Development of corrosion flaws for the production of realistic test specimens

2020 ◽  
Vol 64 (1) ◽  
pp. 23-28
Author(s):  
J. Hodač ◽  
Z. Fulín ◽  
P. Mareš ◽  
J. Veselá ◽  
O. Chocholatý
Keyword(s):  
Power Plants ◽  
Galvanic Corrosion ◽  
Water Solution ◽  
Erosive Wear ◽  
Corrosion Damage ◽  
Water Mist ◽  
Carbon Steels ◽  
Bending Stress ◽  
Solution Flow ◽  
Mechanical Bending

AbstractTo produce realistic test specimens with realistic flaws, it is necessary to develop appropriate procedure for corrosion flaw production. Tested specimens are made from steels commonly used in power plants, such as carbon steels, stainless steels and their dissimilar weldments. In this study, corrosion damage from NaCl water solution and NaCl water mist are compared. Specimens were tested with and without mechanical bending stress. The corrosion processes produced plane, pitting and galvanic corrosion. On dissimilar weldments galvanic corrosion was observed and resulted to the deepest corrosion damage. Deepest corrosion flaws were formed on welded samples. The corrosion rate was also affected by the solution flow in a contact with the specimens, which results in a corrosion-erosive wear. Produced flaws are suitable as natural crack initiators or as realistic corrosion flaws in test specimens.

scholarly journals Impact of corrosion product removal to depth of corrosion damage in weldment joint

2019 ◽  
Vol 63 (4) ◽  
pp. 148-152
Author(s):  
J. Hodač ◽  
Z. Fulín
Keyword(s):  
Corrosion Product ◽  
Power Plants ◽  
Water Solution ◽  
Corrosion Damage ◽  
Corrosion Products ◽  
Test Pieces ◽  
Product Removal ◽  
Metallographic Observation ◽  
Speed Up ◽  
Lower Depth

Abstract Corrosion flaws in pipelines can caused severe financial losses and also can be dangerous for people. One of the most frequently damaged parts are dissimilar pipe welds. We would like to understand how corrosion process reacts on corrosion product removal. Outputs from experiment will be used for production of test specimens. For testing we chose standard dissimilar weldment used in Czech power plants. It is joint with 08Ch18N10T and 22K (GOST) steel. Joint is cut to 24 same specimens. There are exposed to flowing water solution of 5% NaCl. Half of the specimens are regularly mechanically cleaned. The joint is metallographically observed and parts with and without corrosion products are compared. Water salt solution increased pH from 7,25 to 7,86 during 31 days test and conductivity varies around 74 mS cm−1. Metallographic observation indicates that corrosion under corrosion products layer is locally speed up and causes pitting corrosion. Cleaned specimens indicate plane corrosion with lower depth. These results indicate that slag in pipeline could locally speed up corrosion depth penetration. On the other hand, solutions with abrasive particles (which can wipe out the corrosion product) will probably facilitate plane corrosion damage on pipeline walls. This test brings us another knowledge, how to simulate realistic corrosion damage for production of NDT qualification test pieces.

Corrosion surveillance program for tank, fuel cladding and supporting structure of 30 MW Indonesian RSG GAS research reactor

Kerntechnik ◽  
2021 ◽  
Vol 86 (3) ◽  
pp. 236-243
Author(s):  
G. R. Sunaryo ◽  
R. Kusumastuti ◽  
Sriyono
Keyword(s):  
Water Quality ◽  
Power Plants ◽  
Research Reactor ◽  
Visual Analysis ◽  
Galvanic Corrosion ◽  
Steel Wire ◽  
Chloride Ions ◽  
Bottom Surface ◽  
Surveillance Program ◽  
Probe Set

Abstract The objective of this research is to understand the condition of the structural material of the 30 MW RSG-GAS research reactor as input for the aging management program. Furthermore, this should enable a prediction of the remaining life of the components. In the current experiment, corrosion surveillance was carried out at Interim Storage for Spent Fuel (ISSF), that has similar water quality as in reactor pool by using a corrosion probe which is made of aluminum alloy and stainless steel. The probe set is designed to understand the effect of water quality in the ISSF pond. The corrosion processes observed were pitting, crevice and galvanic corrosion. Two sets of corrosion probes were immersed into the ISSF pool in 2007, hanging by steel wire, 1-meter height from the bottom surface. One probe set consists of horizontal and vertical positions. The soaking time was 7 years. The observations made were water chemical content, corrosion rate and visual analysis, macro and micro. For macro visual observations an optical microscope was used, for micro-observations SEM-EDX. From the results of macro-observations, information on the presence of galvanic corrosion, crevice and pitting was obtained. SEM-EDX provides information on the influence of chloride ions on corrosion products. This experience will be very useful in dealing with the aging process of Indonesia’s nuclear power plants in the future.

