Marine Atmospheric Environment Research Articles

SiC-armoured triple-layered superhydrophobic coating with super-robustness and anti-corrosion durability

Continuously enhancing the mechanical stability and durability of superhydrophobic corrosion-resistant materials is a great challenge for researchers. In this paper, we developed a SiC armoured triple-layered superhydrophobic coating with super-robustness on Q235 carbon steel substrates. The triple-layered coating was achieved by sequentially applying an epoxy (EP) resin adhesive layer, a SiC-armored skeleton structure, and a superhydrophobic F-Al2O3@EP layer. The resulting coating demonstrated outstanding non-wetting superhydrophobicity, featuring a static water contact angle (WCA) of 157.7 ± 0.5° and a sliding angle (SA) of 3.7 ± 0.6°. Moreover, the designed triple-layered superhydrophobic coating exhibits ultra-low interfacial adhesion force and demonstrates self-cleaning ability. Its mechanical stability was significantly heightened, enduring more than 2700 sandpaper abrasion cycles, 2200 tape-peeling cycles, and 3000 g sand impact resistance. Additionally, the coating displayed superior corrosion resistance with eight orders of magnitude enhanced charge transfer resistance (Rct), 590 mV positive shift corrosion potential (Ecorr), and six orders of magnitude lower corrosion current density (Icorr) in a 3.5 wt% NaCl solution. Impressively, the SiC armoured triple-layered superhydrophobic coating demonstrated prolonged marine anti-corrosion performance, enduring immersion in a 3.5 wt% NaCl solution for over 1200 h and exposure to the outdoor marine atmospheric environment for more than 3360 h. We believe the development of superhydrophobic materials with high stability and durability contributes to their widespread adoption and multifunctional applications.

Anticorrosion Method Combining Impressed Current Cathodic Protection and Coatings in Marine Atmospheric Environment

In this study, a new anticorrosion method combining impressed current cathodic protection (ICCP) with coatings that can be applied to marine atmospheric environments is proposed. As the corrosion medium fills the cracks and pores of the coating, an electrolyte film layer is inevitably formed on the metal surface. Therefore, a graphene conductive coating with excellent chemical inertness and shielding performance is selected as the intermediate coating to form an electrolytic cell system with a metal substrate serving as the cathode and a graphene coating serving as the auxiliary anode. By studying the surface corrosion morphologies and electrochemical signals of the coating samples at different protection potentials and coating thicknesses, the optimal potential is determined to be 0.6 V, and the optimal coating thickness is determined to be 20 μm. The samples protected by the joint method have lower corrosion rates and better anticorrosion performance than those protected by the coatings alone.

Uncertain process-based integration of ADT and field data of PCB in airborne equipment and PCB residual lifetime evaluation

Accurately evaluating the lifespan of the Printed Circuit Board (PCB) in airborne equipment is an essential issue for aircraft design and operation in the marine atmospheric environment. This paper presents a novel evaluation method by fusing Accelerated Degradation Testing (ADT) data, degradation data, and life data of small samples based on the uncertainty degradation process. An uncertain life model of PCB in airborne equipment is constructed by employing the uncertain distribution that considers the accelerated factor of multiple environmental conditions such as temperature, humidity, and salinity. In addition, a degradation process model of PCB in airborne equipment is constructed by employing the uncertain process of fusing ADT data and field data, in which the performance characteristics of dynamic cumulative change are included. Based on minimizing the pth sample moments, an integrated method for parameter estimation of the PCB in airborne equipment is proposed by fusing the multi-source data of life, degradation, and ADT. An engineering case illustrates the effectiveness and advantage of the proposed method.

Machine Learning-Assisted Prediction of Corrosion Behavior of 7XXX Aluminum Alloys

High-strength and lightweight 7XXX Al alloys are widely applied in aerospace industries. Stress corrosion cracking (SCC) in these alloys has been extensively discussed, and electrochemical corrosion should be brought to the forefront when these materials are used in marine atmospheric environments. This work obtained the corrosion potentials (Ecorr) and corrosion rates of 40 as-cast 7XXX Al alloys by potentiodynamic polarization tests and immersion tests, respectively; then, chemical compositions and physical features were used to build a machine learning model to predict these parameters. RFR was used for the prediction model of Ecorr with the features Cu, Ti, Al, and Zn, and GPR for that of the corrosion rate with the features of specific heat, latent heat of fusion, and proportion of p electrons. The physical meaning and reasonability were discussed based on the analysis of corrosion morphology and precipitated composition. This work provides a reference for the design of corrosion-resistant 7XXX Al alloys and shows a method of conducting corrosion mechanism evaluation by using machine learning.

