scholarly journals Resistance of Thermally Aged DSS 2304 against Localized Corrosion Attack

Metals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 1022 ◽  
Author(s):  
Federica Zanotto ◽  
Vincenzo Grassi ◽  
Andrea Balbo ◽  
Cecilia Monticelli ◽  
Fabrizio Zucchi
Keyword(s):  
Aging Time ◽  
Corrosion Behaviour ◽  
Localized Corrosion ◽  
Corrosion Attack ◽  
Pitting Potential ◽  
Pitting Corrosion Resistance ◽  
Critical Pitting Temperature ◽  
Electrochemical Potentiokinetic Reactivation ◽  
M23c6 Type ◽  
Good Agreement

In this paper, the effects of thermal aging in the 650–850 °C range on the localized corrosion behaviour of duplex stainless steel (DSS) 2304 was investigated. Pitting corrosion resistance was assessed by pitting potential (Epitt) and critical pitting temperature (CPT) determination, while the degree of sensitisation (DOS) to intergranular corrosion (IGC) was evaluated by double loop electrochemical potentiokinetic reactivation (DL-EPR). The susceptibility to stress corrosion cracking (SCC), evaluated in standard NACE TM-0177 solution at pH 2.7 and 25 °C, with the addition of S2O32− at 10−3 M, resulted in general good agreement with pitting and IGC behaviour. In fact, as-received DSS 2304 aged for 5 min at 650 °C or 750 °C presented a high resistance to localized corrosion. The alloy corrosion behaviour was severely impaired with an aging time of 60 min at 650 °C and of 10 or 60 min at 750 °C, due to the precipitation of finely distributed M23C6-type chromium carbides at ferrite/austenite interphases, which determined the formation of chromium and molybdenum depleted areas. The behaviour of samples aged at 850 °C also depended on the aging time, but, at 60 min, the rediffusion of passivating elements produced a recovery of the alloy resistance to pitting, IGC and SCC.

The Corrosion Attack on Stainless Steel 316L and WC-Co in High Sulphate-Chloride Ratio

2015 ◽  
Vol 1087 ◽  
pp. 410-414
Author(s):  
Azzura Ismail
Keyword(s):  
Aqueous Media ◽  
Austenitic Stainless Steels ◽  
Localized Corrosion ◽  
Corrosion Mechanism ◽  
High Concentration ◽  
Stainless Steel 316L ◽  
Corrosion Attack ◽  
Corrosive Media ◽  
Pitting Potential ◽  
Sulphate Chloride

Austenitic stainless steels and cermets alloy has been used extensively in many sectors due to their highly resistance to corrosion attack and excel in mechanical properties. However, in corrosive media both materials are susceptible to corrosion attack especially in seawater and high temperature. Cermet alloys are a combination of ceramic and metal. Therefore, cermets exist in high corrosion resistance in aqueous media and the corrosion rate is complex to identify. This paper presents the corrosion mechanism of 316L and cermets alloy exposed to high concentration of sulphate in the salinity of seawater. The solution (media) was prepared according to the same composition as seawater including pH, salinity and dissolved oxygen. The corrosion mechanism were characterized to breakdown potential (Eb)of 316L which are the potential once reaches a sufficiently positive value and also known as pitting potential. This is the most point where localized corrosion susceptibility to evaluate and considered a potential, which could be an appropriate point according to any given combination of material/ambient/testing methods. TheEbvalue of 316L in high sulphate are higher compared to seawater in every temperature which elucidate that some anions accelerate corrosion attack whereas some anions such as sulphate behaves as inhibiting effect to 316L.

scholarly journals The Effect of Heat Treatment on Microstructure, Microhardness and Pitting Corrosion of Ti6Al4V Produced by Electron Beam Melting Additive Manufacturing Process

2021 ◽  
Author(s):  
Mingzhen Xiu ◽  
Yong Teck Tan ◽  
Srinivasan Raghavan ◽  
Min Hao Goh ◽  
Mui Ling Sharon Nai
Keyword(s):  
Heat Treatment ◽  
Corrosion Resistance ◽  
Electron Beam ◽  
Pitting Corrosion ◽  
Corrosion Behaviour ◽  
Corrosion Properties ◽  
Clear Trend ◽  
Pitting Potential ◽  
Pitting Corrosion Resistance ◽  
Lath Width

Abstract There has been limited studies on corrosion behaviour of post-processed Electron Beam Melted (EBM) Ti6Al4V, given that the factors affecting corrosion resistance of AM Ti6Al4V remain unclear. This paper proposes using heat treatment method to improve the pitting corrosion resistance of EBM Ti6Al4V. Different treatment profiles alter the microstructure of EBM Ti6Al4V. A clear trend is observed between microhardness and α lath width. As-printed EBM Ti6Al4V exhibits an inferior pitting potential, while heat treatment provided a significant improvement in the corrosion resistance. This study finds that the β phase fraction is a better indicator than the α lath width for pitting corrosion resistance. Solution air-cooled & ageing heat treated EBM Ti6Al4V exhibits good mechanical and corrosion properties, and even performs better than commercial cast Ti6Al4V.