scholarly journals Microstructural Characterization and Corrosion-Resistance Behavior of Dual-Phase Steels Compared to Conventional Rebar

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1068
Author(s):  
Hany S. Abdo ◽  
Asiful H. Seikh ◽  
Biplab Baran Mandal ◽  
Jabair A. Mohammed ◽  
Sameh A. Ragab ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Galvanic Corrosion ◽  
Microstructural Characterization ◽  
Carbon Steels ◽  
Dual Phase ◽  
Low Carbon ◽  
Dp Steel ◽  
Dp Steels ◽  
Superior Corrosion Resistance ◽  
Corrosive Environments

Dual-phase (DP) steels consist of a ferritic matrix dispersed with some percentage of martensite, which gives the material a good combination of strength and ductility, along with the capacity to absorb energy and enhanced corrosion protection properties. The purpose of this work was to study the microstructural and corrosion behavior (mainly pitting and galvanic corrosion) of DP steel compared with that of conventional rebar. To obtain DP steel, low-carbon steels were heat-treated at 950 °C for 1 h and then intercritically annealed at 771 °C for 75 min, followed by quenching in ice-brine water. The corrosion rates of DP steel and standard rebar were then measured in different pore solutions. Macro- and microhardness tests were performed for both steels. It was found that DP steels exhibited a superior corrosion resistance and strength compared to standard rebar. The reported results show that DP steels are a good candidate for concrete reinforcement, especially in aggressive and corrosive environments.

Effect of Environmental Corrosion on Fatigue Crack Growth Morphology: A Detailed Investigation of the Boundary between Fatigue and Corrosion Control Regimes

2014 ◽  
Vol 891-892 ◽  
pp. 278-285
Author(s):  
Sandeep R. Shah ◽  
Ian L. Pryce ◽  
Todd B. St John ◽  
James M. Greer
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Driving Force ◽  
Galvanic Corrosion ◽  
Corrosion Damage ◽  
Propagation Path ◽  
Fatigue Properties ◽  
Mode I ◽  
Mode Ii ◽  
Element Analysis

Legacy 7XXX series aluminum alloys were developed primarily for their high strength with less regard for their fatigue properties, corrosion resistance and fracture toughness. The constituent alloying elements in these materials (used to achieve high strengths) markedly increased their corrosion susceptibility. Consequently, aircraft structures made from these alloys have exhibited fatigue and corrosion damage. In the present work, we have investigated a crack finding in a fuselage skin of AA7XXX series alloy. This investigation revealed the crack propagated by a combination of fatigue and corrosion. Through the use of extensive metallography, mechanical analysis and laboratory experiments, we have separated the contributions to the damage growth due to corrosion and fatigue. We have also confirmed that in-service mixed-mode failures like this, observed in these alloys, can be reproduced reliably in the laboratory. Furthermore, it was observed that the presence of corrosion can actually change the propagation of a fatigue crack from mode I, the preferable orientation for fatigue crack propagation, to mode II, the preferable orientation for corrosion propagation. Even though the mechanical driving force is enough to grow the crack in mode I, the presence of corrosion can change it to mode II by electrochemical degradation of the material. Using electrochemical measurements, we relate the change in failure mode to the frequency of cyclic loading. At slow enough cyclic frequency the electrochemical energy released due to galvanic corrosion degrades the material such that the crack turns and propagates in the orientation which has only one third the mechanical driving force as compared to the original crack propagation path. This is the first time such phenomenon has been successfully replicated in the laboratory and modeled with finite element analysis.

Electrical safety of suppressing wildfires near high-voltage transmission lines using water mist

2018 ◽  
Vol 36 (4) ◽  
pp. 295-314 ◽  
Author(s):  
JiaZheng Lu ◽  
Bao-Hui Chen ◽  
Zhen Fang ◽  
Jianping Hu ◽  
Bowen Wang ◽  
...  
Keyword(s):  
Electric Conductivity ◽  
Leakage Current ◽  
High Voltage ◽  
Transmission Lines ◽  
Efficient Method ◽  
Power Transmission ◽  
Water Solution ◽  
Water Mist ◽  
Electrical Safety ◽  
Electrical Transmission