Corrosion Behavior of the 2024 Aluminum Alloy in the Atmospheric Environment of the South China Sea Islands

The 2024 aluminum alloy, a structural material commonly used in aviation aircraft bodies, is susceptible to serious corrosion in marine atmospheric environments. This paper comprehensively studies the corrosion behavior of the 2024 aluminum alloy in the South China Sea atmosphere. Weighing, morphology observation, phase analysis, electrochemical testing, and other methods were used to study the corrosion law and corrosion mechanism of the 2024 aluminum alloy. The main conclusions are as follows: At the initial stage of exposure, pitting corrosion occurred on the surface of the 2024 aluminum alloy. After 3 months of exposure, the self-corrosion current density increased from 0.456 μA·cm−2 to 8.338 μA·cm−2. After 6 months of exposure, the corrosion developed into general corrosion. The main component of the corrosion product was Al2O3·3H2O. The product covered the surface to form a loose corrosion product layer, which had an inhibitory effect on corrosion. The self-corrosion current density was reduced to 2.359 μA·cm−2. After 12 months of exposure, the corrosion product layer fell off and became thinner, and the self-corrosion current density increased to 2.849 μA·cm−2. The corrosion kinetics conformed to the functional equation W = 0.00346t0.73891, indicating that the corrosion products have a certain protective effect on the matrix.

Unraveling the influence of Mo on the corrosion mechanism of Ni-advanced weathering steel in harsh marine atmospheric environments

Ni-advanced weathering steel holds paramount importance in marine atmospheric environments, especially those with heightened Cl− concentrations. The meticulous compositional design plays a crucial role in establishing a rust layer capable of withstanding intrusion by Cl−, making it imperative for the viability of coating-free weathering steel in marine atmospheric environments. This study explores the corrosion evolution and corrosion-resistant mechanisms within a steady-state rust layer in 3Ni weathering steel, with a particular focus on the role of Mo in challenging marine atmospheric conditions. The findings unequivocally demonstrate that the augmentation of the protective properties of the rust layer is directly correlated with an increase in Mo content, transitioning from 0.5 to 1.5 wt.%. This transition is most evident in the reduction of the corrosion rate for the 3Ni-Mo steel, dropping from an initial 1.74 mm a−1 to a robust 1.31 mm a−1 after 768 h of corrosion exposure. The heightened Mo content expedites the formation of a stable and durable rust layer, significantly enriching the proportion of α-FeOOH within this protective layer. The stabilized rust layer of 3Ni-Mo weathering steel exhibits a distinct three-layer structure, comprising an outer layer primarily of γ-FeOOH, an intermediate layer mainly composed of Fe2O3/Fe3O4, and an inner layer predominantly composed of α-FeOOH and β-FeOOH. Additionally, an alkaline interface enriched with NiFe2O4 and CuFe2O4 develops between the inner layer and the substrate. Firstly, Mo promotes the deposition of MoO2, MoO3, and molybdate on both the inner layer and alkaline steel-rust interface to repair corrosion pits and fill cracks. Secondly, Mo facilitates the generation of compounds such as NiFe2O4 and CuFe2O4, which heightens the electronegativity of the intermediate rust layer and the steel-rust interface, preventing Cl−-induced interface acidification and pitting corrosion. The higher Mo content expedites the formation of this alkaline interface and promotes inner layer densification. Most significantly, Mo creates additional nucleation sites for hydroxide oxides through oxide formation, leading to the formation of nano-sized α-FeOOH and β-FeOOH within the inner layer thereby enhancing the stability and compactness of the inner layer. These synergistic effects fortify the resilience of 3Ni-Mo advanced weathering steel in corrosive environments, ultimately strengthening its capacity to withstand environmental challenges.

