scholarly journals Interlaboratory Testing to Assess Repeatability and Reproducibility of the Double Loop Electrochemical Potentiokinetic Reactivation (DL-EPR) Tests for Type 304H Stainless Steels

CORROSION ◽  
10.5006/3559 ◽  
2020 ◽  
Vol 76 (8) ◽  
pp. 742-749
Author(s):  
Raul B. Rebak ◽  
Sheldon W. Dean
Keyword(s):  
Stainless Steels ◽  
Industrial Applications ◽  
Double Loop ◽  
Degree Of Sensitization ◽  
Electrochemical Potentiokinetic Reactivation ◽  
Degree Of Confidence ◽  
Repeatability And Reproducibility ◽  
Epr Test ◽  
High Degree ◽  
Interlaboratory Testing

The sensitization of stainless steels may decrease their corrosion resistance in industrial applications. Traditional immersion tests exist to determine the degree of sensitization (DOS) of the stainless steels. However, electrochemical methods may be preferred because they are less expensive and faster to perform. The fast and robust double loop electrochemical potentiokinetic reactivation (DL-EPR) test has been introduced to the corrosion community some decades ago but an interlaboratory testing study was necessary to assess the repeatability and reproducibility of the DOS results. This work reports on a recent study where 11 laboratories returned results that show a high degree of confidence in the data obtained by DL-EPR.

A New Electrochemical Potentiokinetic Reactivation Test for Determining Degree of Sensitization in Ferritic Stainless Steels

CORROSION ◽  
1986 ◽  
Vol 42 (2) ◽  
pp. 106-110 ◽  
Author(s):  
J. B. Lee
Keyword(s):  
Stainless Steels ◽  
Open Circuit Potential ◽  
Immersion Test ◽  
Open Circuit ◽  
H2so4 Solution ◽  
Ferritic Stainless Steels ◽  
Degree Of Sensitization ◽  
Electrochemical Potentiokinetic Reactivation ◽  
Epr Test ◽  
Aisi 430

Abstract An electrochemical potentiokinetic reactivation (EPR) test has been developed for quantifying the degree of sensitization of ferritic stainless steels (SSs). This test is applicable to AISI 430, 430 Ti, 430 Nb, 434, 444, and 446. The test is conducted at 30 C in a deaerated 3 to 5 N H2SO4 solution. A test specimen is first passivated at + 400 mVSCE for 2 to 10 min, depending on the grade of SS, and then subjected to a reactivation step where the potential is decreased at a rate of 100 to 250 mV/min toward the open circuit potential (OCP) to determine whether a reactivation peak occurs. Results of the EPR test agree well with those of the Cu-CuSO4-50% H2SO4 immersion test.

AEM of Grain-Boundary Precipitation in Type 304 Stainless Steels Containing N

1985 ◽  
Vol 43 ◽  
pp. 246-247
Author(s):  
Hemant S. Betrabet
Keyword(s):  
Stainless Steels ◽  
Intergranular Stress Corrosion ◽  
Intergranular Carbide ◽  
Degree Of Sensitization ◽  
Electrochemical Potentiokinetic Reactivation ◽  
Grain Boundary Precipitation ◽  
Epr Test ◽  
Intergranular Stress Corrosion Cracking ◽  
Type 304 ◽  
N Additions

A systematic analytical electron microscope (AEM) study was conducted on a series of 18Cr-8Ni stainless steels in order to determine the effect of N additions on sensitization. This phenomenon is associated with intergranular carbide (Cr23C6) precipitation, and the subsequent Cr depletion of the surrounding region, and leads to susceptibility to intergranular corrosion and intergranular stress corrosion cracking. Sensitization can be retarded by reducing the C content of the steels, but this causes an unacceptable loss of mechanical properties. A better solution is to replace much of the C by N.A series of steels with varying N (0.04-0.25 wt%) and C (0.02-0.07 wt%) contents were studied in the AEM, and the results compared with electrochemical potentiokinetic reactivation (EPR) test data used to measure the degree of sensitization (DOS). EPR tests indicate that N additions up to 0.16 wt% retard sensitization, but above 0.16 wt% promote it, a result which does not agree with thermodynamic calculations of carbide precipitation which show that N slows the Cr23C6 growth kinetics, even at levels above 0.16 wt%.

