Localized Corrosion of Nuclear Grade Alloy 800 Under Steam Generator Layup, Startup and Operating Conditions

2012 ◽  
Vol 1 (1) ◽  
pp. 13-20 ◽  
Author(s):  
Y. Lu
Keyword(s):  
Corrosion Resistance ◽  
Steam Generator ◽  
Elevated Temperatures ◽  
Chloride Concentration ◽  
Operating Conditions ◽  
Nuclear Grade ◽  
Localized Corrosion ◽  
Pitting Potential ◽  
Alloy 800 ◽  
Secondary Side

The localized corrosion resistance of nuclear-grade Alloy 800, which is one of the preferred steam generator (SG) heat exchange tube materials of CANDU and PWR reactors, was studied under simulated SG secondary side crevice chemistry conditions at ambient temperature as well as at elevated temperatures. Series of cyclic potentiodynamic polarization tests were performed to study the localized corrosion resistance of Alloy 800 as a function of chloride ion concentration in the SG crevice solution at 40°C, 150°C and 300°C. Based on the experimental results, empirical equations were provided for calculating the pitting potential of nuclear grade Alloy 800 in the SG secondary side crevice chemistries with different levels of chloride concentration at SG layup, startup and operating temperatures.

scholarly journals Electrochemical Anodizing Treatment to Enhance Localized Corrosion Resistance of Pure Titanium

2017 ◽  
Vol 15 (1) ◽  
pp. 19-24 ◽  
Author(s):  
Davide Prando ◽  
Andrea Brenna ◽  
Fabio M. Bolzoni ◽  
Maria V. Diamanti ◽  
Mariapia Pedeferri ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Titanium Alloys ◽  
Oxide Layer ◽  
Corrosion Behavior ◽  
Pure Titanium ◽  
Localized Corrosion ◽  
Anodic Current Density ◽  
Anodic Current ◽  
Protective Oxide ◽  
Pitting Potential

Background Titanium has outstanding corrosion resistance due to the thin protective oxide layer that is formed on its surface. Nevertheless, in harsh and severe environments, pure titanium may suffer localized corrosion. In those conditions, costly titanium alloys containing palladium, nickel and molybdenum are used. This purpose investigated how it is possible to control corrosion, at lower cost, by electrochemical surface treatment on pure titanium, increasing the thickness of the natural oxide layer. Methods Anodic oxidation was performed on titanium by immersion in H2SO4 solution and applying voltages ranging from 10 to 80 V. Different anodic current densities were considered. Potentiodynamic tests in chloride- and fluoride-containing solutions were carried out on anodized titanium to determine the pitting potential. Results All tested anodizing treatments increased corrosion resistance of pure titanium, but never reached the performance of titanium alloys. The best corrosion behavior was obtained on titanium anodized at voltages lower than 40 V at 20 mA/cm2. Conclusions Titanium samples anodized at low cell voltage were seen to give high corrosion resistance in chloride- and fluoride-containing solutions. Electrolyte bath and anodic current density have little effect on the corrosion behavior.

Degradation of Alloy 800 Under Steam Generator Secondary Side Crevice Conditions

2009 ◽  
Author(s):  
Y. C. Lu ◽  
G. Goszczynski ◽  
S. Ramamurthy
Keyword(s):  
Steam Generator ◽  
Safety Issue ◽  
Cold Work ◽  
Orientation Imaging Microscopy ◽  
Pressurized Water Reactor ◽  
Pressurized Water ◽  
Electrochemical Tests ◽  
Orientation Imaging ◽  
Alloy 800 ◽  
Secondary Side

Alloy 800 is the preferred steam generator (SG) tube materials for CANDU™ reactors and is also used extensively in SGs in some pressurized water reactor (PWR) systems. Degradation of Alloy 800 SG tubing has only been found in a few tubes at a limited number of stations despite the large number of SG tube operating years accumulated to date. Recently, underdeposit corrosion was detected in a few ex-service tubs removed from some CANDU SGs. Pits like wall loss of about 5% to 10% through-wall depth were found in these ex-service tubes. Evidence of intra-tubesheet cracking of Alloy 800 tubes was detected in a few European PWR SGs. There is no degradation in mechanical properties of these ex-service CANDU SG tubes. In addition, the degradation of Alloy 800 tubes observed so far is not a safety issue. However, the findings suggest that Alloy 800 tubing may have some aging degradation susceptibility after many years of service. Whether the degradation of Alloy 800 tubing is due to imperfections in its compositional or metallurgical properties inherent from manufacturing, or due to the aggressive chemistry conditions that should have been precluded by modern chemistry control strategy require clarification. Comprehensive examinations, including metallurgical examinations, orientation imaging microscopy (OIM), surface analyses and electrochemical measurements were performed on the removed ex-service CANDU SG tubes that had some underdeposit corrosion. The results were compared with a reference nuclear grade Alloy 800 tubing and with archive Alloy 800 new SG tubes from several CANDU stations. High-temperature electrochemical tests, scanning vibrating electrode Technique (SVET) measurements as well as C-ring autoclave tests were performed to determine the possible factors leading to Alloy 800 SG tubing degradation. SCC was initiated in a few C-ring specimens in the presence of artificial cold work flaws under simulated acidic SG secondary-side crevices chemistry conditions. OIM and surface analysis were also performed to characterize the degradation initiated in Alloy 800 tubing under the influence of cold work flaws. The possible factors leading to Alloy 800 SG tubing degradation under SG secondary crevices conditions are discussed.

