Accelerated Corrosion Tests Research Articles

Investigation of Corrosion Product Distribution and Induced Cracking Patterns in Reinforced Concrete Using Accelerated Corrosion Testing

The present study investigates the corrosion development and induced cracks in reinforced concrete specimens submitted to an accelerated corrosion test. The accelerated chloride-induced corrosion test was performed using an impressed current mode. Three current densities (50, 100 and 200 µA/cm2 of steel) and different exposure times were considered. The objective of the experiments is to analyse two distinct types of damage: firstly, internal damage near the steel/concrete interface, which can be observed in the distribution of corrosion products, as well as damage within the concrete cover, which manifests as cracking. Secondly, external damage, which can be observed in the form of rust spots and concrete surface cracks. The aim of this analysis is to elucidate the relationship between internal damage and external damage. The study confirmed that the corrosion products are non-uniformly distributed around and along the steel reinforcing bar. It also highlighted that the accelerated corrosion test conditions, such as current density, duration, environmental conditions and the specimen geometry, have a significant influence on the distribution of the corrosion products and their thickness around the steel reinforcement and therefore on the internal and external crack patterns. The data analysis revealed a substantial dispersion and contrast in terms of the data, which precluded the establishment of a definitive correlation between internal and external deterioration.

An improved methodology for accelerated marine immersed corrosion testing of ship structural components

ABSTRACT Corrosion degradation is a prominent ageing mechanism in engineering structures (e.g. ships and offshore structures), leading to safety concerns and significant economic expenses. This study presents an improved methodology for indoor accelerated corrosion testing of structural components. The method involves controlling natural factors (oxygen saturation, temperature, salinity, and flow rate) to accelerate the corrosion in a controlled environment. The study uses small coupons, medium specimens, and stiffened plates made of steel with different thicknesses. Significant degradation acceleration was achieved compared to natural conditions (approx. twenty times faster). The mean corrosion equals 3.3 mm/year with a maximum 10% variation for different specimen sizes and thicknesses. A novel approach to account for the mass of corrosion products during periodical measurements was proposed and validated. The improved methodology offers an efficient and accurate way to simulate marine immersed corrosion, enabling further research on corrosion degradation behaviour and resistance in ship structures.

Experimental Study on the Characteristics of Corrosion-Induced Cracks and Steel Corrosion Depth of Carbonated Recycled Aggregate Concrete Beams

The durability of carbonated recycled aggregate concrete (C-RAC) beams is still unclear at present. In this paper, the characteristics of corrosion-induced cracks and the steel corrosion depth of C-RAC beams were investigated through the accelerated corrosion test. The results showed that when accelerating corrosion to the 40th day, compared to the non-carbonated recycled aggregate concrete (NC-RAC) beam, the corrosion-induced cracking area of the C-RAC beam with a 100% carbonated recycled coarse aggregate (C-RCA) replacement ratio decreased by 40.00%, while the total length of the corrosion-induced cracks (CCs) increased by 51.82%. The type of probability distribution for the width of the CCs on the tension side of the C-RAC beams was a lognormal distribution. Compared with the NC-RAC beam, the mean value of the width of the CCs of the C-RAC beam with a 100% C-RCA replacement ratio decreased by 66.67%, the crack width distribution was more concentrated, and the quartiles and median were all reduced. With an increase in the C-RCA replacement ratio, the fractal dimension and the scale coefficient of CCs on the tension side of the beams showed an approximate trend of first increasing and then decreasing. The distribution of the corrosion depth of longitudinal tensile steel bars in the C-RAC beams was a mainly normal distribution. When the C-RCA replacement ratio increased from 30% to 100%, the mean value of the corrosion depth of the longitudinal tensile steel bars decreased by 33.46%, and the trend of changes in the quartiles and medians was basically the same as the trend of changes in the mean value. The research results can provide some reference for promoting the engineering application of C-RAC beams.

