corrosion state
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2022 ◽  
Vol 7 (1) ◽  
pp. 77-83
Author(s):  
Andrea Szabó Nagy ◽  
Kálmán Varga ◽  
Bernadett Baja ◽  
Zoltán Németh ◽  
Desző Oravetz ◽  
...  

Our previous studies have revealed that a ”hybrid” structure of the amorphous and crystalline phases is formed in the outermost surface region of the austenitic stainless steel tubes of steam generators (SGs) as an undesired consequence of the industrial application of the AP-CITROX (AP: alkaline permanganate; CITROX: citric and oxalic acid) decontamination technology. The formation of this mobile oxide-layer increased the amount of the corrosion products in the primary circuit significantly, resulting in magnetite deposition on fuel assemblies. Owing to the fact that there is no investigation method available for the in-situ monitoring of the inner surfaces of heat exchanger tubes, a research project based on sampling as well as on ex-situ electrochemical and surface analytical measurements was elaborated. Within the frame of this project, comprehensive investigation of the general corrosion state and metallographic features of 36 stainless steel specimens, cut out from various locations of the 21 steam generators of the Paks NPP in the time period of 2000-2007 has been performed. The present work gives a brief overview on the general corrosion state of the heat exchanger tubes of SGs, concerning the long-term effects of the AP-CITROX procedure on the chemical composition and structure of the protective oxide-layer.


2021 ◽  
Vol 250 ◽  
pp. 578-856
Author(s):  
Rafael Kantyukov ◽  
Dmitry Zapevalov ◽  
Ruslan Vagapov

Products of several currently operated production facilities (Bovanenkovskoye, Urengoyskoye oil and gas condensate fields, etc.) contain an increased amount of corrosive CO2. Effect of CO2 on the corrosion of steel infrastructure facilities is determined by the conditions of its use. Carbon dioxide has a potentially wide range of applications at oil and gas facilities for solving technological problems (during production, transportation, storage, etc.). Each of the aggregate states of CO2 (gas, liquid and supercritical) is used and affects the corrosion state of oil and gas facilities. Article analyzes the results of simulation tests and evaluates the corrosion effect of CO2 on typical steels (carbon, low-alloy and alloyed) used at field facilities. The main factors influencing the intensity of carbonic acid corrosion processes in the main conditions of hydrocarbon production with CO2, storage and its use for various technological purposes are revealed. Development of carbon dioxide corrosion is accompanied and characterized by the localization of corrosion and the formation of defects (pitting, pits, etc.). Even alloyed steels are not always resistant in the presence of moisture and increased partial pressures of CO2, especially in the presence of additional factors of corrosive influence (temperature, aggressive impurities in gas, etc.).


2021 ◽  
Vol 9 (3) ◽  
Author(s):  
Andrea Szabó Nagy ◽  
Kálmán Varga ◽  
Bernadett Baja ◽  
Zoltán Németh ◽  
Deszo Oravetz ◽  
...  

Evaluating the water chemistry in the primary circuit and the effect of chemical econtamination of the heat exchanger tubes performed by the AP-CITROX (AP: alkaline permanganate; CITROX: citric and oxalic acid) procedure at Paks NPP (Hungary), a project dealing with the comprehensive investigation of the general corrosion state of the steam generators (SGs) has been initiated. Owing to the fact that there is no investigation method available for the in-situ monitoring of the inner surfaces of heat exchanger tubes, a research program based on sampling as well as on ex-situ electrochemical (voltammetric) and surface analytical measurements (SEM-EDX, CEMS, XRD, XPS) was developed and elaborated. In the time period of 2000-2008 - within the frame of the above project - 45 stainless steel specimens, cut out from various locations of the steam generators of the Paks NPP were investigated. Based on the measured corrosion characteristics (corrosion rate, thickness and chemical composition of the protective oxide-layer) it was found that these parameters are strongly dependent on the decontamination history of steam generators. The present work gives a brief overview on the general corrosion state of the heat exchanger tubes of SGs, concerning the long-term effects of the AP-CITROX procedure on the chemical composition and structure of the protective oxide-layer.


Coatings ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 960
Author(s):  
Wanggen Li ◽  
Jun Li ◽  
Yinsi Xu

Ni-based alloy powder (NiCrBSi) was applied to prepare coatings on Ti6Al4V by laser cladding to improve the wear resistance of the latter under corrosion. The scanning speed was found to be an essential parameter that could adjust the microstructure of the coatings. Changes in the microstructures of the coatings with the scanning speed were highlighted, and the relationships between the microstructures and microhardness, fracture toughness, corrosion, and corrosion wear resistance of the coatings were established. Results indicated that the matrix changes from Ti2Ni + TiNi to primary γ(Ni) + eutectics (γ(Ni) + Ni3Ti) with increasing scanning speed. Moreover, reinforcement phases changed from TiB2 + TiC (5 mm∙s−1) to TiB2 + TiC + Cr7C3 (11 mm∙s−1) to TiB2 + TiC + Cr7C3 + CrB (17 mm∙s−1). The average microhardness of the coatings first increased and then decreased, and the corresponding fracture toughness showed the opposite trend. The optimum combination of these properties was observed in the coating prepared at 11 mm∙s−1. This coating demonstrated excellent wear resistance in 3.5 wt.% NaCl solution, as well as a high corrosion potential, a low corrosion current density, and a low current density when the electrode initially entered a comparatively stable corrosion state. Moreover, compared with coatings prepared at other scanning speeds, this coating revealed a higher critical potential for oxidation film destruction. The results of this research collectively show that regulating the microstructures of laser-clad coatings by applying different scanning speeds is a feasible strategy to optimize the wear resistance of the coatings under corrosion.