Box-Behnken Design Approach Toward Predicting the Corrosion Response of 13Cr Stainless Steel

CORROSION ◽  
10.5006/3429 ◽  
2020 ◽  
Vol 76 (4) ◽  
pp. 356-365
Author(s):  
Mostafa Kazemipour ◽  
Salar Salahi ◽  
Ali Nasiri
Keyword(s):  
Stainless Steel ◽  
Environmental Factors ◽  
Corrosion Behavior ◽  
Ph Value ◽  
Chloride Concentration ◽  
Localized Corrosion ◽  
Quadratic Model ◽  
Medium Temperature ◽  
Pitting Potential ◽  
Box Behnken Design

13Cr stainless steel, the most commonly used oil country tubular good material with good mechanical and corrosion behavior, has the drawback of sensitivity to localized corrosion, particularly in offshore downhole environments, limiting the life span of the parts. A careful assessment of the corrosion behavior of the material can be done by the perception of the most influential environmental factors combined with the material’s intrinsic microstructure. This study aims to focus on the former, the effect of environmental factors, including pH, temperature, and chloride concentration, varying in the ranges of 4 to 7, 22°C to 80°C, and 1,000 mg/L to 22,000 mg/L, respectively, on the pitting corrosion behavior of 13Cr stainless steel. Adopting a response surface methodology, using a Box-Behnken design, a carefully designed set of corrosion tests at various combinations of the environmental factors were performed. Considering the pitting potential measured from the cyclic potentiodynamic polarization testing, as the response of each experiment, a quadratic model was developed correlating the studied environmental factors and the pitting potential values. Further analysis of the developed model was conducted through analysis of variance, followed by optimizing the model according to the highest, medium, and lowest pitting potentials. The optimized results confirmed that the best corrosion behavior occurs at approximately the lowest chloride concentration and temperature, and the highest pH value. However, contrary to the expectations, the worst corrosion response was detected at the medium temperature of 52°C, instead of the highest temperature of 80°C. It was concluded that at higher temperatures, the corrosion tends to be more uniform, resulting in the formation of a layer of corrosion products that covers the sample’s surface. The corrosion product layer acts as a barrier against the diffusion of the aggressive ions, causing deceleration of the corrosion reactions.

CROLOY 5Si

Alloy Digest ◽  
1958 ◽  
Vol 7 (12) ◽  
Keyword(s):  
Fracture Toughness ◽  
Corrosion Resistance ◽  
High Temperature ◽  
Physical Properties ◽  
Tensile Properties ◽  
Oxidation Resistance ◽  
Elevated Temperatures ◽  
Heat Treating ◽  
Operating Conditions ◽  
Temperature Performance

Abstract CROLOY 5 Si is a chromium-silicon-molybdenum heat resisting steel recommended for operating conditions at elevated temperatures where oxidation resistance is a primary requirement. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness and creep. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: SA-78. Producer or source: Babcock & Wilcox Company.

Effect of Alloy Composition on the Localized Corrosion Resistance of Nickel Alloys

2012 ◽  
Vol 1475 ◽  
Author(s):  
Santiago Sosa Haudet ◽  
Martín A. Rodríguez ◽  
Ricardo M. Carranza
Keyword(s):  
Corrosion Resistance ◽  
Crevice Corrosion ◽  
Chloride Concentration ◽  
Testing Temperature ◽  
Localized Corrosion ◽  
Chloride Solutions ◽  
Equivalent Number ◽  
Engineered Barriers ◽  
Nickel Base ◽  
30 G 35