Friction Stir Welding: Mitigating the Susceptibility to Intergranular Corrosion of Alloy 625

2021 ◽  
Author(s):  
Guilherme Vieira Braga Lemos ◽  
Alexandre Bellegard Farina ◽  
Henrique Piaggio ◽  
Luciano Bergmann ◽  
Jane Zoppas ◽  
...  
Keyword(s):  
Friction Stir Welding ◽  
Intergranular Corrosion ◽  
Double Loop ◽  
Tool Rotational Speed ◽  
Alloy 625 ◽  
Friction Stir ◽  
Degree Of Sensitization ◽  
Electrochemical Potentiokinetic Reactivation ◽  
The Mean ◽  
Epr Test

Abstract In this work, friction stir welding (FSW) was employed to alloy 625 grade I (soft annealed) sheets. Therefore, solid-state based welding was undertaken with a tool rotational speed of 200 rpm and welding speed of 1 mm/s. Microstructural features were analyzed by light optical and scanning electron microscopy (SEM). Moreover, microhardness measurements were performed. The susceptibility to intergranular corrosion was verified by the double-loop electrochemical potentiokinetic reactivation (DL-EPR) test. Complementary, intergranular corrosion was evaluated by ASTM G28 Method A. FSW promoted grain refinement, increased microhardness, and reduction in the degree of sensitization. Finally, the mean corrosion rate observed in the ASTM G28A test was 0.4406 mm/year, which suggests a good weld quality.

Assessment of Thermal Aging of Austenitic Stainless Steel Weld Metal by Using the Double Loop Electrochemical Potentiokinetic Reactivation Technique

CORROSION ◽  
10.5006/2902 ◽  
2019 ◽  
Vol 75 (4) ◽  
pp. 377-388 ◽  
Author(s):  
Xiaodong Lin ◽  
Qunjia Peng ◽  
En-Hou Han ◽  
Wei Ke
Keyword(s):  
Stainless Steel ◽  
Weld Metal ◽  
Thermal Aging ◽  
Double Loop ◽  
Steel Weld ◽  
Stainless Steel Weld ◽  
Steel Weld Metal ◽  
Electrochemical Potentiokinetic Reactivation ◽  
Stainless Steel Weld Metal ◽  
Epr Test

Double loop electrochemical potentiokinetic reactivation (DL-EPR) was applied to evaluate thermal aging of 308L stainless steel weld metal. It was found that the activation and reactivation peaks of DL-EPR curve were induced by dissolution of austenite and δ-ferrite, respectively. Before saturation of hardness, the linear relationship between reactivation ratio and hardness could be used for assessing the thermal aging-induced hardening. In the following thermal aging process, the reactivation ratio is applicable to assess the occurrence of the saturation of thermal aging-induced hardening. The results demonstrated that the DL-EPR test is applicable to assess the evolution of thermal aging.

Evaluation of the Susceptibility to Intergranular Corrosion for a Novel Cr-Mn-N Austenitic Stainless Steel Using DL-EPR

2013 ◽  
Vol 631-632 ◽  
pp. 192-197
Author(s):  
Lei Gang Zheng ◽  
Xiao Qiang Hu ◽  
Xiu Hong Kang ◽  
Dian Zhong Li
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Electrolyte Solution ◽  
Intergranular Corrosion ◽  
Xrd Analysis ◽  
Double Loop ◽  
Chromium Depletion ◽  
Electrochemical Potentiokinetic Reactivation ◽  
Epr Test ◽  
Optical Micrographs

