Steel Structures In Marine Environment Research Articles

Exploring anti-corrosion properties and rheological behaviour of tannic acid and epoxidized soybean oil-based fully bio-based epoxy thermoset resins

This research explores the physicochemical attributes of a fully bio-epoxy thermoset aimed at serving as an anti-corrosion coating for safeguarding carbon steel structures in marine environments. Throughout this investigation, various epoxy thermosets formulations, based on epoxidized soybean oil (ESO) and tannic acid (TA), were synthesized by adjusting the initial ratios of epoxide:hydroxyl groups (epoxy:OH). These formulations were subsequently applied onto carbon steel substrates and subjected to thermal curing at moderate temperatures (170 °C) to evaluate their anti-corrosion effectiveness using electrochemical impedance spectroscopy (EIS). The examination of the total impedance values derived from EIS Bode diagrams (>106 Ω) revealed a notable anti-corrosion efficacy that endured over several months of immersion in 3.5 wt% NaCl solutions. In addition to electrochemical assessment, a rheological analysis was conducted to determine the optimal curing temperature for each formulation and to track the evolution of their mechanical properties throughout the curing process. Furthermore, the progression of corrosion at the coating-metal interphase was quantified using samples featuring artificially created notches to facilitate rapid water penetration, reaching the protected surface. Moreover, cross-cut and pull-off adhesion tests were conducted on coatings cured with various epoxide:hydroxyl ratios, yielding exceptional results on carbon steel substrates. Overall, a great potential for anti-corrosion protection has been demonstrated on the developed fully bio-based coatings with tuneable mechanical properties, regarding the initial component ratio, to reach the specific requirements for specific applications.

Electrolytic co-deposition of Zn-ZnO and Zn-ZnO-CaCO<sub>3</sub> composite substrates on low-carbon steel

Conventionally employed zinc-rich paints and coatings for marine corrosion protection of steel still comprise environmentally unfriendly compounds such as zinc phosphate. This paper is focused on developing eco-friendly zinc ternary composite coatings of Zn-ZnO-CaCO3 utilizing CaCO3 additives derived from tympanotonus fuscatus (periwinkle) shell and calcareous eggshell respectively on low-carbon steel using electrodeposition technique. This is aimed at improving not only the surface corrosion resistance of steel structures in marine environment but also the sustainability of raw materials and minimal environmental pollution. Corrosion studies of uncoated and coated steel samples in simulated marine environment were done using linear polarization technique. Results obtained suggested that CaCO3 (i.e., calcareous eggshell) additive in the composite coating significantly improved the corrosion performance of the substrate. Steel coated with calcareous eggshell additive displayed superior corrosion performance having highest polarization resistance, Rp (156090 Ω), lowest corrosion rate, CR (0.01 mm/year) and highest coating efficiency, Ceff (97%) as against those of uncoated, zinc oxide, and tympanotonus fuscatus shell additives after 30 minutes deposition time. Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDS) results of selected developed coatings indicated presence of a homogeneous surface morphology and a significant amount of calcium in the calcareous eggshell coating.

Root causes for corrosion on painted steel structures in marine environments

AbstractOur understanding of the failure mechanisms of coatings, for example, cathodic disbonding, corrosion creep, blistering, and cracking, have been developed to a high level over the past decades. However, knowing what actually causes coatings to fail in the field is also important. Several atmospheric field tests of coating with duration 2–9 years have been published, showing that epoxy‐based heavy‐duty protective coating systems with zinc‐rich primers have high resistance against corrosion creep from damages in the coating. Despite this, scribe creep corrosion has become the most important evaluation parameter in standardized testing. In this work, inspection pictures from an offshore oil and gas platform, a ballast water tank system, and two coastal road bridges have been analyzed with respect to the root cause for initiation of corrosion on coated steel. The results show that corrosion mainly initiates at edges and welds. Between 50% and 90% of the corrosion attacks could be attributed to this, depending on the type of structure. The paint failed due to low film thickness, that is, the wet paint retracts from sharp edges in the surface so that the cured film has reduced barrier properties.

