Effects of the α/γ-Phase Ratio on the Corrosion Behavior of Cast Duplex Stainless Steel

CORROSION ◽  
10.5006/3464 ◽  
2020 ◽  
Vol 76 (9) ◽  
pp. 815-825
Author(s):  
Ryotaro Yamamoto ◽  
Hiroshi Yakuwa ◽  
Matsuho Miyasaka ◽  
Nobuyoshi Hara
Keyword(s):  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Chloride Ions ◽  
Phase Ratio ◽  
Potential Range ◽  
High Concentration ◽  
Active Dissolution ◽  
Pitting Potential ◽  
Potential Measurement ◽  
Α Phase

The effects of the α/γ-phase ratio on pitting corrosion initiation and growth in cast duplex stainless steel were studied, including the preferential dissolution of the two phases inside the pits, using pitting potential measurement and potentiostatic polarization measurement with a high concentration of chloride ions and a low pH. The initiation of pitting was not dependent on the α-phase ratio. The γ phase preferentially dissolves when a high potential in the active dissolution region is applied, and the α phase preferentially dissolves when a low potential is applied. In addition, with an increase in α-phase ratio, the potential range where the α phase preferentially dissolves enlarged toward the higher potential side. The growth rate of stable pitting increased with the α-phase ratio. Dissolution of the α phase increased with an increase in the α-phase ratio. This phenomenon is presumably caused by the decreased amount of Cr in the α phase, resulting from the increased α-phase ratio, as well as by Cr depletion around Cr nitrides.

Influence of Sigma Phase Precipitation on Pitting Corrosion of 2507 Super-Duplex Stainless Steel

2010 ◽  
Vol 658 ◽  
pp. 380-383 ◽  
Author(s):  
Ying Han ◽  
De Ning Zou ◽  
Wei Zhang ◽  
Jun Hui Yu ◽  
Yuan Yuan Qiao
Keyword(s):  
Stainless Steel ◽  
Corrosion Resistance ◽  
Ambient Temperature ◽  
Duplex Stainless Steel ◽  
Pitting Corrosion ◽  
Super Duplex Stainless Steel ◽  
Phase Precipitation ◽  
Pitting Potential ◽  
Σ Phase ◽  
Pitting Corrosion Resistance

Specimens of 2507 super-duplex stainless steel aging at 850°C for 5 min, 15 min and 60 min were investigated to evaluate the pitting corrosion resistance in 3.5% NaCl solution at 30°C and 50°C. The results are correlated with the microstructures obtained with different aging time. The precipitation of σ phase remarkably decreases the pitting corrosion resistance of the steel and the specimen aged for 60 min presents the lowest pitting potential at both 30°C and 50°C. With increasing the ambient temperature from 30°C to 50°C, the pitting potential exhibits a reduction tendency, while this tendency is less obviously in enhancing the ambient temperature than in extending the isothermal aging duration from 5 to 60 min. SEM analysis shows that the surrounding regions of σ phase are the preferable sites for the formation of corrosion pits which grew up subsequently. This may be attributed to the lower content of corrosion resistance elements in these regions formatted with σ phase precipitation.

scholarly journals Pitting Corrosion Resistance on Annealing Treated Super Duplex Stainless Steel S32750

Crystals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 294
Author(s):  
Shuang Liu ◽  
Chaohua Yue ◽  
Xi Chen ◽  
Qiuhua Zhu ◽  
Yiyou Tu
Keyword(s):  
Stainless Steel ◽  
Corrosion Resistance ◽  
Duplex Stainless Steel ◽  
Pitting Corrosion ◽  
Annealing Temperature ◽  
Super Duplex Stainless Steel ◽  
Boundary Area ◽  
Pitting Potential ◽  
Pitting Corrosion Resistance ◽  
Equivalent Number

The pitting corrosion resistance of S32750 super duplex stainless steel, annealing treated at temperatures of 950–1200 °C for 20–60 min, was investigated using potentiodynamic polarization tests. The results show that the volume fractions of ferrite in the S32750 duplex stainless steel increased from 48.9% to 68.4% as annealing temperatures increased from 950 to 1200 °C. The pitting potential of the sample increased first and then decreased from an annealing temperature of 950 to 1050 °C, and the highest pitting potential was observed after annealing at 1050 °C for 35 min. The pitting corrosion resistance of S32750 stainless steel is due to the combination of pitting resistance equivalent number (PREN) value, phase fraction and grain boundary area fraction, and the imbalance of corrosion potential.

