corrosion depth
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Crystals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 92
Author(s):  
Wencai Liu ◽  
Jianchun Fan ◽  
Jin Yang

In terms of the structural health inspection of storage tanks by ultrasonic guided wave technology, many scholars are currently focusing on the tanks’ floor and walls, while little research has been conducted on storage tank roofs. However, the roof of a storage tank is prone to corrosion because of its complex structure and unique working environment. For this purpose, this paper proposes a reflection/transmission signal amplitude ratio (RTAR) coefficient method for corrosion depth assessment. We studied the relationship between the RTAR coefficient, the corrosion depth, and the guided wave frequency to establish a depth assessment model. More importantly, unlike the traditional reflection coefficient method, the characteristics of guided wave signals, including the propagation and attenuation, are introduced in this model for accurate assessment. To eliminate the interference of residual vibration and improve the detection accuracy of defects, we built a corrosion detection system by using piezoelectric sensors and carried out field tests to verify the performance of the proposed method. We demonstrate that corrosion defects with a minimum depth of 0.2 mm can be quantitatively evaluated.


CORROSION ◽  
10.5006/3842 ◽  
2021 ◽  
Author(s):  
Youde Wang ◽  
Xiaodong Zhou ◽  
Shanhua Xu

Steel structures exposed to the sulfate corrosive environment for a long time will inevitably suffer random corrosion damage, which will lead to uncertain degradation in the mechanical properties of materials and structures. The safety and reliability assessments of corroded steel structures largely depend on the quantification of corrosion characteristics. In order to investigate the corrosion features of structural steel under sulfate attack, six batches of accelerated corrosion experiments were conducted on 18 steel specimens. The surface morphologies of all corroded coupons were firstly measured by a 3D surface profilometer, and then the surface parameters were calculated/extracted and analyzed by a self-written analysis algorithm to clarify the distribution characteristics and evolution laws of corrosion depth, pit depth and pit shape. The results revealed that the corrosion form of structural steel under sulfate attack was a rather uneven general corrosion, which exhibited the intersection of general corrosion and pits. The corrosion depth obeyed a normal distribution, and its average value, standard deviation, and the power spectrum peak increased as the corrosion age increased. The depth and aspect ratio of corrosion pits were both in accord with the lognormal distribution and showed the increasing and decreasing trend with the corrosion time going on, respectively. Besides, the probabilities of different pit shapes in different depth ranges were obtained, in which cone pits accounted for the largest proportion, and the pits gradually changed from cylindrical and hemispherical to conical with the increase of pit depth. In the end, the random models for corrosion depth and pits were established based on the statistical results, which realized the reconstruction and random modelling of corrosion characteristics of structural steel under sulfate attack.


2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Liye Zhang ◽  
Limin Sun ◽  
Lijuan Dong

Due to many nondamage factors such as temperature, humidity, carbonation, and corrosion effects on natural frequency, the key problem of the application frequency-based method to detect damage is to reveal the rules of these factors affect natural frequency and further to eliminate their effects. The long-term characteristics of reinforced concrete structures require a lot of attention, especially in corrosive environment. In this paper, an experimental investigation was conducted to study the deflection and natural frequency of reinforced concrete beam in a marine environmental chamber for six corrosion stages (accelerated corrosion for 0, 20, 40, 70, 100, and 140 days). The experimental results demonstrated that deflection increases with corrosion time, while natural frequency decreases with corrosion time. Based on the accelerate corrosion test data of reinforced concrete beams, the general expression of the relationship between corrosion depth and natural frequency has been established through the fitting curve method. The polynomial model has been selected for establishing the relationship between steel corrosion depth (including the main reinforcement and stirrup) and natural frequency. The reason for selecting the polynomial model is that the sum of squares due to error (SSE) is closer to 0 and the coefficient of multiple determination (R-square) is closer to 1. This investigations help to discriminate the cause of reinforced concrete beams natural frequency change, to eliminate nondamage factors affects, and to apply many structural damage identification methods effectively.


Author(s):  
Huaishuai Shang ◽  
Jirui Liu

In this paper, the cracking of concrete cover caused by steel bar corrosion was discussed and studied based on the three-period model of steel bar corrosion in concrete. In the analysis, according to the non-uniformity of steel bar in reinforced concrete under natural environment, the contour of corrosion layer is simplified into a semi-ellipse. The steel bar corrosion was divided into three different periods by two corrosion points, namely, the void to be filled was exactly filled and the concrete cover was exactly cracked. Different model assumptions are made for each corrosion period. Before the concrete cover cracks, it is developed into an elastic plate. Based on the theory of elastic mechanics, the maximum corrosion depth of steel bar when concrete cover cracks is predicted.....


Brodogradnja ◽  
2021 ◽  
Vol 72 (3) ◽  
pp. 81-95
Author(s):  
Špiro Ivošević ◽  
◽  
Nataša Kovač ◽  
Nikola Momčilović ◽  
Goran Vukelić ◽  
...  

