTRACTThe main aim of the present research was to investigate the effects of a ternary nitrate salt (NaNO3–KNO3–LiNO3) on high-temperature corrosion behaviour of stainless steel 321 (SS 321) in a parabolic trough collector in a concentrating solar power system. The corrosion behaviour of SS − 321 was examined in a ternary salt (LiNO3 (25 wt-%)-NaNO3 (25 wt-%)-KNO3 (50 wt-%)) at 400°C and 550°C for 250 h, 500 h and 1000 h, and the obtained findings were then compared with the results of a solar salt ((NaNO3 (60 wt-%)-KNO3 (40 wt-%)). In order to determine the quantitative corrosion behaviour of SS − 321, the results of immersion tests and microstructural investigations obtained through scanning electron microscopy and energy-dispersive X-ray microanalysis were also considered. It was found that the addition of lithium nitrate (LiNO3) to solar salt formed resistant oxide layers on the surface of SS 321 and subsequently, increased its corrosion resistance ability.

Investigation of Corrosion Behavior of Stainless Steels As a Function of Composition, Grain Size and Austenite to Martensite Phase Ratio

It is well established that the severe plastic deformation of metastable austenitic stainless steels causes martensitic transformation and the annealing of deformation induced martensitic phase induces reverse transformation from martensite to austenite the ratio of which has been found to be a factor of alloy compositions and annealing / sintering temperatures. In this study, nanocrystalline austenitic stainless steels of different compositions will be synthesized from elemental powders by using high energy mechanical milling. As-milled powders will be cold-consolidated and sintered at elevated temperatures up to 1100 ºC in order to facilitate a better densification for the subsequent experiments and alter the microstructure i.e., grain size and austenite to martensite phase ratio. Microstructural evolutions as a function of alloy compositions and sintering temperatures will be investigated using focused ion beam, transmission electron microscopy and in-situ / ex-situ x-ray diffraction techniques to determine the grain sizes and phases upon milling and sintering. The corrosion behavior of austenitic stainless steels will be determined using immersion and electrochemical tests at various temperatures. The electrochemical corrosion tests will be conducted using a flat corrosion test and a potentiostat. The relative importance of compositions, grain sizes and austenite to martensite phase ratios will be discussed with respect to corrosion behavior of the studied stainless steels.

Influence of herbaceous biomass ash pre-treated by alkali metal leaching on the agglomeration/sintering and corrosion behaviors

Partially melted ash particles cause increased ash fouling, agglomeration and sintering behaviors during biomass combustion. In addition, ash fouling facilitates the corrosion behavior of stainless steel. In this work, the agglomeration/sintering and corrosion behaviors of untreated herbaceous biomass ash and that pre-treated by an alkali metal leaching reaction were investigated under combustion conditions. Although the ash agglomeration tendency increased with increasing temperature, the tendency was reduced by alkali metal leaching pre-treatment. During comparison of sintering behavior, the degree of sintering (x/r) increased as a function of time but was substantially alleviated by alkali metal leaching pre-treatment. In comparison to the typical Frenkel sintering model, a modified Frenkel sintering model was shown to fit well with the experimental sintering behavior. Alkali metal leaching pre-treatment inhibited ash particle adhesion and made high melting temperature minerals, which was verified by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), X-ray diffraction (XRD) analysis, the use of ternary mineral phase diagrams and adoption of a new chemical classification system. Furthermore, from SEM-EDX, alkali metal leaching pre-treatment was seen to reduce the corrosion by ash fouling on stainless steel (SUS) 316. Resultingly, the alkali metal leaching pre-treatment significantly alleviated the ash adhesion and corrosion behaviors.