Effect of Uniaxial Tension-Induced Plastic Strain on the Microstructure and Corrosion Behavior of 13Cr Martensitic Stainless Steel

CORROSION ◽  
10.5006/3516 ◽  
2020 ◽  
Vol 76 (12) ◽  
Author(s):  
Salar Salahi ◽  
Mostafa Kazemipour ◽  
Ali Nasiri
Keyword(s):  
Stainless Steel ◽  
Plastic Strain ◽  
Corrosion Behavior ◽  
Chromium Carbide ◽  
Martensitic Stainless Steel ◽  
Electrochemical Impedance ◽  
Passive Layer ◽  
High Concentration ◽  
Pitting Potential ◽  
Heat Treated Sample

This study aims to understand the correlation between the manufacturing process-induced plastic deformation, microstructure, and corrosion behavior of a 13Cr martensitic stainless steel tubing material (UNS S42000). Comparisons were made between the microstructure, crystallographic orientation, and corrosion performance of a texture-free, heat-treated sample and uniaxially tensioned samples to the elongations of 5% and 22%. Cyclic potentiodynamic polarization tests and electrochemical impedance spectroscopy were performed on all samples in aerated 3.5 wt% NaCl electrolyte at room temperature. Overall, the corrosion resistance of the samples was found to decrease with increasing deformation level. A more stable and higher corrosion potential and pitting potential values with a better stability of the passive film were derived for the nondeformed sample, whereas the 5% and 22% elongated samples exhibited lower corrosion and pitting potential values and were characterized by having a less stable passive layer. All samples consistently revealed micropit formation on the lath boundaries where a high concentration of chromium carbide precipitates was detected. Increasing the level of plastic strain in 13Cr stainless steel was found to enlarge the size of sensitized regions along the matrix/coarse chromium carbide precipitates interface, leading to more regions susceptible to initiation and propagation of pitting.

Thermal Embrittlement of a Lean Grade of Duplex Stainless Steel: Alloy 2003

2011 ◽  
Vol 172-174 ◽  
pp. 331-337 ◽  
Author(s):  
Julie D. Tucker ◽  
George A. Young Jr. ◽  
Daniel R. Eno
Keyword(s):  
Thermal Stability ◽  
Stainless Steel ◽  
Phase Separation ◽  
Duplex Stainless Steel ◽  
Steel Alloy ◽  
Service Temperature ◽  
Stainless Steel Alloy ◽  
Α Phase ◽  
Thermal Embrittlement ◽  
Thermal Stability Of

Duplex stainless steels are desirable for use in power generation systems due to their attractive combination of strength, corrosion resistance, and cost. However, thermal embrittlement at intermediate temperatures (~475°C) via α-α' phase separation limits upper service temperatures for many applications. The development of low Cr and Ni equivalent lean grade alloys potentially increases the upper service temperature of these alloys by delaying the onset of α-α' phase separation. The present work assesses the thermal stability of a relatively new lean grade of duplex stainless steel, alloy 2003. In this paper, alloy 2003 has been compared to the most widely used duplex alloy, 2205, through a series of isothermal agings between 260°C and 538°C for times between 1 and 10,000 hours. The thermal stability of these alloys was primarily characterized by changes in microhardness. The microhardness data were fit to a JMA-type equation to quantify embrittlement rates and predict microstructural changes out to 50 years. Additionally, as-received specimens were characterized with the scanning electron microprobe to quantify the chemistry within the ferrite grains relative to the bulk material. Alloy 2003 was shown to be much more resistant to thermal embrittlement than alloy 2205. For 50 years of service at 288°C, it is predicted that alloy 2003 components will have a change in microhardness of about 25 HK where alloy 2205 components would increase approximately 175 HK, which indicates significant embrittlement. These findings show that lean grade alloys will have a greater service temperature range than standard grades. However, additional data, characterization, and modeling are needed to better predict embrittlement kinetics over component lifetimes.