Research progress on microbiological inhibition of corrosion: A review

Steel structures in marine environments are subjected to severe corrosion over a long period due to the complex and harsh characteristics of their environments. Traditional anti-corrosion methods may lead to environmental pollution and high maintenance costs. Microorganisms exist in large quantities in the environment and can not only accelerate the corrosion of materials but also inhibit corrosion to some extent. Microbially influenced corrosion inhibition (MICI) has become a research hotspot as a new environmentally friendly anti-corrosion measure. In this paper, the effects of microorganisms on the inhibition of metal corrosion are summarized and analyzed, with a review of recent research. We discuss the mechanisms by which microorganisms inhibit corrosion including secretion of corrosion inhibitors, shielding effects of biofilms and corrosion products, changes in the local microenvironment, and alteration of anode and cathode processes; as well as their control mechanisms. Some beneficial microorganisms can inhibit corrosion caused by corrosive microorganisms through mechanisms including biological competition, inhibition of microbial attachment, secretion of antibiotic substances, and phagocytic control. Using microbial anti-corrosion facilitates autonomous regulation, in situ remediation, and intelligent protection, provides lifelong protection and is environmentally friendly. Knowledge of the mechanisms of microbiological inhibition of corrosion can provide references for the protection of metals against corrosion. We have outlined the difficulties and problems in the research and application of microbial antiseptic technology, as well as valuable directions for the future development of microbial antiseptic technology.

Superior Surface Protection, Mechanical and Hydrophobic Properties of Silanized Tungsten Carbide Nanoparticles Encapsulated Epoxy Nanocomposite Coated Steel Structures in Marine Environment

Superior Surface Protection, Mechanical and Hydrophobic Properties of Silanized Tungsten Carbide Nanoparticles Encapsulated Epoxy Nanocomposite Coated Steel Structures in Marine Environment

Upgrading of quay walls at the Ravenna port, Italy: evaluation of the steel piles degradation after a long working life

In the context of a challenging project aimed at the upgrading of some old quays in the port of Ravenna (Italy) an extensive survey was conducted to determine the level of degradation of the most significative structural elements. The quays were essentially constituted by anchored sheet pile retaining walls in which the main structural elements were steel profiles. Therefore, the main point of concern was the degradation of the steel piles after a long-lasting exposure to the sea water. The corrosion of steel structures in marine environment is a well-recognized problem for maritime engineering, therefore nowadays a relevant part of the designing effort is oriented towards improving the durability and to minimize the cost of maintenance of infrastructures. However, data from real experience are not frequent. This paper presents some results of the inspection carried out on quays in the Ravenna port after an operative life between 21 to 29 years, focusing on the condition of the steel piles. Data include ultrasonic measurements of the thickness and laboratory analyses of steel samples. Although the environmental conditions were not particularly favourable, the results indicate that the degradation of the profiles in the permanently immersed zone was very limited.

Time-variant reliability analysis of steel plates in marine environments considering pit nucleation and propagation

Corrosion is a severe threat to the integrity of ships and other steel structures in marine environments due to material loss and the associated reduction in their load-carrying capacities. Most existing studies on corrosion of steel plates in marine environments dealt only with general corrosion. However, laboratory experiments and field tests have shown that pitting corrosion can occur and even dominate the material loss of corroded structures, especially for plates with local coating failure, metal with mill scale surfaces, and alloys with special compositions. In this paper, a cellular automata-based model with both numerical and categorical attributes is proposed to analyze steel plates subjected to general and pitting corrosion. The proposed model can depict various corrosion behaviors including uniform loss of plate thickness, pit nucleation, and pit propagation. The parameters of the model are calibrated based on results from existing exposure tests. The calibrated model is then used to evaluate the time-variant reliability of a steel plate in corrosive environments. It is found that the general corrosion model with a time-invariant corrosion rate cannot realistically predict the long-term corrosion material loss and the thickness of corroded plates may show considerable spatial variability due to pitting corrosion.