To ensure the better structural integrity and maximum safety of bulk carriers in the ship design phase, an appropriate corrosion margin is introduced by the classification societies, which should enable the exploitation of ships during the projected 25-year life cycle. The new Common Structural Rules introduce even higher corrosion margin value to ensure the structural integrity of the ship. This directly affects the increase in hull weight and thus the need for more total installed power and higher fuel consumption. Higher fuel consumption results in increased emissions which directly affects environmental pollution. For these reasons, efforts are being made to introduce alternative energy sources, cleaner fuel, ship weight reduction, and the overall economic efficiency of ships. Therefore, using experimental data collected on aging bulk carriers, the paper explores the corrosion margin reduction potential considering its impact on hull weight. Assuming that the corrosive processes occur after four years of operation, a linear model that describes the percentage of plate wear as a function of the as build-in the thickness of inner bottom plates (IBP) of fuel oil tanks (FOT) located on the double bottom of aging bulk carriers, is analyzed. Over the course of 25 years, the IBP segment was monitored on 36 different ships surveys. In this way, 520 input data describing the depth of corrosion were formed. At the same time, records were kept on the mean thickness of the original metal plate, which enabled systematization of the empirical database and grouping of measured values by intervals of original plate thicknesses, and simple conversion of corrosion depth into adequate percentage values. Depth corrosion percentages were represented by standard linear models known in the literature. Based on this analysis, representative numerical and graphical results were obtained. Conclusions from the paper can assist to optimize corrosion margin and the energy efficiency of future vessels.


Brodogradnja ◽  
2021 ◽  
Vol 72 (3) ◽  
pp. 81-95
Author(s):  
Špiro Ivošević ◽  
◽  
Nataša Kovač ◽  
Nikola Momčilović ◽  
Goran Vukelić ◽  
...  

To ensure the better structural integrity and maximum safety of bulk carriers in the ship design phase, an appropriate corrosion margin is introduced by the classification societies, which should enable the exploitation of ships during the projected 25-year life cycle. The new Common Structural Rules introduce even higher corrosion margin value to ensure the structural integrity of the ship. This directly affects the increase in hull weight and thus the need for more total installed power and higher fuel consumption. Higher fuel consumption results in increased emissions which directly affects environmental pollution. For these reasons, efforts are being made to introduce alternative energy sources, cleaner fuel, ship weight reduction, and the overall economic efficiency of ships. Therefore, using experimental data collected on aging bulk carriers, the paper explores the corrosion margin reduction potential considering its impact on hull weight. Assuming that the corrosive processes occur after four years of operation, a linear model that describes the percentage of plate wear as a function of the as build-in the thickness of inner bottom plates (IBP) of fuel oil tanks (FOT) located on the double bottom of aging bulk carriers, is analyzed. Over the course of 25 years, the IBP segment was monitored on 36 different ships surveys. In this way, 520 input data describing the depth of corrosion were formed. At the same time, records were kept on the mean thickness of the original metal plate, which enabled systematization of the empirical database and grouping of measured values by intervals of original plate thicknesses, and simple conversion of corrosion depth into adequate percentage values. Depth corrosion percentages were represented by standard linear models known in the literature. Based on this analysis, representative numerical and graphical results were obtained. Conclusions from the paper can assist to optimize corrosion margin and the energy efficiency of future vessels.


2021 ◽  
Vol 11 (11) ◽  
pp. 5294
Author(s):  
Peer Decker ◽  
Ines Zerbin ◽  
Luisa Marzoli ◽  
Marcel Rosefort

Two different intergranular corrosion tests were performed on EN AW-6016 sheet material, an ISO 11846:1995-based test with varying solution amounts and acid concentrations, and a standard test of an automotive company (PV1113, VW-Audi). The average intergranular corrosion depth was determined via optical microscopy. The differences in the intergranular corrosion depths were then discussed with regard to the applicability and quality of the two different test methods. The influence of varying test parameters for ISO 11846:1995 was discussed as well. The determined IGC depths were found to be strongly dependent on the testing parameters, which will therefore have a pronounced influence on the determined IGC susceptibility of a material. In general, ISO 11846:1995 tests resulted in a significantly lower corrosion speed, and the corrosive attack was found to be primarily along grain boundaries.


2021 ◽  
Vol 1930 (1) ◽  
pp. 012014
Author(s):  
Weifang Zhang ◽  
Duo Xu ◽  
Xiangyu Wang

2021 ◽  
Vol 6 (3) ◽  
pp. 74-80
Author(s):  
Laura Landa-Ruiz ◽  
René Croche ◽  
Griselda Santiago-Hurtado ◽  
Victor Moreno-Landeros ◽  
Josefina Cuevas ◽  
...  

In the present work, it is proposed to include in the theoretical curves of moment-curvature (m- φ) the effect of corrosion by obtaining the decrease in the area of longitudinal reinforcing steel. The corrosion depth will be obtained from the crack width and corrosion length observed in the cover concrete. With the depth of corrosion, the area of steel that is lost will be obtained and this modification will be incorporated into the theoretical procedure to elaborate the m- φ curves. The forces of the steel will be obtained from an elastoplastic model with curved hardening and the forces of the concrete with a model that considers the effect of confinement.


2021 ◽  
Vol 21 (4) ◽  
pp. 2221-2233
Author(s):  
Yaru Liu ◽  
Qinglin Pan ◽  
Xiangdong Wang ◽  
Ye Ji ◽  
Qicheng Liu ◽  
...  

The corrosion mechanisms for different corrosive media on the aged 7A46 aluminum alloy were systematically investigated at nanoscale level. The combination of empirical intergranular and exfoliation corrosion behavior was employed, and coupled with first-principles calculations. Results revealed that the dispersed distribution of matrix precipitates (MPs) leads to the enhancement of the corrosion resistance pre-ageing (PA) followed by double-ageing (PA-DA) alloy. The deepest corrosion depth of PA-DA alloy was in hydrochloric acid, and the calculation result demonstrates that the passivation effect in combination with the accumulation of corrosion products in nitric acid protect the PA-DA alloy from further corrosion.


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