Corrosion Behavior of Austenitic Stainless Steel in High Sulphate Content

2014 ◽  
Vol 893 ◽  
pp. 397-401 ◽  
Author(s):  
A. Ismail
Keyword(s):  
Austenitic Stainless Steels ◽  
Localized Corrosion ◽  
Corrosion Mechanism ◽  
High Concentration ◽  
Corrosion Attack ◽  
Corrosive Media ◽  
Sulphate Content ◽  
Pitting Potential ◽  
Corrosion Susceptibility ◽  
C 50

Austenitic stainless steels especially 316L has been used extensively in many sectors including construction, medical and household appliances due to their highly resistance to corrosion attack, reasonable cost and excel in mechanical properties. However, in corrosive media, 316L are susceptible to localised corrosion attack especially in seawater and high temperature. The corrosiveness of media increased as the anions contents increased. This paper presents the corrosion mechanism of 316L exposed to high concentration of sulphate in the salinity of seawater. The solution (media) was prepared according to the same composition as seawater including pH, salinity and dissolved oxygen. The corrosion mechanism were characterized to breakdown potential (Eb) of 316L which are the potential once reaches a sufficiently positive value and also known as pitting potential. This is the most point where localized corrosion susceptibility to evaluate and considered a potential, which could be an appropriate point according to any given combination of material/ambient/testing methods. The Eb value were identified at 4°C, 20°C, 50°C and 80°C and compared with Eb value of 316L in seawater. The Eb value of 316L in high sulphate are higher compared to seawater in every temperature which elucidate that some anions accelerate corrosion attack whereas some anions such as sulphate behaves as inhibiting effect to 316L.

Influence of MoSi2 Addition in Co Based Alloy Cladding Coating on Microstructure Evolution and Pitting Corrosion Behaviour

2013 ◽  
Vol 456 ◽  
pp. 392-398
Author(s):  
Ze Fen Liang ◽  
Min Zheng
Keyword(s):  
Stainless Steel ◽  
Corrosion Resistance ◽  
Pitting Corrosion ◽  
Stainless Steel Substrate ◽  
Corrosion Behaviour ◽  
Steel Substrate ◽  
304 Stainless Steel ◽  
Pitting Potential ◽  
Pitting Corrosion Resistance ◽  
Coating Microstructure

In the present paper the influence of the addition of MoSi2particles on the microstructure and pitting corrosion behaviour of laser cladding Co based alloy coatings deposited on 304 stainless steel substrate has been reported. The coating microstructure was investigated by SEM, OM, XRD and EPMA etc.. And the pitting corrosion resistance of coating was evaluated in the 3.5% NaCl solution. The results showed that: (1) The microstructure is fined by increasing MoSi2percentage. And the coating microstructure evolved from dendrites and interdendritic eutectics to various faceted dendrites with the bamboo leaf, flower, or butterfly morphology, when the MoSi2content is from 0~20% to 30~40%; (2) the (Epit-Eprot) of Co based alloy/MoSi2composite coating was lower than that of Co based alloy, and which presented higher self-repairing capability. The pitting potential Epitof Co +(0~20wt.%) MoSi2cladding coatings is higher than that of stainless steel, the pitting corrosion resistance is enhanced; When more MoSi2(30wt.%) was added, the pitting corrosion resistance decreases due to microstructure inhomogeneity and exiting of inclusion.

Chloride-Induced Localized Corrosion of Fe3Al-Type Iron Aluminides: Beneficial Effects of Cr And Mo Additions

1990 ◽  
Vol 213 ◽  
Author(s):  
R. A. Buchanan ◽  
J. G. Kim
Keyword(s):  
Corrosion Potential ◽  
Open Circuit ◽  
Iron Aluminides ◽  
Localized Corrosion ◽  
Aqueous Corrosion ◽  
Pitting Potential ◽  
Beneficial Effects ◽  
Protection Potential ◽  
Cr Concentration ◽  
Mo Additions