Antifouling Properties and Release of Dissolved Copper of Cold Spray Cu/Cu2O Coatings for Ships and Steel Structures in Marine Environment

At the submarine screen doors of ships, the flow of water was fast and organic coatings were easy to peel off. To solve the problems of biofouling, the Cu/Cu2O coatings were prepared by cold spray technology. In this paper, the release mechanism of effective antifouling components of the coatings was studied by micro-domain electrochemical potential scanning technique. Cuprous oxide in the coatings and the surrounding copper constituted micro-cells which accelerated the local electrochemical dissolution of copper. Cuprous oxide acted as the cathode, and the surrounding copper acted as the anode. Meanwhile, under the action of current, chloride ions were transferred from cathode to the anode and promoted local electrochemical dissolution of copper. Experiments show that the higher the Cu2O content in the coatings, the greater the release rate of dissolved copper and inhibitory effect on diatoms. In the environments varied in dissolved oxygen, salinity, temperature and flow rate, the coatings maintained sufficient release rate of dissolved copper, unless the salinity was very low. Most of the dissolved copper was provided by the electrochemical dissolution process of copper. Whether in the indoor test or marine environment experiments, 30% Cu2O coatings show the best performance. After insulating layer was sprayed, the effect of antifouling was improved evidently and the coatings were applied to the submarine screen doors of ships.

Pitting Degradation Modeling of Ocean Steel Structures Using Bayesian Network

Modeling depth of long-term pitting corrosion is of interest for engineers in predicting the structural longevity of ocean infrastructures. Conventional models demonstrate poor quality in predicting the long-term pitting corrosion depth. Recently developed phenomenological models provide a strong understanding of the pitting process; however, they have limited engineering applications. In this study, a novel probabilistic model is developed for predicting the long-term pitting corrosion depth of steel structures in marine environment using Bayesian network (BN). The proposed BN model combines an understanding of corrosion phenomenological model and empirical model calibrated using real-world data. A case study, which exemplifies the application of methodology to predict the pit depth of structural steel in long-term marine environment, is presented. The result shows that the proposed methodology succeeds in predicting the time-dependent, long-term anaerobic pitting corrosion depth of structural steel in different environmental and operational conditions.

Effects of Arc Spray Process Parameters on Corrosion Resistance of Ti Coatings

In order to improve the corrosion resistance of carbon steel structures in marine environment, Ti wires were sprayed to a steel substrate using arc spray technique, and orthogonal experimental design was used to investigate the effects of the fluctuation in the main parameters of spray process on the microstructure and the corrosion resistance of sprayed coatings. The results show that the corrosion resistance of sprayed coatings is very sensitive to spray process parameters, corrosion current density can decrease from 997.7 to 5.08 μA cm−2 by optimizing process parameters. The coatings are composed of TiN and Ti2O, and the corrosion resistance of coatings can be improved with the decrease in the contents of oxides. The spray distance should be exactly monitored and controlled in arc spray process because of its great effects on the quality of sprayed coatings.

海洋鋼管構造物のLCC評価に関する研究

海洋鋼管構造物のLCC評価に関する研究

Spectroscopic identification of protective and non-protective corrosion coatings on steel structures in marine environments

Corrosion research, and the need to fully understand the effects that environmental conditions have on the performance of structural steels, is one area in which Mössbauer spectroscopy has become a required analytical technique. This is in part due to the need to identify and quantify the nanophase iron oxides that form on and protect certain structural steels, and that are nearly transparent to most other spectroscopic techniques. In conjunction with X-ray diffraction and micro-Raman analyses, the iron oxides that form the rusts on steels corroded in different marine and other environments can be completely identified and mapped within the rust coating. The spectroscopic analyses can be used to determine the nature of the environment in which structural steels have been, and these act as a monitor of the corrosion itself. Mössbauer spectroscopy is playing an important role in a new corrosion program in the United States and Japan in which steel bridges, old and new, are being evaluated for corrosion problems that may reduce their serviceable lifetimes. Mössbauer spectroscopy has been used to characterize the corrosion products that form the protective patina on weathering steel, as well those that form in adverse environments in which the oxide coating is not adherent or protective to the steel. Mössbauer spectroscopy has also become an important analytical technique for investigating the corrosion products that have formed on archeological artifacts, and it is providing guidance to aid in the removal of the oxides necessary for their conservation.