The sensitization and intergranular corrosion (IGC) behavior of a novel Cr-Mn-N austenitic stainless steel (named as MPMD133) sensitized in the temperature range from 600 oC to 1000oC for 3 hours was investigated by the double loop electrochemical potentiokinetic reactivation (DL-EPR) test. The effects of the sensitization temperature on the susceptibility to IGC of MPMD133 were examined in the 0.5M H2SO4 +0.01M KSCN electrolyte solution. The results show that the degree of IGC increases as the sensitization temperature increasing till 900oC. Meanwhile it decreases rapidly when the sensitization temperature is elevated up to 1000oC, which is confirmed by the subsequent optical micrographs observation. The XRD analysis reveals that the precipitation of Cr23C6 leads to chromium depletion along the grain boundaries, consequently results in the susceptibility to IGC.

scholarly journals Application of electrochemical methods for the investigation of intergranular corrosion welded joint austenitic stainless steel 19Cr-9Ni

2011 ◽  
Vol 65 (2) ◽  
pp. 179-186 ◽  
Author(s):  
Bore Jegdic ◽  
Ana Alil ◽  
Zlatan Milutinovic ◽  
Zoran Odanovic ◽  
Bojan Gligorijevic ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Welded Joints ◽  
Intergranular Corrosion ◽  
Significant Degree ◽  
Electrochemical Methods ◽  
Double Loop ◽  
Quantitative Evidence ◽  
Degree Of Sensitization ◽  
Electrochemical Potentiokinetic Reactivation

Sensitization degree of the austenitic stainless steel welded joints was investigated by electrochemical methods of the double loop electrochemical potentiokinetic reactivation (DL EPR) in H2SO4 + KSCN solution, and by the measurement of corrosion potential of the steel in the drop of the solution of HNO3 + FeCl3 + HCl. The welded joints were tested by X-ray radiographic method in order to check the presence of the weld defects. Grain size of the base metal and the welded joints were determined by optical microscopy. Good agreement between the results obtained by different electrochemical methods was obtained. Heat-affected zone (HAZ) of the austenitic stainless steel welded joints has shown significant degree of sensitization. The double loop electrochemical potentiokinetic method gave quantitative evidence about susceptibility of the stainless steel to intergranular corrosion.

scholarly journals Evaluation of the DOS by DL−EPR of UNSM Processed Inconel 718

Metals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 204 ◽  
Author(s):  
Ulises Martin ◽  
Jacob Ress ◽  
Juan Bosch ◽  
David M. Bastidas
Keyword(s):  
Grain Boundaries ◽  
Inconel 718 ◽  
Bulk Sample ◽  
Area Fraction ◽  
Triple Junctions ◽  
Δ Phase ◽  
Degree Of Sensitization ◽  
Electrochemical Potentiokinetic Reactivation ◽  
Corrosion Susceptibility ◽  
Epr Test

In this work, influence of ultrasonic nanocrystal surface modification (UNSM) on the degree of sensitization (DOS) in Inconel 718 has been studied and correlated with the resulting microstructure. The UNSM processed samples decreased their grain size from 11.9 µm to 7.75 µm, increasing the surface of grain boundaries, and thus enhancing the area where δ phase and niobium carbides precipitate. The effect of the UNSM process on the DOS of Inconel 718 was studied by the double loop electrochemical potentiokinetic reactivation (DL−EPR) test. The DL−EPR showed that for UNSM processed samples with no thermal treatment, the DOS increased up to 59.6%, while for UNSM treated samples that were post-annealed at 1000 °C for 10 min and water quenched the DOS decreased down to 40.9%. The increase of grain boundaries surface area and triple junctions after the UNSM process enables the formation of twice the amount of δ phase compared to the as-received Inconel 718 bulk sample. The area fraction of the grain boundary covered by δ phase was of 9.87% in the UNSM region while in the bulk the area fraction was 4.09%. In summary, it was found that after UNSM process, the annealing at 1000 °C for 10 min and water quenching promoted the transformation of γ″ to form δ phase on the grain boundaries, which reduces the intergranular corrosion susceptibility.