Experimental investigation of the electro-chemical characteristics of SFRCs under the effect of chloride ion intrusion

Steel fiber-reinforced concrete (SFRC) has been recognized for its excellent durability in severe corrosive environments and its ability to improve the mechanical performance of concrete. However, the anti-corrosion mechanisms of steel fibers towards the embedded rebar have not been clarified, and a design that reflects the inherent electro-chemo-mechanical performance of SFRC has yet to be established. To understand the electro-chemical properties, accelerated corrosion tests induced by chloride penetration were conducted in this study using transparent porous materials with embedded steel fibers and rebars, which enabled visualization of the whole polarization areas. The experimental results indicate that steel fibers delay onset of rebar corrosion and inhibit subsequent corrosion progression. Mechanisms of anti-corrosion owing to fibers are explained as: (1) When a difference in chloride ion concentration arises between surface layers and the interior, the anodic reaction gets dominant in the surface layer, but meanwhile, the cathodic reaction dominates inside where reinforcing bars are located, and: (2) A corrosion protection system appears when dispersed steel fibers affects the rate of corrosion current around the rebars. Consequently, a rebar macro-cell circuit would be hardly formed.

Investigation of Cr2SiC Ceramic MAX Phase Coated Metallic Bipolar Plates in Ex-situ Conditions for Proton Exchange Membrane Fuel Cells

Essential for compact and lightweight proton exchange membrane fuel cell (PEMFC) stacks, metallic bipolar plates (MBPs) suffer from durability and conductivity issues due to surface corrosion and passivation. This study conducts ex-situ characterization of Cr2SiC ceramic MAX phase coatings on stainless steel (SS) 316 L substrates to evaluate their suitability for MBP application. The investigation encompasses coating structure, surface morphology, corrosion resistance, surface wettability, in-plane electrical conductivity, and interfacial contact resistance. X-ray diffraction and X-ray photoelectron spectroscopy confirm the presence of Cr2SiC coatings on SS316L, while energy-dispersive X-ray spectroscopy verifies uniform coverage and elemental weight percentage. Corrosion resistance is evaluated using potentiostatic and potentiodynamic polarization tests, showing excellent resistance with low corrosion current density (Icorr) at both 25 °C (3.29E-03 μA/cm2) and 80 °C (4.32E-02 μA/cm2), meeting US Department of Energy (DOE) technical targets. Potentiodynamic polarization reveals large corrosion potential and small Icorr values at both temperatures, outperforming uncoated samples. Electrochemical impedance spectroscopy post-accelerated corrosion tests show high charge transfer resistance at 25 °C (3.68E+05 Ω cm2) and 80 °C (3.02E+05 Ω cm2), indicating stability in acidic environments. Surface wettability analysis indicates low water affinity with a large contact angle (75°) and low surface free energy (28.92 mJ/m2) for the coated samples as compared to the uncoated samples. Electrical conductivity meets DOE targets with an in-plane conductivity of 4.59E+05 S/m and interfacial contact resistance of 8.04 mΩcm2 after 5-h accelerated corrosion tests at 80 °C. These results suggest that Cr2SiC coated SS316L exhibits excellent corrosion resistance, surface wettability, and electrical characteristics, making them viable for PEMFC applications.

Corrosion and mechanical behavior of a new Q450 weathering steel

Weather-resistant steel represents a significant advancement in addressing corrosion challenges. Several types of steel with enhanced weather resistance have already been developed and manufactured. Weathering steel has shown excellent anti-corrosion ability over conventional structural steel. However, research on the corrosion and mechanical behavior of this type of steel after corrosion damage is still limited. Therefore, this paper conducts a detailed experimental investigation of the corrosion behavior and tensile strength of a new Q450 weathering steel after an accelerated corrosion test. Several scanning techniques were employed to examine the development of corrosion damage in the new Q450 weathering steels after being subjected to different corrosion times. Vickers hardness and velocity intensity of the corroded specimen were obtained to reveal the corrosion behavior of the Q450 steel. Based on the test data, predictive models were developed to predict the pit size and mechanical properties of Q450 steel after corrosion damage. The results suggest that, as the corrosion time increases, the types and amounts of corrosion products change significantly, which causes the passivation film to become much denser. Meanwhile, the mechanical properties are degraded by the increasing corrosion damage. Ultimately, the proposed predictive models are proven to be accurate and reliable.