Chemical Reaction between Tantalum and Gallium under High Pressure

and the lead electrodes during the measurement. 7) In this case it is important that tantalum is chemically inactive with the material in order to obtain a stable current during the measurement. The stability of tantalum against low melting metals has been systematically investigated on Zn, In and Sn. 7) Tantalum shows the inactive property over the melting temperature of them. Recently a ternary phase diagram of the Al–Zn–Ga system at atmospheric pressure has been studied for applying the cathode protection by aluminum sacrificial anodes widely used for protecting steel structures in marine environments. 8,9) The isothermal sections of the ternary phase diagram suggest the appearance of a new intermediate phase in the binary Zn–Ga system under high pressure. The new intermediate phase is expected to appear around 30at%Ga content. 10) In order to confirm the interesting phenomenon, the measurement of the phase relation between zinc and gallium must be carried out above liquidus temperature (400C) in the region between 2 and 7 GPa. Tantalum is required to be applied for the electrode as an inactive material. The stability of tantalum against gallium becomes an important problem for the measurement of the electrical resistance under high pressure.

Evaluation of through-porosity of HVOF sprayed coating

Anticorrosion coatings must be impermeable to protect steel structures in marine environments. We evaluated the through-porosity of HastelloyC high-velocity oxyfuel (HVOF) sprayed coatings by quantitatively analyzing dissolved substances derived from coated steel during immersion in HCl solution. This enabled us to detect slight amounts of through-pores, which depended on the coating thickness and on the coating's stacking structure. It also enabled us to separately calculate both coating through-porosity and corrosion resistance when electrochemical measurements could not selectively detect either of these properties.

Electrochemical aspects of protection afforded by finish coat on zinc‐rich primers

A barrier type of finish coat on zinc‐rich primers can effectively prevent corrosion on mild steel structures in marine environments. Chlorinated rubber is well known for its impermeability of water vapours and corrosive ions. Micaceous iron oxide (MIO) and titanium dioxide (Ti02) are the best barrier pigments available in the world. The chlorinated rubber based top coatings have been prepared by incorporating these two pigments separately and applied over three types of zinc‐rich primers (ZRP) (butyl titanate ZRP, cashew nut shell liquid ZRP and epoxy polyamide ZRP). The electro chemical aspects of protection afforded by these coating systems have been evaluated on mild steel substrate in 3 percent NaCI solution by potential‐time, polarisation and impedance techniques. This study revealed an interesting correlation between the polarisation and impedance observations. The inorganic ZRP with top coated systems behave differently to organic ZRP with top coated systems. The MIO pigmented finish coat affords equally higher duration of protection of steel substrate from corrosive saline environment, even though the PVC value is considerably lower than the TiO2 pigmented top coat systems.

An Expert System for Deterioration Assessment of Civil Engineering Steel Structures in Marine Environment

Corrosion deterioration of civil engineering steel structures, such as steel pile piers and sheet pile walls in marine environments, has lately become of interest, and many unsolved problems on corrosion deterioration of the structures are now under investigation in various organizations.At first, we investigated the actual state of steel pile piers and sheet pile walls in port facilities, and developed a corrosion data-base of the structures. Next, we related the data-base to an expert system for corrosion deterioration assessment of the structures, which had some functions, such as stress check up, judgement of maintenance step, and life time prediction.In this paper, we described the data-base, and the outline of the whole advising system for corrosion deterioration assessment.

CORROSION OF STEEL STRUCTURES IN MARINE ENVIRONMENTS BASED ON FIELD INVESTIGATIONS

In order to study the actual states and tendencies of corrosion of steel structures in marine environments, some analyses were performed on the results of the investigations conducted in the various ports and the following results were obtained. Corrosion rate nearby L. W. L varied from structure to structure. The corrosion rate of steel pipe piles was a little larger than that of steel sheet piles. Intensive corrosion under mean low water level, so called concentrated corrosion, were found in many of the structures; the concentrated corrosion had a tendency to occur at steel pipe piles, with having high upper exposed end of steel members, in sea water of poor quality and in sea water with inflow of fresh water.

港湾構造物の腐食実態と防食対策

港湾構造物の腐食実態と防食対策