Optimization of the Double Loop Electrochemical Potentiokinetic Reactivation Method for Detecting Sensitization of Nickel Alloy 690

CORROSION ◽  
10.5006/2562 ◽  
2017 ◽  
Vol 74 (2) ◽  
pp. 210-224 ◽  
Author(s):  
Magalí E. Gonzalez ◽  
Mariano A. Kappes ◽  
Martín A. Rodríguez ◽  
Patricia Bozzano ◽  
Ricardo M. Carranza ◽  
...  
Keyword(s):  
Nickel Alloy ◽  
Nuclear Power ◽  
Potassium Thiocyanate ◽  
Double Loop ◽  
Chromium Depletion ◽  
Epr Method ◽  
Transmission Electron ◽  
Alloy 690 ◽  
Electrochemical Potentiokinetic Reactivation ◽  
Epr Test

Nickel alloy 690 (UNS N06690) is one of the current choices for nuclear power plant steam generator tubing. The severity of certain stress corrosion cracking submodes in Ni-Cr-Fe alloys, such as Alloy 690, may be a function of the alloy sensitization condition. Sensitization results from chromium carbide precipitation at or near grain boundaries when the alloy is exposed to temperatures from 500°C to 800°C, which causes local chromium depletion in the adjacent matrix. The objective of this work was to study the parameters that control the double loop electrochemical potentiokinetic reactivation (DL-EPR) method and to develop an optimized test routine for Alloy 690. Alloy 690 specimens were tested under different thermal treatments, tailored to obtain a variety of concentrations of chromium in solid solution near the grain boundary (GB) region. The DL-EPR method was applied to Alloy 690 in solutions with different concentrations of sulfuric acid and potassium thiocyanate, at 30°C and 50°C. The optimal condition for detecting sensitization of Alloy 690 was 0.5 M H2SO4 + 0.001 M KSCN, at 30°C. Optical micrographs confirmed an intergranular type of attack under thermally aged (sensitized) conditions. The ratio of the reactivation to the activation peak intensities (Ir/Ia) obtained in the DL-EPR test agreed well with mass loss obtained in boiling nitric acid solution with Cr(VI) additions (modified Huey test). Chromium depletion profiles near the GB of thermally treated specimens under different conditions were measured with the energy dispersive x-ray spectroscopy technique, performed on a transmission electron microscope. A model available in the literature was fitted to those results. The Ir/Ia ratio for Alloy 690, obtained when using the optimal DL-EPR testing conditions, correlated well with the Cr depletion zone width and depth near the GB.

scholarly journals Intergranular Corrosion of Low Cr Ferritic Stainless Steel 429 Evaluated by the Optimized Double Loop Electrochemical Potentiokinetic Reactivation Test

2015 ◽  
Vol 2015 ◽  
pp. 1-10
Author(s):  
Xiao-lei Li ◽  
Yi-fan Ni ◽  
Yi-ming Jiang ◽  
Jin Li ◽  
Li Li
Keyword(s):  
Stainless Steel ◽  
Ferritic Stainless Steel ◽  
Intergranular Corrosion ◽  
Aging Treatment ◽  
Double Loop ◽  
Depletion Zone ◽  
Scanning Rate ◽  
Microstructure Observation ◽  
Electrochemical Potentiokinetic Reactivation ◽  
Epr Test

Intergranular corrosion (IGC) of Nb-Ti stabilized ferritic stainless steel (FSS) 429 was investigated using the double loop electrochemical potentiokinetic reactivation (DL-EPR) test combined with the microstructure observation. The results indicated that the optimized DL-EPR test condition for FSS 429 was the solution of 0.5 M H2SO4+ 0.0001 M KSCN with a scanning rate of 100 mV/min at 30°C. Based on this condition, the specimens aging at 400–700°C for different duration were tested and a time-temperature-sensitization (TTS) curve for FSS 429 was obtained, which reveals the sensitization nose was located around 550°C. The criticalIr/Iavalue was determined to be about 3% above which IGC occurred. After aging treatment, Cr depletion zone was detected using energy dispersive spectroscopy (EDS), most possibly due to Cr segregation around intergranular TiC and NbC.

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