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Reinforced concrete structures are often subjected to corrosion, inducing a decreasing reliability over time. This corrosion often exhibits spatial variation, which can be modelled by random fields...

For the long-term service of X65/Incoloy 825 bimetallic composite pipe girth welds in the H2S environment, the corrosion damage behavior was investigated. Characterizations of welded joints were conducted by OM, SEM, XRD, and EDS. The pitting corrosion’s 3D surface morphology of welded joints in NACE-B solution saturated with H2S was investigated. The results show that composition segregation occurs in the welding process, and the Laves phase appears between dendrites, which lead to the decrease in corrosion resistance. The maximum depth of the corrosion pit is 2.46 μm after 30 days, 4.54 μm after 60 days, and 10.94 μm after 180 days. The cell automata (CA) model of corrosion damage was established based on the MATLAB program, and the basic elements of the cell automata model were determined. Through the simulation of the electrochemical reaction and diffusion process, the influence of different parameters of the pitting corrosion morphology was determined. The simulation results were compared with experimental data, which are available for the prediction of the morphology and size of the corrosion pits on the sample surface after 300 days. The results will be beneficial for the long-term service of the bimetallic composite pipe.

The transmission of sulfate ions in concrete results in formation of calcium sulfoaluminate crystals due to chemical reactions. The expansion of calcium sulfoaluminate crystals is the main cause of concrete corrosion damage. In this study, ultrasonic analysis was used to detect the modulus change of concrete due to sulfate corrosion to obtain the basic law of corrosion damage evolution. An exponential growth model was developed for the internal expansion force based on the chemical reaction rate of calcium sulfoaluminate crystallization. Then, the evolution equation of the number density of microcracks was derived based on their initiation and balance conditions. Finally, a statistical model was developed for the concrete damage evolution by integrating the volume of microcracks. It is shown that the statistical evolution model can well characterize the evolution of concrete corrosion damage.

Appraisal of safety of building constructions is one of the main tasks of their performance evaluation. During longterm operation period and permanently acting load together with corrosive medium constructions can sustain damage and failure. Of the most dangerous and widespread damage is construction corrosion. The consequence of the corrosion for reinforced concrete constructions can be the decrease of reinforcement cross and concrete section, distress in concrete under the pressure of corrosion products, decrease of the inner couple forces section arm, increase of the cramped zone height, danger of brickly concrete damage for bended elements.These factors negatively influence on solidity and strain characteristics of the structure and pose a threat to their safe operation.The article considers how dangerous different corrosion damage can be based on studies of different authors. The analysis of calculation results and experimental data is performed.Calculations of the column models were performed using PC LIRA CAD to asses the impact of corrosion damage on the stress-stain state of the joint collective columns and the possibility of their further operation., Оцінка безпеки будівельних конструкцій є однією із основних задач оцінки їх експлуатаційних якостей. При довготривалому терміні експлуатації та при тривалій дії навантаження та агресивних факторів середовища конструкції можуть зазнавати руйнувань та пошкоджень. Одним із найбільш небезпечних та поширених пошкоджень є корозія будівельних матеріалів. Наслідком корозії для залізобетонних конструкції можуть бути зменшення перерізів арматури та бетону, зниження щеплення арматури з бетоном, розтріскування бетону під дією тиску від продуктів корозії арматури , зменшення плеча внутрішньої пари сил перерізу, збільшення висоти стиснутої зони, загроза крихкого руйнування бетону для згинальних елементів. Ці фактори негативно впливають на міцнісні та деформативні характеристики конструкцій і становлять загрозу для їх безпечної експлуатації.В статті розглянуто, наскільки небезпечними, можуть бути різні корозійні пошкодження на основі досліджень різних авторів. Виконано аналіз результатів розрахунків та експериментальних даних. Проведені чисельні дослідження моделей колон з використанням ПК ЛІРА САПР для оцінки впливу корозійного пошкодження на напружено-деформований стан стику збірних колон і можливості їх подальшої експлуатації.