2021 ◽  
pp. 62-71
Author(s):  
Р.К. Вагапов

Many gas and gas condensate fields (Bovanenkovskoye, Urengoyskoye, Kirinskoye, etc.) are distinguished by the presence of corrosive carbon dioxide in the extracted products, which, in the presence of moisture, leads to the formation of local corrosion damage (pits, ulcers and their accumulations). One of the methods for monitoring the corrosion state of pipelines is in-line inspection (ILI), carried out by the magnetic flux leakage method. ILI is especially relevant for underground and subsea pipelines when the use of other methods of corrosion monitoring is limited or costly. Under conditions of gas production, in contrast to oil, corrosion can occur both along the lower generatrix of the pipe (bottom-of-line corrosion) and during condensation of moisture on the upper generatrix of the pipe (top-of-line corrosion). An important process is the correct planning of the ILI, the subsequent processing and interpretation of the obtained data set, which should be carried out taking into account the peculiarities of the development of carbon dioxide corrosion in the gas pipeline and in a comparative analysis with other data of corrosion control. When interpreting ILI data, one should take into account the mechanisms of corrosion development, operating conditions (route relief, etc.) and corrosion monitoring data obtained by other research methods (simulation tests, results obtained at other adjacent sections of pipelines, etc.). Correct and useful information according to ILI data will ensure reliable protection of gas pipelines and planning of measures to protect against internal corrosion.


Author(s):  
Adriana de Araujo ◽  
Claudia de Andrade Oliveira ◽  
Tatiana Regina da Silva Simão

abstract: The heritage of modern architecture in exposed reinforced concrete has been shown pathological manifestations affecting the structural safety and functionality of the buildings. The manifestations are, primarily, associated with the steel corrosion; however published data obtained from site surveys, on the Brazilian architectural heritage and related to the issue, are still scarce in the literature. Thus, the aim of the study is to assess the current condition of the exposed concrete façades reinforcement of the Vilanova Artigas building, a Brazilian architectural heritage, opened in 1969. Legal restrictions limited the destructive tests and sampling areas. The history of the interventions, environmental aggressiveness and preliminary inspection (in the parent concrete and patch repairs) provided qualified information for analyzing in situ testing results. In the sampling areas physical, chemical and electrochemical tests were carried out. The façades surfaces are naturally porous, irregular, with concrete segregation and corrosion products stains; 24% of the concrete was replaced with proprietary mortar repair. In patch repairs, the average carbonation depth ranged from 3 to 29 mm, in concrete it ranged from 15 to 30 mm. The reinforcement cover ranged from 8 to 33 mm. Corrosion potential maps, with equipotential lines drawn at 50 mV intervals, indicated the corrosion-prone areas, where there is a concentration of lines with a variation equal to or greater than 150 mV. The presence of corrosion products, detected in the visual examination of the reinforcement under the patch repairs, validated the active corrosion state. The rough surface of the concrete, the low cover to depassivated reinforcement and the active corrosion state emphasize the need for monitoring the façades and the urgency of implementing a preventive maintenance plan, along with a conservation project in order to preserve the heritage values of the building.


Author(s):  
Peizhen Shi ◽  
Song Ding ◽  
Yuming Chen ◽  
Yiqing Wang ◽  
Guiyun Tian ◽  
...  

As a popular defect of steel, corrosion had been a big challenge to industry safe and structural health. For atmosphere corrosion characterization and evaluation, a clustering by fast search and find of density peaks (CFSFDP) algorithm, combined with gap statistic (GS) method is utilized to corroded Q235 carbon steel tubes. With the proposed method, three natural atmosphere corroded samples are investigated and classified. The proposed method successfully identifies the samples with different service periods. The temperature gradient, which indicates the heat generation and conductivity, is used to analyze cluster center selection. The matching rate is presented as a feature to reflect the corrosion state difference.


Fuel ◽  
2020 ◽  
Vol 275 ◽  
pp. 117979 ◽  
Author(s):  
Kuo Lin ◽  
Zhongjie Shen ◽  
Qinfeng Liang ◽  
Jianliang Xu ◽  
Haifeng Liu

Author(s):  
Alexandr Vasiliev ◽  
Svetlana Daškevič

Based on the results of many research years on concrete carbonisation: both immediately after manufacture (using heat-moisture treatment) and in reinforced concrete elements operated for the periods of various length (in an open atmosphere); the effect of carbonisation on the change in the protective properties of concrete in relation to steel reinforcement; for determination of the dependence of the corrosion state of steel reinforcement on the degree of concrete carbonisation in the area of steel reinforcement; the obtained regression dependences of the change (by time in the cross section) of the degree of concrete carbonisation of various classes in strength, – the analysis of the time of the onset of the boundary values of the degrees of concrete carbonisation (strength classes C12/15–C30/37) for the operating conditions of the open atmosphere was performed. Based on it, the regression dependences of the time variation of the depth of corrosion damage of steel reinforcement were construed (for fixed thicknesses of the concrete protective layer). The obtained nature of dependences made it possible to offer, in a general form, the regression dependences of the depth of corrosion damage and corrosion rate of steel reinforcement for concretes (strength classes C12/15–C30/37) for operating conditions in open atmosphere.


THE BULLETIN ◽  
2020 ◽  
Vol 3 (385) ◽  
pp. 111-118
Author(s):  
K. A. Mammedov ◽  
◽  
N. S. Hamidova ◽  
U. K. Huseynova ◽  
◽  
...  

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