Chloride corrosion resistance of manufactured sand reinforced concrete prepared in plateau environment

The durability of manufactured sand concrete prepared in a simulated plateau environment was investigated. Several factors, such as preparation environment of the specimens, concrete strength and corrosion rate of steel bar, were considered in this study. In these experimental investigations, the accelerated corrosion test on specimens exposed to a chloride salt solution and thereafter the static tensile test on corroded steel bars retrieved from these specimens were carried out. The durability of different specimens was compared by analyzing the surface crack development on the concrete surface, the corrosion morphologies of embedded steel bars, the degradation of mechanical properties of steel bars, and the concrete microstructure. In addition, the differences observed in the crack development of concrete and the degradation of mechanical properties of corroded steel bars between plateau and normal exposure environments were quantified. The results show that the steel bars embedded in the specimens prepared in a simulated plateau environment are prone to non-uniform corrosion attack, especially for the specimens with low concrete strength. The preparation environment of specimens and concrete strength have little influence on the degradation of mechanical properties of steel bar when subjected to a theoretical corrosion rate less than 6 %. Compared with the specimens prepared in a normal environment, the yield strength, ultimate strength and elongation of corroded steel bars subjected to a theoretical corrosion rate in the range 2∼10 % in specimens prepared in a plateau environment decrease by 2.99 %, 4.44 % and 14.78 % on average, respectively. For the specimens prepared in a plateau environment the decreased durability of concrete is explained by insufficient hydration and low compactness inside concrete, so that it is easier for chloride ions to penetrate into concrete, resulting in early corrosion. As a result, the variation of average crack width of concrete with actual corrosion rate and the variation of nominal yield and ultimate strengths of steel bars with their maximum section loss rates no longer satisfy the linear relationship for the specimens prepared in plateau environment, which is different from the specimens prepared in a normal environment. Moreover, the protective effect of concrete on embedded steel bar can be significantly enhanced by improving the strength of concrete produced in a plateau environment.

An accelerated corrosion-fatigue testing method for marine high-strength steel based on equivalence principle of fatigue crack growth

The corrosion-fatigue test is widely used to assess marine equipment. However, due to the low-frequency and high-cycle loading of marine equipment in service, conventional test methods require long cycle times and high costs. This makes it challenging to meet the rapid evaluation demands associated with equipment development effectively. In this study, an accelerated corrosion test method was proposed for steel by adjusting the composition, temperature, pH and H2O2 concentration of environment. Fatigue crack growth tests were conducted under various corrosion environments and load frequencies. The matching relationships between corrosion fatigue acceleration multiplier, corrosion environment parameters and load parameters were established. Additionally, a corrosion fatigue acceleration test method was proposed based on the equivalent principle of fatigue crack growth. The results show that effective coupling between corrosion and fatigue can be achieved by gradually reducing the load frequency as the stress intensity factor amplitude increases throughout the crack growth process. It is consistent with the trend of fatigue crack growth rate in the seawater environment. The 4.85% fatigue life deviation and the 15.68 times corrosion fatigue acceleration can be achieved by our method. This work improves the accuracy and reliability of fatigue performance evaluation for offshore equipment.

Experimental Study on the Mechanical Properties of Squat RC Shear Walls with Corrosion Along the Base