ABSTRACTNickel base alloys are considered among candidate materials for engineered barriers of nuclear repositories. The localized corrosion resistance is a determining factor in the materials selection for this application. This work compares the crevice corrosion resistance of selected nickel base alloys, namely 625, G-30, G-35, C-22, C-22HS and HYBRID-BC1. The crevice corrosion repassivation potential (ER,CREV) of the tested alloys was determined by the Potentiodynamic-Galvanostatic-Potentiodynamic (PD-GS-PD) method. The testing temperature was 60ºC and the chloride concentrations used were 0.1 M, 1 M and 10 M.A linear relationship between ER,CREV and the logarithm of chloride concentration was found. ER,CREV increased linearly with PREN (Pitting Resistance Equivalent Number) in concentrated chloride solutions. ER,CREV is the sum of three contributions: ECORR*, η and ΔΦ. ECORR* and η increased linearly with PREN, while ΔΦ increased linearly with PREN for concentrated chloride solutions, not showing a definite trend with PREN for the less concentrated solutions.

Thermal-Hydraulic Response of the Secondary Side of a PWR Steam Generator With an Internal Structure to a Main Steam Line Break

2015 ◽  
Author(s):  
Jong Chull Jo
Keyword(s):  
Internal Structure ◽  
Steam Generator ◽  
Steam Line ◽  
Operating Conditions ◽  
Analysis Model ◽  
Pressurized Water ◽  
Main Steam Line ◽  
Main Steam ◽  
Secondary Side ◽  
Hydraulic Response

This study addresses a numerical analysis of the thermal-hydraulic response of the secondary side of a steam generator (SG) model with an internal structure to a main steam line break (MSLB) at a pressurized water reactor (PWR) plant. The analysis model is comprised of the SG upper space where steam occupies and the part of the main steam pipe between the SG outlet nozzle and the broken pipe end upstream of the main steam isolation valve. To investigate the effects of the presence of the SG internal structure on the thermal-hydraulic response to the MSLB, the numerical calculation results for the analysis model having a perforated horizontal plate as the SG internal structure are compared to those obtained for a simple analysis model having no SG internal structure. Both analysis models have the same physical dimensions except for the internal structure. The initial operating conditions for both SG models are identical to those for an actual operating plant. To simplify the analyses, it is assumed that steam is constantly generated from the bottom of the SG secondary side space during the blowdown process. As the results, it has been found that the pressure wave significantly attenuates as it passes through the perforated internal structure and as time elapses. This leads to reduction in instantaneous hydraulic load on the internal structure including tubing. However, it is seen that the presence of the internal structure does not affect the transient velocities of steam passing through the SG tube bundle during the blowdown, which are 2 to 8 times the velocities during the normal reactor operation as in the case for the empty SG. Consequently, the present findings should be considered for the design of the steam generator to ensure the reactor safety as such elevated high steam velocities can cause fluidelastic instability of tubes which results in high cycle fatigue failure of the tubes.

Effect of temperature on the crevice corrosion resistance of Ni-Cr-Mo alloys as engineered barriers in nuclear waste repositories

2012 ◽  
Vol 1475 ◽  
Author(s):  
Edgar C. Hornus ◽  
C. Mabel Giordano ◽  
Martín A. Rodríguez ◽  
Ricardo M. Carranza
Keyword(s):  
Corrosion Resistance ◽  
Crevice Corrosion ◽  
Chloride Concentration ◽  
Localized Corrosion ◽  
Effect Of Temperature ◽  
Corrosion Susceptibility ◽  
Engineered Barriers ◽  
Corrosive Environments ◽  
Waste Repositories

ABSTRACTNi-Cr-Mo alloys offer an outstanding corrosion resistance in a wide variety of highly corrosive environments. Alloys 625, C-22, C-22HS and HYBRID-BC1 are considered among candidates as engineered barriers of nuclear repositories. The objective of the present work was to assess the effect of temperature on the crevice corrosion resistance of these alloys. The crevice corrosion repassivation potential (ER,CREV) of the tested alloys was determined by the Potentiodynamic-Galvanostatic-Potentiodynamic (PD-GS-PD) method. Alloy HYBRID-BC1 was the most resistant to chloride-induced crevice corrosion, followed by alloys C-22HS, C-22 and 625. ER,CREV showed a linear decrease with temperature. There is a temperature above which ER,CREV does not decrease anymore, reaching a minimum value. This ER,CREV value is a strong parameter for assessing the localized corrosion susceptibility of a material in a long term timescale, since it is independent of temperature, chloride concentration and geometrical variables such as crevicing mechanism, crevice gap and type of crevice former.