Wildfires near transmission lines are important disasters that affect power transmission. Water mist is a highly efficient method for suppressing wildfires near electrical transmission lines, where it avoids line-tripping to ensure the safety of the grid. However, few studies have investigated the electrical safety during the water mist extinguishing process, including the risk of tripping transmission lines and the shock hazard for users. In this study, we systematically studied the influence of the gap distance and the electric conductivity of the water solution on the insulation characteristics of water mist with a Dv0.99 diameter of the droplets of ca. 500 µm, including the breakdown voltage and leakage current. Furthermore, we investigated the effect of water mist on the development of a long-gap discharge, and the insulation mechanism of water mist was also considered. Finally, water mist with multi-component additives was employed for suppressing wildfires near transmission lines in China, and we demonstrated the effectiveness of this method based on the reduction of line-tripping accidents caused by wildfires near transmission lines.

Failure Analysis for Evaporator Fin-Tubes of HRSG in CCGT

2020 ◽  
Author(s):  
Hong Xu
Keyword(s):  
Pitting Corrosion ◽  
Power Plants ◽  
Ph Value ◽  
Water Pressure ◽  
Carbon Steels ◽  
Combined Cycle ◽  
Normal Operation ◽  
Hydraulic Test ◽  
Commercial Operation ◽  
The Matrix

Abstract The finned evaporator tube of medium pressure evaporator leakage occurred after the no. 1 unit of a combined-cycle gas turbine (CCGT) power station was put into commercial operation for only 40 days (including 24 days of operation and 19 days of shutdown and standby). Cut off a section of failure pipe for a thorough inspection. Macro inspection found that severe corrosion occurred in some local areas of some pipe sections, which led to the obvious thinning of pipe wall thickness, leading to perforation and leakage. Metallographic test and scanning electron microscopy (SEM) showed that the metal materials around the leakage points was qualified and the microstructure was normal. The corrosion products around the leakage points were mainly iron oxide which were generated before the unit had been put into commercial operation. The root cause was that the pH value of water used in the hydraulic test during the commissioning of the unit was as low as 9.2, and after the completion of the hydraulic test, the filled water remained in the boiler for a month and a half before being drained. Researches indicated that if carbon steels were prolonged immersed in demineralized water with a lower pH value, it would inevitably occur severe local corrosion which was due to pitting induced by the activation of inclusions in the steel. After pitting corrosion induced by active inclusions, no obvious pitting corrosion occurred in the surrounding inclusions. Accompanied with the extending of corrosion spots that had been formed, the activation zone continued to expand. Along with the formation of surface rust spots, corrosion developed along the inclusion boundary to the depth of the matrix, and finally caused the perforating and leaking of the tubes. The inner pitting corrosion of fin-tube of evaporator in HRSG could be avoided as long as the relevant provisions of “Guidelines of chemical supervision for combined cycle power plants” (DL/T 1717-2017) were strictly implemented during normal operation of boiler, standby maintenance and water pressure test after overhaul.

On-Site Evaluation of Bending Stresses at the Root of Small Bore Pipes by Accelerometric Measurements

2003 ◽  
Author(s):  
J. Guillou ◽  
L. Paulhiac
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Numerical Models ◽  
Operating Conditions ◽  
Strain Gauges ◽  
Bending Stress ◽  
Piping Systems ◽  
Bending Stresses ◽  
Site Evaluation

Several vibration-induced failures at the root of small bore piping systems occurred in French nuclear power plants in past years. The evaluation of the failure risk of the small bore pipes requires a fair estimation of the bending stress under operating conditions. As the use of strain gauges is too time-consuming in the environmental conditions of nuclear power plants, on-site acceleration measurements combined with numerical models are easier to handle. It still requires yet a large amount of updating work to estimate the stress in multi-span pipes with elbows and supports. The aim of the present study is to propose an alternate approach using two accelerometers to measure the local nozzle deflection, and an analytical expression of the bending stiffness of the nozzle on the main pipe. A first formulation is based on a static deformation assumption, thus allowing the use of a simple analog converter to get an estimation of the RMS value of the bending stress. To get more accurate results, a second method is based on an Euler Bernoulli deformation assumption: a spectral analyzer is then required to get an estimation of the spectrum of the bending stress. A better estimation of its RMS value is then obtained. An experimental validation of the methods based on strain gauges has been successfully performed.

scholarly journals Advances in Corrosion-Resistant Thermal Spray Coatings for Renewable Energy Power Plants. Part I: Effect of Composition and Microstructure