In corrosive environments containing chloride and sulfate, the corrosion of steel bars is common along the base of squat RC shear walls (SRCSW) due to problems such as construction quality, concrete stress concentration, local defects, and accumulation of water and corrosive media. In this paper, three SRCSWs are designed and constructed and their mechanical properties assessed. One side of each SRCSW was exposed to a corrosive environment for 70 days, while the other side was subject to the same conditions over different corrosion times (i.e., 0 day, 42 days, and 70 days). Then, the corrosion-induced cracking process, the mechanical properties of SRCSWs corroded along the base, the relationship between the mass loss of total steel bars (MLTSB) in the corroded area and the wall mechanical properties, and the relationship between the average width of corrosion-induced cracks (CICs) and the wall mechanical properties were studied through an accelerated corrosion test and a loading failure test. The results indicate that the area of corrosion-induced cracking on SRCSWs increased with the corrosion time, and the cracking area on the different SRCSWs was approximately identical when the SRCSWs were exposed to the same corrosion time. When the degree of corrosion was different, the loading failure characteristics of the SRCSWs were obviously different, but the failure mode always corresponded to shear failure. The load–displacement curves of the SRCSWs with different degrees of corrosion along the base basically coincided and were linear when the loading was in the elastic stage. Compared to SW-1, the peak load of SW-2 decreased by 4.0%, but that of SW-3 increased by 2.7%. Compared to SW-1, the yield loads of SW-2 and SW-3 decreased by 22.4% and 11.8%, respectively. When the MLTSB increased from 13.05% to 16.71%, the crack, yield, and peak loads of the SRCSWs corroded along the base decreased by 8.8%, 22.4%, and 6.8%, respectively. The cracking, yield, and peak loads of the SRCSWs corroded along the base decreased linearly with the increase in MLTSB and the average width of the CICs, and the corresponding fitting relations were established. The results of this study can serve as a reference for the durability design of SRCSWs in corrosive environments.

Cellular Automata-Based Experimental Study on the Evolution of Corrosion Damage in Bridge Cable Steel Wire

Cable-stayed bridges have become the preferred bridge type for large-span bridges due to their unique advantages, and the long-term performance of the cable under the extreme conditions has been facing great challenges. An accelerated corrosion test was carried out using in-service cable, and the evolution model of the etch pit was established based on cellular automata to study the evolution law of corrosion damage to steel wire. This study showed that with the increase in the number of dry-wet cycles in the electrified accelerated corrosion, the macro- and micromorphology of the steel wire showed more serious corrosion damage, the tensile strength decreased, the ductility index decreased, and the tensile strength of the steel wire after corrosion decreased by nearly 5%; the geometric dimension of the steel wire etch pits all met a right-skewed distribution with a broader range of etch pit depth, mainly consisting of shallow spherical etch pits and deep ellipsoidal etch pits. The length, width, and depth sizes were mainly distributed in the range of 0.005 mm to 0.015 mm, 0.005 mm to 0.02 mm, and 0 mm to 0.04 mm; at the early stage of corrosion, the etch pits were first developed along the longitudinal direction. As the corrosion process progressed, the iron matrix participated in the electrochemical reaction, leading to the rapid expansion of the etch pits’ dimensions. The stress concentration effect at the bottom of the etch pit caused the maximum stress to approach 1800 MPa, with a stress concentration coefficient of more than 3.0; when the cable anchorage system was located in the connecting sleeve and the threaded splice seam, where corrosion protection was prone to failure, the outer steel wire bore most of the corrosive effects, and the internal cable was less eroded by the corrosive medium.

Development of a Reliable Accelerated Corrosion Test for Painted Aluminum Alloys Used in the Aerospace Industry

New environmental regulations have led to major changes in aluminum corrosion protection by prohibiting, for example, Cr(VI). Thus, the assessment of the corrosion behavior of Cr-free systems under atmospheric conditions is a major topic of interest for the aerospace industry. One major difficulty in this task is the lack of robust and reliable accelerated corrosion test(s) in this field. The aim of the present study is to compare the results of various accelerated corrosion standards (ASTM B117, ISO 4623-2, VCS 1027,149) to results obtained after 5 years of exposure at a marine atmospheric site in Brest, France. Additional accelerated corrosion tests were designed by varying several parameters in the VCS 1027, 149, such as the salt concentration, the time of wetness, and the relative humidity. The different modes of failure obtained in accelerated corrosion tests on the painted samples were then compared to field exposures in a marine atmospheric site. The first results obtained showed that the developed tests are more representative of service conditions than standard tests.

