Marine Steel Structures Research Articles

Experimental study on bond behavior between wet lay-up CFRP and corroded steel plates

Corrosion of steel in marine environments is a major safety concern for marine steel structures throughout their service lives. Strengthening these corrosion-damaged structures with carbon fiber-reinforced polymer (CFRP) shows great potential for extending their service lives. However, the bond behavior between CFRP and corroded steel, especially the influence from adhesive properties and corrosion degree, has not been fully understood. This paper therefore presents the results of a comprehensive experimental study on the bond behavior between wet lay-up CFRP and corroded Q355B steel plates. Tensile tests on double-lap CFRP-to-steel joint specimens with different bonded lengths, adhesives and corrosion durations were then conducted. The failure modes, load-displacement curves, strain and local shear stress distributions, effective bond lengths, and bond-slip relationships of the test joint specimens were investigated in detail. The result showed that the influence of corrosion on the CFRP-to-steel bond performance varied depending on the failure modes resulting from the material properties of adhesives. However, corrosion has insignificant influence on the general patterns of load-displacement curves, strain distribution, local shear stress distribution, local bond-slip curves with same adhesives. When failure occurred in the adhesive or the steel-adhesive interface, the corrosion tended to have a more accentuated effect on the bond performance.

Welding-induced corrosion and protective measures for clad rebars in neutral chloride environments

Corrosion-resistant steel plays a vital role in marine steel structures. This study developed an SS304/HRB400 stainless-steel-clad rebar for application in a cross-sea bridge in Zhejiang Province. CO2 gas shielded welding was employed in the prefabricated steel structure, with SS304 steel as the welding wire. This study investigated the welding on the corrosion resistance of clad rebars and explored corrosion protection measures for welded joints.The results indicated that refined grains appeared in both stainless steel and carbon steel due to distinct dynamic recrystallization (DRX) during welding. The corrosion resistance, as determined by potentiodynamic polarization curve analysis of the material’s interaction with the solution ranked as follows: clad rebar (polished) > clad rebar welding (CRW) > painting the clad rebar after welding (PCRW) > clad rebar (unpolished) > carbon-steel welding (CSW) > carbon-steel bar > cold spraying zinc after clad rebar welding (ZCRW). However, an accelerated corrosion test with four samples for 600 s with a corrosion current of 0.8 A revealed minimal corrosion damage on zinc-coated surfaces. Hence, welding joints for clad steel structures are considered feasible and must be subject to cold zinc spraying after polishing to enhance their corrosion resistance.

Experimental Study on Low-Cycle Fatigue Characteristics of Marine Structural Steel

This research focuses on the experimental investigation of the low-cycle fatigue characteristics of marine structural steel. The study aimed to explore the behavior of marine-grade steel under low-cycle fatigue conditions. The experimental parameters include the fatigue life of the material, crack propagation behavior, and a comprehensive analysis of mechanical properties associated with various loading conditions. Based on the experimental results, a low-cycle fatigue crack propagation rate model for marine structural steel plates was established using CTOD as a characterization parameter. The primary objective of this research is likely to enhance the durability and safety of maritime structures, providing valuable technical insights for the field of naval engineering.

Corrosion Control and its Application in Marine Environment - A Review

It is natural to define marine corrosion in terms of the different zones in which the corrosion occurs such as atmosphere splash, tidal and sea mud etc. However, this study focused on issues affecting the marine structures, different types of corrosion and their impact on the marine steel structures as well as the machinery/equipment. Furthermore, several control measures of corrosion necessary to avert corrosion in marine environments were discussed. However, it was established that prolonged contact of marine structures with seawater would lead to corrosion as well as ruing the safety elements present. Thus, the study provides potential information to material scientists on the need for using structural steels of adequate mechanical properties.

Development of an Al-Zn-Bi alloy sacrificial anode for the protection of steel in artificial seawater: an electrochemical analysis

The Al-Zn sacrificial anodes are widely used for cathodic protection in marine steel structures. This study evaluates the impact of bismuth addition on the electrochemical properties of the Al-Zn sacrificial anode in artificial seawater. The microstructure analysis confirms the presence of uniformly distributed intermetallic β-AlFeSi and spherical Bi within the α-Al matrix. The open circuit potential (OCP) comparison between Al-Zn-Bi and carbon steel reveals a potential difference of approximately 400 mV, indicating sufficient cathodic protection for the steel. Electrochemical impedance measurements indicate the initial hindered dissolution of the anode due to surface film formation, which later dissociates due to the aggressive attack of Cl− species in the electrolyte. The sufficiently negative surface potential (−0.875 Vvs. Ag/AgCl) observed at 10 mA cm−2 demonstrates the suitability of anode for fulfilling the cathodic protection criteria of steel structures.