Evaluation of Marine Atmospheric Environmental Adaptability of 3238A/CCF300 Composite Material

Composite material has been widely used in various industries because of its superior properties. But when used in harsh environment the composite material is susceptible to aging under the influence of UV radiation, water, temperature, humidity and other natural environmental medium. To evaluate the environmental adaptability of composite material, exposed 3238A/CCF300 in marine atmospheric environment for 3 year. The results show that the morphology exhibit brightness enhancement and surface resin decomposition. And the mechanical properties including 90° tensile strength, 0° compressive strength, bending strength, shear strength have all decline, amongst which the 90° tensile strength declines 55.4%, is most sensitive to marine atmospheric environment. Finally analyses the failure mechanism of 3238A/CCF300 due to the combination of heat-humidity aging and photo-degradation process.

Study of the role of aluminium and corrosion mechanism in galvalume coating in the marine atmospheric environment

PurposeThis study aims to investigate the role of aluminium (Al) in marine environment and the corrosion mechanism of galvalume coatings by conducting accelerated experiments and data analysis.Design/methodology/approachSamples were subjected to accelerated corrosion for 136 days via salt spray tests to simulate the natural conditions of marine environment and consequently accelerate the experiments. Subsequently, the samples were examined using various test methods, such as EDS, scanning electron microscopy (SEM), X-ray diffraction (XRD) and electrochemical impedance spectroscopy (EIS), and the obtained data were analysed.FindingsGalvalume coatings comprised interdigitated zinc (Zn)-rich and dendritic Al-rich phases. Corrosion was observed to begin with a Zn-rich phase. The primary components of the corrosion product film were Al2O3 and Zn5(OH)8Cl2·H2O. It was confirmed that the role of Al was to form a dense protective film, thereby successfully blocking the entry of corrosive media and protecting the iron substrate.Originality/valueThis study provides a clearer understanding of the corrosion mechanism and kinetics of galvalume coatings in a simulated marine environment. In addition, the role of Al, which is rarely mentioned in the literature, was investigated.

Effect of Mo on the Corrosion Resistance of Cr-Containing Steel in a Simulated Tropical Marine Atmospheric Environment

In this manuscript, the effect of Mo addition on the corrosion resistance of the low-alloy steel in a simulated tropical marine atmospheric environment has been studied through microstructure characterization, corrosion immersion experiments, electrochemical measurement, and a series of microscopic characterization methods. The results show that Mo has the ability to reduce the corrosion rate of low-alloy steel in a marine atmospheric environment, with a more pronounced reduction effect observed over longer corrosion periods. The addition of Mo enhances the corrosion product film’s compactness when coupled with Cr, subsequently improving corrosion resistance. Simultaneously, MoO42−, acting as a slow-release ion, can effectively suppress localized corrosion in low-alloy steel. The research findings can offer data support and a theoretical foundation for the design of low-alloy steels with enhanced corrosion resistance in a tropical marine atmospheric environment.

Microstructural Effect on the Corrosion Behavior of 3Ni Weathering Steels in Tropical Marine Atmospheric Environments: Outdoor Exposure and Indoor Tests

Microstructural Effect on the Corrosion Behavior of 3Ni Weathering Steels in Tropical Marine Atmospheric Environments: Outdoor Exposure and Indoor Tests

Corrosion behavior of 700 MPa grade weathering steel with 4.0 wt% Ni and 5.0 wt% Cr in simulated marine atmospheric environment

The dry-wet cycle corrosion behavior of low alloy steel (Q355B) and 700 MPa grade Ni, Cr composite weathering steel (4 wt% Ni-5 wt% Cr) in 2 wt% NaCl solutions was studied. The distribution characteristics of elements and phases in the corrosion products after 360 h corrosion cycle were analyzed by SEM and Raman spectroscopy. The formation mechanism of protective rust layer of Ni, Cr composite weathering steel in simulated marine environment was briefly described. The results show that the corrosion products of Q355B appear obvious stratification, and the rust layer of Ni, Cr composite weathering steel has no longer stratified. The Ni, Cr composite weathering steel forms a cationic selective rust layer during the corrosion process, which effectively prevents the penetration of Cl- and exhibits excellent corrosion resistance, the corrosion rate of Ni, Cr composite weathering steel after 72 h-360 h corrosion cycle is 1/8–1/3 of that of Q355B. The value of α/γ * increases with the extension of corrosion cycle, which is reach to 1.0 after 360 h corrosion cycle. The corrosion potential increases with the extension of corrosion cycle, the corrosion current density fluctuates slightly around 100 × 10−6 A/cm2.