Steam Generator Fretting-Wear Damage: A Summary of Recent Findings

1999 ◽  
Vol 121 (3) ◽  
pp. 304-310 ◽  
Author(s):  
F. M. Gue´rout ◽  
N. J. Fisher
Keyword(s):  
Steam Generator ◽  
Wear Test ◽  
Operating Conditions ◽  
Fretting Wear ◽  
Measuring System ◽  
Effect Of Temperature ◽  
Design Parameters ◽  
Wear Depth ◽  
Alloy 800 ◽  
Wear Damage

Flow-induced vibration of steam generator (SG) tubes may sometimes result in fretting-wear damage at the tube-to-support locations. Fretting-wear damage predictions are largely based on experimental data obtained at representative test conditions. Fretting-wear of SG materials has been studied at the Chalk River Laboratories for two decades. Tests are conducted in fretting-wear test machines that simulate SG environmental conditions and tube-to-support dynamic interactions. A new high-temperature force and displacement measuring system was developed to monitor tube-to-support interaction (i.e., work-rate) at operating conditions. This improvement in experimental fretting-wear technology was used to perform a comprehensive study of the effect of various environment and design parameters on SG tube wear damage. This paper summarizes the results of tests performed over the past 4 yr to study the effect of temperature, water chemistry, support geometry and tube material on fretting-wear. The results show a significant effect of temperature on tube wear damage. Therefore fretting-wear. The results show a significant effect of temperature or tube wear damage. Therefore, fretting-wear tests must be performed at operating temperatures in order to be relevant. No significant effect of the type of water treatment on tube wear damage was observed. For predominantly impacting motion, the wear of SG tubes in contact with 410 stainless steel is similar regardless of whether Alloy 690 or Alloy 800 is used as tubing material or whether lattice bars or broached hole supports are used. Based on results presented in this paper, an average wear coefficient value is recommended that is used for the prediction of SG tube wear depth versus time.

Effect of Hazardous Impurities on Steam Generator Tube Degradation

2010 ◽  
Author(s):  
Yucheng Lu
Keyword(s):  
Steam Generator ◽  
Chloride Concentration ◽  
Electrochemical Corrosion ◽  
Accelerated Corrosion ◽  
Alloy 800 ◽  
Accelerated Corrosion Tests ◽  
The Status ◽  
Corrosion Behaviors ◽  
Corrosion Susceptibility ◽  
High Concentrations

Steam generator (SG) tubing materials are susceptible to corrosion degradation in certain electrochemical corrosion potential (ECP) regions under aggressive local chemistry conditions developed under deposits or in SG crevices. Because of the hideout of impurities, the areas under sludge and inside SG crevices may be very aggressive and contain high concentrations of chlorides and other impurities. These areas are the locations where SG tubing materials are susceptible to the major forms of degradation such as pitting, crevice corrosion, intergranular attack (IGA) and stress corrosion cracking (SCC). The corrosion susceptibility of each SG alloy is different and is a function of ECP and chemical environment. Electrochemical corrosion behaviors of major SG tube alloys were studied under plausible aggressive crevice chemistry conditions. The potential hazardous conditions leading to SG tube degradation and the conditions, which can minimize SG tube degradation, have been determined and documented in a form of safe ECP/pH zones for SG operation. SCC tests and accelerated corrosion tests were carried out to verify and revise the safe ECP/pH zones. This information has been incorporated and updated into a system health monitor tool, ChemAND®, which was developed by AECL for utilities to monitor online the status of the SG alloys and prevent material degradation surprises through appropriate SG water chemistry management. Recently, further studies were performed to investigate the effect of several aggressive SG impurities on the boundary conditions that will lead to the degradation of SG alloys. These aggressive species include chloride, different sulphur species, lead, copper, magnesium, and calcium. This paper presents the effect of chloride concentration and copper contamination on Alloy 800 SG tubing corrosion degradation at 300°C under SG crevice chemistry conditions. The data provide important information to support SG materials degradation and life management.

UNITEMP HX

Alloy Digest ◽  
1964 ◽  
Vol 13 (5) ◽  
Keyword(s):  
Fracture Toughness ◽  
Corrosion Resistance ◽  
High Temperature ◽  
Physical Properties ◽  
Base Material ◽  
Heat Treating ◽  
Operating Conditions ◽  
High Temperature Strength ◽  
Temperature Performance ◽  
Nickel Base

Abstract Unitemp-HX is a nickel-base material recommended for high temperature applications. It has outstanding oxidation resistance at high temperatures under most operating conditions, and good high-temperature strength. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness and creep. It also includes information on low and high temperature performance, and corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: Ni-91. Producer or source: Universal Cyclops Steel Corporation.

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