An intelligent framework for forecasting and investigating corrosion in marine conditions using time sensor data

Corrosion of marine steel structures can be regarded as a time-dependent process that might result in critical strength loss and, eventually, failures. The availability of reliable forecasting models for corrosion would be useful, enabling intelligent maintenance program management, and increasing marine structure safety, while lowering in-service expenses. In this study, an intelligent framework based on a data-driven model is developed that employs a group method of data handling (GMDH) type neural network to forecast free atmospheric corrosion as time-series problem. Therefore, data from sensor data with a 30-min interval over a 110 day period that includes free atmospheric corrosion as well as environmental factors are used. In addition, the Shapley additive explanations (SHAP) technique is used to investigate the impact of the surrounding environmental factors on free atmospheric corrosion. For the performance evaluation of the proposed intelligent framework, selected comparative metrics are used. Findings demonstrate the high accuracy and efficiency of the time series data-driven framework for tackling free atmospheric corrosion progression in marine environments.

Microbiologically influenced corrosion inhibition of two marine structural steels caused by Halomonas titanicae in aerobic environments

Corrosion is a global problem, especially in marine environments. The currently popular corrosion mitigation methods have the drawbacks of being costly, susceptible to environmental limitations, or causing environmental contamination. Microbiologically influenced corrosion inhibition (MICI), as a widespread phenomenon, can provide a new strategy utilizing bacteria to control corrosion. This study investigated the MICI mechanism of Halomonas titanicae on two marine structural steels (EH36-low alloy steel (E-LAS) (with copper) and Q235-carbon steel (Q-CS) (without copper)) in aerobic environments. Results show that the corrosion of E-LAS and Q-CS was both inhibited by H. titanicae in an aerobic enriched seawater. It was found that the aerobic respiration mode of H. titanicae was very different from its anaerobic respiration. The former respiration mode significantly reduced the dissolved oxygen (DO) concentrations in the medium. In addition, the DO levels in the biotic medium immersed with the two steels were similar, but the corrosion inhibition degree of E-LAS (22% drop) caused by H. titanicae was weaker than that of Q-CS (55% drop), indicating that the MICI mechanism of H. titanicae goes beyond simply reducing the DO concentration. The number of sessile cells on E-LAS was only 20% of that on Q-CS due to Cu in E-LAS, which led to a thinner extracellular polymeric substance (EPS) film and a corrosion product film with less Fe(II) content. This reduced the Rf values significantly. Therefore, the EPS and corrosion product films caused by H. titanicae aerobic respiration are also important in the corrosion inhibition process.

Electrode array probe designed for visualising and monitoring multiple localised corrosion processes and mechanisms simultaneously occurring on marine structures

An electrode array probe has been specially designed and demonstrated for in situ monitoring and visualising multiple localised corrosion processes and mechanisms, including crevice, weldment and pitting corrosion, occurring simultaneously on marine steel structures. It enabled the probing of time-dependent development of multiple localised corrosion processes, mechanisms and kinetics, thereby facilitating more in-depth understanding of the initiation, propagation and kinetics of localised corrosion of steel marine structures.

Report on Investigation Results of Exposure Durability of Titanium-Coated Marine Steel Structures

Report on Investigation Results of Exposure Durability of Titanium-Coated Marine Steel Structures

The exploration and annotation of large amounts of visual inspection data for protective coating systems on stationary marine steel structures

The application of protective coating systems is the major measure against the corrosion of stationary marine steel structures. During their service, protective coatings are exposed to various loads, and their protectiveness deteriorates. Digital visual inspection tools are becoming a standard for the condition monitoring of coatings for large and complex structures. One of the challenges with the use of these tools is the accumulation of large amounts of visual data to be evaluated and assessed in short time intervals. A comprehensive interpretation of such image collections requires detection, classification, and quantification processes, which are usually performed by domain experts (coating inspectors). However, the data volume and the rich content of the images make the support by software tools inevitable. This contribution defines requirements for image data annotation, and it presents for the first time the application of an online exploration and annotation tool to coating condition monitoring data and its introduction into a prescriptive coating maintenance model. The software architecture of the system is described, special features are illustrated with different use-cases, and future developments are discussed. The utilization of machine learning-based assessment tools is presented.

Extracellular electron transfer corrosion mechanism of two marine structural steels caused by nitrate reducing Halomonas titanicae

The extracellular electron transfer (EET) mechanism for corrosion of EH36 steel (with copper) and Q235 steel (without copper) caused by Halomonas titanicae was investigated. Due to copper cytotoxicity, the sessile H. titanicae cells on the EH36 surface was only 18% of that on Q235. This led to its lower EET rate, resulting in EH36 corrosion being 0.67 times of Q235 corrosion. The EET corrosion mechanism was further proven by the increased corrosion of the two steels after injection to the H. titanicae broth of 20 ppm (w/w) (in the broth) riboflavin, an electron mediator known to accelerate EET.