Corrosion behavior and oxide layer of selective-laser-melted Al-Mg-Sc-Zr alloy in marine atmospheric environment with different Cl−concentration

In this study, the corrosion response of the Al-Mg-Sc-Zr alloy produced by selective laser-melting in marine atmospheric environments with different Cl− concentrations was studied by electrochemical and immersion. Microstructural observations showed the microstructural of Al-Mg- Sc -Zr alloy featured a double grain microstructure, making up a coarse and fine grain area. TEM showed that some white precipitates enriched with Zr and Sc were dispersed in the samples. The potentiodynamic polarization test indicated increasing the Cl− concentration led to a negative shift of corrosion potential and narrowed the potential range of the passive zone, which also caused the increase of corrosion current density value. The electrochemical impedance spectroscopy showed that higher Cl− concentration was greatly detrimental to generating a compact and dense oxide film on the Al-Mg-Sc-Zr alloys, as indicated by decreasing the resistance of the corrosion product layer and charge transfer resistance. The immersion test demonstrated that the samples suffered serious pit corrosion when the Cl− content increased to 1.5 and 3.5 wt%, showing a larger size and more depth of corrosion pits. This study is expected to provide data to determine the reliability of the SLM-manufactured Al-Mg-Sc-Zr alloy in marine atmospheric conditions.

Effect of ultraviolet light on the corrosion behavior of weathering steel in simulated marine atmospheric environment

PurposeThis paper aims to study the effect of ultraviolet (UV) light on the corrosion behavior of BC550 weathering steel in simulated marine atmospheric environment.Design/methodology/approachThe effect of UV light on the corrosion behavior of BC550 weathering steel in simulated marine atmospheric environments were investigated by the corrosion weight gain experiment, in situ electrochemical noise, scanning electron microscope and X-ray diffraction.FindingsUV light accelerated the corrosion process of BC550 weathering steel in the simulated marine atmospheric environment during the first 168 h. The maximum influence factor of UV light was 0.32, and it was only 0.08 after 168 h of corrosion process.Originality/valueAs the extension of corrosion time, the thickness and density of the corrosion product layer increased, which weakened the acceleration effect of UV light.

Galvanic corrosion behavior of welded joint in marine atmosphere environment based on capillary microcell

The kinetical behavior and mechanism of micro-galvanic corrosion of Q690 bainitic weathering steel welded joint in marine atmosphere were investigated. The results showed that a micro-galvanic corrosion cell formed among different regions of the Q690 welded joint. The kinetical behavior of micro-galvanic corrosion could be divided into four stages: the initiation and development of micro-galvanic corrosion, the decreasing of galvanic corrosion rate, the polarity reversal of galvanic couple, and the disappearance of galvanic effect. The difference of corrosion rate between Q690 steel and its welded joint is closely related to the micro-galvanic corrosion kinetic behavior.

Optimizing microstructure for enhanced atmospheric corrosion resistance of a novel Ni–Mo weathering steel: A field exposure study in Thailand's tropical marine environment

This study compares the weathering performance of steel with three microstructures: ferrite, ferrite + bainite, and bainite. The rolling and cooling processes of a novel and cost-effective Ni–Mo weathering steel (WS) were manipulated to achieve these microstructures. Validation of these microstructures was performed through field exposure tests in Trat, Thailand, representing a typical tropical marine atmospheric environment. The bainitic steel exhibited better weathering resistance. After 12-month of exposure, the corrosion rates for ferritic + bainite and bainitic steels were 105.6 % and 97.9 % respectively, compared to ferritic steel. The variation in corrosion rates confirm that modifying the microstructure, with emphases on bainite, improves the WSs' resistance to atmospheric corrosion. Changes in corrosion rate mainly depend on the rust layer's adherence. Interestingly, α-FeOOH predominantly characterizes the rust layer on the skyward side of the samples following 12-month of exposure, while the earthward side is mainly composed of Fe3O4/γ-Fe2O3.

STUDY ON THE ACCELERATED CORROSION BEHAVIOR OF A GALVANIZED X80 PIPELINE STEEL WELDED JOINT DURING A CYCLIC SALT SPRAY TEST

The corrosion behavior of galvanized X80 pipeline steel welded joints in a marine atmospheric environment was studied using the cyclic salt spray accelerated corrosion test. The corrosion weight loss, corrosion morphology and corrosion products of samples under different cycles were characterized by means of appearance inspection, SEM and EDS. The results show that with the rupture of the galvanized layer, cracks first appear when the weld metal is exposed for eight days. With the infiltration of the corrosive liquid, pitting pits first appear in the weld metal. In the early stage of corrosion in the heat-affected zone, the fracture degree of the zinc layer is more serious than that in the other two areas. The corrosion products of the zinc layer accumulate irregularly and more pits appear, resulting in early cracks and pitting pits in the later stage. Compared with the first two regions, the base metal shows better corrosion resistance.