Corrosion detection using a pulsed laser scanning system can be performed via ultrasonic wave propagation imaging. This method outputs illustrations of the wave field within the host structure, thus, it can depict wave&ndash, corrosion area interactions. Additionally, post-processing can be performed to enhance the visualization of corroded areas. The wavefield energy computed using RMS (Root Mean Square) is a validated post-processing tool capable of displaying the location and area of corrosion-damaged regions. Nonetheless, to characterize corrosion, it is necessary to determine its depth. The measurement of depth in conjunction with that of the corroded area via the RMS distribution enables the determination of all dimensions of corrosion damage. Thereafter, the flaw severity can be evaluated. This study employed a wavefield within a plate on which corrosion was developed artificially to generate frequency&ndash, wavenumber dispersion curves. The curves were compared with their counterparts from a corrosion-free plate. Alternatively, they could be compared with dispersion curves drawn using the depth and material properties of a pristine plate via a computer program. Frequency&ndash, wavenumber pairs were extracted from the dispersion curves produced using the portion of the wavefield within the corroded area. These were inserted into the Rayleigh&ndash, Lamb equation, from which depths were calculated and averaged.

The work carried out studies of corrosion processes when in contact with carbon steel aggressive media. As an aggressive environment are considered water-oil emulsions with different concentrations of oil, we revealed the corrosion rates of oil’s dependency concentration.

Water pipe surface deterioration is the result of continuous electrochemical reactions attacking the surface due to the interaction of the pipe surface with environments through the time function. The study presents corrosion characterization at the surface and sub-surface of damaged ductile iron pipe (DIP) and galvanized steel (GS) pipes which served for more than 40 and 20 years, respectively. The samples were obtained from Addis Ababa city water distribution system for the analysis of corrosion morphology patterns at different surface layers. Mountains 8.2 surface analysis software was utilized based on the ISO 25178-2 watershed segmentation method to investigate corrosion features of damaged pipe surface and to evaluate maximum pit depth, area, and volume in-situ condition. Based on the analysis maximum values of pit depth, area and volume were 380 μ m, 4000 μm2, and 200,000 μm3, respectively, after 25% loss of the original 8 mm thickness of DIP. Similarly, the pit depth of the GS pipe was 390 μm whereas the maximum pit area and volume are 4000 μm2 and 16,000 μm3, respectively. In addition, characterizations of new pipes were evaluated to study microstructures by using an optical microscope (OM), and a scanning electron microscope (SEM) was used to analyze corrosion morphologies. Based on the SEM analysis, cracks were observed at the sub-surface layer of the pipes. The results show that uniform corrosion attacked the external pipe surface whereas pitting corrosion damaged the subsurface of pipes. The output of this study will be utilized by water suppliers and industries to investigate corrosion phenomena at any damage stage.

The accumulated research data of tubing fragments after operation made it possible to generalize and systematize information on the prevailing type of corrosion damage and operating conditions that determine the mechanism of their development. Understanding basic laws of the development of corrosion processes in specific operating conditions, allows to select the optimal type of tubing for these conditions more accurately. © The Authors, published by EDP Sciences, 2019.

In order to study the restoring force characteristics of corroded steel frame beams in an acidic atmosphere, based on different corrosion damage degrees, tests on the material properties of 48 steel samples and six steel frame beam specimens with a scale ratio of 1/2 under low cyclic repeated loading were conducted. According to the test results, the relationship between the weight loss rate and the mechanical properties of corrosion damage steel was obtained by numerical regression analysis, and the hysteresis curves and skeleton curves of the corroded steel frame beams were also obtained. The simplified trilinear skeleton curve model of the corroded steel frame beams and the expression of the corresponding feature points were determined by analyzing the failure process. The strength and stiffness degradation rule of the steel frame beam was analyzed furtherly. The hysteresis rule was established by introducing the cyclic degradation index which considers the effect of different corrosion degrees, and finally the restoring force model based on the corroded steel frame beams in an acidic atmospheric environment was established. Comparison with the test results show that the skeleton curve and the restoring force model established in this paper can accurately describe the seismic performance of corrosion damaged steel frame beams and can provide a basis for the seismic calculation analysis of corroded steel structures in an acidic atmosphere.