Experimental investigation of using Ultra-High-Performance Concrete coating for anti-corrosion protection of reinforced concrete induced by chloride ions

The emergence of Ultra High-Performance Concrete (UHPC) is one of the latest developments in concrete technology. Repairing and rehabilitating damaged structures by applying a thin layer of several centimeters on conventional concrete (with or without reinforcement) has been one of the applications of UHPC. Due to its very small porosity and excellent permeability, UHPC has extremely high durability against the penetration of destructive substances such as water, chloride ions, oxygen, etc. In this work, we investigated the durable effect against external aggressive corrosive substances by coating a 2.5 cm thickness layer of UHPC on conventional concrete. The desired composite concrete consists of a conventional concrete core with a compressive strength of 40 MPa and a coating with a thickness of 2.5 cm of UHPC cover. Then, this concrete went through oxygen penetration, Rapid Chloride Permeability Test (RCPT), and electrical resistance tests. Finally, to verify the results of the durability tests, two sets of comparison reinforced concrete specimens with 5 cm as their covers were exposed to an accelerated corrosion test. It is found that the substitution of a 2.5 cm layer of UHPC instead of the conventional concrete resulted in a 30-times increase in resistance against water penetration, 41 times against chloride ion penetration, 307 times against oxygen penetration, and 8 times in its electrical resistance. Based on corrosion acceleration test results, after 30 days of applying a current with a voltage of 31 volts, the control specimens with a 5 cm cover started to corrode after one week. After 30 days, 47 % corrosion was observed. Even though after 365 days, no signs of corrosion were found in the UHPC-coated specimens.

Chloride corrosion resistance of wet joints in manufactured sand reinforced concrete prepared in plateau environment

The durability of three types of wet joints in manufactured sand concrete prepared in simulated plateau environment was investigated. And the accelerated corrosion test on specimens in the chloride salt solution and the static tensile test on corroded steel bars in specimens were carried out by sequence. The durability of different types of specimens prepared in plateau environment was compared by analyzing the development of concrete cracks, the corrosion morphologies of internal steel bars, the degradation of mechanical properties of steel bars, and the concrete microstructure. The results demonstrate that the development of concrete cracks and the distribution of crack width are affected by wet joint. The nonlinearity of variation of average crack width with actual corrosion rate is enhanced by wet joint. The strength and elongation of steel bars in concrete decrease evidently by wet joint. The strength and elongation loss of steel bars after corrosion is effectively reduced by the punched treatment on joint interface. There is no clear superiority or inferiority pattern for the durability of wet joint specimens with untreated interface (UI) and chiseled interface (CI), and the durability of wet joint specimen with punched interface (PI) is better than that of UI and CI specimens.

Experimental study on bond behavior of corroded reinforced concrete under coupling effect of fatigue load and elevated temperature

The bond properties of corroded reinforcing bars in concrete are mainly determined by the failure time and ultimate capacity of reinforced concrete (RC) structures. In this study, 98 cube specimens were used to study the corrosion effect on the bond failure mechanism of RC structures under transient high temperature. Firstly, an electrification accelerated corrosion test was carried out to fabricate the corroded specimen with various corrosion degrees (0 %, 5 %, 10 %, and 15 %). Secondly, the undamaged specimen was conducted by pull-out test at ambient temperature to obtain the initial bond strength, and then a transient temperature test under sustained load was also performed to analyze the effects of different load ratios, concrete strength, and corrosion degrees on the bond behavior. SEM (Scanning Electron Microscope) was conducted to verify the damage level by comparing the interfacial transition zone. Test results indicate that the coupling effect of corrosion, fatigue load, and high temperature increases the carbonization level of the specimens and reduces the concrete compressive strength after bonding damage. The ultrasonic pulse velocity decreases with increasing corrosion degree and sustained load level and decreases with increasing concrete strength grade. Under the coupling effect of corrosion, high temperature, and sustained load, the bonding failure time is significantly affected by the sustained load ratio, and the failure slip is determined by corrosion and temperature. Finally, an empirical slip-location constitutive model was proposed, incorporating the sustained load ratio, corrosion degree, and temperature. The accuracy of the predicted model agrees with the error requirement, and the constitutive model provides a theoretical basis for the collapse warning of corroded structures under fire.