Analysis of wind time-varying performance of reinforced concrete electric pole under Marine atmospheric environment

Bearing capacity calculation model of concrete electric pole considering concrete long-term performance degradation and steel corrosion is established. The horizontal bearing capacity and wind resistance of typical concrete electric pole under Marine atmospheric environment are analyzed with service time. The effects of concrete protective layer thickness, stirrup diameter and strength coefficient on the long-term wind resistance of electric pole are discussed. It is found that with the increase of service time, the shear strength of the concrete pole deteriorates faster than that of the flexural strength, and the failure mode changes from bending failure to shear failure. The wind resistance of the pole after long service can be improved by increasing the thickness of the protective layer, adopting larger diameter stirrup and higher strength coefficient. The bearing capacity calculation model of concrete electric pole considering concrete long-term performance degradation and steel corrosion is established. The horizontal bearing capacity and wind resistance of typical concrete electric pole under Marine atmospheric environment are analyzed with service time. The effects of concrete protective layer thickness, stirrup diameter and strength coefficient on the long-term wind resistance of electric pole are discussed. It is found that with the increase of service time, the shear strength of the concrete pole deteriorates faster than that of the flexural strength, and the failure mode changes from bending failure to shear failure. The wind resistance of the pole after long service can be improved by increasing the thickness of the protective layer, adopting larger diameter stirrup and higher strength coefficient.

Corrosion failure analysis of engineering structural steels in tropical marine atmospheres: A comparative study of ordinary and new weathering steels

Reliable applications for weathering steels face challenges in harsh tropical marine atmospheric environments. The development of new weather steel suitable for tropical marine atmospheric environments is of great significance. In the paper, the corrosion failure behavior of ordinary and newly designed weathering steels exposed to tropical marine environments for two years was studied by employing various analytical methods. The results indicate that the extensive formation of akaganeite and lepidocrocite occurs deep inside the abnormally thick corrosion products of ordinary weathering steel with the accumulation of Cl−, which is laborious to be affected by the rinsing effect of rainfall. Based on the study of the composition, phase, and structure of abnormally thick corrosion products, a chain evolution mechanism of corrosion failure is proposed. By optimizing the content of Cu, Mo, and Ni, the newly designed weathering steel can effectively suppress the chain failure process and increase the corrosion resistance by approximately doubling. On the whole, the newly designed weathering steel can be well applied to tropical marine atmospheric environments.

Effect of La on the Corrosion Behavior and Mechanism of 3Ni Weathering Steel in a Simulated Marine Atmospheric Environment

Effect of La on the Corrosion Behavior and Mechanism of 3Ni Weathering Steel in a Simulated Marine Atmospheric Environment

Synergistic Effects of Multiple Environmental Factors on Degradation of Silicone Rubber Seals under Marine Atmosphere.

In this research, the degradation behavior and failure mechanism of silicone rubber seal rings under the synergistic effects of multiple factors in the marine atmosphere are fully investigated. Firstly, four aging factors of air, temperature, compressive stress, and chemical medium were determined by analyzing the service environment profile of silicone rubber seal under a marine atmosphere environment. Secondly, to better simulate the actual service environment of silicone rubber and shorten the test period, an artificially accelerated aging test was designed and carried out in the laboratory. In this paper, temperature is utilized as the accelerating stress. According to the results of the pre-test, the accelerating stress level is finally determined to be 110-150 ∘C. In addition, the compression set applied is consistent with the constant compression permanent deformation value of 28% of the silicone rubber in the actual service process. Finally, through the macroscopic physical properties and microstructure analysis of the samples before and after aging, the corresponding test results are given, and the failure mechanism is analyzed and discussed in detail. Through the above test results and discussion, it can be concluded that the aging process of multi-factor coupling on the lower silicone rubber seal ring is uneven, and its aging process is not a simple superposition of multiple environmental factors. More importantly, the above test data and results are of great significance for evaluating the service life of silicone rubber seals, which can be utilized in the future to improve the reliability and durability of related equipment in the marine environment.