Fatigue Crack Growth Behavior of Different Zones in an Overmatched Welded Joint Made with D32 Marine Structural Steel

Applying fracture mechanics theory to heterogeneous welded joints might lead to an uncertain assessment of fatigue crack propagation behavior and, consequently, an inaccurate estimation of the cyclic loading capacity and fatigue life of welded structures. Combining experimental testing and analytical equations of the marine overmatched welded joints of D32 marine structural steel provided a view of the influence of strength heterogeneity on fatigue crack growth (FCG) behavior under constant cyclic loading. FCG testing was conducted using compact tension specimens under different stress ratios. The effect of residual stress on the FCG behaviors of the heat-affected zones (HAZs) and fusion zones (FZs) of the compact tension (CT) specimens was examined in the overmatched welded joints. Subsequently, the welding residual stresses were removed by post-welding heat treatment (PWHT) to focus the FCGR assessment on the microstructural effect. The results indicated that the FCG rates (FCGRs) of the FZ and HAZ materials obviously varied in as-welded and stress-relieved states. The existence of residual stress in the overmatched welded joints led to a decrease in FCG rates and prolonged the fatigue crack propagation life for the FZs and HAZs. Moreover, the FCGR increased in the base metal (BM), HAZ, and FZ with the increase in the stress ratio. The FCG curves of these materials were fitted to correct the stress ratios using the NASGRO equation. Finally, an analytical analysis of the FCGR based on the NASGRO equation revealed the relationship between different stress ratios for different materials.

Inhibition of microbial extracellular electron transfer corrosion of marine structural steel with multiple alloy elements

The microbial corrosion of marine structural steels (09CrCuSb low alloy steel (LAS) and Q235 carbon steel (CS)) in Desulfovibrio vulgaris medium and Pseudomonas aeruginosa medium based on seawater was investigated. In the D. vulgaris medium, the weight loss and maximum pit depth of 09CrCuSb LAS were 0.59 and 0.56 times as much as those of Q235 CS, respectively. Meanwhile, in the P. aeruginosa medium, the values were 0.53 and 0.67 times, respectively. Compared to Q235 CS, 09CrCuSb LAS contains more alloy elements (Cr, Ni, Cu, Al and Sb), which led to obvious inhibition of sessile bacteria growth but had no effect on planktonic bacteria. The number of live sessile cells on the 09CrCuSb LAS surface was 23.4 % and 26.9 % of that on the Q235 CS surface in the D. vulgaris medium and P. aeruginosa medium, respectively. Fewer sessile cells on the steel surface led to a lower extracellular electron transfer (EET) rate so that less corrosion occurred. In addition, the combined effect of alloying elements on grain refinement and passive film formation also improved the anti-corrosion property of the steels.

Preparation of textured epoxy resin coatings for excellent hydrophobicity and corrosion resistance

Because of the severe corrosion of marine structural steel under the splash zone, it is proposed to prepare surface textures in widely used epoxy resin (ER) coatings to improve the hydrophobicity and corrosion resistance. However, the surface texture preparation technology of organic coatings is flawed and needs to be improved. Template method, one of the textured preparation technologies of organic coatings, has the trouble that the air bubbles, which diminish the coating quality. In this paper, the method of curing at room temperature and vacuum treatment is used to reduce the generation of air bubbles. Scanning electron microscope (SEM) images show the complete morphology and texture dimensions of the textured ER coatings. The hydrophobic properties of the textured ER coatings were systematically investigated, the contact angles of the textured ER coatings were significantly improved, and all the textured ER coatings samples met the hydrophobic criteria. And the wetting state model of the textured ER coatings was determined by modifying the Wenzel wetting mode. Furthermore, the electrochemical impedance spectroscopy (EIS) analysis of the textured ER coatings shows that the corrosion resistance is improved by two orders of magnitude compared to the smooth ER coatings. That shows excellent corrosion resistance, and the effect of the texture parameters on the corrosion resistance and hydrophobic properties of the textured ER coatings showed a high degree of consistency. The preparation technology of surface textured coatings has great potential in the preparation and application of marine anti-corrosion organic coatings.

Thermal analysis of marine structural steel EH36 subject to non-spreading cryogenic spills: Part III: structural response assessment

ABSTRACT An experimental study that allows for thermal-structural analysis of steel structures subject to non-spreading cryogenic spills is described. A local, non-spreading cryogenic spill was replicated by building a liquid nitrogen pool in the middle of six EH36 steel plates with a central crack of different length. The results of the temperature measurement and the thermal analysis are reported in the first and second part of this three-part companion paper. The computational study reported herein comprises stress analysis based on temperature-dependent von Mises plasticity combined with the SED failure criterion. Comparison of experimental and numerical results for stresses, fracture initiation and crack path shows satisfactory agreement. The numerical study indicates that the SED failure criterion is a useful concept for practical design of ship and offshore structures subjected to sub-zero temperatures and thus exposed to the risk of brittle failure when exposed to cryogenic spills .