Effect of Fluoride in Alkali-Free Liquid Accelerator on Corrosion of Reinforced Shotcrete by Chloride Ion.

Shotcrete is a crucial component of tunnel engineering. To investigate the impact of fluoride-containing alkali-free liquid accelerators on the structural safety of shotcrete, this study prepared shotcrete using three different fluoride-based alkali-free liquid accelerators: magnesium fluosilicate, fluosilicic acid, and hydrofluoric acid. The corrosion of steel rebar within the shotcrete was examined and compared with that of shotcrete prepared using a fluoride-free alkali-free liquid accelerator. Analysis of the hydration products and pore structure of the shotcrete revealed that fluoride-containing accelerators inhibited the hydration of C3S, increased the content of harmful pores, reduced the pH value, and decreased the chloride ion binding capacity of the shotcrete. As a result, steel reinforcement within the fluoride-containing shotcrete was not effectively protected during the early stages. Detection of corrosion products indicated that shotcrete containing fluosilicic acid and hydrofluoric acid accelerators led to the rapid formation of loose corrosion products, primarily Fe2O3, thereby accelerating the corrosion rate of the steel reinforcement. Among the accelerators studied, hydrofluoric acid posed the most severe threat to the reinforcement, with the open circuit potential reaching -520.2 mV after 24 days of accelerated corrosion testing. Additionally, the mechanisms by which fluorides influence the corrosion of steel reinforcement in shotcrete were explored through the analysis of concrete hydration products and corrosion products on the steel rebar.

Meso-crack propagation of RC induced by non-uniform rebar corrosion and the predictive model of time to concrete cover cracking

Non-uniform corrosion expansion in reinforced concrete (RC) structures will lead to concrete cracking, bond degradation, and an overall reduction in load-bearing capacity, severely threatening structural safety and durability. Accordingly, meso-crack propagation of RC induced by non-uniform rebar corrosion and the predictive model of time to concrete cover cracking are investigated in this paper, and the theoretical solutions for the critical corrosion rate and the corresponding time are proposed for structural durability evaluation and design. Firstly, based on the mesh-mapping technique of multi-shape random aggregates, a finite-element generation method for three-dimensional concrete three-phase meso-scale model is proposed, with modeling corrosion-expanded cracking of RC, reproducing the crack morphology and propagation process of concrete cracking due to non-uniform rebar corrosion. Subsequently, single factor influence analysis and multi-factor orthogonal test were employed to reveal the degrees of influence of various factors on the critical corrosion rate as follows: concrete strength > cover thickness > interface layer strength > aggregate content > aggregate grading > aggregate shape. A theoretical predictive model for the corrosion expansion cracking time of the RC cover was proposed, considering the influence of key factors including concrete strength and cover thickness. Finally, the validity of theoretical prediction method and the numerical model’s damage mode are verified through accelerated corrosion tests of RC.

Experimental study on mechanical aging properties of self‑swelling anchorage bolt under chemical corrosion

ABSTRACT Chemical corrosion is found to influence the strength of grouted rockbolt reinforcement in underground excavations leading to catastrophic. As such, in this paper, we investigated the impact of the chemical corrosion on the new self-swelling anchorage rockbolt, designed by us, during long-term corrosion processes and accelerated corrosion tests with different chemical solutions. The self-swelling anchorage rockbolt uses a self-swelling anchoring agent that hydrates and expands, providing high anchoring force. The impact of pure water, acidic, and salt solutions on the load-bearing capacity and deformability of self‑swelling anchorage bolts was analysed. Additionally, a microscopic XRD component analysis method was used to reveal the changes in microscopic composition of self‑swelling anchoring agents. It was found that after 180 days of accelerated corrosion, pure water and salt solutions had a small effect on the anchorage force of self‑swelling anchorage bolts, whereas the anchorage force of self‑swelling anchorage bolts decreased by 73.4% in an acidic solution with a PH of four. In addition, the deformation capacity of the bolt deteriorates with the time regardless of the chemical solutions. Combined with XRD micro-composition analysis, the effects of different solutions on the mechanical properties of self‑swelling anchorage bolts were as follows in descending order: PH = 4>6% NaSO4>6% NaCl>3% NaSO4 + 3% NaCl>water.