2019 ◽  
Vol 28 (8) ◽  
pp. 1749-1788 ◽  
Author(s):  
Esmaeil Sadeghi ◽  
Nicolaie Markocsan ◽  
Shrikant Joshi
Keyword(s):  
High Temperature ◽  
Thermal Spray ◽  
Power Plants ◽  
Corrosion Damage ◽  
Clean Energy ◽  
High Temperature Corrosion ◽  
Thermal Spray Coatings ◽  
Corrosion Resistant ◽  
Spray Coatings ◽  
Corrosion Resistant Coatings

Abstract Power generation from renewable resources has attracted increasing attention in recent years owing to the global implementation of clean energy policies. However, such power plants suffer from severe high-temperature corrosion of critical components such as water walls and superheater tubes. The corrosion is mainly triggered by aggressive gases like HCl, H2O, etc., often in combination with alkali and metal chlorides that are produced during fuel combustion. Employment of a dense defect-free adherent coating through thermal spray techniques is a promising approach to improving the performances of components as well as their lifetimes and, thus, significantly increasing the thermal/electrical efficiency of power plants. Notwithstanding the already widespread deployment of thermal spray coatings, a few intrinsic limitations, including the presence of pores and relatively weak intersplat bonding that lead to increased corrosion susceptibility, have restricted the benefits that can be derived from these coatings. Nonetheless, the field of thermal spraying has been continuously evolving, and concomitant advances have led to progressive improvements in coating quality; hence, a periodic critical assessment of our understanding of the efficacy of coatings in mitigating corrosion damage can be highly educative. The present paper seeks to comprehensively document the current state of the art, elaborating on the recent progress in thermal spray coatings for high-temperature corrosion applications, including the alloying effects, and the role of microstructural characteristics for understanding the behavior of corrosion-resistant coatings. In particular, this review comprises a substantive discussion on high-temperature corrosion mechanisms, novel coating compositions, and a succinct comparison of the corrosion-resistant coatings produced by diverse thermal spray techniques.

Finite Element Reliability Analysis of Steel Containment Vessels with Corrosion Damage

2015 ◽  
Vol 10 (3) ◽  
pp. 527-534 ◽  
Author(s):  
Xiaolei Wang ◽  
◽  
Dagang Lu ◽  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Reliability Analysis ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Corrosion Damage ◽  
Element Analysis ◽  
Containment Vessel ◽  
Reliability Method

Containment vessels, which contain any radioactive materials that would be released from the primary system in an accident, are the last barrier between the environment and the nuclear steam supply system in nuclear power plants. Assessing the probability of failure for the containment building is essential to level 2 PSA studies of nuclear power plants. Degradation of containment vessels of some nuclear power plants has been observed in many countries, so it is important to study how the corrosion has adverse effects on the capacity of containment vessels. Conventionally, the reliability analysis of containment vessels can be conducted by using Monte Carlo Simulation (MCS) or Latin Hypercube Sampling (LHS) with the deterministic finite element analysis. In this paper, a 3D finite element model of an AP1000 steel containment vessel is constructed using the general-purpose nonlinear finite element analysis program ABAQUS. Then the finite element reliability method (FERM) based on the first order reliability method (FORM) is applied to analyze the reliability of the steel containment vessel, which is implemented by combining ABAQUS and MATLAB software platforms. The reliability and sensitivity indices of steel containment vessels under internal pressure with and without corrosion damage are obtained and compared. It is found that the FERM-based procedure is very efficient to analyze reliability and sensitivity of nuclear power plant structures.

Electromigration of Cu Interconnect Lines Prepared by a Plasma-based Etch Process

2008 ◽  
Vol 1079 ◽  
Author(s):  
Guojun Liu ◽  
Yue Kuo
Keyword(s):  
Activation Energy ◽  
Bending Stress ◽  
Lifetime Test ◽  
Lower Activation ◽  
Diffusion Paths ◽  
Mechanical Bending ◽  
Cu Interconnect ◽  
Interconnect Lines ◽  
A Current ◽  
Lower Activation Energy

ABSTRACTThe electromigration performance of Cu lines patterned by a Cl2 plasma-based etch process has been studied with the accelerated isothermal lifetime test. An electromigration activation energy of 0.6 eV and a current density acceleration exponent of 2.7 were obtained. Both the copper-silicon nitride cap layer interface and the copper grain boundary were active diffusion paths. The applied mechanical bending stress changed the electromigration void distribution in the film, which leaded to the shorter lifetime and lower activation energy.

Sign in / Sign up

Export Citation Format

Share Document