ABSTRACTIn this study, an acid-chloride electrolyte at pH = 4 (H2SO4) and containing 200 ppm Cl- was used to define the effects of Cr concentration (0–6 at.%) and Mo additions (0–2 at.%) on the aqueous corrosion behavior of iron aluminides containing 28 at.% Al. For the Fe-28Al composition, cyclic-anodic-polarization testing indicated passivation, but with a relatively low breakdown potential for pitting corrosion, and a protection potential lower than the open-circuit corrosion potential. Cr additions alone proved beneficial by continuously increasing the pitting potential. However, even at the highest Cr level, 6%, the protection potential was still lower than the corrosion potential, indicating that pitting could initiate after an incubation period. Mo additions were found to raise the protection potential, such that at 1 and 2% Mo levels (4 % Cr), it was higher than the corrosion potential, indicating significantly improved resistance to the initiation of localized corrosion. Immersion testing showed that the latter compositions remained passivated with no localized corrosion for a period of four months, at which point the tests were terminated. The overall results indicated that for satisfactory resistance to chlorideinduced localized corrosion, both higher Cr levels (4–6 at.%) and Mo additions (1–2 at.%) are desirable.

Pitting corrosion prediction from cathodic data: application of machine learning

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Mohamed Nadir Boucherit ◽  
Fahd Arbaoui
Keyword(s):  
Machine Learning ◽  
Physicochemical Properties ◽  
Input Data ◽  
Surface Condition ◽  
Recurrent Network ◽  
Localized Corrosion ◽  
Potential Region ◽  
Pitting Potential ◽  
Content Type ◽  
Nuclear Installation

Purpose To constitute input data, the authors carried out electrochemical experiments. The authors performed voltammetric scans in a very cathodic potential region. The authors constituted an experimental table where for each experiment we note the current values recorded at a low polarization range and the pitting potential observed in the anodic region. This study aims to concern carbon steel used in a nuclear installation. The properties of the chemical solutions are close to that of the cooling fluid used in the circuit. Design/methodology/approach In a previous study, this paper demonstrated the effectiveness of machine learning in predicting the localized corrosion resistance of a material by considering as input data the physicochemical properties of its environment (Boucherit et al., 2019). With the present study, the authors improve the results by considering as input data, cathodic currents. The reason of such an approach is to have input data that integrate both the surface state of the material and the physicochemical properties of its environment. Findings The experimental table was submitted to two neural networks, namely, a recurrent network and a convolution network. The convolution network gives better pitting potential predictions. Results also prove that the prediction by observing cathodic currents is better than that obtained by considering the physicochemical properties of the solution. Originality/value The originality of the study lies in the use of cathodic currents as input data. These data contain implicit information on both the chemical environment of the material and its surface condition. This approach appears to be more efficient than considering the chemical composition of the solution as input data. The objective of this study remains, at the same time, to seek the optimal neuronal architectures and the best input data.

scholarly journals Effect of Microstructural Bands on the Localized Corrosion of Laser Surface-melted 316L Stainless Steel

CORROSION ◽  
10.5006/3779 ◽  
2021 ◽  
Author(s):  
Yoon Hwa ◽  
Christopher Kumai ◽  
Nancy Yang ◽  
Joshua Yee ◽  
Thomas Devine
Keyword(s):  
Stainless Steel ◽  
316L Stainless Steel ◽  
Microscopic Investigation ◽  
Outer Edge ◽  
Chromium Concentration ◽  
Laser Surface ◽  
Localized Corrosion ◽  
Pitting Potential ◽  
Primary Austenite ◽  
Potentiodynamic Anodic Polarization

The localized corrosion of laser surface melted (LSM) 316L stainless steel is investigated by a combination of potentiodynamic anodic polarization in 0.1M HCl and microscopic investigation of the initiation and propagation of localized corrosion. The pitting potential of LSM 316L is significantly lower than the pitting potential of wrought 316L. The LSM microstructure is highly banded as a consequence of the high laser power density and high linear energy density. The bands are composed of zones of changing modes of solidification, cycling between very narrow regions of primary austenite solidification and very wide regions of primary ferrite solidification. Pits initiate in the outer edge of each band where the mode of solidification is primary austenite plane front solidification and primary austenite cellular solidification. The primary austenite regions have low chromium concentration (and possibly low molybdenum concentration), which explains their susceptibility to pitting corrosion. The ferrite is enriched in chromium, which explains the absence of pitting in the primary ferrite regions. The presence of the low chromium regions of primary austenite solidification explains the lower pitting resistance of LSM 316L relative to wrought 316L. The influence of banding on localized corrosion is applicable to other rapidly solidified processes such as additive manufacturing.

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.

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