Pitting Behavior of 304 Stainless Steel in Simulated Condensate in Refining High Sulfur and Salt Heavy Oil

2015 ◽  
Vol 814 ◽  
pp. 249-255
Author(s):  
Xiao Hong Wang ◽  
Xiao Hua Guo ◽  
Yuan Hua Lin ◽  
Ying Ying Li ◽  
Shu Liang Wang ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Heavy Oil ◽  
Salt Content ◽  
Chloride Ions ◽  
304 Stainless Steel ◽  
Pitting Potential ◽  
Condensed Water ◽  
Sulfide Ions ◽  
Corrosion Pits ◽  
Static Immersion

The pitting behavior of 304 stainless steel in the simulated condensate with different salt content (4 mg/L, 8 mg/L, 16 mg/L, 32 mg/L, 64 mg/L) and sulfur content (1.2 g/L, 2.5 g/L, 5 g/L) was studied using potentiodynamic polarization curve and static immersion methods. The simulated condensate was simulating the condensed water in the unit of refining heavy oil with high salt and high sulfur. The results showed that with the increase in chloride ions concentration, the pitting potential of 304 stainless steel decreased and the pitting sensitivity increased. The pitting sensitivity of 304 stainless steel also increased with the increase in sulfide ions concentration. In several experimental mediums, when the concentration of chloride ions and sulfide ions were 64 mg/L, 5 g/L respectively, the number and the size of corrosion pits both were the largest, the pitting behavior was the most serious.

Pitting corrosion and effect of Euphorbia echinus extract on the corrosion behavior of AISI 321 stainless steel in chlorinated acid

2019 ◽  
Vol 37 (3) ◽  
pp. 259-271 ◽  
Author(s):  
Y. Koumya ◽  
R. Idouhli ◽  
M. Khadiri ◽  
A. Abouelfida ◽  
A. Aityoub ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Pitting Corrosion ◽  
Electrochemical Impedance ◽  
Chloride Concentration ◽  
Analysis Data ◽  
Chloride Ions ◽  
General Corrosion ◽  
Visible Absorption ◽  
Pitting Potential ◽  
Aisi 321

AbstractStainless steel (SS) is a very corrosion-resistant alloy used in different industrial plants because of its chemical and mechanical properties. However, the high chloride concentration in sulfuric acid (H2SO4) may promote both general corrosion and pitting corrosion. The pitting corrosion susceptibility in SS in chlorinated H2SO4 and the effect of Euphorbia echinus extract (EEE) on both general corrosion and pitting corrosion have been studied using potentiodynamic polarization, electrochemical impedance spectroscopy, chronoamperometry, cyclic voltammetry, and scanning electron microscopy (SEM). The pitting potential has been found to shift slightly in the presence of chloride ions (Cl−) in H2SO4. Also, pitting corrosion initiation has been demonstrated in the recorded chronoamperograms as a linear straight line having a positive slope. EEE has reduced the general corrosion and the inhibitor adsorption was found to follow the Langmuir isotherm. SEM micrographs showed that the tested inhibitor has efficiently acted on pitting corrosion for different concentrations of Cl−. Also, the kinetic findings were in good agreement with the surface analysis data. Fourier transform infrared spectroscopy and ultraviolet-visible absorption spectrophotometric measurements provided more insights on the interaction between the chemical functional groups of the inhibitor and the SS surface.

Atmospheric pitting corrosion of 304L stainless steel: the role of highly concentrated chloride solutions

2015 ◽  
Vol 180 ◽  
pp. 251-265 ◽  
Author(s):  
Steven R. Street ◽  
Na Mi ◽  
Angus J. M. C. Cook ◽  
Haval B. Mohammed-Ali ◽  
Liya Guo ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Pitting Corrosion ◽  
Large Data ◽  
304 Stainless Steel ◽  
Data Sets ◽  
304L Stainless Steel ◽  
Active Dissolution ◽  
Pitting Potential ◽  
Enhanced Dissolution ◽  
Heterogeneous Alloy

The morphology of atmospheric pitting corrosion in 304L stainless steel plate was analysed using MgCl2 droplets in relation to changes in relative humidity (RH) and chloride deposition density (CDD). It was found that highly reproducible morphologies occur that are distinct at different RH. Pitting at higher concentrations, i.e. lower RH, resulted in satellite pits forming around the perimeter of wide shallow dish regions. At higher RH, these satellite pits did not form and instead spiral attack into the shallow region was observed. Increasing CDD at saturation resulted in a very broad-mouthed pitting attack within the shallow dish region. Large data sets were used to find trends in pit size and morphology in what is essentially a heterogeneous alloy. Electrochemical experiments on 304 stainless steel wires in highly saturated solutions showed that the passive current density increased significantly above 3 M MgCl2 and the breakdown pitting potential dropped as the concentration increased. It is proposed that the shallow dish regions grow via enhanced dissolution of the passive film, whereas satellite pits and a spiral attack take place with active dissolution of bare metal surfaces.

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