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.

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.

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%.

Evaluation of biocorrosion on stainless steels using laboratory-reared barnacle Amphibalanus amphitrite

2014 ◽  
Vol 61 (6) ◽  
pp. 402-408 ◽  
Author(s):  
Luciana V.R. de Messano ◽  
Leila Y. Reznik ◽  
Lucio Sathler ◽  
Ricardo Coutinho
Keyword(s):  
Stainless Steels ◽  
Design Methodology ◽  
Open Circuit Potential ◽  
Corrosion Behaviour ◽  
Skeletonema Costatum ◽  
Open Circuit ◽  
Breakdown Potential ◽  
Content Type ◽  
Polarisation Resistance ◽  
And Control

Purpose – The purpose of this paper was to use the barnacle Amphibalanus amphitrite reared in the laboratory to investigate the effects of juveniles on corrosion behaviour of three stainless steels (SS): UNS S31600, N08904 and UNS S32760. Design/methodology/approach – Barnacle larvae were maintained in a laboratory until they reached the cypris larval stage. A total of 100 cyprids were added to four individual containers; each SS coupon (70 × 50 × 2 mm3) was immersed into the containers. After the cyprids attached to the coupons, juveniles were reared for 21 days with the microalgae Skeletonema costatum (Greville) Cleve. Values of open circuit potential (OCP), breakdown potential (Eb) and polarisation resistance (Rp) were evaluated, along with surface examinations. Findings – OCP differences between barnacles and control coupons were not apparent. However, the lowest values of Eb and Rp were observed in the presence of juvenile barnacles, demonstrating the SS corrosion caused by these organisms. Crevice corrosion around the base of the barnacles was detected during visual inspections, despite the small size of the barnacles and the short duration of the experiments. Originality/value – The A. amphitrite assays were useful as a tool for testing corrosion behaviour of the SS under laboratory conditions. This was the first study to test the use of this common protocol in anti-fouling research as a method to study marine biocorrosion.

Corrosion Behaviors of Ultrapure Ferritic Stainless Steels in Simulated Urban Refuse Leachate

2011 ◽  
Vol 261-263 ◽  
pp. 749-752
Author(s):  
Li Yan Qin ◽  
Guang Wei Fan ◽  
Fang Hong Xu
Keyword(s):  
Stainless Steel ◽  
Passive Film ◽  
Stainless Steels ◽  
Open Circuit ◽  
Passive State ◽  
Film Stability ◽  
Ferritic Stainless Steels ◽  
Stainless Steel 304 ◽  
Corrosion Behaviors ◽  
Relaxation Curves

The corrosion behaviors of ultrapure ferritic stainless steels in simulated urban refuse leachate were investigated by means of different measurement methods including steady-state polarization curves, potentiostatic open-circuit relaxation curves and scanning electronic microscope. The results show that the ultrapure ferritic stainless steel 443, 444 and the austentic stainless steel 304 maintained good passive state after being immersed in the simulated leachate for 720h. The descending order of pitting resistance is 444>443>304. According to the passive film equivalent resistance Rp and the interface capacitance Cd obtained by fitting the potentiostatic open-circuit relaxation curves, the descending order of passive film stability is also 444>443>304.

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.

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