Purpose. The scientific work supposed: 1) the search of accounting ways of the local corrosion damages influence to the car design, that were expired the appointed time, for the purpose of renewal; 2) experimental verification of conformity of material construction requirements of the normative documentation and justification for extending the services of passenger cars with pockets of corrosion after 30 years of operation; 3) the conformity assessment of residual life of the structure of car bodies operating pressures in the next 5 years of use. Methodology. The developed algorithm of technical diagnostics of cars with pockets of corrosion of the center sill contains several stages. First, a survey of technical condition of structures is conducted by a visual-optical method and nondestructive control methods, and the degree of damage is determined. In the next phase the experimental verification of conformity of the structure and mechanical properties of the center sill of the car with the pockets of corrosion to regulatory requirements are executed. Next, the study of strength of the supporting structures of car bodies on the basis of experimental static and impact tests of strength is executed. Finally, the endurance tests are conducted on the effect of the longitudinal forces and the evaluation and prediction of compliance resource car bodies for the next period are executed. Findings . The actual work is completed by obtaining the experimental data on the feasibility of extending the service life of passenger cars as from the point of view of an operating time of load-bearing elements of the car body to the resource, and from the point of view of chemical composition, structure and mechanical properties of the center sill with pockets of corrosion. The presence of local corrosion damages of the center sill of the presented size is not a threat to the structural strength and safety. Originality. The authors conducted a comprehensive study to validate the service life of passenger cars both on the part of the operating time of the car bodies elements on impact toughness and the evaluation the mechanical properties of the metal from which the elements of the car are produced. For the first time the possibility of further operation of cars with corrosion damages in the center sill is grounded. Practical value. The obtained results allow without the additional activities to extend the service life of passenger cars with pockets of corrosion in the center sill.

A multi-scale modeling approach for simulating the tensile behavior of the corroded aluminum alloy 2024 T3 was developed, accounting for both the geometrical features of corrosion damage and the effect of corrosion-induced hydrogen embrittlement (HE). The approach combines two Finite Element (FE) models: a model of a three-dimensional Representative Unit Cell (RUC), representing an exfoliated area and its correspondent hydrogen embrittled zone (HEZ), and a model of the tensile specimen. The models lie at the micro- and macro-scales, respectively. The characteristics of the HEZ are determined from measurements of nanoindentation hardness, conducted on pre-corroded specimens. Using the model of the RUC, the local homogenized mechanical behavior of the corroded material is simulated. Then, the behavior of the exfoliated areas is assigned into different areas (elements) of the tensile specimen and final analyses are performed to simulate the tensile behavior of the corroded material. The approach was applied to model specimens after 8, 16 and 24 h exposure periods of the Exfoliation Corrosion (EXCO) test. For validation of the approach, tensile tests were used. The numerical results show that this approach is suitable for accurately simulating the tensile behavior of pre-corroded experimental specimens, accounting for both geometrical features of corrosion damage and corrosion-induced HE.

Design for durability of road infrastructures is becoming increasingly important in view of its large impact on economics. Reinforcement corrosion is the most common cause of concrete deterioration of bridge structures in Latvia. The ingress of chlorides is often considered to be the major threat to durability of concrete structures. During the winter season de-icing salts are spread out on roads to avoid formation of ice and ensure the anti-sliding properties of the road surface. The melting water mixes with de-icing salt are splashed and sprayed on reinforced concrete pier structures by passing vehicles. Absorbed water with chloride ions initiates and accelerates the reinforcement corrosion process. This paper highlights the results of investing accumulation of chlorides in reinforced concrete bridge piers located near high traffic volume roads in Latvia. The chloride contents were determined on different surfaces of reinforced concrete piers. Environmental conditions were analysed and prediction of remaining service life for chloride induced reinforcement corrosion was performed.