Effect of chloride ion content on pitting corrosion of dispersion-strengthened-high-strength steel

Chloride ion is an important corrosion factor in marine environment. Chloride ion has a small radius and strong permeability, which can destroy the oxide film on the surface of marine structural steel. The uneven adsorption of chloride ion on the metal surface will cause pitting corrosion. The effect of chloride ion content on pitting corrosion of the as-cast and heat-treated Dispersion-Strengthened-High-Strength (DSHS) steel was studied by electrochemical test, composition analysis and surface analysis. The results showed that high content of chloride ion reduced the content of dissolved oxygen in the solution, and the corrosion rate of DSHS steel was the slowest in 5.0 wt.% NaCl solution. In high content chloride ion solution, the formation of α-FeOOH was inhibited and the protection of corrosion products was weakened. Pitting corrosion of DSHS steel before and after heat treatment was the most serious in 2.0 wt.% NaCl solution. After heat treatment, grain size of DSHS steel decreased, and more dense and stable protective corrosion products were produced. Therefore, the induction and development of pitting corrosion of heat-treated DSHS steel were inhibited.

Upgrading the mechanical properties of marine structural steel by enhancement of acicular ferrite formation

AbstractThis work reports the results of an investigation of the effect of magnesium addition on microstructure evolution, acicular ferrite formation together with the change in the mechanical properties of micro‐alloyed steel plates. The investigated steel is subjected to high heat input (4.5 kJ mm−1) simulating the thermal cycle of heat affected zones, conducted by induction heating in a computer controlled weld thermal cycle simulator. Both magnesium and magnesium free steel samples have carbon and aluminum contents of 0.08 wt.% and 0.009 wt.%, respectively, are investigated. The change in microstructure, hardness and crack tip opening displacement fracture toughness properties due to magnesium addition is evaluated, and compared with the other steel having the same chemical compositions but without Magnesium. The fracture toughness tests reveal the increase of magnesium steel‘s crack tip opening displacement values. In contrast, the hardness measuring presents the decrease of its hardness due to the decrease of martensite volume fraction and reduction in ferrite grain size. Optical and transmission electron microscopy observations detect some microstructural morphology that can affect the mechanical properties of such steels. Hence, the improved toughness of magnesium containing steel are attributed to both the generation of acicular ferrite nucleated within the matrix, refined microstructure and the bainite dominated microstructure in steel.

Effect of tempering on carbides and hydrogen embrittlement in E690 high strength marine structural steel

Effect of tempering on carbides and hydrogen embrittlement in E690 high strength marine structural steel

Corrosion behavior of marine structural steel in tidal zone based on wire beam electrode technology and partitioned cellular automata model

The initial corrosion evolution of marine structural steel in tidal zone is studied using wire beam electrode (WBE). The electrochemical experiment results show that the WBE in the high and middle tidal zones are in the anodic dissolution state for less time than that in the low tidal and immersion zones. The fitting results of WBE experiment provide the boundary conditions for the partitioned cellular automata (PCA) model, which is adopted to simulate the initial corrosion evolutions of steel in the tidal zone. The proposed independent variable of the electrolyte concentration (ρ), corrosion probability (Pc), passivation probability (Pp), and movement direction probability (Pm) on the corrosion behavior of steel are studied. The calculated results demonstrate that ρ and Pm can well characterize the corrosion evolutions of the steel in ocean tidal zones. This model is effective in predicting the corrosion evolution of marine structural steel in tidal zone. It provides a new method for predicting the corrosion evolution of marine structural steel in tidal zone.

Experimental study of hysteretic behavior of corroded steel with multi-angle welding joints

To rationally characterize the macroscopic behavior of in-service offshore structures affected by the coupled welding-corrosion action in steel components, the hysteretic behavior of corroded D36 marine structural steel with multi-angle welding joints is experimentally studied. To simulate possible corrosion-welding scenarios, the tested specimens are prepared with the gas arc welding (MAG) method for three welding angles and processed with the accelerated electrochemical corrosion for five corrosion degrees. The elasticity modulus, tensile strength, and elongation of welded-corroded steel is observed in the monotonic tensile test conducted before the cyclic test where the hysteretic performance and energy dissipation ability is mostly concerned. On the basis of these test results, a generalized hysteretic material model for welded-corroded steel which consists of a skeleton curve, an unloading curve and a reloading curve is proposed. All the parameters used to describe these curves are related to the degree of corrosion and welding angle, determined by the regression on the test data. The effectiveness of the proposed model is verified with the tested data, including those from the specimens additionally and specifically tested.