ЗАЩИТНЫЕ СВОЙСТВА МОДИФИЦИРОВАННЫХ БИТУМНЫХ ПРАЙМЕРОВ ДЛЯ ПРОТИВОКОРРОЗИОННОЙ ЗАЩИТЫ СЕЛЬСКОХОЗЯЙСТВЕННОЙ ТЕХНИКИ И ОБОРУДОВАНИЯ

In order to protect agricultural machinery from atmospheric corrosion during the nonworking period, it is possible to use bitumen primers (BP), which are compositions of petroleum bitumen with the addition of solvents and, possibly, other additives. The protective properties of compositions based on the bitumen primer "Orgkrovlya No. 1" diluted with white spirit with modifying additives on samples of 08kp steel were studied in the work. Accelerated corrosion tests in 0.5 M NaCl solution showed the following: dilution of BP with 40 wt. % white spirit when applied in one layer leads to a decrease in the protective efficiency to 75%, 67 wt. % - to 37%; the introduction of additives (5 wt.%) of P2 paraffin into the diluted BP with 40 wt. % white spirit increases its protective efficiency (Z) to 98%, KO-SZhK - up to 87%, Emulgin - up to 94%; When diluting BP with 67 wt.% white spirit, the maximum Z = 60% is provided by the addition of 1 wt.% drying oil +1 wt.% POOM. Accelerated tests in the G-4 heat and humidity chamber and the salt spray chamber showed the best results for BP coatings diluted with 40 wt.% white spirit and with the addition of 5 wt.% P2 paraffin. The highest values of protective efficiency in the G-4 heat and humidity chamber for BP diluted with 67 wt.% white spirit are provided by coatings with 2 wt.% drying oil (Z = 97%), 5 wt.% POOM (Z = 97%), 1 wt.% drying oil +1 wt.% POOM (Z = 96%). According to the 9-month results of full-scale bench tests of modified BP diluted with 40 wt.% white spirit, the best results are provided by the coating with the addition of 5 wt. % paraffin P2 and Emulgin. These 2 additives effectively protect steel in a concentrated solution (200 g/l) of mineral fertilizer borofoska.

Test and simulation of corroded high strength steel wires: From scanned morphology feature to mechanical degradation

This paper presents a coupled experimental-numerical study aimed at understanding the mechanical behavior of corroded high-strength steel wires. Accelerated corrosion tests were conducted on steel wires to achieve varying corrosion levels, and the mechanical properties of the corroded wires were characterized by tensile test. The surface morphology of the corroded wires was derived by 3D optical scanning and point cloud models was generated that precisely captured the surface pits. These models were then converted into solid models by surface reconstruction and finite element discretization. Numerical simulations, based on reconstructed surface morphology, effectively predict key mechanical characteristics and align closely with experimental data. The research establishes relationships between statistical pit parameters and macro-mechanical properties, providing valuable insights for predicting the mechanical performance of corroded wires and evaluating the integrity of structures compromised by corrosion.

Detection and Assessment of Hull Plate Corrosion Damage Based on Image Recognition Techniques

Corrosion damage can lead to a decrease in the ultimate strength and carrying capacity of ship structures, and even result in buckling or fracture. With the rapid development of deep learning, image recognition processing, and convolutional neural networks (CNN) are playing an important role in the field of corrosion damage detection and assessment. In this paper, corrosion damage images are obtained by taking photos of test pieces of accelerated corrosion tests, and a corrosion damage database is established to provide data for the establishment of the subsequent image corrosion damage level dataset and the training of the CNN model. Digital image processing methods and unsupervised learning clustering algorithms are used to identify and process corrosion images and obtain corrosion parameters. Based on the corrosion parameters, the images are classified into different corrosion damage levels to establish a corrosion damage dataset with corrosion damage level labels. This dataset is used to train a CNN model and establish a corrosion damage level assessment interface. By inputting corrosion damage images, the corrosion damage level assessment results can be obtained.