A simplified hybrid linear/nonlinear dynamic finite element analysis (SHDFEA) based on visual inspection is introduced as part of a proposed semi-quantitative assessment approach of aged bridge columns. The focus is on the evaluation of the dynamic characteristics and behaviour of slab-on-girder bridges under moving trucks when their columns are subjected to severe corrosion damage. The proposed SHDFEA uses nonlinear finite element analysis to evaluate the damaged columns stiffness, mass and damping throughout the step-by-step time history analysis. The efficiency, accuracy and stability of the proposed SHDFEA are verified through different case studies, where very high numerical stability and fast convergence are achieved. The results show that the nonlinear dynamic analysis presents the most general approach to evaluate the effects of any level of corrosion damage in the column for any case of loading, boundary conditions and any progressive change in the column properties. However, linear dynamic analysis is found to be the most economical alternative when the columns are overdesigned. It is found that with severe local corrosion damage in traditionally designed slab-on-girder bridges columns, their static behaviour mostly remains in the elastic range, and the traffic load magnitude remains below their ultimate static capacity. It is also found that the changes in the bridge dynamic performance parameters are marginal when over-designed columns have severe corrosion damage and their safety and stability are critical.

The role of existing corrosion damage on the fatigue performance of 6156 AA laser beam welds in T3 state, with additional post weld heat treatment T8, has been assessed. The welds were subjected to salt fog environment for 720 hours and then metallographically examined to characterize corrosion behaviour. The corrosion results demonstrate that T3/T8 treatment provides high corrosion susceptibility in the weld area, where localized damage in the form of large pits prevails. Fatigue performance of corroded samples is drastically degraded by the presence of corrosion pits which act as stress raisers and accelerate crack initiation in the corroded samples. Fatigue cracks initiate at the root of corrosion pits on the large specimen surfaces in the weld metal area and propagate in through thickness direction. The obtained results have been compared to results from 6156 welds with T4 treatment in as welded conditions.

The durability of reinforced concrete (RC) exposed to severe environments depends largely on its ability to resist the penetration of aggressive compounds. This paper deals with the corrosion of reinforcement bars (rebars) in cracked concrete exposed to chlorides. A simple U-shaped specimen was used in the study, with a high yield strength deformed bar of 12 mm diameter placed at with 20 mm clear cover. Concrete specimens with three water to cement ratios (w/c) and pre-cracks exposed to chlorides were studied for quality assessment and quantifying the corrosion damage in terms of gravimetric weight loss. Water absorption and rapid chloride permeability tests indicated that as the w/c decreases, the water absorption and the charge passed were decreased. Accelerated corrosion test results indicate that flexural cracks cause macrocell corrosion of rebars in reinforced concrete. Concrete with higher w/c suffers higher rebar weight loss, even under cracked conditions. It appears that the corrosion induced crack width decreases as the pre-crack width increases and increases as the w/c decreases. The simple U-shaped specimen is found to be useful for the comparative evaluation of corrosion in different concretes under cracked conditions. Copyright � 2011 Tech Science Press.

Corrosion is one of the important structural integrity concerns of aging aircraft, and it is estimated that a significant portion of airframe maintenance budgets is directed towards corrosion-related problems for both military and commercial aircraft. In order to better understand how environmental factors influence the corrosion damage initiation and propagation on aircraft structure and to predict pre-corrosion test pieces of fatigue life and structural integrity of an effective approach, this paper uses the cellular automaton (CA) method to character the effect of electrolyte concentrations, dissolution probabilities, and temperature on the corrosion damage of a metal structure exposed to an aggressive environment, and the procedure for applying the local rules between the cells of the CA to simulate the corrosion damage evolution is formulated. The simulation results show that the different electrolyte concentrations, dissolution probabilities and temperature, the laws of the dissolution current with time are investigated and they obey the time power function.